Abstract
Baked goods, as staple foods, represent a key element in the daily human diet. For this reason, the study of the digestibility and functionality of leavened bakery goods has recently been entered in the context of human health. Specifically, the protein and starch hydrolysis that occurs during the manufacturing of baked goods, the use of nutrients, gastrointestinal manifestation after the intake and generation of end-products and metabolites from digestion and gut microbial fermentation, hold a strong relationship with the digestion process. Different valid and scientifically approved in vitro static and dynamic models were used as a powerful tool to exploit the benefits of fermented foods on human health. The combined application of these in vitro models allowed an evaluation of the digestibility of a large number of fermented bakery products. In the first part of the study, we produced forty-six breads, as a result of a multiple combination of raw materials and technological parameters. In order to cover a wide range of factors such as different flours, fungal proteases, lactic acid bacteria (LAB) cytoplasmic extract, type of sourdough (fresh, liquid, or dried), pools of starter culture (LAB and yeast), time and temperature of sourdough fermentation were used to make breads. A first screening was carried out by evaluating acidic parameters, total free amino acids (FAA) concentration, in vitro protein digestibility (IVPD) and predicted glycemic Index (pGI). The evaluation of the total FAA and IVPD mainly allowed an in-depth investigation of the six breads on peptides, ammino acids profile and protein quality indexes. The findings demonstrated a greater digestibility resulting from the use of longer fermented sourdough in breads made with whole wheat, spelt and rye flours. In addition, the use of LAB strains selected for their high peptidase activity, the addition of fungal proteases and the fermentation at 37°C yielded breads with improved digestibility and protein quality nutritional indexes. In a second study, the digestibility of baked goods was also assessed after in vitro small intestinal digestion. Different processes of indirect fermentation, including sourdough “biga” fermentation, in the manufacturing of the popular Italian baked good Pinsa Romana was investigated through a simulated in vitro model (INFOGEST), which allows to evaluate the end-products of digestion that occurs in small intestine. Five Pinsa Romana made by indirect process (biga) and different fermentation times, and one Pinsa Romana made with direct process, were firstly mainly investigated for the in vitro digestibility and protein quality. The inclusion of sourdough in biga, according to the previous study, resulted in the lowest pGI, and in the higher content of peptides, FAA, protein efficiency ratio and nutritional index. Furthermore, the static in vitro simulation of food digestion, has allowed us to determine the relationship between nutritional characteristics and hydrolysis of macronutrients at small intestinal level. The digesta of Pinsa Romana made with biga including sourdough showed higher availability of sugars, representing the lower glycemic response. The sourdough generated high numbers of peptides, total FAA and compounds that are important for human health such as the essential amino acids, as a result of in vitro small intestinal digestion. Furthermore, the effect of fermented foods at the colon level on the gut metabolome, was investigated through a dynamic in vitro model (Simulator of Human Intestinal Microbial Ecosystem-SHIME®). In particular, fermentation with Weissella confusa A16 was used as sustainable tool to exploit food by-products, as brewer's spent grain (BSG), and to produce bread enriched with exopolysaccharides (EPS). Two fortified (rich in fiber-proteins) fermented BSG breads with (EPS+) and without (EPS-) the addition of sucrose, were analyzed through the SHIME ®model. The effect of exopolysaccharides synthesis on fermented BSG-based bread, was evaluate with the release of short chain fatty acids (SCFAs) and free amino acids from the gut microbiota ecosystem. The SCFAs concentration showed moderate deviations after BSG breads intake, but the presence of maltosyl-isomalto oligosaccharides (MIMO) in EPS+ bread was correlated with the release of butyric acid at the colon level. When SHIME ® was fed with bread containing dextran and MIMO, the individual FAA evaluation showed higher bio accessibility and lower metabolic waste products (NH3) in the fecal lumen. Here, we assessed the beneficial effect of a wide range of tailor-made leavened baked goods by improving their in vitro digestibility and functionality, investigating the consequences at the small intestinal level and at the colon site through in vitro models.