Erythritol has the lowest caloric density of the polyols— 0.2 cal per gram in the United States.
Polyols as a group provide the bulk of sugar, without as many calories as sugar. Since the compounds as a class are poorly absorbed, substantial percentages my enter the large intestine and undergo metabolism by the colonic bacteria. This can cause adverse gastrointestinal events. Gastrointestinal events are usually mild and temporary. These events are controlled by either reducing the polyol intake, and/or by gradually increasing the intake to achieve the desired level over time. This provides an opportunity for the colonic bacteria to adapt to the presence of the polyol in the large intestine.
Compared with sucrose, polyols as a class are lower in calories, have little effect on blood glucose levels, require moderate to no insulin for metabolism, are not cariogenic, replace the bulk of sugar on a one-to-one basis, and have valuable food processing properties. For sugar-reduced and -free food products, the polyols are central to food formulation.
Polydextrose is a randomly bonded polymer of dextrose containing minor amounts of bound sorbitol and citric acid. It was designed to replace the body and texture lost when sugar or carbohydrates were removed from a traditional food or beverage. Important in its commercialization and utilization is its reduced calorie content, deemed as 1 kcal/ g by the U.S. Food and Drug Administration.
Polydextrose is made from food-grade starting materials by vacuum polycondensation. Dextrose is thermally polymerized using sorbitol as a plasticizer and citric acid as a catalyst. The resulting product is a slightly acidic, water-soluble polymer. Through further processing, vari ous grades are produced with bland, desirable features. Polydextrose is not sweet.
Polydextrose is used in confectionery to achieve calorie and sugar reduction in hard and chewy candy; to replace sucrose in chocolate; to replace the bulk, creaminess, smoothness, and mouth-feel of sugar and fat in frozen desserts; to provide viscosity without gumminess in cultured dairy products; to replace sugars and some fat in baked applications; and to replace sugars and build solids in fruit spreads and filling applications.
Food ingredient manufacturers have responded to the desire for reduced calorie/fat nutrition claims with a diverse array of products that help food processors reduce the level of fat in formulated foods. These include lipid or lipidlike materials including salatrim and olestra, micro-particulated proteins (Simplesse), and carbohydrate-based ingredients. The carbohydrate-based food ingredients are reviewed here.
Fiber sources from cereal products—oat, wheat, corn and combinations of the three—are available. Through a series of purification steps, manufacturers can provide products that are light in color, essentially bland in flavor, and neutral in odor. Typically these products have the ability to absorb water, from 2 to more than 6 g of water per gram of fiber. The hydrated fiber products are frequently used in place of fats and oils on a gram for gram basis.
Similar products are available based on starch technology. Combinations of starch and water are able to replace fats and oils in some low-heat applications, ice cream, and processed meats. Limitations in this technology are the inability to carry flavors, and the inability to cook and fry with these reduced-fat products.
Hydrocolloids have also found favor in replacing fat and oils in formulated food products. M. Glicksman classified hydrocolloids into a number of major classes including (1) exudates (gum Arabic), (2) extracts from seed weed (carrageenans) and land plants (pectin) and animals (gelatin), (3) flours from seeds (guar) and cereals (starches),
(4) biosynthesis or fermentation (xanthan gum), and
(5) cellulose and chemically modified cellulose derivatives.
Food hydrocolloids provide a wide array of technological benefits in formulated food products. In calorie-reduced foods, reduced in fats and/or sugars, these products restore the eating qualities associated with full-fat and full-sugar formulations. In an era of full nutritional disclosure, the bulking agents can facilitate the reduction or removal of fats and oils while achieving products that are acceptable to calorie- and fat-conscious consumers.
Hydrocolloids can perform many and varied functions, including as adhesives, binding agents, bodying agents, crystallization inhibitors, clarifying agents, clouding agents, fibers, emulsifiers, encapsulating agents, film formers, flocculating agents, foam stabilizers, gelling agents, moldings, flavor emulsifiers, suspending agents, swelling agents, syneresis inhibitors, thickening agents, whipping agents, and more.
