Free Radicals

Phenolic Antioxidants

Phenolic antioxidants including, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tertiary butylhydroquinone (TBHQ), are used in foods primarily to delay autoxidation of unsaturated lipids. The first report on the antibacterial effectiveness of BHA was that of Chang and Branen (42) in which E. coli, Salmonella typhimurium, and Staphylococcus aureus were inhibited in nutrient broth. Subsequent studies generally demonstrate that Gram-positive bacteria are more susceptible to BHA than Gram-negative bacteria. BHT is generally less effective than other phenolic antioxidants (43). TBHQ is an extremely effective inhibitor of Gram-positive bacteria including S. aureus and Listeria monocytogenes at concentrations generally less than 64 g mL (43). A number of studies have been carried out to determine the antimicrobial effectiveness of phenolic antioxidants in foods (43). In nearly all studies, the concentration of phenolic antioxidants required for...

Chainbreaking Antioxidants

Control of free radicals is an effective method to prevent both autoxidation and oxidation accelerated by pro-oxidants, since free radicals are a universal reaction intermediate for all lipid oxidation reactions. Chain-breaking antioxidants inhibit free-radical reactions by scavenging radicals resulting in inactivation of the original free radical and formation of a more stable antioxidant radical (1). The effectiveness of a chain-breaking antioxidant is a function of its chemical and physical properties. For a chain-breaking antioxidant to be effective, it must possess a hydrogen, which is weakly bound to the antioxidant so that it can be freely donated to the free radical. As the bond energy of the hydrogen on the chain-breaking antioxidant decreases, the transfer of the hydrogen to the free radical is more rapid (1,2). The effectiveness of a chain-breaking antioxidant is also related to its ability to decrease radical energy so that the antioxidant radical cannot promote further...

Antioxidant Micronutrients And The Immune System

Free radicals, highly reactive molecules with one or more unpaired electrons, often contain reactive oxygen species. Free radicals are generated during cellular metabolism, can be ingested or inhaled as environmental pollutants, or can be generated during the metabolism of certain drugs or xenobiotics.

Essential micronutrients with antioxidant activities

Antioxidants interfere with the production of free radicals and or inactivate them once they are formed. There are four enzymes which have anti-oxidant capacity and contain essential minerals. These include two types of superoxide dismutases a manganese-containing enzyme and an enzyme containing both copper and zinc. The third enzyme, catalase, an iron-containing enzyme, catalyzes the decomposition of hydrogen peroxide. Selenium is an essential component of the fourth enzyme, glutathione peroxidase, important in the decomposition of hydrogen peroxide and lipid peroxides, termination products of free radical attack on lipids. Three other essential micronutrients can directly interfere with the propagation of, as well as scavenge, free radicals. Vitamin E (a-tocopherol), the major lipid-soluble anti-oxidant present in all cellular membranes, protects against lipid peroxidation and prevents the loss of membrane fluidity. Vitamin E has been characterized as the most critical antioxidant...

Antioxidants Found Within the Human Body

The structures of the human body are exposed continuously to a variety of ROS. Humans have evolved an effective antioxidant system to defend against these damaging agents. Different sites of the body contain different antioxidants or contain the same antioxidants but in different amounts. Differences are likely to reflect the different requirements and characteristics of these sites. Human plasma and other biological fluids are generally rich in scavenging and chain-breaking antioxidants, including vitamin C (ascorbic acid) and 'vitamin E.' Vitamin E is the name given to a group of eight lipid-soluble tocopherols and toco-trienols. In the human diet, 7-tocopherol is the main form of vitamin E, but the predominant form in human plasma is a-tocopherol. Bilirubin, uric acid, glutathione, flavonoids, and carotenoids also have antioxidant activity and are found in cells and or plasma. Scavenging and chain-breaking anti-oxidants found in vivo are derived overall from both endogenous and...

Antioxidant and Prooxidant Actions of Ascorbate

Chemically, ascorbate is a potent reducing agent, both reducing hydrogen peroxide and also acting as a radical trapping antioxidant, reacting with superoxide and a proton to yield hydrogen peroxide or with the hydroxy radical to yield water. In each case the product is monodehydroascorbate, which, as shown in Figure 1, undergoes dismutation to ascorbate and dehydroascorbate. In studies of ascor-bate depletion in men there is a significant increase in abnormalities of sperm DNA, suggesting that vitamin C may have a general, nonspecific radical-trapping antioxidant function. Ascorbate also acts to reduce the tocopheroxyl radical formed by oxidation of vitamin E in cell membranes and plasma lipoproteins. It thus has a vitamin E sparing antioxidant action, coupling lipo-philic and hydrophilic antioxidant reactions. The antioxidant efficiency of ascorbate is variable. From the chemistry involved, it would be expected that overall 2 mol of tocopheroxyl radical would be reduced per mole of...

Classifying natural antioxidants

Natural antioxidants occur mainly in plants but also in fungi and microorganisms and to lesser extent in animal tissues. They are mostly disubstituted phenolic derivatives, most often 1,2-dihydroxybenzene, more rarely 1,4-dihydroxybenzene derivatives. A hydroxyl group or both can be replaced with a methoxy, ester or another active group. However, cholesteryl esters of ferulic or caffeic acids are less active than the respective free acids (Marinova et al., 1998). Phenolic acids are the most widely occurring antioxidants in higher plants, especially in those used as food. They belong to derivatives of either benzoic acid or cinnamic acid. Gallic acid (3,4,5-trihydroxy-benzoic acid) is a typical example of the benzoic acid group, while caffeic acid (3,4-dihydroxy-1-acryloyl-benzoic acid) is the most important derivative of the cinnamic acid series (Fig. 3.1). Caffeic acid is frequently esterified with quinoic acids, forming chlorogenic acid isomers. Another important class of...

Antioxidants from vegetables overview

The antioxidants present in commonly consumed vegetables include ascorbic acid, tocopherols, carotenoids and phenolic compounds such as flavonols and phenolic acids (Table 3.3). In comparison to fruits and berries, vegetables generally contain much lower amounts of antioxidant compounds. A large amount of vitamin C is found in sweet red pepper (1850mgkg-1) and significant amounts in Brussels sprouts (up to 900mgkg-1) and broccoli (750-830 mg kg-1), while Table 3.3 Antioxidant compounds in selected vegetables and their products, mgkg fresh weight Table 3.3 Antioxidant compounds in selected vegetables and their products, mgkg fresh weight the amounts of vitamin E are generally below 10mgkg-1 in vegetables. According to Hussein et al.68 although there was significant loss in vitamin C during storage of broccoli and green peppers, in most cases there was no difference in loss of vitamin C or beta-carotene between the processed and unprocessed vegetables, and the packaging systems. After...

Antioxidants from fruits vegetables herbs and spices

All fruits and vegetables contain antioxidants their high consumption, and therefore, high intake of antioxidants, are the main advantages of the Mediterranian diet (Visioli and Galli, 2001). The most important group of active antioxidants in fruits and vegetables are various flavones, anthocyanins and related compounds (Zhang, 1999). Some compounds of these groups are able to increase vitamin C activity, protecting it against oxidative degradation. They are called bioflavonoids. In red wine and deep-red coloured fruit juices, various anthocyanins and their polymers are present, which are soluble in the aqueous phase, and possess moderate antioxidant activity. In addition to these compounds, various terpenic derivatives could act as potent inhibitors of lipid oxidation (see more in the next section). Another group of active compounds are carotenoids (Stahl and Sies, 1999), e.g., lycopene present in tomatoes. They possess antioxidant activities as mentioned in section 3.3.1. The best...

Using natural antioxidants in food

The main guideline is that natural antioxidants are preferred to synthetic antioxidants only insofar as the consumers prefer them, and people feel that humans became adapted to them over the many generations they were consumed. Only food components, and not all natural substances should be accepted for use in foods. Material Generally Regarded As Safe (GRAS) can be added to foods without limitations. The best application of antioxidants is the direct addition of the respective ingredients, found as active antioxidants, to food without any previous fractionation or concentration herbs and spices belong to this group. Some simple fractionation could be used, e.g., extraction of the oil fraction and utilization of the extracted meal, or distillation of the volatile essential oils, and the use of the nonvolatile residue. high concentrations of active substances could become a health risk. The use of supercritical carbon dioxide for extraction of antioxidants is a very safe process. It may...

Effect of different processing technologies on antioxidant activity

Food processing involves changes in structural integrity of the plant material and this produces both negative and positive effects. When the negative and positive effects counterbalance each other, no change in the antioxidant activity occurs.115 The antioxidant activity is diminished owing to inactivation of antioxidant compounds caused by oxidation, for example, by enzymes (polyphenoloxidase and others) or leaching into the cooking water. Both negative changes have a greater impact on the water-soluble antioxidants, vitamin C, flavonoids and phenolic acids, than on the lipid-soluble antioxidants, carotenoids and tocopherols. The positive effects of food processing include transformation of antioxidants into more active compounds, such as the deglycosylation of onion quercetin,106 as well as an increase in the antioxidant activity owing to inhibition of enzymes.81 Peeling and juicing result in substantial losses of carotenoids, anthocyanins, hydroxycin-namates and flavanols as the...

Application of natural antioxidants for the stabilization of fish and fish oil

Fish oils are very sensitive to oxidation as they contain fatty acids with four to six double bonds, therefore it is rather difficult to stabilize them against rancidification. The most common natural antioxidants are tocopherols. At low concentrations (about 100mg kg), a-tocopherol is more active than 7- and S-tocopherols while at high concentrations (about 1000mg kg) it is the reverse, and S- and 7-tocopherols are more active than a-tocopherol. The same could be said in the case of vegetable oils (see below). Lecithin and ascorbyl palmitate are synergists in fish oils enriched with tocopherols. Both choline and ethanolamine bound in phospholipids inhibit the accumulation of hydroperoxides in sardine oil. Different flavonoids, especially quercetin, stabilize fish oils against rancidification, shown as synergism with a-tocopherol under conditions of the Schaal Oven Test at 60 C and in glass bottles at 2.50C. The most efficient derivative was Flavonoids, such as myricetin, quercetin...

