The 5th International Conference on Food Digestion . Introduction

Unravelling the fate of food in the gastrointestinal tract is essential to better understand the health effects of the food and to fight against diet-related pathologies such as cardiovascular diseases and type-2 diabetes. Digestion is the process that transforms food into nutrients. The first step of digestion occurs in the mouth, where mastication transforms solid and semi-solid foods into particles while mixing with saliva allows bolus formation and initiates digestion of carbohydrates.Then the bolus is transferred into the stomach, where acid conditions and specific enzymes (pepsin, gastric lipase) start hydrolyzing macronutrients like proteins and triglycerides. The next step occurs in the small intestine, where other digestive enzymes further degrade macronutrients allowing their absorption. In the small intestine, proteins are hydrolyzed by trypsin, chymotrypsin, elastase, carboxypeptidase etc, lipids by pancreatic lipases, and carbohydrates by pancreaticamylase. Small intestinal digestion is completed by the enzymes of the brush border membrane that release macronutrients, which can be absorbed by enterocytes to reach the bloodstream. Undigested material,fiber for example, reaches the large intestine where it is further metabolized by the intestinal microbiota.Investigating food digestion requires the use of models and a myriad of in vitro (static and dynamic), animal and human models have been described in the literature with the objectives of understanding the fateof food in the gastrointestinal tract. In particular, static in vitro digestion simulations are extremely popular because they are very easy to use and do not require sophisticated equipment. They have been shown to beadapted for screening large series of similar samples in identical conditions or to understand interactions at the molecular scale (Bohn et al.,2017). However, they are too simple to study more complex phenomenaand the kinetics of food digestion for which dynamic in vitro models are more appropriate (Dupont et al., 2018).There was a high heterogeneity between the different static in vitro digestion models that were used by the research groups all around the world. Models were differing in the pH used in the different phases(gastric and intestinal), their duration, the digestive enzyme/substrate ratio, etc For that reason, comparing results obtained from one study to another was impossible and there was a crucial need for a harmonizedmethod that could be used by everyone allowing comparison between studies. This was one of the main objectives of the INFOGEST COST Action