New food antioxidant additive based on hydrolysis products of lactose

Abstract

The hydrolysis products of lactose, D-glucose and D-galactose, were oxidized in two consecutive steps using appropriate bimetallic catalysts (Bi–Pd, Bi–Pt on charcoal) to the corresponding 2-ketoaldonic acids. The latter were further processed to provide two stereoisomers of L-ascorbic acid (vitamin C), D-ascorbic acid (D-lyxoascorbic acid) and erythorbic acid (D-araboascorbic acid). The antioxidant activity of these two isomers as well as that of the equimolar mixture thereof was evaluated by measuring their reducing activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and their scavenging activity of O₂⁻ species in the presence of NBT (Nitro Blue Tetrazolium). The compounds and their equimolar mixture were found to exhibit the same antioxidant activity as L-ascorbic acid suggesting that they may be used as cheap alternatives to L-ascorbic acid as food antioxidant additives when the vitamin C activity is not required.