Improving antioxidant functionality 361 Use of mixtures of inhibitors

The application of high concentrations of an antioxidant is limited for several reasons. Antioxidant activity generally decreases with increasing concentration of the antioxidant so that the optimum concentration should not be exceeded. The maximum concentration is most often regulated by legislation from safety concerns, by the effect on sensory properties or by the price therefore other ways are sought to improve stability against oxidation. The application of mixtures of antioxidants is advantageous in the case of synthetic antioxidants as it allows some countries to increase the addition of a mixture of antioxidants above the 0.01 or 0.02 permitted for a single antioxidant. Activity is, however, raised only moderately, as all antioxidants compete for the same free radicals. The synergism between a-tocopherol with rosemary extracts was observed in systems containing ferrous ions and hemoprotein (Fang and Wada, 1993). Synergism also exists between rosemary and sage extracts, even...

Application of mixture consisting of antioxidants and synergists

A more efficient solution is to add mixtures of antioxidants and synergists. Synergists have no antioxidant activity of their own in the absence of phenolic antioxidants but they increase the activity of phenolic antioxidants if they are present. Polyvalent organic acids (such as succinic acid), hydroxy acids (such as citric or tartaric acids), amino acids, peptides (Park et al., 2001) or phospholipids belong to this group (see also 3.3). The synergism is based on various mechanisms, and the same synergist may act following several mechanisms. They may convert the oxidized compounds, such as tocopheryl quinones, back to the respective original antioxidants, such as tocopherols. The main sources of free radicals in oxidizing lipids are hydroperoxide decomposition products free R-O* and R-OO* radicals. The decomposition is efficiently catalyzed by transient valency heavy metal ions or complexes, such as copper, iron, cobalt or manganese. Therefore, metal chelating agents, such as...

Microcomponents antioxidants and vitamins

Ripe tomatoes are relatively rich in antioxidants vitamin C (160-240mgkg-1), lycopene (30-200mgkg-1), provitamin A carotenes (6-9mgkg-1) and phenolic compounds flavonoids (5-50mgkg-1) and phenolic acids (10-50mgkg-1).14 Also present in small quantities are vitamin E (5-20 mg kg-1) and trace elements such as copper (0.1-0.9mgkg-1), manganese (1-1.5mgkg-1) and zinc (1-2.4mgkg-1) which are present in several antioxidant enzymes. Most often the tomato variety is not indicated and the reported values are a mean concentration of the constituents in tomatoes found in local markets.

Natural antioxidants

Foods containing fats and other lipids, terpenes and branched hydrocarbons are not stable on long storage or intensive heating. Unsaturated, and particularly, polyunsaturated fatty acids bound in lipids are oxidized following different mechanisms with formation of free radicals, which are further converted into hydroperoxides. Hydroperoxides are odourless and tasteless, but they decompose with formation of volatile compounds, such as alkanals, alk-2-enals, alka-2,4-dienals, different ketones, alcohols and hydrocarbons. These products give rise to specific objectionable off-flavours, called rancid flavour notes. The sensory value, and thus the food acceptability, is substantially deteriorated by rancidification. The rancidification can be prevented by different methods, such as by using fat materials poor in polyenoic (polyunsaturated) fatty acids, by protecting food products against the access of oxygen or, most often, by adding inhibitors of oxidation. The most important inhibitors...

Antioxidants from oilseeds cereals and grain legumes

Olive oil is very stable against oxidation, not only because of low linoleic acid content, but also because of a group of natural antioxidants, derived from hydroxytyrosol. Oleuropein aglycone belongs to this group of antioxidants. The oxygen radical absorbance capacity of extra-virgin olive oils is related to the content of total phenolics (Ninfali et al., 2001). The same antioxidants were detected in olive leaf and olive fruit extracts. Another interesting group of phenolic antioxidants is present in sesame seed. They belong to lignans, which are decomposed during roasting of sesame seeds, and some decomposition products are extracted from seeds into oil during oilseed processing, such as sesamol, possessing substantial antioxidant activity even in polyenoic edible oils (Fukuda et al., 1988). Traditional cottonseed contained gossypol and related pigments, imparting high stability to cottonseed oil. As gossypol is toxic both for humans and animals, new glandless varieties free of...

Aging Exercise and Antioxidant Defense System

The oxidant antioxidant balance is an important determinant of immune cell function, including maintaining integrity and functionality of membrane lipids, cellular proteins, nucleic acids, and for control of signal transduction and gene expression in immune cells. Enzymatic and nonenzymatic antioxidants play a vital role in protecting tissues from excessive oxidative damage during exercise. Antioxidant enzymes play an important role in defending the cells against free-radical-mediated oxidative damage. In rats, hepatic and myocardial antioxidant enzymes are declined at older age, whereas activity of glu-tathione-related enzymes in the liver and mitochondrial enzymes in the heart are increased significantly. Skeletal muscle antioxidant enzymes are uniformly elevated during aging. The generation of oxygen free radicals and other reactive oxygen species may be the underlying mechanism for exercise-induced oxidative damage, but a causal relationship remains to be established. Depletion of...

Applications of natural antioxidants for the stabilization of essential oils and cosmetics against oxidation

Essential oils are not lipids because they do not contain bound fatty acids, but they are as easily oxidized as lipids are and their oxidation proceeds along similar lines. Many essential oils contain components resistant to oxidation or even possessing antioxidant properties, but other essential oils are very sensitive to oxidation, especially citrus essential oils. During their oxidation, citrus odour notes disappear, and intensities of woody, acidic and heavy odour notes develop (Pokorny et al., 1998). Limonene was found to be the most sensitive compound and herbal oleoresins were efficient in its stabilization (Lee and Widmer, 1994). During the oxidation of bergamot oil at 40-60 C, sensory acceptability decreased but rosemary extracts inhibited oxidation and minimized the odour changes (Pudil et al., 1998). Similar activity was also observed in Citrus hystrix essential oil, where the rosemary extracts were also found to be efficient. Methanolic extracts of herbs and spices were...

Phenolic Acids As Antioxidants

As discussed earlier, phenolic compounds have the capacity to function as antioxidants. Consequently, natural antioxidants are primarily plant phenolic compounds including flavonoids, phenolic acid derivatives, coumarins, tocopherols, and poly-functional acids.31 Synthetic antioxidants as well as tocopherols and ascorbic acid are commercially exploited as antioxidants and will not be discussed further as the focus of this chapter is on some of the natural phenolics previously reviewed. Phenolic compounds function as primary antioxidants by performing the role of free radical terminators. They interfere with lipid oxidation by rapidly donating a hydrogen atom to the lipid radicals, and the efficiency of these antioxidants (AH) increases with decreasing A-H bond strength. Phenolic antioxidants are excellent hydrogen or electron donors, and their radical intermediates are relatively stable due to resonance delocalization and general lack of suitable sites for attack by molecular...

Other ways of improving antioxidant functionality

Sufficient to apply antioxidants, especially spices, only on the surface. The process is particularly useful in the case of oxylabile (sensitive to oxidation) material, such as fish muscle. Food may be packaged, e.g. vacuum packed in plastic materials with a low or very low Oxygen Transmission Rate (0-TR) thus reducing or inhibiting oxygen diffusion from the air into the package. Food may also be packaged in an active packaging where antioxidants are incorporated in the packaging material with a controlled release of antioxidants to the surface of the food during the storage period. During storage, free radicals are slowly produced in food even at low temperatures and react with antioxidants, which are thus gradually consumed. The antioxidant functionality can be improved by reduction of the rate of free radical production. The safest way is to use stable lipids in the recipe. Instead of traditional edible oils rich in oxylabile polyunsaturated fatty acids, new modified high-oleic...

Antioxidant Activity Of Vaccinium Empetrum Rubus

Apple showed strong antioxidant activity towards oxidation of methyl linoleate, although the apple extracts tested were low in total phenolics as well as ascorbic acid.4,54 In apple juice, vitamin C activity represented a minor fraction of the total antioxidant activity, with chlorogenic acid and phloretin glycosides as the major identifiable antioxidants.17,55 Dihydrochalcones such as phloretin glucosides and phloridzin amount to 5-223 mg kg-1 in apple juice, this content being greater than that of fresh apples.55 According to Plumb et al.,36 chlorogenic acid contributes about 27 of the total activity of apple extract in scavenging hydroxyl radicals. Apple polyphenols isolated from gala apple pomace such as epicatechin, its dimer (procyanidin B2), trimer, tetramer and oligomer, guercetin glucosides, chlorogenic acid, phloridzin and 3-hydroxy-phloridzin showed strong antioxidant activities using beta-carotene linoleic acid system and DPPH radical scavenging activities.36 During...

Of host antioxidant response

Investigations so far in food grade clonal herb systems (1) and legume sprouts (112-114) led to the development of the model that activity of CCP, proline linked pentose-phosphate pathway is important for stress induced phenolic biosynthesis such as RA and phenolics and that this stimulation of phenolics is likely closely linked to stimulation of antioxidant response pathways (Figure 8.4) (96,112-114). Further research has indicated that the proline biosynthesis pathway coupled to stress induced antioxidant response pathways could be also stimulated in legume sprouts using exogenous treatment of phenolic extracts from clonal oregano (113,115,116). Phenolic extracts from these clonal oregano lines have high free radical scavenging activity (47). Proline linked stimulation of antioxidant enzyme response pathways may also be stimulated by low pH and salicylic acid (117). Further, exogenous seed treatment with oregano phenolic antioxidant extracts enhanced endogenous phenolic content, GPX...

