β-Lactoglobulin/polysaccharide interactions during in vitro gastric and pancreatic hydrolysis assessed in dialysis bags of different molecular weight cut-offs |
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Authors: | J Mou.écoucou C Villaume C Sanchez L Méjean |
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Affiliation: | 1. Laboratoire des Sciences Animales, ENSAIA-INPL, USC INRA 2, Avenue de la Forêt de Haye BP 172, F-54505 Vandoeuvre-lès-Nancy Cedex 5, France;2. Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition, EMI 0014 INSERM and URM 20 IFREMER, Faculté de Médecine, 54500 Vandoeuvre-lès-Nancy, France;3. Laboratoire de Physico-Chimie et Génie Alimentaires, ENSAIA-INPL, USC INRA 2, Avenue de la Forêt de Haye, F-54505 Vandoeuvre-lès-Nancy Cedex 5, France |
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Abstract: | The effects of gum arabic, low methylated (LM) pectin or xylan at levels of 0 and 50 wt.% on beta-lactoglobulin (β-lg) digestibility were studied as well as the interactions between the two macromolecules during in vitro hydrolysis. The proteolysis was performed in a system involving a two-step hydrolysis: either pepsin alone, or pepsin followed by a trypsin/chymotrypsin (T/C) mixture in dialysis bags with molecular weight cut-offs (MWCO) 1000 or 8000 Da. Digestibility was estimated by the N release and by a SDS-PAGE electrophoresis of retentates from the two dialysis bags after hydrolysis. Turbidimetric measurements monitored the structural evolution of mixtures during the two-step hydrolysis. Results showed that β-lg was almost resistant to peptic digestion and that polysaccharides increased the N release despite a reduction of pepsin activity. This is due to the formation of electrostatic complexes between polysaccharides and β-lg, which reduced β-lg aggregation, increasing its solubility. The polysaccharides reduced significantly the β-lg T/C digestibility as determined using a dialysis bag with a MWCO 1000 Da, without a modification of their enzymatic activities. No significant effect of polysaccharides on the β-lg digestibility was detected using the dialysis bag with a MWCO 8000 Da. The electrophoresis pattern did not show differences in the profile of retentates in relation with the dialysis bag used. This suggests that non-specific interactions could occur during the second step of hydrolysis between polysaccharides and amino acids or peptides smaller than 8000 Da. |
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Keywords: | Beta-lactoglobulin/polysaccharide interaction N release Turbidity Enzymatic activity β-lg beta-lactoglobulin pHi isoelectric point DE degree of esterification LM pectin low methylated pectin MWCO molecular weight cut-off NTU nephelometric unit T/C trypsin/chymotrypsin |
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