The property of proteins to fonn stable foams is important in the production of a variety of foods. Foam can be defmed as a two-phase system consisting of air cells separated by a thin continuous liquid layer called the lamellar phase. Food foams are usually very complex systems, including a mixture of gases, liquids, solids, and surfactants. The size distribution of air bubbles in foam influences the foam product's appearance and textural properties; foams with a unifonn distribution of small air bubbles imparts body, smoothness, and lightness to the food. Proteins in foams contribute to the unifonn distribution of fme air cells in the structure of foods. Body and smoothness of food foams is related to the fonnation of air bubbles that allow volatilization of flavors with enhanced palatability of the foods.The most widely used protein foaming agents are: egg white, gelatins, casein, other milk proteins, soy proteins, and gluten. Proteins vary significantly in their foaming properties; for example, serum albumin is an excellent foaming agent while purified ovalbumin is poor. Protein foaming agents should possess the following properties. They should stabilize foams rapidly and effectively at low concentrations; perfonn as an effective foaming agent over the pH range which exists in various foods; perfonn effectively as a foaming agent in the medium with foam inhibitors such as fat, alcohol or flavor substances.Our understanding of the functions of proteins in the fonnation of adsorbed protein films has been improved by studies in which radio-labelled proteins were used to obtain surface concentrations. Foamability and whippability of foaming agents are used interchangeably in the literature. The tenn whippability is applied when foam is obtained by a high blending or whipping treatment. The tenn foamability is applied when foam is prepared by injecting air or gas through the protein solution. The foaming properties of proteins are influenced by the source of the protein, methods and thennal parameters of processing, including protein isolation, temperature, pH, protein concentration, mixing time, method of foaming. Among many factors influencing foaming capacity (FC) of proteins the type of foaming equipment and method of agitation are important. Speed of whipping is important to foam properties and consumer acceptance.

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Functional properties of two corn germ protein (CGP) preparations, supercritical CO* (SC-CO>) and hexane defatted, were studied in model systems using response surface methodology. The protein preparations had different fat and moisture content. The SC-CO* CGP was whiter (L), less red (a) and less yellow (b) in color measurement than hexane CGP. Temperature of incubation influenced the functionality of the SC-CO: and hexane-defatted CGP in model system. SC-CO2 CGP had higher fat binding and water retention than hexane CGP. Fat binding decreased during the heat treatment for SC-CO, CGP. Water retention in both preparations increased as temperature increased to 70°C. The different functional properties of hexane CGP may be due to the extent of protein denaturation.

The purpose of this study was to evaluate substitution of nonmeat proteins for meat protein on the thermo-rheology, quality characteristics, and microstructure of frankjimers. Batters were formulated to contain either 2 % sodium caseinate or soy protein isolate, or 3.5 % whey protein concentrate or wheat germ flour. The storage modulus (G ') of all treatments initial1.y decreased during temperature ramping from 20-5OC. then increased rapidly from 60-80C, with all-meat batter exhibiting the highest G' at 8OC. Substitution with nonmeat proteins decreased G ' , shear force, compression force, and red color of meat compared with all-meat frankfurters. lncreased protein content, cooking yield, and decreased fat content were obtained with nonmeat protein formulations. Electron micrographs showed that nonmeat proteins were able to bind to the meat protein and fat, forming a protein-fat matrix wirh less coalescence of fat droplets. Sodium caseinate, soy protein isolate, whey protein concentrate, and wheat germ flour can be used as protein additives in comminuted meat producrs without adversely affecting their physical Characteristics.

Functional properties and microstructure of frankfurters containing 1.5% or 2.5% salt and 15% preemulsified fat (PEF) stabilized with 2% pea protein, soy protein, or sodium caseinate were studied. With the exception of frankfurters with pea protein and 1.5% NaCl, all the others made with PEF" had greater (p < 0.01) thermal stability than all-meat frankfurters. Frankfurters containing soy protein or sodium caseinate had greater (p < 0.01) shear force than those with pea protein. Reducing NaCl in the frankfurters containing PEF did not influence the shear force. Microstructure examination revealed that many fat globules were entrapped physically within soy protein or sodium caseinate, which stabilized the meat emulsions and contributed to a firmer texture.

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