Antioxidant Properties Of Inositol Phosphates In Vitro

Phytate is a very stable and potent chelating agent that exhibits the ability to complex a variety of divalent and trivalent ions. At physiological pH, InsP6 forms complexes with Cu2+, Zn2+, Co2+, Mn2+, Fe2+, and Ca2+ 3 . Because phytate binds essential minerals and can prevent their absorption, most human nutritionists view the compound negatively. However, its unique chelating action with iron provides phytate with antioxidant characteristics. In the iron-assisted Haber-Weiss reaction, the formation of OH requires the availability of at least one reactive iron coordination site, as well as iron solubility. Evidence that all six phosphates on myoinositol are not required for the inhibition of hydroxyl radical formation was presented by Hawkins et al. 6 . They showed that Ins(1,2,3,4,6)P5 and DL-Ins(1,2,3,4,5)P5 were effective at inhibiting hydroxyl radical formation to a greater degree than Ins(1,3,4,5,6)P5 and DL-Ins(1,2,4,5,6)P5 and concluded that the 1,2,3-trisphosphate grouping...

Antioxidant Assays Based on Free Radical Neutralization

Many antioxidant assays are based on their ability to neutralize or quench free radicals. The two free radicals that have been most commonly used for assessing antioxidant activity are 1,1-diphenyl-2-picrylhydrazyl (DPPH) (43,44), and acid) (ABTS) (45,46) (Figure 10.3). The DPPH free radical is a stable radical with one electron delocalized over the molecule (Figure 10.3). This delocalization gives a deep purple color with absorption maxima at 517 nm in an ethanol solution (43,44). When an antioxidant capable of donating a hydrogen reacts with the DPPH radical it gives rise to a nonradical reduced form of DPPH which has a yellow color. The decrease in the absorption is measured spectrophoto-metrically and is compared with an ethanol control to calculate the DPPH free radical scavenging activity (43,44). This method is a very quick and simple method for the measurement of antioxidant activity. The antioxidant capacity in this assay depends on the chemical structure of the antioxidant...

Antioxidant Properties Of Wild Rice In Cooked Meat Products

A cheaper alternative to phytate is the addition of high-phytate grains to cooked ground meats. Textured soy proteins (TSP) or textured vegetable proteins (TVP) are economical extenders of ground beef patties 31 . Lower thio-barbituric acid (TBA) values were reported for ground beef patties extended with TSP 32 , indicating possible antioxidant effects during storage. Addis and coworkers 3,33-35 at the University of Minnesota demonstrated the feasibility and acceptability of wild rice addition to ground beef patties and pork sausage 36 . In addition to a lowering ofTBA values with the addition of wild rice (Table 12.5), panel evaluations indicated an actual preference for beef patties with 15 or 30 cooked wild rice, compared to all beef controls 33 . Whole-grain wild rice was a more effective antioxidant in ground beef patties than ground wild rice 3 . The antioxidant properties of wild rice kernels were due to the presence of phytic acid 34 , as indicated by the identical HPLC...

Oxidative Stress and Antioxidant Responses

There is substantial evidence that oxidative damage in the brain increases in normal aging, that it is greater in persons with AD, and greatest in the brain regions that are most vulnerable in AD, but the source of the oxidative stress resulting in these changes has been elusive (50,231,364). Regions of the brain that degenerate in AD (e.g., cerebral cortices) have been found to have a significant increase of aluminum and iron compared with age-matched controls (421). (See also ref. 251.) Surprisingly, redox-active iron has been found to be reversibly associated with the plaques and tangles of the AD brain (364). This iron may be a source of oxidative stress if there are not adequate levels of iron-binding proteins or antioxidants in the vicinity, since ferrous iron will catalyze the production of damaging hydroxyl or peroxyhydroxyl radicals in the presence of reactive oxygen species. High levels of RNA and protein for the inducible enzyme heme oxygenase-1 also are associated with AD...

In Vitro and Ex Vivo Evidence of Antioxidant Properties of Polyphenols

Radicals and reactive oxygen species. In fact, in vitro, many polyphenols found in fruits and vegetables are better scavengers than the essential nutrient antioxidants. For example, compared to vitamin E and vitamin C, flavonols (quercetin, kaempferol, and rutin) are 1.3- to 4.7-fold more effective at scavenging free radicals. Flavan-3-ols and theaflavins are 2.5-6.9 times more effective than vitamin C and vitamin E at free radical quenching. Tea beverage has strong antioxidant properties, being 3.5-3.8 times more effective than vitamin C and vitamin E at free radical scavenging. Green tea is more effective than oolong tea, which is more effective than black tea. In comparison, carotenoids (lycopene, a-carotene, and -carotene) and xanthophylls ( 3-cryptoxanthin, zeaxanthin, and lutein) are 1.3- to 2.9-fold more effective at in vitro free radical scavenging. In addition to scavenging radicals and oxidants, tea polyphenols have also been demonstrated in vitro to be able to chelate...

Antioxidant and Biomarker Evidence from Intervention Studies in Humans

There are limited data from diet-controlled randomized crossover studies of humans on tea and other flavonoid-containing foods. Most intervention studies, apart from design considerations, suffer from lack of diet control, making them difficult to interpret. Results from intervention studies that employ dietary recalls, food records, and self-administered diets are notorious for introducing error that can mask treatment effects. Clinical studies in humans have focused on the antioxidant capacity of blood and oxidative damage to protein, lipid, and DNA as well as a number of risk factors associated with cardiovascular disease, including lipids, hemostasis, platelet aggregation, endothelial function, and blood pressure. Interventions have included high- and low-flavonoid diets, tea, chocolate, cocoa, wine, grape extracts, and fruit juices.

Changes in Antioxidant Capacity

Antioxidant capacity of the blood may be one indicator of a food's ability to act as an in vivo antiox-idant. Two commonly used measures of overall antioxidant capacity are the ORAC assay (oxygen radical absorbance capacity) and the FRAP assay (ferric reducing ability of plasma). Dietary interventions do alter the antioxidant capacity of blood. For example, individuals consuming a high cocoa and chocolate diet for 2 weeks have higher serum ORAC than when they consume a control diet. However, these results are not always consistent. For example, in individuals consuming pro-cyanidins in similar amounts of cocoa powder and chocolate, there is no change in plasma ORAC after 6 or 12 weeks. Green tea consumption rapidly increases FRAP but the effect appears to be short-lived and is perhaps related to the short half-life of the antioxidant tea phytochemicals in plasma. Moreover, green tea appears to have a greater antioxidant capacity (FRAP) than black tea, and the consumption of black or...

Tocopherols as Antioxidants

Cellular systems have evolved a powerful and complex antioxidant defence system to limit inappropriate exposure to these stressors. a-Tocopherol is quantitatively the most important chain-breaking antioxidant in plasma and biological membranes. The antioxidant activities of chain-breaking antioxi-dants are determined primarily by how rapidly they scavenge peroxyl radicals, thereby preventing the propagation of free radical reactions. When the chromanol phenolic group of a-tocopherol (TOH) encounters a ROO it forms hydroperoxide (ROOH), and in the process a tocopheroxyl radical (TO ) is formed The rate constant (k1) for hydrogen abstraction from a-tocopherol is 2.35 x 106M21 s2 1, which is higher than that for the other tocopherols and related phenols. Because the rate constant (k2) for the chain propagation reaction between ROO and an unsatu-rated fatty acid (RH) (ROO' + RH ROOH) is much lower than k1, at approximately 102M_1s_1 a-tocopherol outcompetes the propagation reaction and...

Antioxidant Defense System

Although zinc is not itself an antioxidant, there are several ways in which it participates in the antiox-idant defense system of the body, with important implications for health. It can bind to thiol groups in proteins, making them less susceptible to oxidation. By displacing redox-reactive metals such as iron and copper from both proteins and lipids it can reduce the metal-induced formation of hydroxyl radicals and thus protect the macromolecules. Its role in inducing MT has already been mentioned, and this protein scavenges hydroxyl radicals. Increased oxidative stress results in the release of zinc from MT, presumably making it more available for other proteins. Copper zinc superoxide dismu-tase is an important zinc-containing antioxidant enzyme whose activity is impaired in the deficient state. In general, animal studies have revealed an association between zinc deficiency and increased oxidative stress. The likelihood of increased oxida-tive stress under conditions of zinc...

Herbs and spices as sources of antioxidants

Herbs are stems or leaves from various plants, used for the preparation of infusions, extracts, dressings, soups or sauces. Many species of this class of food ingredients are active antioxidants, mainly because of the content of phenolic compounds. The most important representatives of this group are tea leaves obtained from both green or fermented tea (Camellia sinensis L. or Camellia assamica L.) or dust left after their preparation. Green tea is particularly rich in catechins and related compounds, usually more than 20 (Yamamoto et al., 1997). Phenolics obtained from tea contain not only catechins, but also epicatechin, gallocatechin and the respective gallates. They were active for the protection of meat lipids against oxidation (Shahidi and Alexander, 1998). Extracts from fermented (black) tea leaves are less active antioxidants because a substantial part of the catechin has been oxidized during the fermentation and converted into tea pigments, especially theaflavins and...

Plant phenolics in human health and as antioxidants

It is evident that plant phenolic compounds constitute one of the most numerous and widely distributed groups of substances with more than 8000 phenolic structures currently known (28). In addition to stress linked phenolics coming only from the shikimate and phenylpropanoid pathways, a number of the phenolic compounds are found in plants, including the flavonoids that contribute to the characteristic flavor and fragrance of vegetables, fruits, tea, and wine. These compounds, which come from phenylpropanoid and polyketide (acetate-malonate) pathways, also have biological properties that are beneficial to human health. Flavonoids such as quercetin and catechin and isoflavonoids, genistein for example, are being investigated for properties which may reduce the incidence of cancer (22,23). Flavonoids and isoflavonoids are a class of phenolic compounds that have appeared sequentially during plant evolution and are simple aromatic compounds generated from both the phenypropanoid and...

