New Ca-sequestering materials . based on the oxidation of the hydrolysis products of lactose

Abstract

The Ca-sequestering capacity of the equimolar mixture of aldonic acids or aldaric acids obtained by selective catalytic oxidation of the hydrolysis products of lactose (D-glucose and D-galactose) was determined using a Ca ion selective electrode. Also, the Ca-sequestering capacity of each component of these mixtures was quantified. The addition of boric acid at pH = 10 enhanced the Ca-sequestering capacity substantially, especially for D-gluconic acid and D-glucaric acid. Apparently the configuration of the vicinal diol moiety at the 3,4-position is of major importance in defining the Ca-sequestering capacity of aldonic and aldaric acids in the presence of borate. The effect of the concentration of NaOH on the Ca-sequestering capacity was evaluated in the range of 1–5 wt.% by titration with 0.1 M calcium acetate. The polyhydroxycarboxylic acids exhibit an optimum Ca-sequestering capacity up to one mol Ca ions per mol carboxylate group at these high pHs.