High in‐vivo (rat) digestibility of faba bean (Vicia faba), lupin (Lupinus angustifolius) and soya bean (Glycine max) soluble globulins

The in‐vivo digestibility of soluble globulin proteins purified from faba bean ( Vicia faba ), lupin ( Lupinus angustifolius ) and soya bean ( Glycine max ) seed meals was studied in two acute (1 h) experiments with growing rats. Commercial insoluble denatured lactalbumin (Sigma) was used as control. In experiment 1, five groups (four rats each) of overnight fasted rats were intubated with the different proteins (300 mg) suspended in distilled water (1.5 ml). Controls were intubated only with water. In experiment 2, the proteins (300 mg) were added to a basal diet (1.0 g) which contained maize starch (500 mg), glucose (300 mg) and glycerol (200 mg). The animals (five groups) were offered the solid diet after overnight fasting. One hour after feeding, the animals were killed, the digesta of stomach and small intestine were washed out with cold water, freeze‐dried and their protein content determined. The digestibility of denatured lactalbumin in the rat small intestine after 1 h was 66‐9 and 67‐0% of the amount given in experiments 1 and 2, respectively. Digestibility of legume proteins ranged from 96‐5 to 99‐9% and from 80.1 to 86.9% in experiments 1 and 2, respectively. The differences between control and test groups were significant ( p < 0.001) in both experiments. These data suggest that legume globulins are highly digestible in the small intestinal tract of the rat.