Fruit processing by the food industry generates large quantities of by-products rich in bioactive compounds, which might be used for other purposes. Nevertheless, much of the waste produced from fruit processing is discharged, creating environmental problems. A solution to minimize the environmental impact and add economic value to this waste is its use in the development of new foods with functional potential. At the same time, consumption of soy-based products is increasing, due to the health benefits caused by their consumption, as well as the need for new alternatives to milk, mainly because of lactose intolerance and nutritional option, as in the case of vegetarians. The benefits of soy may also be increased when the food product is fermented with probiotic microorganisms and supplemented with prebiotic fibers, leading to a synbiotic functional product. Thus, this project aims to develop a synbiotic fermented soy product added of fruit processing by-products and to assess the impact of this product on the composition and metabolic activity of the gut microbiota, using a model that simulates the intestinal conditions in vitro. Therefore, this project will be divided into three stages: (i) Obtaining the powdered by-products (peels and seeds) from orange juice and from mango and acerola pulps processing and evaluating them regarding their physical, chemical, and microbiological characteristics. Also in the first stage, 10 or more probiotic strains will be tested for their ability to deconjugate bile salts, for their proteolytic activity, and the fermentation capacity of the fruit by-products obtained. The fruit by-products and the two probiotic strains that show the best features will be selected to be used in the soy fermented product (FS) development; (ii) Development of the fermented soy product: for this purpose, a completely randomized factorial 23 type experimental design will be used, totalizing eight trials to be produced in triplicates, in which the tested factors will include the probiotic strains (X1 and X2) and the fruit by-product (X3), in two levels (presence or absence). The different formulations will be evaluated according to their microbiological, physico-chemical, and sensory features for up to 28 days of storage at 4 ºC. Moreover, the resistance of the probiotic cultures present in the various FS formulations and in pure culture to in vitro simulated gastrointestinal conditions at 1, 14, and 28 days of refrigerated storage will be evaluated. The four FS formulations with better results will be selected to be tested in the next stage of the project; iii) Evaluation of the impact of the FS formulations on the composition and metabolic activity of the intestinal microbiota in an in vitro model of the large intestine (TIM-2), which simulates the conditions of the proximal colon lumen. This stage will be conducted at TNO Nutrition and Food Research and at the Wageningen University (Zeist and Wageningen, the Netherlands). Samples will be collected from TIM-2 for the quantification of the probiotic microorganism, Lactobacillus spp, Bifidobacterium spp., and of total bacteria, through quantitative PCR (qPCR), using specific primers, and for the determinations of short-chain fatty acids, lactate, and ammonium, produced during the passage of the products through the intestinal tract model. The results will be evaluated, according to the experimental design proposed, using the statistical program Statistica.
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