Orientadora: Profa. Dra. Graciette Matioli

Data da Defesa: 02/12/2020

INTRODUCTION. The arrival of a population that looks for foods that are not only a source of energy and nutrients but also provide health benefits has driven the interest of researchers in discovering new foods that offer nutritional and functional properties, as well as a sensory quality. The most popular functional products are those with probiotics and prebiotics in their formulations, due to their potential to improve general health. However, for the probiotic microorganisms added to these foods to perform health benefits, they must survive not only the shelf life of the product but also the passage through the gastrointestinal tract. Thus, the joint incorporation of prebiotics consists of a way to increase the survival rate of these microorganisms. Inulin is a prebiotic ingredient found in several plants, such as Jerusalem artichoke and chicory. Its structure consists of a variable number of fructose units and usually contains terminal glucose. Inulin can have a protective effect on probiotic bacteria because it increases their survival and activity during storage, and passage through the gastrointestinal tract. Another type of prebiotic is represented by β-glucans, which are soluble fibers commonly found in algae, plants, yeasts, fungi, and bacteria. These ingredients are immunological stimulants and potent tumor antagonists. Among the β-glucans, succinoglycans are characterized as extracellular acidic heteropolysaccharides, which are synthesized by microorganisms such as Sinorhizobium and Agrobacterium. Succinoglycans are constituted by galactose and glucose monomers, present in the proportion of 1-7. Its structure also includes succinate, acetate and pyruvate as non-carbohydrate substitutes. Probiotic cultures are usually added to dairy products, such as fermented milk and yogurt. However, due to the high number of people with lactose intolerance, allergies to milk proteins, or who have opted for a vegetarianism/ vegan lifestyle, there is a growing demand for vegetable-based probiotic products. In this scenario, soy and rice represent great options to produce fermented beverages, the first one consists of a good source of proteins, dietary fiber, minerals, and vitamins, while the second offers nutrients and energy.
OBJECTIVES. The purpose of this work was to elaborate a soy and rice-based fermented beverage, incorporated of Lactobacillus paracasei, and to evaluate, in four formulations, the effect of the inulin and oligosaccharides addition from commercial succinoglycan enzymatic hydrolysis, in relation to physicochemical properties, texture, rheology, syneresis, microbiological risk, phenolic compounds and probiotic viability. The analyses were performed during the 28 days of storage under refrigeration at 5 ºC.
MATERIALS AND METHODS. The oligosaccharides were produced by hydrolysis of commercial succinoglycan through the enzyme Viscozyme. The size of the oligomer chain was estimated as the ratio of glucosyl monomer concentration divided by the concentration of the reducing end of the molecule. For the production of the fermented beverage, a water-soluble soy and rice extract was produced at a ratio of 70:30, respectively. Subsequently, four formulations were elaborated from the previously prepared extract: I. Control (without the addition of prebiotics); II. Inulin (3.5% of inulin); III. Succinoglycan (0.5% of succinoglycan oligosaccharides) and IV. Mix (3.0% of inulin and 0.5% of succinoglycan oligosaccharides). The formulations were stored for 28 days at 5 ºC and analyzed for pH, titratable acidity, total soluble solids, water activity (Aw), instrumental color, syneresis, microbiological risk, phenolic compounds, texture, rheology, and probiotic viability.
RESULTS AND DISCUSSION. Succinoglycan oligosaccharides were obtained with an average degree of polymerization (DP) of 8. Regarding the physicochemical analyses, all the formulations presented a reduction of the pH values, with a proportional increase of the titratable acidity during the storage. This behavior was associated with post-acidification of the product due to the production of organic acids resulting from the fermentation of carbohydrates by starter culture microorganisms and probiotics. The addition of prebiotics to the formulations reduced the amount of total soluble solids due to the partial replacement of sucrose with inulin and succinoglycan oligosaccharides, ingredients with larger and therefore less soluble chains. The added prebiotics to the formulations did not cause a sufficient increase of solutes to decrease the water activity and thus reduce the metabolism of microorganisms. The addition of inulin and/or succinoglycan oligosaccharides affected the coloring of the formulations, which showed to be slightly yellow-greenish. These changes were attributed to the presence of pigments in the raw material, the addition of prebiotics and also to variations in storage time and pH.
The incorporation of succinoglycan oligosaccharides increased the firmness, cohesiveness, consistency, and viscosity of the formulations. On the other hand, the addition of only inulin to the formulation resulted in texture parameters similar to the formulation without prebiotics, showing the low viscosity of this ingredient. As for rheology, all the formulations presented non-Newtonian behavior and were characterized as pseudoplastic fluids, in other words, fluids whose apparent viscosity decreases with the increase in the deformation rate.
The formulations supplemented with succinoglycan oligosaccharides showed reduction of syneresis. The higher viscosity observed in these formulations is an indication that they presented greater hydration potential, which contributed to the reduction of this property. On the other hand, the addition of only inulin to the formulation was not able to reduce the syneresis.
The incorporation of inulin increased the content of phenolic compounds, while the addition of succinoglycan oligosaccharides reduced this attribute. Overall, the formulations showed an increase in phenolic compounds with the storage, and these variations were related to the molecular interactions between these compounds and the food matrix, as well as the dietary fibers.
No formulation presented microbiological risk during the evaluated period. As for probiotic viability, all formulations maintained viable Lactobacillus paracasei cell counts above 108 CFU mL-1 during 28 days of storage, indicating that the food matrix provided the necessary nutrients to ensure survival of the microorganism until the end of the study. However, after exposure to simulated gastrointestinal conditions, only the formulations added with inulin and/or succinoglycan oligosaccharides showed probiotic cell counts in sufficient amounts to provide health benefits. This result highlighted the importance of supplementing this type of product with prebiotic ingredients.
CONCLUSION. The fermented beverage produced in this study proved to be an excellent functional food option for people seeking alternatives to dairy beverages, as it adds the nutrients present in soy and rice to the benefits resulting from the addition of the microorganism with probiotic functions and also to the positive results of supplementation with inulin and succinoglycan oligosaccharides. Furthermore, it is an innovative product that can collaborate with the food industry in meeting the aspirations of the population with regards to functional foods.
Keywords: Fermented beverage, succinoglycan oligosaccharides, prebiotic, inulin, probiotic.

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