Proteins for foods, in addition to providing nutrition, should also possess specific functional properties that facilitate processing and serve as the basis of product performance. Functional properties of proteins for foods connote the physicochemical properties which govern the behavior of protein in foods. This general article collates the published information concerning the major functional properties of food proteins, e.g., solubility, binding properties, surfactant properties, viscogenic texturizing characteristics, etc. The effects of extraction and processing on functional properties and possible correlations between structure and function are discussed, in relation to practical performance in food systems. Modification of proteins to improve functional characteristics is briefly mentioned.

Functional properties of proteins in foods: A survey

This review is a survey of studies on protein-stabilized foams and emulsions in relatively simple, well-defined systems (rather than in food products per se). The emphasis is on the extent of basic understanding developed, particularly in terms of the physicochemical properties involved. The stability of the system, its formation, and its rheology are covered. Unfortunately, much work is of limited fundamental value because of poorly designed experimental approaches and the failure to measure key parameters. Reasonable generalization can be made concerning the effects of a number of variables, particularly protein solubility, pH, protein structure and the presence of small molecule surfactants. However, several possible explanations of these effects in terms of surface properties remain tenable. A number of observations can fairly confidently be ascribed to the influence of rheology on flow processes within foams and emulsions.

Protein‐stabilized foams and emulsions

Functional properties of protein concentrates from alfalfa leaves (ALP) prepared by several methods were determined. Minimum solubilities occurred around pH 3.5–4; sodium chloride 0.05–0.2M had little effect on minimum solubility. Extraction of the lipids from ALP with acetone decreased solubility slightly; increased the bulk density (2-3-fold); and reduced water and fat absorption capacities by 50% compared to the controls. Both emulsifying activities and emulsion stabilities of ALP samples were generally better than those of soy protein concentrate but poorer than those of soy sodium proteinate i.e., average of 57, 48 and 87 and 60, 50 and 90%, respectively. Emulsifying capacity of ALP samples were reduced following acetone extraction.

Functional properties of novel proteins: alfalfa leaf protein [for food applications].

Functional properties of novel proteins: alfalfa leaf protein

Functional Properties of the Myofibrillar System and Their Measurements

SUMMARY

A simple method was developed for estimating the emulsifying capacity of protein extracts. Several variables influenced the amount of oil that could be emulsified by 1 mg of soluble protein. The amount of soluble protein in the original aliquot used, the speed of mixing, the final temperature of the emulsion, and the amount of oil initially added, each influenced the emulsifying capacity of the soluble protein. The rate of addition of oil did not affect the amount of oil emulsified. Any differences in the effect of rate of addition of oil could be attributed to a temperature difference. Photomicrographs were made of emulsions showing the protein-oil relationship at increasing amounts of oil before and after emulsion breakdown. A method for predicting the stability of emulsions was used to verify the method developed.

A Simple Method of Estimating the Emulsifying Capacity of Various Sausage Meats

SUMMARY– Surface tension responses for solutions of salt-soluble protein from cow meat, beef hearts, beef cheek meat, pork trim and pork cheek meat were found to follow the Type III curves assigned to surface-active agents. The stability of emulsions prepared utilizing salt-soluble protein of the meats was significantly affected by concentration of protein and level of oil. As either concentration of protein or of oil was increased, higher and more significant stability of the emulsions was observed. Emulsions prepared from protein of each type of meat had similar responses for stability. High and significant correlation was found between protein surface activity and emulsion stability. Little change in emulsion viscosity was found except at the upper protein and oil levels tested.

STABILITY OF OIL‐IN‐WATER EMULSIONS. 1. Effects of Surface Tension, Level of Oil, Viscosity and Type of Meat Protein

Emulsifying capacity of muscle protein: phase volumes at emulsion collapse

Quantitative determination of combined hemoglobin and myoglobin in various poultry meats

The effects of air velocity, relative humidity, temperature and presence of glucono delta lactone (GDL) on the quality of frankfurters, were evaluated. Rate of heating was inversely proportional to rate of weight loss during processing. High humidity processes at slow air flows had the fastest heating rates; however, quality was unacceptable because of fat separation and pale color. A process where the smokehouse temperature was slowly increased by 6°C increments, and where a low relative humidity and high air flow were used, gave the best quality. Color and texture was more desirable on products having higher shrink. The presence of GDL had no effect on the final color of products processed under the same conditions; however, maximum color appeared to develop earlier in samples containing GDL.

R. L. Saffle

Papers

A Simple Method of Estimating the Emulsifying Capacity of Various Sausage Meats

STABILITY OF OIL‐IN‐WATER EMULSIONS. 1. Effects of Surface Tension, Level of Oil, Viscosity and Type of Meat Protein

Emulsifying capacity of muscle protein: phase volumes at emulsion collapse

Quantitative determination of combined hemoglobin and myoglobin in various poultry meats

Effect of smokehouse temperature, humidity and air velocity on rate of heating and quality of frankfurters