The Ratio of Casein to Whey Protein Impacts Yogurt Digestion In Vitro
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- Rioux, L. & Turgeon, S.L. Food Dig. (2012) 3: 25. doi:10.1007/s13228-012-0023-z
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Recent findings suggest that the form and texture of food impact appetite and food intake. For example, viscous milk beverages elicit lower food consumption when compared to less viscous beverages. Additionally, individual proteins exert different enzyme susceptibilities that can affect the digestion kinetics of protein and the liberation of satiating peptides and amino acids. The effect of yogurt composition on satiety has been studied, but mostly with regards to added fiber (inulin and guar) and/or increased amounts of protein (Lluch et al. Food Qual Prefer 21:402–409, 2010; Perrigue et al. J Am Diet Assoc 109:1862–1868, 2009); little information has been reported on the satiating effect of yogurt containing different ratios of casein and whey proteins. Yogurts with different casein to whey protein ratios (4.5:1, 2.8:1 and 1.5:1) were prepared and an in vitro digestion was performed to assess the protein disappearance and amino acid release. A significantly higher viscosity for the 1.5:1 ratio was related to a lower disintegration in the gastric phase. However, all of the ratios were similarly digested at the end of the duodenal phase. After 5 min of duodenal digestion, most of the proteins were completely digested regardless of the ratio. The viscosity at the end of each digestion step was significantly different. Ratio 2.8:1 showed a significantly higher viscosity after oral digestion, while after gastric digestion, both ratio 2.8:1 and 1.5:1 were more viscous than ratio 4.5:1. However, the three yogurt formulations reached a similar viscosity after duodenal digestion. It can be concluded that the digestion kinetics of nitrogenous compounds are influenced by the viscosity of the food matrix and therefore could impact its satiating properties.