PROTEIN-PHYTIC ACID RELATIONSHIP IN PEANUTS AND COTTONSEED

Abstract

Phytin, the calcium, magnesium, and potassium salt of phytic acid (inositol hexaphosphoric acid), is the principal storage form of phosphorus and inositol in all seeds (l-5).Although phytin or phytic acid was long considered to occur only in plants, recent work has shown that its occurrence is more widespread.Thus Rapoport and Guest (6) have demonstrated that the erythrocytes of the chicken and turtle contain appreciable amounts of phytic acid, while other investigators (7-10) have shown that phytin is also present in various soils.Furthermore, the nutritional significance of inositol ( 11) and phytic acid (12-14) is fairly well established.Phytic acid exhibits rachitogenic properties because it is capable of forming insoluble salts with calcium that are not absorbed through the intestinal wall.This rachitogenic activity can be destroyed under certain conditions by the enzyme phytase (15) which normally occurs in most seeds.In the course of investigations on peanut and cottonseed meals in this Laboratory, it was found that there is present in these meals a dialyzable substance that exerts a pronounced effect on the solubility characteristics of the meal proteins ( 16).This dialyzable meal constituent has now been identified as phytin.Since phytin is normally present in seed meals in relatively large quantities, and since its effectiveness in influencing the solubility characteristics of the meal proteins is marked, it was deemed advisable to invest,igate thoroughly the protein-phytic acid relationship in seeds with the view of contributing toward the eventual elucidation of the rdle played by phytic acid in the economy of the plant and of pointing the way to possibilities for the fuller industrial utilization of the protein constituents of both peanut and cottonseed meals.The protein-phytic acid solubility relationship over a wide pH range has been determined for peanut and cottonseed meals and the corresponding dialyzed meals and isolated proteins, and is presented in this paper.A limited number of comparative data on the protein-phytic acid solubility relationship in