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Implications of the Maillard reaction on bovine alpha-lactalbumin and its proteolysis during in vitro infant digestion

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Abstract

This study investigated the functionality and digestibility of Maillard reaction products (MRPs) of alpha-lactalbumin (α-la), a major whey protein and component of infant formulas. The impact of different carbohydrates (glucose, galactose or galacto-oligosaccharides (GOS)) and heating duration was studied. SDS-PAGE, UV and color measurements monitored reaction extent, which varied between carbohydrates whereby galactose reacted more readily than glucose. Surface hydrophobicity and antioxidant capacity were found to be significantly (p < 0.05) higher following Maillard conjugation, with GOS-based MRPs elevating antioxidant capacity ∼50-fold compared to α-la. In addition, the digestive proteolysis of MRPs was evaluated using an infant in vitro gastro-duodenal model. SDS-PAGE analyses of digesta revealed Maillard conjugation generally increased α-la's susceptibility to proteolysis. Interestingly, GOS-based MRPs presented an optimization challenge, since heating for 12 h delayed proteolysis, while extended heating resulted in the highest susceptibility to proteolysis. Proteomic analyses further demonstrated the differences in enzymatic cleavage patterns and helped identify bioactive peptides rendered bioaccessible during the digestion of α-la or its MRPs. Bioinformatic mining of the proteomic data using PeptideRanker also gave rise to two potentially novel bioactive peptides, FQINNKIW and GINYWLAHKALCS. Finally, antioxidant capacity of luminal contents, measured by DPPH, revealed Maillard conjugation increased the antioxidant capacity of both gastric and duodenal digesta. Overall, this work draws a link between the Maillard reaction, digestive proteolysis and the bioaccessibility of bioactive peptides and antioxidant species in the infant alimentary canal. This could help rationally process infant formulas towards improved nutritional and extra-nutritional benefits.

Graphical abstract: Implications of the Maillard reaction on bovine alpha-lactalbumin and its proteolysis during in vitro infant digestion

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Publication details

The article was received on 18 Apr 2017, accepted on 27 May 2017 and first published on 30 May 2017


Article type: Paper
DOI: 10.1039/C7FO00588A
Citation: Food Funct., 2017, Advance Article
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    Implications of the Maillard reaction on bovine alpha-lactalbumin and its proteolysis during in vitro infant digestion

    Y. Joubran, A. Moscovici, R. Portmann and U. Lesmes, Food Funct., 2017, Advance Article , DOI: 10.1039/C7FO00588A

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