Antioxidants from fruits and berries overview

Fruits and berries are good sources of antioxidants, including carotenoids, ascorbic acid, tocopherols, flavonoids and phenolic acids. It has been known for a long time that the phenolics, as well as some of the other antioxidant components, are closely associated with the sensory attributes of fresh and processed fruits, berries and other plant foods. Especially, the contribution to colour by carotenoids (yellow to orange and red) and anthocyanins (red to purple and blue) is well known. Also the specific involvement of some of the phenolic substances in flavour development and taste sensation is amply documented.1 Phenolic compounds, including those having potent antioxidant activity, are also substrates for undesirable, oxidative browning reactions occurring during bruising of fruits, when fruits are cut or during their processing. The possible beneficial biological functions of the traditional antioxidant vitamins, i.e. ascorbic acid, a-tocopherol and to a certain extent...

Antioxidant Properties Of Inositol Phosphates In Vivo

A question that remains is whether this antioxidant property of phytate might function in vivo, and whether it mediates the potential disease-sparing characteristics of phytate that have been observed in cancer studies 10 . To test this hypothesis, researchers have used cells in culture or animal models and measured the ability of phytate to attenuate the oxidative stress induced by various means. To date, the literature on this question is equivocal, with some studies indicating that InsP6 provides some antioxidant protection, whereas other studies have found no effect or a pro-oxidant effect. It is important to recognize that oxidative stress protection in biological systems is a complex and multifaceted process 11,12 , thus the ability of phytate to contribute as an antioxidant in vivo may only be evident under conditions in which stress is invoked. In contrast to the previously discussed studies in which some evidence of antioxidant function in vivo was presented, other studies...

Relevance of phenolic antioxidants for functional food and comparative metabolic biology considerations

It is clear that food plants are excellent sources of phenolic phytochemicals, especially as bioactives with antioxidant property. As is evident, phenolic antioxidants from dietary sources have a history of use in food preservation, however, many increasingly have therapeutic and disease prevention applications (69-72). Therefore, understanding the nutritional and the disease protective role of dietary phytochemicals and particularly phenolic antioxidants is an important scientific agenda well into the foreseeable future (73). This disease protective role pf phytochemicals is becoming more significant at a time when the importance of in the prevention of oxidation linked chronic diseases is gaining rapid recognition globally. Therefore, disease prevention and management through the diet can be considered an effective tool to improve health and reduce the increasing health care costs for these oxidation linked chronic diseases, especially in low income countries. As discussed earlier,...

The Observational View of Dietary Antioxidants

Cancer and cardiovascular disease (CVD) are the two leading causes of death worldwide, diabetes mellitus is reaching epidemic proportions, and dementia and maculopathy are largely untreatable irreversible disorders that are increasingly common in our aging population. The prevalence and standardized mortality rates of these diseases vary considerably between and within populations. Mortality from CVD varies more than 10-fold amongst different populations, and incidences of specific cancers vary 20-fold or more across the globe. This enormous variation highlights the multiple factors at play in the etiology of chronic age-related diseases. These factors include smoking habit, socioeconomic status, exposure to infectious agents, cholesterol levels, certain genetic factors, and diet. Dietary factors have long been known to play an important role in determining disease risk. Indeed, 30-40 of overall cancer risk is reported to be diet-related, and there is a wealth of compelling...

Oxidative Stress Antioxidants And Lipid Peroxidation

A weakening of antioxidant defenses has been convincingly demonstrated in both human diabetic patients and experimentally diabetic rodents, although there appear to be tissue-dependent differences (cf. van Dam 1995 Low et al. 1999 for references). In several non-neural tissues, GSH concentrations as well as Cu-Zn superoxide dismutase and catalase activities are decreased in diabetes. In the case of the peripheral nerve, information is relatively scant, but as compared to the brain and liver, the activities of free-radical scavenging enzymes, except for superoxide dismutase, in the normal tissue are markedly lower (Low et al. 1999). In experimental diabetic neuropathy, Cu-Zn superoxide dismutase activity is substantially reduced, whereas reports conflict regarding changes in glutathione peroxidase (Low and Nickander 1991 Hermenegildo et al. 1993 Kishi et al. 2000). GSH is also decreased in diabetic nerve, whereas catalase activity is enhanced (Nickander et al. 1994 Nagamatsu et al....

Non Nutrient Antioxidants

Plant-based foods contain a multitude of antioxi-dants other than vitamin C and vitamin E. The two major classes of these other dietary-derived antioxidants are the carotenoids and the polypheno-lic flavonoids. There are hundreds of different car-otenoids and thousands of flavonoids, and these compounds give fruits, vegetables, teas, and herbs their wonderful colors in shades of red, orange, yellow, and purple. These compounds are synthesized exclusively in plants and have no known function in human metabolism. No deficiency state for either class of compounds has been identified in humans. Consequently, there is no recommended daily intake or agreed requirement for any of these compounds, and they are regarded as 'non-nutrients.' Nonetheless, there is evidence that diets rich in carotenoids and flavonoids are beneficial to health. For example, in a study of 1299 elderly people in the USA, those with diets rich in carote-noid-containing fruits and vegetables were found to have a...

Dietary Recommendations for Increased Antioxidant Defense

Dietary recommendations that would result in increased antioxidant defense are not inconsistent with accepted recommendations for healthy eating. The recommendation to increase the consumption of plant-based foods and beverages is one that is widely perceived as health promoting, and the consistent and strong epidemiological links between high fruit and vegetable intake and the greater life expectancy seen in various groups worldwide whose diet is high in plant-based foods indicate that more emphasis should be given to this particular dietary recommendation. Vitamin C, vitamin E, various carotenoids, flavonoids, isoflavonoids, phenolic acids, organosul-fur compounds, folic acid, copper, zinc, and selenium are all important for antioxidant defense, and these are found in plant-based foods and beverages such as fruits, vegetables, nuts, seeds, teas, herbs, and wines. Dietary strategies for health promotion should be directed towards optimizing the consumption of these items. people in...

Antioxidants from cereals and grain legumes

Cereals belong to the most voluminous components of the diet. They contain several classes of phenolic compounds, possessing antioxidant activity (Zielinski, 2002). The relevant phenolic compounds are mainly soluble in water or in polar organic solvents, such as ethanol, but some phenolics are oil soluble, such as tocotrienols or phenolic acids bound to diacylglycerols. Buckwheat and oat flours (Xing and White, 1997) are the most active source of antioxidants and they were proposed for the stabilization of food before the Second World War. Most phenolics are concentrated in hulls and in bran. Rice bran is commercially used for the production of oil as it contains oryzanol and related phenolic antioxidants. Cereal flours contain both reducing sugars and free amino acids, both precursors of Maillard reactions. An addition of D-glucose enhances the protective effect on lipids in extruded products (Yokata et al., 1987). During heating they interact with the formation of brown...

Free Radical Inhibitors Antioxidants

Beginning in the 1970s, theories that oxygen free radicals might be implicated as a cause for central nervous system injury in Down syndrome began to emerge in the context of similar beliefs about the cause of a number of degenerative diseases (de Haan, 1997). Further in vitro (test tube) laboratory studies of the neuronal tissue of Down syndrome fetuses raised additional concerns about possible free radical effects (Busciglio and Yankner, 1995). Procedure. Treatments involve the oral administration of supplementary or excess doses of antioxidant vitamins and other substances believed to have antioxidant effects. The oral administration of cofactors for the action of antioxidants such as the minerals zinc and selenium is frequently included. Antioxidants and their cofactors have been included in nutritional supplements advocated for people with Down syndrome such as Nutravene-D. Rationale. Oxidative processes in living cells produce oxygen free radicals, which in turn result...

Phytate As An Antioxidant In Chicken And Beef

Graf and coworkers 2,12 were the first to evaluate phytate as an antioxidant in a meat system. In cooked, minced chicken breast muscle +10 added water, phytic acid (1.5 mM, pH 6.0) was highly effective in reducing thiobarbituric acid (TBA) values (Figure 12.1) and warmed-over flavor (WOF) intensity (Figure 12.2), compared to controls 12 . Phytic acid (2 mM) was more effective than other antioxidants (2 mM ascorbic acid, BHT, or EDTA) for lowering TBA values in fresh beef homogenates incubated for 60 min at 37 C 13 .

Autoxidation And Antioxidants

Of unsaturation of the oil, presence of pro- and antioxidants, presence of heme-containing molecules and lipoxi-dase, light exposure, nature of packaging material, and storage temperature. The propagation reaction can be followed by termination if the free radicals react with themselves to yield non-active products bond, resulting in a free radical stabilized by resonance. These free radicals are then transformed into a number of isomeric hydroperoxides of the general structure

Combining antioxidants with other preservation techniques

The amount of antioxidants necessary for efficient stabilization may be reduced if food preservation by means of antioxidants is combined with another preservation technique. Cold storage is a typical example as the rate of free radical formation and thus also of antioxidant destruction is much lower under refrigeration. Refined rapeseed oil containing about 500 mg of tocopherols per kg is stable only for 2-4 weeks at 40 C, when the concentration of tocopherols approaches zero. If the same oil is stored at 10 C, no perceptible deterioration of sensory quality was observed even after 15 months of storage. On the contrary, frozen storage is not always preferable in foods containing water, such as meat or fish, as water crystallizes out of the hydrated protein layer protecting lipids against access of oxygen, and air has then free access to lipids. Natural antioxidants present are then rapidly consumed in spite of low temperature. Another factor catalyzing the formation of free radicals...

