EVALUATION OF THE PHYTATE, ZINC, COPPER, IRON AND MANGANESE CONTENTS OF, AND ZN AVAILABILITY FROM, SOYA-BASED TEXTURED VEGETABLE-PROTEIN MEAT-SUBSTITUTES OR MEAT-EXTENDERS

The Zn, Cu, Fe, Mn, protein (N .times. 6.25) and phytic acid contents of 19 soyabean-based textured-vegetable-protein (TVP) meat-extenders and meat-substitutes and of 3 ready-prepared canned meals containing TVP were studied. Phytate analysis was performed using a newly-developed method based on Holt''s procedure. This method enabled the phytate content of mg quantities of TVP to be estimated, with an SD for 6 replicates of 3%. The Fe, Cu and Mn contents (mg/kg) of the meat-extenders or meat-substitutes varied, with values of 59.4-144, 14.1-19.7 and 19.5-29.1, respectively. The protein content of the products was approximately 500 g/kg. The phytate content of the meat-extenders and meat-substitutes ranged from 11.0-20.2 g/kg and the Zn content from 35.0-49.4 mg Zn/kg. The calculated molar ratio, phytate:Zn varied from 25-42. The trace element, phytate and protein contents of the ready-prepared canned meals were 30-50% lower than the meat-extenders and meat-substitutes. Cooking the ready-prepared meals specified by the manufactures was without effect on the trace element or phytate content. When TVP was fed to rats as the only protein source, they had significantly lower growth rates and plasma Zn concentrations than rats given an egg-albumen-based diet of similar Zn content (14.5 mg Zn/kg). Supplementation of the TVP diet with Zn (100 mg Zn/kg) significantly increased growth rate and plasma Zn concentration whereas Zn supplementation of the albumen diet had no effect. The possible implications of consumption of TVP products in relation to Zn status of the human population is discussed.