Bioavailability of zinc in beef with and without plant protein concentrates

Abstract

The bioavailability of zinc in freeze-dried ground beef, soy protein concentrate (SPC), Tower (Brassica napus) rapeseed protein concentrate (RPC), beef+SPC (2:1) and beef+RPC (2:1) was determined by a rat assay, using body weight gain or total femur zinc as the indicator. The basal diet contained 25% egg white solids providing 19.5% protein and the zinc content was 0.7 mg/kg. The zinc levels in beef, SPC and RPC were 132, 34 and 129 mg/kg air-dry weight respectively. The standard source of zinc (ZnSO 4 .7H 2 O) and the test sources provided 3, 6 and 12 mg/kg zinc. All the diets were isonitrogenous and isocaloric and the crude fibre content was equalized. By a slope-ratio assay based on log 10 total femur zinc (μg) and zinc consumed in 3 weeks (mg), the relative biological value (RBV) of zinc (ZnSO 4 =100) was: beef, 104; SPC, 47; beef+SPC, 94; RPC, 53; beef+RPC, 83. The RBV for zinc in beef was greater than that for the mixtures and the zinc in beef+SPC was slightly more available than that from beef+RPC. The difference between the RBVs for zinc in SPC and RPC was not significant (P>0.05). Using body weight gain (g) at 0, 3 and 6 mg/kg added zinc and zinc consumption, the respective RBVs were higher: 116, 63, 122, 80, 110. The RBVs for zinc in SPC and RPC were similar and they were significantly less than those for beef and mixtures (P