Micronização como alternativa para valorização do bagaço de uva: caracterização e aplicação em snack extrusado

Abstract

Grape pomace, the winemaking by-product, is characterized by a significant amount of dietary fiber and phenolic compounds. Most of these compounds are associated with the fibrous matrix. Physical modifications, such as micronization, have been used to modify the functionality of dietary fiber by caused by the breakdown of its polymeric constituents. Because it is underused by the wine industry, there is growing interest in its use. Few studies evaluate the effect of incorporation of micronized ingredients in food products as well as their influence on in vitro digestibility. Therefore, the aim of the present study was to evaluate the effect of micronization on the physicochemical properties of dietary fiber from grape pomace in order to enhance the functional properties of an extruded product. The effects of micronization of grape pomace and its fiber concentrate on dietary fiber fractions, physicochemical properties, phenolic compounds, and antioxidant capacity were evaluated. Factorial design with two independent variables (22) – speed and time – was used to determine the best milling conditions to increase the soluble fiber content. The insoluble fiber constituents, such as cellulose and lignin, were partially degraded and the content decreased after milling, resulting in higher soluble fiber content, which demonstrates the compound redistribution. Micronization had a significant effect on reducing the particle size, as evidenced by scanning electron microscopy. FT-IR spectra revealed changes in typical absorption bands of polysaccharides. After milling, powder solubility increased and water holding, oil and cation binding capacities decreased. Furthermore, micronization enhanced phenolic compound extraction, mainly catechin and epicatechin, and the antioxidant capacity evaluated by ABTS and ORAC assays. The results obtained indicate that micronization modifies the dietary fiber composition of grape pomace, increasing possibilities for use as a functional ingredient in the food industry. In this way grape pomace and micronized grape pomace were added to an extruded product. Physicochemical, technological and sensory characteristics, including phenolic and anthocyanin content, antioxidant capacity, and in vitro starch digestibility, were evaluated. The addition of grape pomace influenced the expansion ration, bulk density, and water absorption and solubility indexes. Regarding the composition, total, insoluble and soluble fiber content increased in fortified formulations. The inclusion of grape pomace and micronized grape pomace increased the total phenolic content, total monomeric anthocyanin and, consequently, the antioxidant capacity (ABTS and ORAC assays). The color and flavor attributes had the highest scores at the sensory analysis. The in vitro starch digestibility showed an increased in resistant starch fraction with addition of grape pomace and micronized grape pomace, which had lower glycemic index. The results demonstrate that the extruded products fortified with grape pomace and micronized grape pomace have interesting technological and functional characteristics, and could be considered as promising ingredients for using in the food industry.