Impact of human saliva on proteolysis during in vitro gastric digestion of dairy products

This conference is a major event in the field of Food, Nutrition and Health.It is organized in the frame of the INFOGEST research network(www.cost-infogest.eu) whose objective is to “improve the health properties of food by sharing our knowledge on the digestive process”. INFOGESTis a global network of approximately 582 research scientists (academic and food companies) from 150 institutions across 46 countries.

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anglais. Background Saliva may play a role in digestion through its enzymatic content or physico-chemical impact on the food bolus or chyme. Salivary proteins also interact with tannins, which could counteract their effect on digestive enzymes. We here evaluated the impact of saliva on gastric proteolysis of solid or liquid dairy products, including one contaning tannins.MethodSwiss-type cheese (C), milk in water (M) or milk in black tea (T), all in presence of human saliva vs water, were digested using semi-dynamic (C) and static conditions (M,T), respectively. Proteolysis was monitored throughout gastric digestion by OPA assay in all samples. The degree of hydrolysis was also calculated for cheese using acid titration data.ResultsFor cheese, the presence of saliva delayed slightly the initiation of proteolysis. OPA measurements suggested a small proteolytic inhibition by saliva. For milk, the presence of tannins increased gastric proteolysis (possibly by denaturing the pepsin substrates) but saliva had no substantial impact on OPA measurements, whether the matrix contained tannins or not.Conclusion In the conditions used, saliva had a moderate, if any, impact on gastric digestion of dairy products. Due to the documented effect of saliva on emulsions stability, the study could be extended to lipolysis.