Factors in the Formation of Acid-Sensitive Fraction from Soybean Protein

Abstract

Acid-sensitive fractions (ASFs) were prepared from defatted meals by two procedures. ASF I was prepared by precipitation at pH 4.5 and removal of 1M NaCl-soluble materials from the precipitate. ASF II was prepared by precipitation with 1M NaCl at pH 4.5. ASF I always gave the higher yield than ASF II. ASF I seems to contain ASF II in its inner part. Some factors, wich influence on the formation of ASFs, were investigated. The sorts of acid, the addition procedure of the presence of phytate and the concentration of proteins did not have any effect on the yields of ASF I and II. However, some interactions between lipids and proteins were suggested, because further removal of lipids from defatted meals gave the lower yield of ASFs. Solubilities of ASF II in the presence of salts, ethylenediamine tetraacetic and reducing or oxidizing reagents indicated the little possibility of electrostatic, chelating or disulfide bonds. Its good solubility in sodium dodecyl sulfate and urea solutions suggested that hydrophobic interactions were predominant in ASFs.