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"Code of Federal Regulation (CFR) Title 21.

"Code of Federal Regulation (CFR) Title 21.

• Synthesize chemicals

Food enzymes are usually classified into the following categories:

• Carbohydrases (amylases are commercially the most important subgroup hydrolyzing 1,4 glycosidic bonds in carbohydrates)

• Proteases, hydrolyze peptide bonds in proteins

• Lipases, split hydrocarbons from lipid

• Pectic enzymes and cellulases, hydrolyzing the plant cell wall material

• Specialty enzymes

These enzyme categories can be divided further into around 15 to 20 subgroups. Traditional roles of enzymes in the food industry have been in the processing of bakery goods, alcoholic beverages, and starch conversion. But interest is now focused on newer and more varied applications, such as hydrolysis of lactose, the preparation of modified fats and oils, the processing of fruit juices, and other processes where newer enzymes are being identified. Important food applications of enzymes are listed in Table 5.

The commercially important food enzymes are a amylase, glucoamylase, and glucose isomerase, which are es pecially significant in the United States because of their widespread use in the conversion of cornstarch into high-fructose corn syrup (HFCS). Rennin, which is used in cheese making, is also of significant volume, followed by a host of other enzymes, including pectinases, invertase, lactase, and maltase (used for the modification of starches and sugars), catalase, pepsin, glucoseoxidase (an antioxidant for canned foods), and bromelin, ficin, and papain (plant proteases used for tenderizing meat and producing easily digestible foods). Enzymes are extremely specific and can act only on a single class of chemicals such as proteins, carbohydrates, or fats.

Enzymes are produced from animal tissues (eg, pancre-atin, tripsin, lipase), plant tissues (eg, ficin, bromelin), and most frequently by microorganisms (eg, pectic, or starch enzymes). Microbial production from a variety of species of molds, yeast, and bacteria is increasingly becoming the predominant source of enzymes.

Application of genetic engineering to the development of enzymes has already made a significant impact. The first food ingredient produced by genetic engineering was chymosin, "Chy-Max®," a microbial rennet developed by Pfizer (now Cultor Food Science), which has been approved by the regulatory agencies in the United States, Canada, the United Kingdom, Australia, Italy, and several other countries.

Table 5. Enzyme Applications

Dairy products

Baking and cereals

Sugar processing Starch conversion

Oils and fats

Flavors

Alcohol fermentation Brewing

Fruit juices, and wines

Coffee processing

Chemical processes

Analytical Waste treatment

Milk coagulation (rennet), milk protein modification, cheese flavor development, enzyme modified cheeses, and removal of hydrogen peroxide Antistaling, dough improvement, improved crust color, and gluten hydrolysis Removal of starches and processing from cane sugar Starch modification, liquefaction, isomerization, saccharification, modification, and increasing yield Improving yields, interesterification, oil extraction, and lecithin production Synthesis of flavors, production of natural esters Starch liquefaction, improving yeast growth

Adjunct liquefaction, enhanced fermentability, filtration improvement, production of light beer, and removal of protein haze Increasing press yields, juice clarification, shelf-life extension Separation of bean, viscosity control of concentrate Biotransformation, synthesis (eg, emulsifiers) Tests for dietary fiber, sugars Breakdown of cellulose, lignin, oil residues, and other solid waste material

Firming Agents

Fruits and vegetables contain pectin components that are relatively insoluble and form a firm gel around the fibrous tissues of the fruit and prevent its collapse. Addition of calcium salts causes the formation of calcium pectate gel, which supports the tissues and affords protection against softening during processing. The calcium salt is sometimes added to the canned vegetable in the form of a tablet containing both sodium chloride and calcium chloride.

Canned vegetables, canned apples, frozen apples, and tomatoes are sometimes treated during processing with calcium chloride, calcium citrate, monocalcium dihydrogen phosphate, or calcium sulfate to prevent them from becoming soft and disintegrating. Suggested level of use of these calcium salts is 0.02%, calculated as calcium in the final food product. In canned potatoes, calcium chloride and calcium citrate at a level of 0.5% (calculated as calcium) are used.

Aluminum sulfate, ammonium aluminum sulfate, potassium aluminum sulfate, and sodium aluminum sulfate are used as firming agents in pickles and relishes. A more recently introduced firming agent is aluminum sulfate for canned crabmeat, lobster, salmon, shrimp, and tuna. Calcium chloride acts as a firming agent in cheddar and cottage cheese.