Effective Utilization Of Antioxidants In Foods

Utilization of antioxidant additives and preservation of endogenous antioxidants can be effective methods for improving food quality. Maximizing protection by endogenous antioxidants can be accomplished by minimizing antioxidant removal during the processing of raw materials, minimizing inactivation of antioxidants during processing (eg, inactivation of antioxidant enzymes during thermal processing operations) (20), selecting food sources that are naturally high in antioxidants, and including antioxidants in the diet of livestock (21). When antioxidant additives are used, several factors should be considered, including the antioxidant's mechanism of action in relation to the pro-oxidants in the food, the solubility characteristics of the antioxidant in relation to the physical location where oxidative reactions are most prevalent, how the antioxidant will interact with other food components (eg, prooxi-dative nature of ascorbate in the presence of transition metals), and how food...

Antioxidants

Oxidative reactions cause damage to lipids and proteins, thus influencing food quality. For example, oxidation of lipids results in the formation of volatile compounds that cause rancidity, oxidation of pigments (eg, carotenoids and myoglobin) leading to color changes, and oxidation of vitamins (eg, A, C, and E) leading to alterations in nutritional composition. The biological tissue from which we derive foods contains several distinctively different mechanisms to control oxidation catalysts, reactive oxygen species, and free radicals. In addition, many antioxidant additives are available to increase the oxidative stability of foods. Utilization of antioxidant additives and protection of endogenous antioxidants can be effective methods to increase the quality and shelf life of foods.

Dietary Antioxidants

The human endogenous antioxidant system is impressive but incomplete. Regular and adequate dietary intakes of (largely) plant-based antioxi-dants, most notably vitamin C, vitamin E, and folic acid, are needed. Fresh fruits and vegetables are rich in antioxidants (Figure 6), and epidemio-logical evidence of protection by diets rich in fruits and vegetables is strong. To decrease the risk of cancer of various sites, five or more servings per day of fruits and vegetables are recommended. However, it is not known whether it is one, some, or all antioxidant(s) that are the key protective agents in these foods. Furthermore, it may be that antioxidants are simple co-travellers with other, as yet unidentified, components of antioxi-dant-rich foods. Perhaps antioxidants are not 'magic bullets' but rather 'magic markers' of protective elements. Nonetheless, the US recommended daily intakes (RDIs) for vitamin C and vitamin E were increased in 2000 in recognition of the strong evidence that...

Free Radicals

Free radicals are compounds characterized by having an unpaired electron. They are in general highly reactive species, particularly those involving elements of the second row of the periodic table like O, N, C, etc. by the drive to form another chemical bond and complete the valence shell. Because a normal chemical bond consists of two electrons and two electrons only, radicals cannot react covalently with nucleophiles or two-electron species they can only react with other radicals or they can abstract a hydrogen atom from a neutral molecule to generate a new radical or abstract an electron to form an anion and generate a radical cation. While neutral, they can be considered to be electron deficient, but from the perspective that the addition of another electron to form the anion or the reaction with another radical to form a chemical bond satisfies the rule of eight and completes the second quantum level. For example, they can be deactivated by abstracting an electron from vitamin E...

Antioxidant Defense

An antioxidant can be described in simple terms as anything that can delay or prevent oxidation of a susceptible substrate. Our antioxidant system is complex, however, and consists of various intracel-lular and extracellular, endogenous and exogenous, and aqueous and lipid-soluble components that act in concert to prevent ROS formation (preventative antioxidants), destroy or inactivate ROS that are formed (scavenging and enzymatic antioxidants), and terminate chains of ROS-initiated peroxidation of biological substrates (chain-breaking antioxi-dants). In addition, metals and minerals (such as selenium, copper, and zinc) that are key components of antioxidant enzymes are often referred to as antioxidants. There are many biological and dietary constituents that show 'antioxidant' properties in vitro. For an antioxidant to have a physiological role, however, certain criteria must be met. 1. The antioxidant must be able to react with ROS found at the site(s) in the body where the putative...

Root and tuberous vegetables

Potato tubers (Solanum tuberosum), sweet potatoes (Ipomoea batatas), carrots (Daucus carota) and red beets (Beta vulgaris L.) all contain antioxidant substances, but they are very different types of chemicals. Potatoes contain ascorbic acid and are characterised by high levels of conjugated hydroxycinnamates, Homogenised potatoes and sweet potatoes only exhibited medium ORAC compared with, for example, kale, garlic, spinach and onions.79 Ethanolic extracts of whole potatoes have been demonstrated to reduce oxidising DPPH radicals and to inhibit linoleic acid oxidation in suspension.85 More concentrated extracts of potato peels efficiently retarded carotene bleaching coupled to linoleic acid oxidation,84 and slowed the oxidation of soybean oil (active oxygen method).86 By 1964 hot water extracts of potato peels had been demonstrated to exert weak antioxidant activity in retarding development of thiobarbituric acid reactive substances when added to beef slices and in slowing the...

Cruciferous vegetables

Broccoli (Brassica olearacea L. cv Italica L.), Brussels sprouts (B. olearacea L. Gemmifera), red cabbage (B. olearacea L. cv Rubra), white cabbage (B. olearacea L. cv Alba) and cauliflower (B. olearacea L. cv Botrytis) have been reported to show significant antioxidant properties against lipid peroxidation.97 Phenolic compounds such as flavonols and hydroxycinnamic acids in the cruciferous vegetables may be responsible for the antioxidant activity rather than the main bioactive compounds in cruficers, namely glucosinolates.98,99 According to Plumb et al.78 purified glucosinolates exhibited only weak antioxidant properties and thus are unlikely to account for the antioxidant effects of extracts from cruciferous vegetables. Compared to other vegetables and cauliflower, kale (B. olearacea L. cv Acephala), Brussels sprouts and broccoli were found to exert higher antioxi-dant activity.70,80,97,100 White cabbage was reported to show more than 80 inhibition of coupled oxidation of...

Sources of further information and advice

As interest in functional foods and other products with possible health effects is escalating a large number of industrial enterprises are now producing various 'antioxidant' concentrates. Industrial enterprises range from the traditional juice producers and large companies specialising in natural flavours and colours to new companies specialising in health promoting supplements. There is a sparcity of published knowledge available on the molecular composition and the proven health effects of most of these antioxidant concentrates, but many of them are nevertheless claimed and marketed as having potential physiological benefits, or at least to 'supply high amounts of antioxidants'. Some caution in the evaluation of these advertisements is recommended. At the time of writing, the precise action mechanisms of antioxidants and their individual and combined efficiency have not been elucidated in detail. Thus, despite our rather detailed understanding of the various mechanisms by which...

Introduction role of processed fruits and vegetables in the modern diet

Vegetable products, including tomatoes, contain many substances which may have beneficial effects on health, providing protection from certain pathologies correlated to oxidative processes. These substances have differing functions, such as free radical scavengers, singlet oxygen quenchers, metal chelants and inhibitors of enzymes involved in the formation of the active species of oxygen.3 Epidemiological studies have demonstrated that tomato consumption provides a protective effect against some types of cancers and ischaemic heart diseases. This protective effect has mainly been ascribed to the antioxidant activity of some tomato components. rich in one of them lycopene. Tomato is the main dietary source of lycopene, the typically red-coloured carotenoid. Othercarotenoids,such as b-, g-and Z-carotene, lutein, phytoene and phytofluene, are also present, though in much lower concentrations, with vitamin C, andvitaminEintheseeds.4 Moreover, there is a growing interest in other...

Nutritional quality of processed tomato

Today, the consumer faces new socio-economic and therefore food factors which tend to favour service (or convenience) quality. A service which, first of all, meets the requirements of new life systems but which also takes into account the renewed attention to hygienic and dietary aspects of food i.e. its nutritional quality, particularly in the light of the supposed antioxidant activities of some microcom-ponents, particularly lycopene. Tomato products are important foods from a sensory point of view, with good service quality and positive effects towards the prevention of the most important and common diseases of the modern world.

Guidelines for nonsulphite dipping

If chlorine or other oxidising decontamination agents are used, then it is recommended that fresh prepared produce items be subjected to a final rinse in potable water prior to non-sulphite dipping. This final rinse step will help to reduce the levels of residual oxidising agents, which if too high can substantially counteract the antioxidant properties of the constituents of non-sulphite dips. As a guide, 0.51 of rinse water should be applied for every kilogram of fresh prepared produce.

Genetic modification of plants to improve shelflife

The manipulation of antioxidant biosynthesis in lettuce has been achieved using a construct consisting of chimeric genes encoding elements of the ascor-bate-glutathione pathway (Garratt et al., 2001b). Overexpression of these transgenes enhanced the oxyradical scavenging potential and antioxidant content of transgenic plants. Homozygous plants exhibited up to a six-fold increase in foliar reduced glutathione compared to their azygous controls. Foliar hydrogen peroxide was up to three-fold lower in the upper leaves and up to two-fold lower in the middle and lower leaves of homozygous plants, compared to controls. Lipid peroxidation was also significantly decreased, indicating that membrane integrity was maintained. Furthermore, leaf discs excised from transgenic plants and floated on water for 7 days to induce senescence, expressed foliar hydrogen peroxide concentrations which were 40 lower than those concentrations detected in leaf discs excised from azygous (control) plants. The...

Health benefits of whole foods over isolated components

There are many claims made in the media and promotional literature about the qualities and benefits of specific (or groups of) compounds found in fruits and vegetables. We are told that wrinkles, absentmindedness, cancer and clogged arteries (among many other disorders) can be prevented, or alleviated, by consuming these compounds in the form of isolates or concentrated extracts. In such claims the words 'tested', 'effective', 'safe', 'essential' and 'proven' are freely used. In the world of nutritional science, however, the picture is not so clear. The following two quotes provide an example of this apparent contradiction. The first relates to a study of antioxidant vitamins and risk factors for cardiovascular disease, 'These results back-up the findings of previous studies and point to a positive role for antioxidant supplementation among those suffering from coronary artery disease'.25 The second statement is again related to antioxidants and chronic disease, 'Current evidence is...

