Soybeans and Soybean Products

Abstract

BEUCHAT, CHERRY, QUI" egg white was due to heat denaturation of the ovomucin-lysozyme complex. In general, foam persistence is the result of the interaction of several factors, including surface tension, viscosity, temperature, pH, ionic strength, and concentration of protein in solution (Briskey, 1968; Hansen and Black, 1972). All yeast protein isolates except those prepared by heat precipitation at pH 6.0 from alkaline extracts showed good emulsifying activity and were slightly superior than soy isolate. The yeast protein isolates prepared from water extracts and precipitated with heat possessed lower emulsify-ing activity than the samples precipitated without heat. Lawhon and Cater (1971) also found that some functional properties of protein isolates from glandless cottonseed processed with heat were inferior to those of isolates from unheated meal. The yeast proteins lowered the surface tension of aque-ous solutions. However, they were not as effective as soy isolates in this respect. This property was reflected in the lower foam stability of the yeast protein isolates compared to soy isolate. Yeast protein isolates, especially those obtained by water extraction (Vananuvat and Kinsella, 1975b, 1975c) which are low in nucleic acids and have a good amino acid balance , should have potential commercial application in meat emulsions, ground meats, and bakery goods. These isolates possess a light creamy color, little flavor, and good emulsi-fying properties. Defatted peanut flour was hydrolyzed with pep-sin, bromelain, and trypsin. Nitrogen solubility was increased substantially in water a t pH 4.0-5.0, and in 0.03 M Ca2+ at pH 4.0-11.0. Water adsorp-tion by the flour when exposed to various relative humidities was increased as a result of hydrolysis. Emulsion capacities in water and in 0.5 M NaCl were completely destroyed during digestion and water-and oil-retaining properties were reduced when compared to control samples. Gel electro-phoretic patterns showed substantial qualitative changes in enzyme-treated peanut protein. Patterns were different for each of the hydrolysis treatments. Physicochemical properties of defatted peanut flour depend upon naturally occurring characteristics associated with the peanut kernel as well as processing conditions to which the kernel is exposed during conversion to flour. Be-havioral properties of peanut proteins in the presence of carbohydrates, fat, water, and other food ingredients are of greatest interest, since protein comprises approximately 60% of defatted flour. Peanut flours represent potentially valuable ingredients in the formulation of protein-fortified food products. ~~