An 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

Abstract

1. A study has been made of the zinc, copper, iron, manganese, protein (nitrogen x 625) and phytic acid contents of nineteen soya-bean-based textured-vegetable-protein (TVP) meat-extenders and meat-substitutes and of three ‘ready-prepared’ canned meals containing TVP. 2. Phytate analysis was performed using a newly-developed method based on Holt's (1955)procedure. This method enabled the phytate content of milligram quantities of TVP to be estimated, with an SD for six replicates of 3%. 3. The Fe, Cu and Mn contents (mg/kg) of the meat-extenders or meat-substitutes varied, wzith values of 59.4–144, 14.1–19.7 and 19.5–29.1 respectively. The protein content of these products was approximately 500 g/kg. 4. The phytate content of the meat-extenders and meat-substitutes ranged from 11.0to 20.2 g/kg and the Zn content from 35.0 to 49.4 mg Zn/kg. The calculated molar ratio, phytate:Zn varied from 25 to 42. 5. The trace element, phytate and protein contents of the ‘ready-prepared’ canned meals were 30–50 %: lower than the meat-extenders and meat-substitutes. 6. Cooking the ‘ready-prepared’ meals as specified by the manufacturers was without effect on the trace element or phytate content. 7. 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 (14.5mg 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 was without effect. 8. The possible implications of consumption of TVP products in relation to Zn status of the human population is discussed.