Online detection of plant stress nonvolatile compounds

Blank Nursing Concept Map

3,5,4'-Trihydroxystilbene (trans-resveratrol) is an antioxidant compound naturally produced in a huge number of plants, including grapes, as a phytoalexin. Figure 12.5 shows its structural formula. In Vitis spp., trans-resveratrol is accumulated in vine leaves and grape skin in response to various fungal organisms,

Genetic control of leaf senescence and fruit ripening

Phloem during senescence and are regarded as the main transportable amino acids (Buchanan-Wollaston and Ainsworth, 1997). ATP sulphurylase is involved in the biosynthesis of cysteine and methionine. It has been proposed that during senescence the up-regulation of ATP sulphurylase leads to a subsequent increase in the cysteine pool. Cysteine is the precursor for glutathione biosynthesis, a major antioxidant, which, in addition to its role in the recovery of ascorbate and scavenging of reactive oxygen species (ROS), also acts in the transport and storage of sulphur (Rennenberg, 1982), the regulation of cell division and development (Earnshaw and Johnson, 1985), the regulation of gene expression and signalling (Wingate et al., 1988 Herouart et al., 1993 Moran et al., 2001) and the detoxification of xenobiotics and heavy metals (Delhaize et al., 1989 Halliwell and Gutteridge, 1986 Timmerman, 1989). Several differentially regulated isoforms of catalase have been described, many of which...

Bioavailability of lycopene

As long as lycopene remains in the aqueous matrix and more so if it remains inside the undamaged cells it is very stable but has little reactivity. Its bioavail-ability is therefore small and its efficacy as antioxidant almost zero. In contrast, its high solubility in a lipid medium (for instance in certain products formulated with oil) imparts considerable reactivity as well as complete bioavailability. Its assimilation is decidedly better if foods are cooked and homogenised so as to disrupt the cells and even more so if this occurs in the presence of oils or fats. However this effect is inevitably counteracted by a more rapid degradation of its antioxidant power. When lycopene solubilises in a lipophilic matrix, it has considerable reactivity and more availability, thus enabling it to undertake its antioxidant activity. However, this greater reactivity also means that it is more unprotected against the degradation effects of environmental conditions (air, biological matrix...

Future trends

Dietary antioxidants are gaining a considerable amount of interest as bioactive components with possible health effects. The physiological role of some of these antioxidants, such as vitamin E and vitamin C, is well established. Intervention trials with beta-carotene have proved disappointing with respect to finding a possible positive biological role of dietary carotenoids. On the other hand, flavonoids are very effective antioxidants and it has been proposed that they protect against cardiovascular disease by reducing the oxidation of LDL. There is some epidemi-ological evidence for this, but as flavonoids are generally absorbed only in very small amounts, their bioactivities in vivo remain to be established. A European collaboration has been formed (QLK1-1999-00124, 2000-January 2003) to examine the functional properties, bioavailability and bioactivities of dietary anthocyanins especially towards human cardiovascular health. Thus, before any new information on the identity,...

Stone fruits

Cherries, both sweet and sour, appear to be richer in anthocyanins as well as in hydroxycinnamic acid derivatives than peaches, nectarines and plums. Sweet cherries contain up to 3500-4500mgkg-1 of anthocyanins, 100-1900mgkg-1 hydroxycinnamates as caffeic acid and p-coumaric acid derivatives, where especially 3'-p-coumaryl quinic acid can account for 50-75 and neochlorogenic acid for 15-60 of the hydroxycinnamates, depending on the variety.28-30 Sour cherries have been shown to harbour higher levels of flavan-3-ols than sweet cherries, mainly epicatechin and catechin estimates of total contents are in the range 70-170 mg kg-1 for sour cherries in contrast to 20-60 mg kg-1 in sweet cherries (Table 3.1).28-31 Individually these compounds exhibit strong antiradical activity, for example in the DPPH in vitro assay, when evaluated at different micromolar concentrations.32 The flavanols are also effective inhibitors of human LDL oxidation in vitro.33 Catechin especially is one of the...

Citrus fruits

Citrus fruits are characteristic in containing high levels of ascorbic acid as well as relatively high levels of certain flavonoids. In their peel, citrus fruits also contain the unique glucaric and galactaric acid conjugates of hydroxycinnamic acids, mainly as feruloyl and p-coumaroyl conjugates at levels of 170-250mgkg-1 in oranges and 3-10 times less in lemons and grapefruits.39,40 It appears that the antioxidant potencies of these particular conjugates have not been systematically tested. Ascorbic acid is considered one of the major nutrients in citrus fruits, owing to its activity as vitamin C, and it seems plausible that the presence of ascorbic acid may influence the antioxidant potency of citrus products. The ascorbic acid levels in various processed citrus juice products manufactured in Florida (orange juices, grape juices) range from 300 to 450mgl-1.41 Flavonoids in the edible part of citrus fruits are dominated by hesperidin, which is a compound exhibiting only limited...

Edible coatings

One possible 'packaging' method for extending the post-harvest storage of minimally processed fruit and vegetables is the use of edible coatings. These are thin layers of material that can be eaten by the consumer as part of the whole food product. Coatings have the potential to reduce moisture loss, restrict oxygen entrance, lower respiration, retard ethylene production, seal in flavour volatiles and carry additives (such as antioxidants) that retard discoloration and microbial growth (Baldwin et al., 1995).

Grapes

Grapes (vitis vinifera and vitis lubruscana), especially the dark red varieties, contain generous amounts of flavonoids and relatively high levels also of hydrox-ycinnamates that all exert potent anti-oxidant activities in various assay systems. The antioxidant activity of wines have received much attention owing to their possible physiological benefits. However, several of the phenolics present in fresh grapes and grape juice are also potent antioxidants in various in vitro assays, including several containing biologically relevant lipid substrates, notably human LDL. In fresh grapes and grape juices the polyphenolic compounds are primarily present as glucosides, while the phenolics in wines are principally aglycones. Glycosylation is generally considered to dampen the antioxidant potency of polyphenolics, but the available data on this are conflicting, as the impact of gly-cosylation and in turn antioxidant solubility and partitioning are very system dependent. of phenolic...

Nonsulphite dipping

Given the deleterious effects of PPO activity upon the sensory and nutritional quality of fresh prepared produce, it is not surprising that considerable research has been devoted to inhibit the activity of this enzyme (Duncan, 1999). Sulphites have long been used as food additives to inhibit enzymic and non-enzymic discolorations, to control the growth of microorganisms and to act as bleaching agents and antioxidants (Sapers, 1993 Laurila et al., 1998). The most frequently used sulphiting agents for fresh prepared produce are sodium and potassium bisulphites and metabisulphites. Sulphites act as PPO inhibitors and antimicrobial agents and are most effective in acidic conditions (e.g. pH 3-5). For low-acid (e.g. pH 5-8) fresh prepared produce items such as mushrooms, bananas, potatoes and lettuce, sulphites have the tendency to accelerate bacterial decay by adversely affecting cell wall or membrane integrity which may stimulate the growth of certain spoilage bacteria (Duncan, 1999)....

Preface to the First Edition

Part III describes the key oxidation reactions in both edible oils and plant and animal or muscle tissues. Lipid oxidation is a major cause of quality deterioration of processed and unprocessed foods. Methods to measure lipid oxidation in fats and oils are given. The mechanism of antioxidant actions in arresting or improving the oxidative stability of foods is discussed. This section has tremendous implications for food technologists and nutritionists as the consumer continues to demand and expect nothing but high-quality foods and food products. Part IV deals with the role of fats and oils in overall nutrition. The importance of antioxidants in nutrition and food preservation is presented. Excess fat intake is associated with many disease conditions. This section describes various omega fatty acids and their sources, the role of dietary fats in atherosclerosis, eicosanoids production, immune system, coronary heart disease and obesity. The various types of lipid-based synthetic fat...

Antimicrobial Compounds

Food antimicrobials are chemical compounds added to or present in foods for the purpose of retarding microbial growth or killing microorganisms. The major targets for antimicrobials are bacteria, molds, and yeasts that are either pathogenic or cause spoilage of foods. The effectiveness of food antimicrobials against viruses and parasites carried by foods is less well characterized. Food antimicrobials are sometimes referred to as food preservatives however, the latter include food additives that are antimicrobials, antibrowning agents, and antioxidants. Under normal use conditions, food antimicrobials are bacteriostatic or fungistatic rather than bactericidal or fungicidal. The former indicates inhibition of growth of cells while the latter indicates killing of a population. Bacteriostasis is often reversible. Because food antimicrobials are generally static in nature, they will not preserve a food indefinitely. Depending on storage conditions, the food product eventually spoils or...

Effects of Alcohol on Muscle

Weakness, and myalgia and improves with abstinence. Histology correlates with symptoms and shows selective atrophy of type II muscle fibers. Ethanol causes a reduction in muscle protein and ribonucleic acid content. The underlying mechanism is unclear, but rates of muscle protein synthesis are reduced, whereas protein degradation is either unaffected or inhibited. Attention has focused on the role of acetaldehyde adducts and free radicals in the pathogenesis of alcoholic myopathy.

