Total and soluble oxalate content in legume vegetables used in the preparation of frozen products for consumption

Abstract

The aim of the investigation was to compare oxalate retention in two types of frozen product prepared for consumption after frozen storage: one obtained using the traditional method (blanching-freezing-frozen storage-cooking) and a convenience food involving cooking-freezing-frozen storage-defrosting and heating in microwave oven. The investigation included three species of legume vegetables: immature (wax-stage maturity) seeds of broad bean and green pea, and French bean. Fresh broad bean seeds contained 53 mg total oxalates in 100 g fresh matter; pea 38 mg; and French bean 88 mg. Soluble oxalates comprised 53, 58 and 72% of total oxalates. The treatments applied resulted in reduction of the level of total and soluble oxalates, and oxalate to calcium ratio (broad bean and French bean); there was no influence on the level of calcium bound as calcium oxalate; true retention of oxalates was lower than apparent retention (green pea and French bean).