Nutritional Improvement of Soy Flour Through Inactivation of Trypsin Inhibitors by Sodium Sulfite

Abstract

Treatment of raw soy flour at 75°C with 0.03M sodium sulfite for 1 hr completely inactivated trypsin inhibitors leaving no sulfite residues in the soy proteins. Rat feeding studies showed that the protein efficiency ratio (PER) increased from 1.55 for raw flour to 2.11 for heated flour and 2.49 for flour heated in the presence of sulfite. This nutritional improvement was accompanied by enhancement in in viva nitrogen digestibilities. Pancreas weights were elevated in rats fed raw soy flour, but not in those consuming heated soy flour, with or without sodium sulfite. Knowledge of the factors that decrease the stability of potentially toxic trypsin inhibitors may be useful for improving the quality of certain foods.

Effects of Sulfhydryl Compounds, Carbohydrates, Organic Acids, and Sodium Sulfite on the Formation of Lysinoalanine in Preserved Egg

“…Similar inhibition effects of sodium sulfite on LAL formation in casein, wool, and lysozyme were reported by Friedman (). According to the analysis of Friedman () and Friedman and Gumbmann (), at least 2 different mechanisms could be responsible for this phenomenon. First, when negatively charged protein‐bound cysteine (P‐S − ) or sulfocysteine (P‐S‐SO − ) are obtained during cleavage of protein disulfide bonds in the presence of SO 3 2− , the general effect is that the potential source of dehydroalanine for LAL formation is reduced.…”

“…Various chemical additives, such as certain sulfhydryl compounds, glucose, malic acid, ascorbic acid, sodium sulfite, acylation reagents, and metal salts, have been used to reduce the formation of LAL in model systems or actual food samples during alkali or heat‐treatment processes (Friedman , , ; Dworschak and others ; Friedman and others ; Friedman and Gumbmann ; Chang and others ; Al‐Saadi and others ). They presented effective mitigation of LAL formation not only by inhibiting or reducing dehydroalanine intermediate formation, but also by diminishing lysine precursor for LAL formation, besides bringing about some other changes through protein chemical modifications (Friedman ).…”

Biological Significance of Polymorphism in Legume Protease Inhibitors from the Bowman-Birk Family

“…It has been suggested that the modification of disulphide bonds by sulphydryl-disulphide interchange and sulphitolysis may be a useful strategy for the inactivation of PI in raw soy flour [41]. Sulphite treatment has been reported to improve the nutritional quality of soy flour [42].…”

Effect of Bisulfite on Lobster Shell Phenoloxidase

“…Extensive research has been carried out on these compounds; however, the mechanism of this inhibition is still not completely understood. Sulfite inhibition of phenoloxidase (PO) has been very controversial because the observed effects are dependent upon the assay method (Golan-Goldhirsh and Whitaker, 1984). Most inhibition studies have been done in fruits and vegetables; mushroom tyrosinase being examined the most.…”

“…Most inhibition studies have been done in fruits and vegetables; mushroom tyrosinase being examined the most. Inhibition studies have shown that sulfiting agents have more than one mode of action including: (1) inactivation of enzyme(s) (Embs and Markakis, 1965); (2) inhibition of colored oxidation products (Haisman, 1974;Embs and Markakis 1965;Golan-Goldhirsh and Whitaker, 1984); and (3) cleavage and rearrangement of disulfide bonds in proteins (Schroeter, 1966;Friedman and Gumbmann, 1986). However, this latter reaction has not been detected in the inhibition of PO by sulfurous salts (Sayavedra-Soto and Montgomery, 1986).…”