In vivo and in vitro methods of measuring nutritive value of leaf-protein preparations

Abstract

1. Several in vitro methods were compared with in vivo methods for estimating the nutritive value of leaf-protein concentrates (LPC), using a freeze-dried preparation from wheat (A) fresh, (B) after heating moist, (C) after heating moist and then extraction with chloroform, and (D) after extraction with an acidified solvent.2. The treatments had little effect on the biological value (BV) of the samples for rats.3. Heating moist decreased true digestibility (TD), net protein utilization (NPU) and protein efficiency ratio (PER), but the original values were almost restored by lipid extraction. Acidified solvent extraction decreased TD, NPU and PER of LPC perhaps by making it brittle and difficult to wet.4. Papain solubility and TD were well correlated. Pepsin-pancreatin solubility and TD were less well correlated.5. Microbiological estimations of available amino acids, involving predigestion with pepsin, correlated poorly with TD determinations.6. Unsaturated fatty acids, particularly linolenic, formed complexes during heating of LPC. The effect of this on enzyme solubilization procedures and on digestion in vivo is discussed.7. Some comparisons are made between the effect of heat and of extraction with solvents on LPC and on fish meal.