Vegetable matrices as potential carriers for probiotic bacteria viability

Resumen

According to the Hippocrates´ aphorisms (460-370 BC) “Let food be your medicine and medicine be your food” and “All diseases begin in the gut”, nowadays, scientists studying the human microbiome suggest that healthy diets should include fermented foods to transiently strengthen living microbes in our gut. As a result, fermented food has gained popularity and consumers demand this type of food. However, most commercial probiotic foods in the market are dairy fermented foods and certain sectors of the population such as those allergic to milk proteins, strictly vegetarian and lactose intolerants, cannot consume them. Therefore, the need arises to explore new non-dairy matrices as carriers of probiotics to offer consumers an alternative to fermented dairy products. However, the use of probiotic cultures in alternative food matrices remains a critical problem because it could represent a major challenge for probiotic viability. Therefore, careful selection of food matrices as probiotic carriers is an essential factor in the development of probiotic foods to ensure a high viability of probiotics to reach the large intestine. Accordingly, the main objective of the PhD Thesis was to determine the influence of different vegetable matrices (polymeric matrices and beverages) as potential carriers for probiotic bacteria in order to ensure their viability in the range of 106-107 CFU/mL or g of food at the consumption time, to reach the large intestine in high amounts. The following aspects have been also investigated as part of the specific objectives: probiotic viability during manufacturing, storage and under gastrointestinal in vitro digestion, the synergistic effect of prebiotics and probiotics, the fermented beverages physicochemical parameters, antioxidant properties, sensory acceptance, and biotransformations of the phenolic compounds, and the influence of fruit juices as probiotic carriers on the ability of a probiotic strain to improve in vitro epithelial intestinal barrier integrity and the microbial intestinal adherence and potential cytotoxic effect to Caco-2 cells. The results demonstrated that the probiotics studied were able to grow and survive during fermentation and manufacturing, remaining above the recommended concentrations during storage and under gastrointestinal in vitro digestion conditions in the different vegetable matrices. However, significant differences were observed in the probiotic viability in the polymeric and beverage matrices. The growth, survival and the lactic acid production of the probiotic bacteria were strongly dependent of the chemical characteristics of the beverages; Inulin was metabolized by probiotics when the monosaccharides were at limited concentrations in the beverages during the fermentation and storage. The prebiotic effect of inulin on probiotic survival during in vitro gastrointestinal digestion was mainly observed after long periods of storage. The fermentation of vegetal beverages with different probiotic bacteria led to the biotransformation of phenolic compounds, suggesting a possible prebiotic effect of these phenolic compounds during the fermentation period and under the gastrointestinal in vitro digestion process. At the same time, the probiotic functional properties were strongly influenced by the different fermented matrices.