Application of vacuum and convective drying processes for the valorization of Pisco grape pomace to enhance the retention of its bioactive compounds

Abstract

Abstract Purpose Pisco grape pomace is a waste product from the pisco industry, and their research is minimal compared to other wastes. However, in recent years, with the growing interest in reducing the environmental impact and converting these residues into novel by-products, the research, and their evaluation in each stage can contribute significantly to ensuring their recovery. This study evaluated the kinetics of vacuum and convective drying from grape pomace at different temperatures and the influence on the retention of polyphenolic compounds and antioxidant activity, as scalable alternatives for agro-industry. Methods Liquid chromatography and spectrophotometry were used for polyphenols profile characterization and antioxidant activity evaluated. Results The best drying grape pomace process was vacuum drying at 60 °C with a short drying time (210 min), and diffusivity values were higher (6.64 x 10-10 m2s-1) than those obtained by other drying conditions. The model that best fits the experimental data was the Midilli Kucuk model. Vacuum drying at 60 °C obtained the highest content of polyphenols and flavonoids, and significant antioxidant capacity was obtained. The gallic acid, 4-hydroxybenzoic acid, catechin, epicatechin and rutin were found in grape pomace. Conclusions To preserve the bioactive compounds in pisco grape pomace and reduce energy costs, vacuum drying at 60 °C is an attractive alternative to revalue this waste, maintain the bio-compounds, and reduce drying times. The results of this study will contribute to the careful and efficient use of this residue, which in the future can have commercial value due to the biological properties of its bioactive compounds present.