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Impact of Maillard Modification on the in vitro Carbohydrate Digestibility of WP-Dextran Glycates
Whey protein (WP) conjugation with dextran (DX) by the Maillard reaction might provide an alternative approach to decrease the immunogenicity of milk proteins. Protein digestibility of whey protein-dextran (WP-DX) glycates has recently been investigated by our group using an in vitro infant digestion model. The digestibility of carbohydrate part of the glycates is unknown. According to human colonic fermentation models, DX can be entirely degraded by the colonic microflora. In this study, we investigated the in vitro carbohydrate digestibility to find out the impact of conjugation on the glucose release of dextran from WP-DX glycates compared with maltodextrin and a mixture with dextran and whey protein isolates (WPI).
WP-DX glycates were made with dextran (molecular weight 10kDa) and WPI via our patented aqueous Maillard reaction method. The glycates were separated and purified by chromatography. The glycates were digested at 37°C by in vitro model using an enzyme mixture including pepsin, pancreatin and amyloglucosidase, which represent enzymes in the digestion system of animals and humans. The free glucose was measured at 0, 10, 20, 60, 120, 180 min and 24 hours by HPLC with ion-exchange chromatography and RI detector.
The percentage glucose release of dextran and maltodextrin were 6.3 and 64.5% (g glucose/ 100g carbohydrates) respectively, during the first 10 min. The glucose release from WP-DX glycates was 9.5, 13.2 and 16.1% at 60, 120, and 180 min, respectively. The glucose release of glycates were lower (p<0.05) than that of dextran alone at 60, 120, and 180 min of digestion. However, no difference was observed in glucose release rate between WP-DX glycates and dextran alone at 0, 10 and 20 min of digestion.
The results indicated that both dextran and WP-DX glycates can be digested into glucose by this mixture of digestion enzymes. The rate of glucose release and extent of release were lower for DX compared to maltodextrin. The conjugation of dextran and WP slowed down the glucose release of dextran. Slower digestion of dextran in conjugates might help maintain a possible protective impact of the polysaccharide for reducing WP allergenicity during digestion.
Keywords: In vitro, Digestion, WP-DX Glycates.