Produção de farinha nutricional e proteica via processo de cultivo microbiano a partir da casca e Semente da Uva Isabel

Abstract

The skins and seeds (pomace) of grapes are a source of bioactive compounds with antioxidant properties beneficial to health. However, this pomace is often wasted. Its use as a substrate in solid-state fermentation (SSF) emerges as a promising strategy for its reuse, enhancing its bioactive compounds and transforming it into a nutritious food. This study aimed to produce flour from Isabel grape skins and seeds, nutritionally and protein-enriched through a microbial cultivation process. The fresh grape pomace was characterized in terms of chemical composition, total phenolic compounds (TPC), and antioxidant activity (AA) using the ABTS method. The kinetics of protein enrichment were analyzed to identify the conditions that provided the highest increase in protein in the fermented medium, followed by a drying process in a fixed bed at 70°C until obtaining the fermented flour. Protein enrichment of the grape pomace was conducted at 30°C, relative humidity of 70%, and with Saccharomyces cerevisiae yeast concentrations of 3% and 6%. The highest protein production was observed with a 3% yeast concentration and a fermentation time of 2 hours, resulting in a 1.8-fold increase in protein compared to time zero. The fermented flour was characterized for total phenolic compounds and antioxidant activity. The reduction in TPC in the natural pomace compared to the fermented one, respectively, (1810.28 ± 37.6 to 1446.81 ± 35.5 mg GAE.100g⁻¹) can be attributed to enzymatic action and extrinsic factors. The further reduction in TPC and AA between the wet and dried fermented samples (1446.81 ± 35.5 to 1012.41 ± 12.5 mg GAE.100g⁻¹ and 408 ± 1.54 to 287 ± 1.50 μM TEAC.100g⁻¹, respectively) may be related to the sensitivity of the biocompounds to temperature or the formation of new compounds with lower antioxidant capacity. Nevertheless, the fermented grape pomace flour still maintains a high concentration of bioactive compounds, preserving more than 55% of the initial value (natural pomace). This result highlights its potential for use in the formulation of new food products as a functional ingredient, considering its rich nutritional composition.