Abstract
The effects of extrusion and frying of soybean protein isolate (SPI) on plasma cholesterol level and protein value were studied in growing male rats given five different diets, The control diet consisted of 20% casein. In the other diets, 50% of the casein in the control diet was replaced by SPI (N-SPI), SPI textured by extrusion (T-SPI), fried T-SPI (F-SPI) or fried chicken (F-Ckn). Total plasma cholesterol levels in the N-SPI, T-SPI, and F-SPI diet groups were significantly lower than in the control or F-Ckn group. Fecal neutral and acidic steroid excretion in the N-SPI, T-SPI, F-SPI and F-Ckn diet groups were all higher than in the control group. There were no differences in plasma cholesterol level, fecal steroid excretion, apparent protein digestibility or biological value among the NSPI, T-SPI and F-SPI diet groups, These results suggest that extrusion and frying of SPI does not affect the protein value or plasma cholesterol-lowering effect of SPI.
