Protein Quality of Raw and Autoclaved Plant Protein Blends

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The protein quality of both raw and autoclaved plant protein blends was evaluated in weanling male rats by determining the net protein ratio and the net protein utilization derived from liver nitrogen values. True digestibility of these blends was also determined in order to evaluate whether digestibility was the only factor that affected protein quality as revealed by the other parameters. Casein and lactalbumin were reference standards. Combinations of corn meal, whole wheat meal, ground polished rice, oats, white beans, and solvent-extracted meals of soybean, peanut and sesame were studied. All blends were autoclaved at 1.034 kg/cm2 (15 lb.) pressure for 20min. Improvements in protein quality were obtained when each of the blends was autoclaved, but some blends showed greater improvements than others. In most cases the heat treatment resulted in greater digestibility which was directly reflected in higher net protein ratio and net protein utilization values. However, the relatively high true digestibility value for one of the raw blends was reduced by autoclaving. In spite of this, both the net protein ratio and net protein utilization were improved significantly by autoclaving. Therefore, other factors besides digestibility had an effect on protein quality. Certain plant protein blends can be effective substitutes for good quality animal proteins if adequate heat treatment is used.