Sulfur Containing Amino Acids Cysteine and Methionine

Methionine is nonpolar, but cysteine is polar. Cysteine can form weak hydrogen bonds with oxygen and nitrogen it is also weakly acidic and is sometimes found at the active site of enzymes. Cysteine also acts as a reducing agent within the cell, both as the free amino acid and in the form of the antioxidant tripeptide glutathione. The sulfydril groups of two cysteine residues can be oxidized to form the double amino acid cystine, and this is the predominant form of the amino acid in extracellular fluid. When the same reaction occurs between cysteine residues in adjacent polypeptide chains, a strong, covalent disulfide bond is formed that gives the protein a rigid structure. This appears to be particularly important in stabilizing extracellular or secreted proteins. Methionine can be converted to S-adenosyl-methionine, the donor of methyl groups in transmethylation reactions. Methionine can be converted to cysteine in the body, but not vice versa. Selenium can replace sulfur in some...

Amino acid Deficiencies and Supplementation

Gluconeogenesis Cysteine precursor (see arginine) Antioxidant Bile acid conjugation, neuronal cell development, regulation of membrane potential, calcium transport, antioxidant Ammonia disposal Gluconeogenesis Antioxidant Inhibition CNS Antioxidant Improves antioxidant status in undernutrition,

Glutamine Glutamic acid and Ornithine aKetoglutarate Figure

Following conversion to glutamic acid and subsequently a-ketoglutarate, glutamine may supplement intermediates of the citrate cycle. In this manner glutamine serves as the preferred fuel for rapidly dividing cells of, for example, the immune system cells and intestinal mucosa. In the brain glutamic acid is the most abundant excitatory neurotransmit-ter and the precursor for gamma-aminobutyric acid, which is an important inhibitory neurotransmitter. Glutamine is a direct precursor for purine and pyr-imidine and therefore is involved in RNA and DNA synthesis and cell proliferation. In addition it is a constituent of the tripeptide glutathione, which is the principal intracellular antioxidant in eukaryotes (see also sections on cysteine and glycine). (gluconeogenesis) (excitatory (antioxidant)

Amyotrophic Lateral Sclerosis 721 Introduction

Disorders such as Parkinson's disease, Alzheimer's disease and ALS. Transition metals in the organism like Fe are thought to promote the generation of free radicals such as O-, and to cause oxidative stress. On the other hand, there are enzymes called super-oxide dismutase (SOD) that dissociates free radicals. Cu Zn SOD, which is the major SOD in human bodies, utilize coordinated Cu and Zn to dissociate free radicals. This enzyme is encoded by the SOD1 gene and converts O- into H2 O2, which is then metabolized by gluathion peroxidase 3 . The generally accepted mechanism of dismutation involves cyclic reduction and reoxidation of Cu(II) and Cu(I), respectively by single molecules of superoxide 4 . Recently a series of mutations in a Cu Zn SOD located on chromosome 21 have been identified in 15 to 20 of FALS cases and 5 of SALS cases 1,5 . It is generally accepted that the mutant Cu ZnSOD gains novel, cytotoxic activity rather than the loss of dismutase function leads to the generation...

Ischaemiareperfusion injury

This phenomenon is not confined to the bowel as other organs and systems may also suffer when a reduction in blood flow is followed by revascularization or successful resuscitation. The release of mediators initially causes regional damage but with spillage into the systemic circulation other organs or systems are affected. Ischaemia-reperfusion injury to the lower limb may lead to non-cardiogenic pulmonary oedema and changes in intestinal morphology. Similarly, reperfusion of ischaemic bowel may damage the liver parenchyma and lungs. Such local and remote organ injuries may be abrogated by pretreatment with ibuprofen and mannitol, suggesting that the generation of oxygen-derived free radicals and the activation of the arachidonic acid cascade have important roles to play.

Epidemiology Setting the Scene

The risk of developing a disease can be increased by exposure to a disease-promoting factor or decreased by a protective factor. In terms of antioxidants, high risk is generally assumed to be associated with low intakes, plasma levels, or tissue concentrations of antioxidants. Epidemiological studies often express

Summary and Research Needs

Strong evidence from a variety of sources indicates that a high intake of vitamin C or something very closely associated with it in the diet is protective against cancer and CVD, the major causes of disability and death in our aging communities. Indeed, it may be that plasma ascorbic-acid concentration can predict overall mortality risk. This interesting concept remains to be confirmed. The evidence for the benefits of a high intake of vitamin E is also strong, but research is needed into which member(s) of the vitamin E family are most important. The evidence for the benefits of carotenoids and flavo-noids stems largely from observational studies that show a decreased risk of disease in association with a high intake of foods or beverages rich in these non-nutrient antioxidants rather than the agents themselves. However, individuals who take these foods in large quantities are often more health conscious, take fewer total calories, do not smoke, exercise more, and eat less red meat...

Possible Explanations for the Disagreement between the Findings of Observational Studies and Clinical Trials

Various explanations have been given for the different findings of observational studies and intervention trials. Clearly, nonrandomized studies are unable to exclude the possibility that antioxidants are simply acting as a surrogate measure of a healthy diet or lifestyle and that the protective effect of certain dietary patterns, which has been presumed to be associated with dietary antioxidants, may in fact be due to other compounds in plant foods, substitution of these foods for others, or a reflection of other health behaviors common to people who have a high fruit and vegetable intake. However, although intervention studies provide a more rigorous source of evidence than observational studies, they are not without The nature of the supplements used It has been suggested that the synthetic forms used in most trials may have different biological activity or potency from natural forms of these vitamins, although trials using the natural forms have not found different clinical...

Vitamin and Mineral Supplementation

Most studies involving vitamin or mineral supplementation in RA have focused on either the antioxidant nutrients (vitamin C, vitamin E, beta carotene, selenium) or B vitamins. Various studies have examined the effects of vitamins C, E, and selenium supplementation on the management of RA. In general, results from randomized controlled trials of vitamin E supplementation have been of relatively short duration and have led to conflicting results so that there continues to be a lack of concrete evidence to support vitamin E supplementation at a particular dosage. Nonetheless, patients with RA could certainly be encouraged to increase their intake of vitamin E-rich foods, including edible vegetable oils (sunflower, safflower, canola, olive), unprocessed cereal grains, and nuts. Similarly, the effect of dietary sources of other antiox-idant nutrients, such as selenium and vitamin C, on inflammatory symptoms in RA has also been ambiguous. It should be emphasized that providing individual...

Well Established Metabolic Functions of Vitamin C that are Impaired in Deficiency

In the course of its functional roles, ascorbic acid is oxidized in two successive one-electron reversible steps, and it is thought that most, if not all, of its essential biological actions are centred around this key redox cycle. The first oxidation product is the free-radical form of the vitamin, which is known variously as 'mono-dehydroascorbate,' 'semidehydroascorbate,' or 'ascorbate free radical' (AFR). Although this intermediate shares with most other free radicals the properties of having a relatively short half life and a high degree of chemical reactivity, it is, nevertheless, more stable than many other free radicals, contrasting with the highly reactive and damaging radicals such as hydroxyl or superoxide radical that are derived from molecular oxygen. By reacting with, and thus quenching, these damaging oxygen free radicals, ascorbate can act as a free-radical chain terminator and can thereby protect vulnerable macromolecules such as DNA, lipids, and proteins from...

Micronutrients and Mental Function

Groups of micronutrients antioxidants and B-com-plex vitamins. Research into the effects of antioxi-dant vitamins, whilst showing some promise in that correlational studies show that levels of these vitamins (vitamin E most consistently) are associated with function in a range of cognitive domains, is more contradictory when one considers the clinical intervention trials. The work on B-complex vitamins is, however, more consistent and supported by a strong hypothetical basis. This relies on the roles of vitamins B12 and folate in methylation of membrane phospholipids (see below) and neurotransmitters and in breaking down the toxic sulfur amino-acid homocysteine. High levels of homocysteine are now considered by some to be a far greater risk factor for the development of coronary and vascular problems than are high levels of cholesterol. Elevated levels of homocysteine may be a cause of minor ischemic events, which, cumulatively, lead to a degradation of cognitive function due to...

Control Of Browning In Foods

Extensive studies have been carried out to control enzymatic browning ever since Lindet (1) recognized in 1895 that the change in color occurring in freshly pressed cider was enzymatic. The practical control of enzymatic browning in foods has been carried out by several methods. The method of choice is dependent upon the food product and the intended use. The enzymatic browning in fruits and vegetables can be controlled at the beginning by selecting cultivars that are least susceptible to discoloration either because of the absence of the certain phenolic substrate or because the substrate or enzyme is present at low concentration. It is also possible to select fruits and vegetables at stages of maturity where discoloration is at minimum. Other methods include the removal of oxygen from fruit and vegetable tissues as well as from the atmosphere surrounding the food the addition of acids to reduce the pH and thus reduce PPO activity the addition of antioxidants or reducing substances...

Evasive strategies by the organism

Anything written on evasion strategies in nematodi-ases remains speculative. The parasite alters its surface and secreted antigens during its tissue migrations, and it has been suggested that this functions to keep the parasite ahead of the immune response. This would not, however, be compatible with the continuous recruitment of parasites known to occur in infected humans. The larvae secrete proteinases which could cleave bound antibody and or complement. Parasitic nematodes commonly secrete antioxidants, such as superoxide dismutase, but this has not been examined for Ascaris. If, like the related nematode Toxocara canis, Ascaris has a surface that rapidly sheds antigens, then continuous loss of bound antibody, complement and or cells would provide an immune evasion mechanism. It also might simply be that it is not possible for the immune system to deal with a rapidly migrating multicellular parasite. The intestinal stage of Ascaris is thought to live for at least 1 year, and there...

Prooxidants in lipid systems

Contrary to antioxidants, prooxidants decrease the stability of food lipids on storage. The most important prooxidants are heavy metals of transient valency, especially copper, manganese and iron ions or complexes. They catalyze the decomposition of lipid hydroperoxides into free radicals, which initiate further oxidation of unsaturated fatty acid derivatives. Another type of prooxidants are photosensitizers. Green parts of plant material always contain chlorophyll pigments, which are photosensitizers in presence of light, catalyzing the oxidation of polyunsaturated lipids by converting the triplet oxygen into substantially more reactive singlet oxygen. The presence of carotenoids can transform the singlet oxygen back into its less reactive triplet form. Stability against oxidation is thus much improved. Carotenes and different carotenoids have thus an antioxidative activity, at least in the presence of light.

