Jean-Paul Lallès

Susceptibility of phaseolin to in vitro proteolysis is highly variable across common bean varieties (Phaseolus vulgaris).

A study was conducted to investigate the amino acid (AA) composition and the susceptibility to in vitro proteolysis (pepsin, 120 min and pancreatin, 240 min) of a collection of purified phaseolins ( n = 43) in unheated or heat-treated form. The AA composition of phaseolin varied little across bean varieties. At 360 min of in vitro proteolysis, the degree of hydrolysis varied from 11 to 27% for unheated and from 57 to 96% for heated phaseolins ( P < 0.001). Heat treatment markedly increased the susceptibility of phaseolin to proteolysis ( P < 0.001). The AA scores (AAS) and the protein digestibility corrected for AAS indicated S-containing AA as the limiting AA (39 +/- 3 and 30 +/- 5%, respectively). In conclusion, susceptibility to proteolysis of heat-treated phaseolin rather than its AA composition affects the nutritional value of phaseolin estimated in vitro. Therefore, it should be the criterion of choice in breeding programs aimed at improving the nutritional value of common beans for humans.

Morphology and enzyme activities of the small intestine are modulated by dietary protein source in the preruminant calf

A study was undertaken to assess the impact of the protein nature and soya antigenicity on the morphology and some enzyme activities of the jejunum in preruminant calves. Twenty Holstein calves fitted with a duodenal cannula were fed a liquid diet based on skimmed milk powder (SMP) for 2 weeks. They were then switched onto diets containing a mixture of SMP and either antigenic heated soybean flour (HSF; n = 12) or hypo-antigenic soya protein concentrate (SPC; n = 8) for 8 weeks, after which they were reverted back to the SMP diet for 2 weeks. The diets contained similar amounts of digestible nitrogen and energy, and were fed at a rate of 55 g DM/kg(0.75)/d. Proximal jejunal biopsies were collected just before (week 0), during (weeks 2 and 8) and after (week 10) feeding of the soya-based diets, and were used for morphology measurements and the determination of total alkaline phosphatase, lactase, amino-peptidases A and N, and dipeptidyl peptidase IV activities. Feed intake and growth were similar between the HSF and SPC groups during the experimental period. The effects of antigenicity and the antigenicity x time interaction were never significant (P > 0.05). Villus height decreased (P < 0.01) between weeks 0 and 2, and increased (P < 0.05) between weeks 8 and 10. Villus width increased between weeks 2 and 8 (P < 0.001). Crypt depth also increased between weeks 0 and 2 (P < 0.001). Specific activities of alkaline phosphatase (P < 0.01) and amino-peptidase N (P < 0.05) decreased between weeks 0 and 2. Conversely, those of alkaline phosphatase (P < 0.0001), lactase (P < 0.01) and dipeptidyl-peptidase IV (P < 0.0001) increased between weeks 8 and 10. Specific activities for lactase and amino-peptidase N decreased (P < 0.01) between weeks 2 and 8. The treatments had little effects on the amino-peptidase A activity. In conclusion, the present work demonstrated that soybean protein markedly depressed the morphology and most enzyme activities of the calf small intestine. On the contrary, the in vitro antigenicity of soybean protein had little influence on these parameters in this study.

Legume Proteins of the Vicilin Family are More Immunogenic Than Those of the Legumin Family in Weaned Piglets

Two experiments were conducted to study the systemic and local immune responses to legume proteins in piglets weaned at 28 d of age. The pigs were fed a control diet (C) based on casein or diets in which 50% of crude protein (CP) was supplied by soya bean meal (SBM), pea (P), faba bean (FB), or lupin (L) seeds in experiment 1, and white chickpea (WCP) or black chickpea (BCP) seeds in experiment 2. Blood samples and intestinal secretions were collected at slaughter four weeks later and analysed for specific antibodies using ELISA and western blotting. Piglets fed the legume-containing diets had higher ( P < 0.10) plasma immunoglobulin (Ig) G ELISA titres to legume proteins than did piglets fed a casein-based diet. Many protein bands in the molecular weight range of 94.0-14.4 kDa were recognized by plasma IgG and IgA antibodies. The most immunogenic bands belonged to proteins of the vicilin family and to other unidentified minor proteins. No specific IgA antibodies were detected in intestinal secretions by ELISA and western blotting.