Nutritional evaluation of biologically treated white kidney beans (Phaseolus vulgaris L.) in pigs: ileal and amino acid digestibility.

We studied the effect of feeding young growing pigs a semisynthetic diet containing 7.5% white kidney beans-germinated (GB), pancreatin treated (PTB), or untreated (raw beans RB)--on protein and amino acid (AA) digestibilities at the terminal ileum. Eleven castrated male pigs (12.2 kg live weight) fitted with a post-valve T-cecal cannula and two blood catheters were used. The 15N-isotope dilution method was used to determine the amount of endogenous protein passing the terminal ileum and the true ileal protein digestibility. Ileal crude protein losses in pigs fed the RB, GB, and PTB diets were 51.9, 27.4, and 51.1 g/kg of DMI, respectively. The total amounts of AA passing the terminal ileum of the pigs fed the RB, GB, and PTB diets were 48.6, 21.4, and 42.2 g/kg DMI, respectively. The apparent ileal crude protein and AA digestibilities of the RB, GB, and PTB diets were 74, 87, and 75% and 76, 89, and 78%, respectively. True ileal protein digestibilities were 88, 93, and 93% for the RB, GB, and PTB diets, respectively. On the basis of this research, germination of white kidney beans improves the digestion of protein by decreasing the content of bean antinutritional factors and increasing the bean true ileal protein digestibility.

The degradation of lectins, phaseolin and trypsin inhibitors during germination of white kidney beans, Phaseolus vulgaris L.

White kidney beans (Phaseolus vulgaris), cv Processor, contain a relatively high content of phaseolin (storage protein), lectins and a special group of glycoproteins as well as a considerable amount of protein-type trypsin inhibitors. Protein digestion of raw 'Processor' beans in monogastrics, for example pigs, is disturbed by poorly digested, phaseolin lectins, which can bind to carbohydrates in brush border membranes of the small intestinal epithelium, and trypsin inhibitors. The effect of the germination of white kidney beans on lectins, phaseolin and trypsin inhibitors was studied in order to achieve a degradation of lectins, phaseolin and trypsin inhibitors and an increase of in vitro enzymatic hydrolysis of the protein of bean flour. Therefore, whole bean extracts were examined throughout a germination period of up to seven days for their lectin and phaseolin pattern, lectin content, binding capacities of functional lectins towards brush border membranes and trypsin inhibitor content. In addition the in vitro enzymatic hydrolysis by pepsin and pancreatin of the protein from flours of (un)germinated white kidney beans was studied. SDS-PAGE demonstrated a degradation of E-lectins and a disappearance of L-lectins and phaseolin during germination. Results indicated a decrease of the lectin content by 85%, a loss of binding capacities of functional lectins towards brush border membranes by 91%, and a decrease of trypsin inhibitors by 76%, in bean flour after germination for seven days. A maximum in in vitro enzymatic hydrolysis of protein from bean flour was already established after germination for half a day.

In vitro enzymatic hydrolysis of protein and protein pattern change of soya and faba beans during germination.

In addition to technological processes like heat treatment, germination can be an alternative process for the improvement of protein quality of legumes. This was demonstrated by enzymatic protein hydrolysis of flour of germinated faba and soya beans, using a pepsin-pancreatin enzyme system. SDS-PAGE was used to study the changes in protein pattern of these legumes during germination. In addition, the effect of germination on the content of condensed tannins in flour from germinated faba beans and trypsin inhibitors in flour from germinated soya beans were studied. Germination for five days resulted in a maximum increase in enzymatic protein hydrolysis by 21.3% in flour from faba beans and by 25.7% in flour from soya beans after 12 hours of germination. Protein patterns, obtained with SDS-PAGE demonstrated a considerable protein breakdown during germination between day 2 and 3 in faba beans and between day 1 and 2 in soya beans. The tannin content in flour from faba beans decreased by 29.7% after seven days of germination, but the tannin content of the hulls of the faba beans did not change during that period of germination. The trypsin inhibitors in flour from soya beans decreased by 25.5% after seven days of germination. We conclude that the increased enzymatic hydrolysis of protein in both legumes cannot be explained by a decrease of tannins or trypsin inhibitors. The possible explanation is that through degradation of proteins during germination of the legumes, the cleaved protein fragments are more susceptible for hydrolysis by pepsin-pancreatin.

The presence and inactivation of trypsin inhibitors, tannins, lectins and amylase inhibitors in legume seeds during germination. A review.

During the germination of legume seeds, enzymes become active in order to degrade starch, storage-protein and proteinaceous antinutritional factors. The degradation of storage-protein is necessary to make peptides and amino acids available in order to stimulate seed growth and early plant growth. Proteinaceous antinutritional factors such as amylase inhibitors, lectins and trypsin inhibitors are present in legume seeds and protect them against predators. However, during germination, they degrade to a lower level by the action of several enzymes. The effect of germination on the content and activity of amylase inhibitors, lectins, tannins and trypsin inhibitors is discussed.