Water Soluble Vitamins

Ascorbic acid (vitamin C) is actively transported into the brain extracellular fluid through the blood-CSF barrier, from which it is actively transported into cells. Brain ascorbate pools show minimal fluctuations over a wide range of plasma ascorbate concentrations, which presumably explains the absence of CNS signs in ascorbate deficiency. To date, the only defined biochemical function of ascorbic acid in brain is as a cofactor for the enzyme that converts dopamine to noradrenaline (norepinephrine) (though ascorbate is thought by some to function as an antioxidant).

Function Of Carotenoids

It is tempting to propose a single universal function for the carotenoids since they are found in such diverse tissues. Failing this, it is tempting to ascribe some function, wherever a carotenoid is found. Although the function of the carotenoids has been proven in some cases, their universal function, if any, remains to be determined. Where the function has been proven, it generally is with some aspect of the light-absorbing property of the carotenoid pigment. The critical role of these pigments in photosynthesis has been the best documented. Phototropism and phototaxis responses of plants seem to be related to the light absorption spectra of the carotenoids. Functions in animals are related to the antioxidant and to the light-absorbing property of these pigments. The function in vitamin A formation has been discussed. Because these pigments are found in many reproductive tissues, it has been suggested that they have a role in reproduction. The results in this area are less...

Hints For Understanding Chemical Mechanisms

Hydrogen atom abstraction from a molecule has been proposed as an intermediate during the oxidation of C-H bonds by cytochromes P450. Hydrogen atom abstraction can also occur during oxidative stress when reactive oxygen-free radicals are formed. An arrow representing the movement of electrons with two barbs represents the movement of two electrons while an arrow with only one barb represents the movement of only one electron. If a bond is broken by moving two electrons in one direction, it will result in a positive charge on the tail of the arrow and a negative charge at the head of the arrow. These charges are often dissipated by the loss or gain of a proton, i.e., the loss of a proton will remove the positive charge on a molecule while gaining a proton will eliminate a negative charge on a molecule. However, if a bond is broken by a single electron leaving that bond, no charge is produced but rather free radicals are generated. This is symbolized by an arrow with a single barb...

Examples Of Proven Laboratory Interventions

People need oxygen. Without it, human beings cannot generate enough energy to live and quickly die. However, the oxygen that keeps people alive is a double-edged sword, for it also can break down within the cell to yield highly chemically reactive molecules of various kinds that are termed collectively reactive oxygen species (ROS) or, less accurately, free radicals. These ROS chemically combine with any of the cell's components and transform them into oxygen-based damage products, a process referred to as oxidative stress. In lay terms, one might envision the cell undergoing something akin to self-perpetuating rusting.

Applications for the stabilization of vegetable oils and plant foods

Vegetable oils are mainly rather polyunsaturated so that they are less stable against oxidation than animal fats but they usually contain natural antioxidants, in most cases tocopherols, almost in optimum concentrations. At low levels (up to 50 mg kg) a-tocopherol was found more active than 7-tocopherol, but at high levels (more than 100 mg kg), on the contrary, 7-tocopherol was found more active than a-tocopherol, when tested at 40 C in the dark (Lampi et al., 1999). Even when considerable losses (higher than 30 ) of tocopherols occur during crude oil refining (Gogolewski et al., 2000), stability against oxidation is not much affected by refining. A synergism was observed between 7- and S-tocopherols (Wagner and Elmadfa, 2000), but the contents of the latter are very low compared to the former. Tocopherols present in frying oils stabilize fried potatoes (M rquez Ruiz et al., 1999). Phospholipids are natural constituents of crude edible oils, but they are almost completely removed in...

Section 2 Plant And Animal Food Applications And Functional Foods

Chapter 2.09 Potential Health Benefits of Soybean Isoflavonoids and Related Phenolic Antioxidants Patrick P. McCue and Kalidas Shetty Chapter 2.12 Bioprocessing Strategies to Enhance l-DOPA and Phenolic Antioxidants in the Fava Bean (Vicia faba) Kalidas Shetty, Reena Randhir, and Preethi Shetty Chapter 2.26 Biochemical Markers for Antioxidant Functionality

Reactive oxygen species

The production of oxygen-free radicals peaks during the first 2-10 minutes of reperfusion after coronary artery occlusion. Sources of oxygen free radicals include the xanthine oxidase reaction, mitochondria, and polymorphonuclear cells. The superoxide dismutase pathway, normally responsible for the clearance of superoxide anions, may be altered after an ischaemic insult. Administration of superoxide dismutase in combination with catalase led to a notable reduction of no-reflow, and ultrastructural signs of endothelial injury in animal studies14 also free radical scavengers were shown to prevent functional vascular dysfunction after ischaemia and reperfusion.

Hydrocarbon Carotenoid aCarotene

A-Carotene, another carotenoid frequently present in food, also has provitamin A activity. Based on its structure, it is only converted to one molecule of biologically active retinol after central cleavage. Like other carotenoids, it has antioxidant and possibly anticarcinogenic properties, and may enhance immune function as well. Some, but not all, epide-miological studies observed that higher a-carotene intake was associated with lower risk of cardiovascular disease and cancer, whereas others did not. Clinical trials to test a-carotene influences in humans have not been conducted to date. This is probably because a-carotene is usually associated with ample amounts of fi-carotene when found in fruits and vegetables and singling out a-carotene is difficult.

Non Nutrients of Potential Benefit

Minor amounts, that have the potential to exert beneficial physiological effects. Some of these phy-tochemicals, which include phytic acid, sterols, phe-nolics, and flavonoids, have been shown to have in vitro antioxidant and oestrogen-like activities. Fiber and phytochemicals are found at their highest levels in bran and unrefined grain. Thus, these components may play an important role in the protective effects against heart disease and certain cancers that are conferred by diets rich in whole grains.

The late response to injury

An interesting avenue of research is into bacterial translocation and the development of sepsis. Glutamine enteral nutrition has been shown to decrease this phenomenon, but isolation of specific protein involved in bacterial translocation, and their antagonism, may be possible future therapeutic options. In the future, care of the severely injured patient is likely to undergo some exciting changes, with the emergence of combination antioxidant therapy, activated protein-C trials, and blood substitutes, which may improve outcome and ultimately survival.

Therapeutic Approaches

Aging is associated with the decline in multiple areas of immune function, but, to date, no single mechanism has emerged as responsible for all of the observed changes. It is being increasingly acknowledged that autoimmune processes play a proinflammatory role in the development of many pathological conditions, such as atherosclerosis. It is likely that the mechanisms underlying age-related changes in immunity are multifactorial, with both genetic and environmental factors playing a significant role (Burns et al., 1997). The progression of and recovery from infectious diseases depends, at least in part, on immune responses and nutritional status in the elderly. Nutrition therapy may improve the immune responses of elderly people, particularly those with total-, protein-, fat-, or micronutrient-energy balances on prescribed low protein or fat diets (Lesourd, 1997). Micronutrient supplementation improves the immune status in the aged individuals. Episodes of disease in the aged leads to...

Animal Fats And Fish Oils General

Composition refers to the fatty acid profile, and hardness is affected by chain length and degree of unsaturation of fatty acids. Color may not be associated with nutritional value, but it can indicate the product composition or source. Moisture or unsaponifiable matters have no nutritional value, whereas ether insolubles can reduce the fat quality. Moisture can also deteriorate fat. Fats and oils are prone to oxidation, which can reduce palatability and quality, and thus must be stabilized with antioxidants.

Conditionspecific Nutritionals Hypermetabolic Stress or Trauma

Recent nutrition research has focused on the clinical benefits of enterally feeding hypermetabolic patients. Several trials have reported significant decreases in infections and or wound healing complications (17-20), hospital length of stay (17,20,21), and multiple organ failure (19) in patients fed specialized enteral formulas compared with patients fed standard enteral formulas. These specialized enteral formulas contain ingredients shown to enhance the immune response, improve wound healing, reduce free radical formation, and alter the inflammatory response. Included are the amino acids arginine (22) and glutamine (23) as conditionally essential nutrients during trauma, omega-3 fatty acids (24), and antioxidants (25-27).

Using instrumental data in sensory predictions

In other cases, a supervised method is used. In supervised methods, the analyst has a priori knowledge of the grouping of samples. Thus, one can use sample knowledge in the development of optimal classification rules. Multiple regression analysis (MRA), canonical correlation analysis (CCA), partial least squares (PLS), linear discriminant analysis (LDA), and linear learning machine (LLM) methods are commonly used in this classification (Ashima and Nakai 1991). The a priori knowledge may be geographical classification of samples, grape used in wine production, storage time, use of an antioxidant, etc. For

The Biology Of The Stage Of Promotion

A variety of chemicals have been shown to induce and or influence the stage of promotion. However, unlike chemicals inducing the stage of initiation, there is no evidence that promoting agents or their metabolites directly interact with DNA or that metabolism is required at all for their effectiveness (Chapter 3). Figure 7.4 shows some representative structures of various promoting agents. Tetradecanoyl phorbol acetate (TPA) is a naturally occurring alicyclic chemical that is the active ingredient of croton oil, a promoting agent used for mouse skin tumor promotion. Saccharin is an effective promoting agent for the bladder, and phenobarbital is an effective promoting agent for hepatocarcinogenesis. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is probably the most effective promoting agent known for rat liver carcinogenesis, but is also effective in the lung and skin. Butylated hydroxytoluene (BHT) is an antioxidant chemical that has been added to foodstuffs to prevent oxidation and...