Flavors

The word flavor describes a complex sensation provided by compositions of many defined aromatic ingredients. Flavorings are concentrated preparations used to impart a specific aroma to food or beverage. Flavoring ingredients are the most numerous single group of intentional additives utilized by the food industries. Flavors should not be viewed as a single homogeneous class of food additives but as a composite of closely interrelated and somewhat overlapping sectors with differentiated characteristics, as discussed next.

Essential oils and natural extracts are usually defined as the volatile material obtained from a particular plant species by the process of distillation, expression (cold pressing), and maceration. Essential oils represent complex aroma mixtures containing as many as hundreds of chemical constituents. Included are vanilla, cocoa, cola, spice oleoresins, and so on. Essential oils may be used for imparting scent or aroma to consumer products, as raw materials for compounding flavor compositions, or as the source of isolated aroma chemicals, also used in compounding.

Aroma chemicals comprise organic compounds with a defined chemical structure that are isolated from microbial fermentation, plants, or animal sources or are produced by organic synthesis. Included are anethole, vanillin, citro-nellol, geraniol, and so on. Aroma chemicals may be added directly to foods and beverages or used as raw materials in flavor compositions.

Flavor compositions consist of complex mixtures of various aromatic materials from a few to 100 or more constituents. Compounded flavors may contain aroma chemicals, natural extracts, essential oils, solvents, and in some cases other functional additives (eg, antioxidants, acidulants, emulsifiers, etc).

Flavor compositions are added to foods and beverages to

• Create a totally new taste;

• Enhance, extend, round out, or increase the potency of flavors already present;

• Supplement or replace flavors to compensate for losses during processing;

• Simulate other more expensive flavors or replace unavailable flavors; and

• Mask less desirable flavors—to cover harsh or undesirable tastes naturally present in some food, other than hide spoilage.

Flavoring substances may be classified as follows:

• Natural flavoring substance. Obtained by physical separation, enzymatic process, or microbial process from vegetable or animal sources, either in the raw state or after processing (including drying, torréfaction, and fermentation)

• Nature-identical flavoring substance. Obtained by synthesis or isolated by chemical processes, chemically identical to substances naturally present in vegetable or animal sources (this classification is used in Europe, but not allowed in the United States)

• Artificial flavoring substance. Obtained by chemical synthesis and not found to occur in nature

• Flavoring preparation. Products other than natural substances, whether concentrated or not, with flavoring properties, obtained by physical separation, or enzymatic or microbial processes, from material of vegetable or animal origin, either in the raw state or after processing (including drying, torrefaction, and fermentation)

• Process flavorings. Products obtained by heating to a temperature not exceeding 180°C for a period not exceeding 15 min using a mixture of ingredients, not necessarily themselves having flavoring properties, of which at least one contains nitrogen (amino) and another is a reducing sugar.

• Smoke flavorings. Smoke extracts used in traditional foodstuff smoking processes

• Flavor enhancers. Some amino acids and nucleotides, as well as sodium salts (such as monosodium glutamate, sodium inositate and sodium guanylate), have only a weak taste by themselves but have the power to considerably enhance the taste sensation caused by other ingredients in savory flavors.

The types of flavor compositions, their manufacturing processes, the starting materials for manufacturing them, and the common product forms are summarized in Table 6.

Glazing and Polishing Agents

Glazes and polishes are used on coated confections to give luster to the otherwise dull coating. Chemicals that are used for this purpose include acetylated monoglycerides, beeswax, carnauba wax, gum arabic, magnesium silicate, mineral oil, petrolatum, shellac, and zein. Generally these compounds are used at levels of about 0.4%, with the exception of mineral oil and petrolatum, which are used at 0.15%, and zein at 1.0%.

Humectants

Substances that have affinity to water, with stabilizing action on the water content of a material, are termed humectant or moisturizing agents. These are hygroscopic materials that prevent loss of moisture when incorporated into foodstuffs. Ideally, a humectant maintains within a rather narrow range of moisture content caused by humidity fluctuations. Among commonly used humectants are the following substances: glycerin, mono- and diglycerides of fatty acids, propylene glycol, pectin, molasses, potassium polymethaphosphate, and sorbitol.

pH-Adjusting Agents

A large group of chemical additives that are widely used in foods might be considered under the broad heading of pH-adjusting agents. Other terms that describe these chemicals include acidulants, acids, alkalis, buffers, and neutralizers. These chemicals are used in most segments of the food processing industries, including:

• the baking industry as chemical leavening agents,

• in soft drinks to provide tartness,

• in certain dairy products to adjust the acidity,

• in cheese spreads for emulsification,

Table 6. Commercial Flavor Compositions

Type of flavor

Classification

Manufacturing process

Raw materials

Product form

Compounded flavors

Natural extracts

Natural or synthetic Blending, mixing

Natural Natural

Reaction flavors

(thermally processed) Enzymatically Natural modified flavors

Extraction, enzymatic treatment Heating/pressure cooking

Essential oils, natural extracts, fruit juice concentrates, aroma chemicals Food substrates (eg, plants, fish, meat, etc) Amino acids and sugars, hydrolyzed proteins

Enzymatic/microbial reaction Food substrates (eg, cheese)

Liquid Spray-dried, encapsulated

Liquid Paste

Paste powder

Paste powder

• in confectionery products as flavoring, to control the degree of inversion of sugars, and to control the texture in the processing of chocolates,

• in jams and jellies to provide proper gel formation.

