Characteristics of Zinc-rich Fraction Prepared from Oyster

Abstract

We have already obtained zinc-rich fraction (ZRF) from boiled oyster by extraction with 0.1 N HCl followed by neutralization and heating (patent No. 3267962 ). In the present study, to evaluate a nutritional availability of the ZRF, several characteristics of the ZRF were investigated. An insolubilization of zinc in the 0.1 N HCl-extract of boiled oyster was promoted with an elevation of pH. In particular, a rapid insolubilization was observed at pH 6.5 to 7.5 independently to the insolubilization of ninhydrin positive substances. This indicates that zinc recovered into the ZRF by the neutralization is mostly present as zinc hydroxide. Zinc in the ZRF was more soluble in solutions containing citrate or casamino acids than zinc as a form of zinc carbonate. Zinc in the ZRF could be solubilized by digest of protein or organic acids in a digestive tract; intestinal absorption of zinc in the ZRF may be higher than that of zinc carbonate.