Water binding capacity, protein

Extrusion texturization minimizes the water binding capacity of dairy protein products, in decreasing order, WPI > WPC > NDM, as temperature increases, making them interact better with starch. 

Chemical reactions Polymerization of casein and whey proteins are due to some kind of chemical reactions. The different proteins as found in the supernatant of milk after precipitation at pH 4.6 are collectively called whey proteins. These globular proteins are more water soluble than caseins and are subject to heat dena-turation. Denaturation increases their water-binding capacity. The principal fractions are P-lactoglobulin, a-lactalbumin, bovine serum albumin (BSA), and immunoglobulins (Ig). 

Hagenmaier (12) reported that proteins may be ranked in order of water binding capacity at one relative humidity and that this order should hold true at other relative humidities. He evaluated water binding of several oilseed proteins at 84% RH water binding increased as the number of hydrophilic groups of the different proteins increased. 

Water Uptake and Retention. The water binding capacity of soy protein isolate can be increased by treatment with neutral fungal protease (20). Since the number of free amino and carboxyl groups increases as a result of digestion and because moisture uptake by proteins is proportional to the number of ionic groups present ( ), it is not surprising that moisture uptake is increased by enzyme treatment. 

Both hydrocolloids and emulsifiers increase the water-binding capacity in the mix (increased % of hydrogen atoms with low T2 and decreased T2 values). A synergistic effect is observed when both ingredients are present. From studies described earlier in this chapter, the effect of hydrocolloids is assumed to be due to simple water binding and increased thickness of protein layers around the fat globules, whereas the effect of emulsifiers may be due to the increased hydration of interfacially bound protein as well as increased hydration of polar groups of emulsifier at the oil-water interface. 

If Swanbeck s 80-A layer is assumed to represent most of the hygroscopic substance, its water-binding capacity may be attributed to concentric hydrophilic interfaces (Figures 14B and 15). A myelin-like packing with the substitution of bimodal ER protein for the phospholipids of... 

Aside from applications to fermented products, UF-standardized milk may also be used for the manufacture of several other dairy products. For instance, Lee and White [136] reported an increase in the protein value of ice cream when UF retentate rather than NDM was used for solids-not-fat (SNF) source in the formulation at substitution levels of 25%-75%. They also reported that because of the high level of casein in the ice cream made from UF retentate, its water-binding capacity increased, which resulted to an improvement in flavor and stability of body and texture. 

Due to protein-water binding, human skin has the capacity to absorb five to six times its weight in water. The extent of skin hydration is directly related to the penetration rate of toxic materials. Controversy exists about whether hair follicles contribute to increased penetration, but some studies do show increased absorption through hairy skin. Inflammation in the skin leads to vasodilatation and increased blood flow and subsequently increased penetration of toxic material. Aging contributes to decreased lipid barrier protection and decreased intercellular cohesion and increased penetration of toxic material. 

Thus we have seen that endogenous and exogenous enzymes can markedly affect such physical properties of meat proteins as toughness or tenderness, emulsification properties, cohesion, and water binding capacity. 

Proteins can be concentrated by isoelectric precipitation, heat precipitation, alcohol precipitation, ultrafiltration, microfiltration, and freeze concentration. Numerous references report differences in function in relation to the method of concentration of the protein. Whey protein produced by acid-heat precipitation (lactalbumin) is essentially insoluble but shows high water binding capacity and for this reason is the whey protein of choice for baking and for formulation of cereal products [89]. The use of ultrafiltration instead of acid precipitation of soy protein provides products with quite different characteristics [108], However, caseinate produced via acid precipitation is nearly as suitable for the production of imitation cheese as is rennet casein produced by the action of chymosin on skim milk [88],... 

Rheological properties. Viscosity, an important physicochemical property of many foods, can be modified by proteins or polysaccharides. The caseins form rather viscous solutions, a reflection of their rather open structure and relatively high water-binding capacity. While the high viscosity of caseinate may be of some importance in casein-stabilized emulsions, it causes production problems for example, due to very high viscosity, not more than about 20% protein can be dissolved even at a high temperature. The low protein content of caseinate solution increases the cost of drying and results in low-density powders which are difficult to handle. 

Dairy products such as skim milk, buttermilk, whey and casein are added to flour in combination with the ingredients or additives mentioned so far. These dairy products are used in either powdered or liquid form as well as either whole or in the form of defatted powder. In such cases, the proteins added to the dough increase its water binding capacity and provide a juicy crumb. 

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