Citric acid is the most versatile and widely used of the food acidulants, and very large volumes of phosphoric acid are required for cola beverages. Other acidulants frequently used in processed foods include acetic, adipic, fu-maric, hydrochloric, lactic, malic and tartaric acids, and glucono-i-lactone.

Important alkalies used in the food field include ammonium bicarbonate, ammonium hydroxide, calcium carbonate, calcium oxide, potassium bicarbonate, potassium hydroxide, sodium bicarbonate, sodium carbonate, sodium hydroxide, and sodium sesquicarbonate.

Quite often, the pH may be difficult to adjust or to maintain after adjustment. Stability of pH can be accomplished by the addition of buffering agents that, within limits, effectively maintain the desired pH even when additional acid or alkali may be added. Examples of representative buffer solutions are as follows:

• Phosphoric acid : dibasic potassium phosphate

• Formic acid : sodium formate

• Acetic acid : sodium acetate

• Sodium bicarbonate : sodium carbonate

• Dibasic sodium phosphate : sodium hydroxide

Preservatives

Chemical preservatives play a very important role in the food industry, from manufacture through distribution to the ultimate consumer. The choice of a preservative takes into consideration the product to be preserved, the type of spoilage organism endemic to it, the pH of the product, period of shelf life, and ease of application. No one preservative can be used in every product to control all organisms, and therefore combinations are often used. In certain foods, specific preservatives have very little competition. In the concentrations used in practice, none of the preservatives discussed here is lethal to microorganisms in foods. Rather, their action is inhibitory.

Preservatives may be divided into two main groups: (1) antioxidants and (2) antimicrobials. Antioxidants are food additives that retard atmospheric oxidation and its degrading effects, thus extending the shelf life of foods. Examples of food oxidative degradation include products that contain fats and oils in which the oxidation would produce objectionable rancid odors and flavors, some of which might even be harmful. Antioxidants are also used to scavenge oxygen and prevent color, flavor, and nutrient deterioration of cut or bruised fruits and vegetables.

Food antioxidants may be divided into oil- and water-soluble compounds (Table 7) and also classified as natural or synthetic.

The most frequently used natural antioxidants are ascorbic acid (vitamin C), its stereo isomer erythorbic acid, and their sodium salts (sodium ascorbate, sodium erythor-bate), plus the mixed 3- and y-tocopherols. Vitamin C finds more major use as a nutritive supplement or in pharmaceutical preparations. Smaller amounts, however, are intentionally used for antioxidant purposes. Erythorbic acid (¿so-ascorbic acid) is virtually devoid of vitamin C activity (only 5% that of ascorbic acid). Citric acid and tartaric acid are also natural antioxidants (and antioxidant synergists) but are predominantly added to foods as acidulants.

Synthetic antioxidants used as direct food antioxidants include butylated hydroxyanisole (BHA), butylated hy-

Table 7. List of Major Food Antioxidants

Oil-soluble antioxidants

Butylated hydroxyanisole (BHA) Butylated hydroxytoluene (BHT) ieri-Butyl hydroquinone (TBHQ) Propyl gallate (PG) Tocopherols Thiodipropionic acid Dilauryl thiodipropionate Ascorbyl palmitate Ethoxyquin

Water-soluble antioxidants

Ascorbic acid

Sodium ascorbate

Erythorbic acid

Sodium erythorbate

Glucose Oxidase/catalase enzymes

Gum Guaiac

Sulfites

Rosemary extract droxytoluene (BHT), ferf-butyl hydroquinone (TBHQ), and propyl gallate (PG). These antioxidants are oil-soluble compounds. Their primary application is in fats and oils to retard the development of rancid taste.

To improve the performance of antioxidants, two other types of food additives, sequestrants (eg, EDTA, citric acid) and synergists (eg, mixtures of antioxidants and lecithin), are frequently used with them. Antioxidants may also be present in food packaging as indirect food additives.

