Improvement of the Functionalities of Soy Protein Isolate through Chemical Phosphorylation

Abstract

A method of chemical phosphorylation was developed to modify soy protein so as to improve its functional properties. The reaction was carried out by incubating soy protein isolate and cyclic sodium trimetaphosphate in an aqueous solution at pH 11.5 and 35'C for about 3 hours. The reactions ensued were the phosphoesterification of serine residues and the phosphoramidation of lysine residues in soy protein. The phosphorylated soy protein isolate prepared therefrom exhibited much improved functional properties in terms of aqueous solubility, water-holding capacity, emulsifiability and whippability. The nutritive bioavailability of soy protein isolate was not impaired by phosphorylation.

Mild method of simultaneous methionine grafting and phosphorylation of soybean globulins improves their functional properties

“…Methionine grafted on the globulin phosphate groups did not change their activity in promoting formation of emulsion and increasing its stability. Generally, the improvement of the emulsifying properties of the phosphorylated proteins agrees well with the results of Sung et al [3], Hirotsuka et al [12] and Huang and Kinsella [6]. These authors attributed this improvement to the increase of number of negative charges on the phosphorylated proteins which tends to induce strong electrostatic repulsions between the negatively charged emulsion surfaces reducing thus the coalescence of the emulsions.…”

“…Consequently, the enhanced hydrophilicity of the modified protein will decrease the hydrophobically driven aggregations so frequently observed in the plant proteins and improve the general protein solubility. Few studies were performed on the phosphorylation of soybean proteins under conditions involving relatively high amounts of a phosphorylating agent and concentrated inorganic bases [3,12] subjecting the modified proteins to degradation and other uncontrolled changes. The proteins involved in these studies were mixtures of whole protein isolates.…”

Microwave-assisted phosphorylation of soybean protein isolates and their physicochemical properties

“…Zinc pyrophosphate was then dissolved in ammonium buffer prior to the titration of zinc ions with EDTA disodium salt, using Solochrome Black T as indicator. This method is especially suitable for the determination of pyrophosphate in the presence of ortho-and trimeta-phosphates (Sung et al 1983).…”

Preparation of microwave-phosphorylated soy protein isolates through a Box–Behnken model optimization

“…The evaluation was carried out with a reference method of Sung, Chen, Liu, and Su (1983) with some modifications. Aliquots (5 mL) of the reaction mixture were taken from reaction system just after the end of phosphorylation.…”