Exudates. Exudates from various plants are among the oldest gums available to humans. The gums are exuded in teardrop or flake shapes that are normally harvested by hand, brought to a central location for sorting, and ground into powder for final sale. For food applications, it is common to spray-dry the gums to reduce the bacterial content and yield a clean, white powder. The four commercial gums include arabic, ghatti, karaya, and traagacanth.
Gum arabic is exuded from the Acacia trees where it forms in scars or wounds on the tree. Gum arabic is a complex, highly branched, globular molecule with low viscosity, and extremely high solubility in water, up to 55%. The stabilizing and emulsifying properties of gum arabic are highly prized characteristics. The other three gums are much more viscous in aqueous solutions. Gum arabic is used for many important functions, including for flavor fixation, for prevention of sugar crystallization and to keep fatty components distributed in confectionery products, as an emulsifier in flavor emulsion concentrates, for preparation of glazes and toppings in baked applications, and to prepare coatings for vitamin and mineral supplements.
Extracts. Extract examples include carrageenan, pectin, and gelatin. Carrageenan is isolated from certain members of the class Rhodophyceae (red seaweeds). It is a hydrocol-loid consisting mainly of the potassium, sodium and magnesium, calcium, and ammonium sulfate esters of galactose, and 3,6-anhydrogalactose copolymers. Carrageenans are soluble in hot water and hot milk. Carrageenan reacts with the casein fraction of milk and is very effective in stabilizing milk-based products. Carrageenans are used in the formulation of milk and milk-based beverages, ice cream products, milk puddings, dessert gels, meat analogs, salad dressings, and more.
Pectin is the designation for a group of valuable polysaccharides extracted from edible plant material and used extensively as gelling agents and stabilizers. Pectic substances are abundant in fruits and vegetables and to a large extent are responsible for firmness and form retention of their tissue. Pectin and pectic substances are het-eropolysaccharides mainly consisting of galacturonic acid and galacturonic acid methyl ester residues. Pectin is obtained by aqueous extraction of citrus peels and apple pom-ance.
Pectin solutions show relatively low viscosity compared with other plant hydrocolloids; hence, pectin has limited use as a thickener. Pectin is primarily used as a gelling agent to impart texture to jams, jellies, and preserves. Other applications include bakery fillings and glazings, yogurt fruit preparations, fruit beverages and sauces, fruit jellies and jelly centers, and dairy products.
Gelatin is extracted from cowhides, pigskins, and animal bones. Gelatin is prepared by either alkaline or acid treatment of collagenous tissue and is a form of hydro-lyzed, denatured collagen; it is well known for its ability to form food gels. Collagen has an unusual amino acid distribution, containing repeating triplets of-(Gly-X-Y)-where a large percentage of X and Y are proline or hydroxyproline residues. In vivo collagen self-assembles to give a triple helical structure; the structure is stabilized by the formation of chemical cross-links. Above about 40°C, cross-linked collagen unwinds and forms a random, denatured configuration. On cooling, such denatured collagen gels. Gelation is thought to occur through development of junction zones with partial reformation of the collagen triple helix structure.
Gelatin can be used as a thickening agent at low concentrations, and a gelling agent at high concentrations. Gelatin is unique in the spectrum of gelling agents in that it can form aqueous gels with water at any pH and without the need for any other additives. Gelatin gels are thermally reversible and can be melted and reset by heating and cooling.
Flours from Seeds and Cereals. Flours containing gums such as guar and starch are separated by mechanical means from the plant seed or cereal. The guar plant, Cyamposis tetragonolobus, is a member of the legume family. The endosperm of guar seed is an important hydrocol-loid. The guar molecule is a straight-chain galactomannan with galactose on every other mannose unit. Guar gums form a colloidal dispersion to yield a highly viscous system. Guar gum solutions of 1% concentrations or higher are thixotropic with thixotropy decreasing below 1%. In comparison with other hydrocolloids, guar gum at equivalent solids in water has the highest viscosity.