Recently, definitive studies have shown and widely publicized in the news media that antioxidant nutrients such as ascorbic acid (vitamin C) and tocopherols (vitamin E) can protect against harmful cell damage and thus prevent certain human diseases. Foods formulated with antioxidants and other vitamins are now recommended to prevent and cure cancer, cardiovascular diseases, and cataracts. The same antioxidants that are used to prevent oxidative deterioration of food may be used in functional foods (also called nutraceuticals, designer foods, etc) to create products that prevent or cure certain chronic diseases.

Antimicrobials are capable of retarding or preventing growth of microorganisms such as yeast, bacteria, molds, or fungi and subsequent spoilage of foods. The principal mechanisms are reduced water availability and increased acidity. Sometimes these additives also preserve other important food characteristics such as flavor, color, texture, and nutritional value. The primary food additives used for this function are sorbic acid, potassium and sodium sor-bates, calcium and sodium propionates, benzoic acid, sodium and potassium benzoates, and parabens.

In addition to these compounds, several organic acids such as citric, malic, lactic, ascorbic, phosphoric, and tartaric also act as antimicrobial agents, but because of their greater use as acidulants, they are covered elsewhere.

Sulfur dioxide and sulfites are also applied extensively for controlling undesirable microorganisms in soft drinks, juices, wine, beer, and other products. Salt, sugar, alcohol, spices, essential oils, and herbs also inhibit growth of microorganisms, but usually their primary function is different when added to food.

Major uses of antimicrobial preservatives by food industry include the following:

• Sorbates are used as mold and yeast inhibition in processed cheese and spreads, salad dressings, and dried fruits, and are effective in the acidic pH range up to pH 6.5.

• Benzoates are used in beverages, fruit juice, and pickles, and are effective in the pH range between 2.5 and 4.0.

• Propionates are used as mold and rope inhibitors in bread and baked goods.

• Parabens are effective in low-acid foods (pH greater than 5.0), such as meat and poultry products.

• Sulfur dioxide and sulfite salts (eg, potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite, and sodium sulfite) are the most effective inhibitors of deterioration of dried fruits and fruit juices. Sulfur compounds also used in the fermentation industry to prevent spoilage by microor ganisms and as a selective inhibitor of undesirable organisms.

Release Agents

Release agents are used to prevent confectionery, and to a lesser extent baked goods, from sticking to equipment or to the container in which they are heated. They are also used to prevent pieces of confection from adhering to each other. Included are acetylated monoglycerides, calcium stearate, magnesium carbonate, magnesium silicate, magnesium stearate, mannitol, mineral oil, mono- and diglyc-erides, sorbitol, and stearic acid.

Sequestering Agents

Also called chelates, sequestering agents combine with polyvalent metal ions to form a soluble metal complex to improve the quality and stability of products as free metallic ions promote oxidation of food. They are used in various aspects of food production and processing chiefly to obviate undesirable properties of metal ions without the necessity of precipitating or removing these ions from solutions.

Ethylenediaminetetraacetic acid (EDTA) is the most commonly used sequestering, or metal-complexing, agent used in the food industry. This compound, as well as the disodium or calcium disodium salts of tetraacetic acid retards discoloration of dried bananas, beans, chickpeas, canned clams, pecan pie filling, frozen potatoes, and canned shrimp. Also, these compounds improve flavor retention in canned carbonated beverages, salad dressings, mayonnaise, margarine, and sauces; retard struvite formation in canned crabmeat and shrimp; and protect against rancidity in dressings, mayonnaise, sauces, and sandwich spreads. EDTA is used at concentrations of 33 to 800 ppm.

Other chemicals that may be included in this category are calcium acetate, calcium gluconate, calcium sulfate, citric acid, stearyl citrate, tartaric acid, sodium tartarate, calcium monoisopropyl citrate, sodium hexametaphos-phate, phosphoric acid, potassium citrate, and various calcium, potassium, and sodium phosphates.

Sweeteners

Sweeteners are used in formulated foods for many functional reasons as well as to impart sweetness. They render certain foods palatable and mask bitterness; add flavor, body, bulk, and texture; change the freezing point and control crystallization; control viscosity, which contributes to body and texture; and prevent spoilage. Certain sweeteners bind the moisture in food that is required by detrimental microorganisms. Alternatively, some sweeteners can serve as food for fermenting organisms that produce acids that preserve the food, thus extending shelf life by retaining moisture. These auxiliary functions must be kept in mind when considering applications for artificial sweeteners.

Sweeteners may be classified in a variety of ways:

Table 8. Polyols: Their Calorie Value and Relative Sweetness to Sugar

Polyol sweetener

Relative sweetness, sucrose = 100

Calorie value (U.S. FDA allowance), Kcal/g

Erythritol

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