nutritional and functional properties of whey and lactose

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FUNCTIONAL PROPERTIES OF WHEY PRODUCTS While the on-going research into whey proteins, utilization and functionality continues, whey ingredients already offer numerous functional benefits to food formulators. They possess solubility, create viscosity through water binding, form gels, emulsify, bind fat, facilitate whipping, foaming and aeration, enhance color, flavor and texture, and bring with them numerous nutritional advantages. SOLUBILITY Whey protein is highly soluble, especially when compared to sodium caseinate and soy protein (see Figure 5). Solubility is an important functional property in fluid and semi-fluid products. In ready-to-drink beverages, solubility prevents protein flocculation or sedimentation, which improves both product appearance and texture. In processed soups and sauces, curdling, sedimentation and separation associated with insoluble proteins are highly undesirable. In chopped meats, salad dressings, dairy and bakery products, proteins provide emulsification, gelation and water binding. In most processed foods, processing is simplified and product consistency is improved by using ingredients that are soluble and easily dispersed. The effect of heating on solubility is a second concern of food formulators. Many foods are heat processed for preservation purposes. Cream soups and sauces may be canned and commercially sterilized for shelf stability, and these will be further heated by the consumer. Denaturation and loss of solubility can occur when protein solutions with a pH of 3.5–5.5 are heated to 60°C and higher. Loss of solubility is enhanced by calcium ions in the solution. In high-acid systems with pH less than 3.5, such as fruit-flavored beverages and salad dressings, undenatured whey proteins remain soluble when heated to temperatures of 90°C or higher for 5 minutes. Likewise, proteins in dilute solutions above pH 6.5 remain soluble when heated at a temperature of 80°C for10 minutes or longer. In milk, as well as chocolate-, vanillaor coffee-flavored beverages, a neutral pH provides the best flavor characteristic. Caseins and whey proteins are soluble in these food systems, and protein choice is based on other properties, including nutrition, flavor and cost. In fruit- or cola-flavored beverages and fruit juice blends, an acidic pH enhances flavor. While whey proteins are soluble in acidic solutions, soy protein and caseins are likely to precipitate. Figure 5 Solubility of proteins as affected by pH Soluble Protein % 100 80 60 40 20 Whey Casein Soy 0 2 4 6 pH 8 10 38 e38
WATER BINDING AND VISCOSITY Water binding and viscosity are related functional properties. Products that bind large quantities of water, such as starches and gums, create viscosity. When whey proteins are heated, the bonds that are responsible for their globular structure break down. As the protein molecule unfolds, additional water binding sites are created, which increases the viscosity of the solution. In nutritional beverage products, low viscosity allows product developers to increase protein levels in a drink without damaging visual appeal, taste or texture. In addition, whey can add turbidity or opacity. In products such as puddings and yogurts, water binding properties help produce a more viscous texture and control separation. Yogurts fortified with WPC synerese (lose water) significantly less than yogurts fortified with nonfat dried milk. In chopped meats and bakery products, water binding contributes to the texture of the meat emulsion and bakery dough. In these products, water binding reduces cooking and baking losses, improves yields and contributes to the moistness of the final product. Increased moisture content in dairy foods helps enhance the sensory profile by increasing flavor release. Water binding properties contribute to the formulation of reduced-fat products by adding fat-like attributes such as lubricity and mouthfeel. In addition, certain whey products add opacity to reduced-fat dairy formulations. GELLING Under specific conditions, whey proteins form non-reversible gels. Gel characteristics depend upon the protein concentration, the pH of the solution, calcium ion concentration and sodium ion concentration. For example, gels formed in solutions with 3%–5% protein concentrations and at a temperature of 55°–70°C tend to be more translucent and softer. More opaque gels are formed when higher protein concentrations (10%) are heated to higher (90°–100°C) temperatures. In acidic conditions, gels tend to be opaque, wet and weak. In neutral and higher pH solutions, gels tend to be more translucent and elastic. Microparticles of whey protein gels maintain moistness in baked goods and meats; add opacity to beverages and dairy products; and improve texture and mouthfeel in reduced-fat products, bakery products, processed cheese, yogurt, puddings and custards, and chopped meats and seafood. EMULSIFYING Whey proteins have both hydrophilic (water attracting) and hydrophobic (water repelling) groups. Whey protein functions as well as traditional emulsifiers (such as egg yolk powder) in mayonnaise type dressings, and they are lower in cholesterol. The stability of whey protein emulsions can be further enhanced by adding gums or heating the system to create a protein gel. The emulsification properties of whey proteins can be an advantage in most processed food products, including margarine, sauces, chopped meats and seafood, ice cream mixes, bread dough and cake batters. e39 39
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