Guar gum modifies the behavior of water in food systems in a highly efficient manner. It reduces and minimizes friction in food products, thereby aiding processing and palatability of foods. Guar viscosity aids in the control of crystal size in saturated sugar solutions. Guar imparts smoothness to ice cream by promoting small ice crystals. Guar yields a homogeneous finished texture to cottage cheese. The addition of guar to cold-packed cheese eliminates syneresis and results in more uniform texture and flavors.
Biosynthesis or Fermentation. Fermentation or biosynthesis is the route of production of xanthan gum. Microorganisms that produce extracellular polysaccharides are widely distributed in marine and land environments. Xanthomonas campestris, a naturally occurring bacterium originally isolated from the rutabaga plant, is grown in fermentation vats to produce xanthan gum, a high-molecular-weight polysaccharide gum. The gum is extracted with isopropyl alcohol, dried, and milled. It contains d-glucose and d-mannose as the dominant hexose units, along with d-glucuronic acid, and is prepared as the sodium, potassium, or calcium salt. The polymer backbone consists of 1,4-linked /?-d-glucose and is, therefore, identical to that of cellulose. At the 3-position of alternate glucose monomer units is a trisaccharide side chain containing a glucuronic acid residue between two mannose units.
Xanthan gum is completely soluble in hot or cold water. Low concentrations of xanthan gum exhibit high viscosity. Solutions of xanthan gum at 1% or higher concentration appear almost gel-like at rest, yet these solutions pour readily and have low resistance to mixing and pumping.
Xanthan gum has found application in bakery fillings and icings; in beverages to build body, clouding agent, and to suspend insoluble ingredients; in confectionery in processing starch jelly candies and in xylitol-coated chewing gum; in dairy products where it performs as a stabilizer;
in dairy substitutes as a stabilizer; and in pourable dressings as an emulsion stabilizer.
Powdered Cellulose and Cellulose Derivatives. Powdered cellulose is a polymer composed of carbon, hydrogen, and oxygen. Chemically, it is a chain of glucose units linked in a 4-(/?-d-glucosido)-d-glucose, not to be confused with a-1,4-glucan, which is common in starch. The manufacture of powdered cellulose begins with wood pulp that undergoes a series of bleaching steps and drying. Following drying, the pure white, virgin cellulose is cut to the desired fiber length by cutters or by a ball mill. The lengths are varied to achieve specific applications in the food industry. Due to its nature, powdered cellulose is more than 99% fiber and considered to have zero calories.
Powdered cellulose has a number of interesting properties, including (2) a greater affinity for water than fat, (2) hydrogen bonding that restricts displacement of water by fat, (3) no nonenzyme browning, and (4) increased pliability of powdered cellulose-containing foods.
Powdered cellulose has a number of food applications, including (1) increasing the fiber content of formulated foods, (2) reducing the caloric content of the food by displacement of fats, and (3) increasing water retention capacity and viscosity.
Being a white, flavorless, and odorless powder enhances the use of powdered cellulose as a noncaloric bulking agent in food products. Low-level inclusion of powdered cellulose in fried food formulations can result in reduced fat pickup during frying. This is attributed to the hydrophilic nature of powdered cellulose and its molecular structure, which permits the formation of significant amounts of additional hydrogen bonds that require more energy to break during the frying process.
Other uses for powdered cellulose include binding and thickening (with gums and stabilizers), anticaking, anti-sticking extrusion aid, enhancing the volume of baked goods, as a texturizing agent, and more.
There are a variety of chemically modified cellulose products, including carboxymethylcellulose, methylcellu-lose, hydroxypropylcellulose, and hydroxypropylmethyl-cellulose with food applications.
There are a variety of reasons a food scientist may wish to reduce the content of simple sugars and or fat in food products. Among the reasons are to reduce calories, reduce simple sugars, reduce fat, attain nutrition labeling advantages, attract consumers who seek diet or dietetic foods, and more. In the case of sugar-reduced foods, these are normally formulated with a high-intensity sweetener and certain bulking agents that fill the space occupied by sugar(s).
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