An in vitro batch fermentation protocol for studying the contribution of food to gut microbiota composition and functionality.

Knowledge of the effect of foods on gut microbiota composition and functionality is expanding. To isolate the effect of single foods and/or single nutrients (i.e., fiber, polyphenols), this protocol describes an in vitro batch fermentation procedure to be carried out after an in vitro gastrointestinal digestion. Therefore, this is an extension of the previous protocol described by Brodkorb et al. (2019) for studying in vitro digestion. The current protocol uses an oligotrophic fermentation medium with peptone and a high concentration of fecal inoculum from human fecal samples both to provide the microbiota and as the main source of nutrients for the bacteria. This protocol is recommended for screening work to be performed when many food samples are to be studied. It has been used successfully to study gut microbiota fermentation of different foodstuffs, giving insights into their functionality, community structure or ability to degrade particular substances, which can contribute to the development of personalized nutrition strategies. The procedure does not require a specific level of expertise. The protocol takes 4-6 h for preparation of fermentation tubes and 20 h for incubation.

Effect of Cooking Methods on the Antioxidant Capacity of Foods of Animal Origin Submitted to In Vitro Digestion-Fermentation.

The human body is exposed to oxidative damage to cells and though it has some endogenous antioxidant systems, we still need to take antioxidants from our diet. The main dietary source of antioxidants is vegetables due to their content of different bioactive molecules. However, there are usually other components of the diet, such as foods of animal origin, that are not often linked to antioxidant capacity. Still, these foods are bound to exert some antioxidant capacity thanks to molecules released during gastrointestinal digestion and gut microbial fermentation. In this work, the antioxidant capacity of 11 foods of animal origin has been studied, submitted to different culinary techniques and to an in vitro digestion and gut microbial fermentation. Results have shown how dairy products potentially provide the highest antioxidant capacity, contributing to 60% of the daily antioxidant capacity intake. On the other hand, most of the antioxidant capacity was released during gut microbial fermentation (90-98% of the total antioxidant capacity). Finally, it was found that the antioxidant capacity of the studied foods was much higher than that reported by other authors. A possible explanation is that digestion-fermentation pretreatment allows for a higher extraction of antioxidant compounds and their transformation by the gut microbiota. Therefore, although foods of animal origin cannot be compared to vegetables in the concentration of antioxidant molecules, the processes of digestion and fermentation can provide some, giving animal origin food some qualities that could have been previously unappreciated.

Effect of Cooking Methods on the Antioxidant Capacity of Plant Foods Submitted to In Vitro Digestion-Fermentation.

The antioxidant capacity of foods is essential to complement the body's own endogenous antioxidant systems. The main antioxidant foods in the regular diet are those of plant origin. Although every kind of food has a different antioxidant capacity, thermal processing or cooking methods also play a role. In this work, the antioxidant capacity of 42 foods of vegetable origin was evaluated after in vitro digestion and fermentation. All foods were studied both raw and after different thermal processing methods, such as boiling, grilling roasting, frying, toasting and brewing. The cooking methods had an impact on the antioxidant capacity of the digested and fermented fractions, allowing the release and transformation of antioxidant compounds. In general, the fermented fraction accounted for up to 80-98% of the total antioxidant capacity. The most antioxidant foods were cocoa and legumes, which contributed to 20% of the daily antioxidant capacity intake. Finally, it was found that the antioxidant capacity of the studied foods was much higher than those reported by other authors since digestion-fermentation pretreatment allows for a higher extraction of antioxidant compounds and their transformation by the gut microbiota.