IMPROVEMENT IN THE SAFETY OF FOODS BY SH-CONTAINING AMINO-ACIDS AND PEPTIDES - A REVIEW

Most food toxicants have specific groups responsible for their deleterious effects. Modifying such sites with site-specific amino acids, peptides, and proteins should lessen their toxicity. Sulfhydryl (SH) groups are particularly suited to achieve this objective because of their great reactivity. The chemical reactivities of SH compounds are much greater than would be expected from their pK values. This enhanced reactivity results from (a) polarization of outer shell sulfur electrons; (b) the availability of d-orbitals in the electronic structure of sulfur, permitting d-orbital overlap during the formation of transition states; and (c) the ability of sulfur to act as a free-radical trap, whereby free electrons in highly reactive oxygen radicals are transferred or dissipated to sulfur atoms. This overview covers the biological utilization and safety of sulfur amino acids and possible approaches to ameliorating adverse effects of representative food ingredients, based on the reactivity of the sulfhydryl group with electrophilic centers. The latter include (a) the double bond of the furan ring of aflatoxins to suppress mutagenicity, (b) the double bond of dehydroalanine to prevent lysinoalanine formation, (c) the conjugated system of quinones to inhibit nonenzymatic and enzymatic browning in potatoes and other foods, and (d) the disulfide bonds of soybean inhibitors of digestive enzymes to facilitate inactivation through sulfhydryl-disulfide interchange. Possible benefits of these transformations to food safety, food quality, nutrition, and health and suggestions for future research are discussed.