Production of antioxidant pectin fractions, drying pretreatment methods and physicochemical properties: towards pisco grape pomace revalue

Grape pomace is a high potential by-product due to its content of valuable compounds, such as pectin. It is highly perishable and requires pretreatment for its conservation. Therefore, this work aims to evaluate the effect of four drying methods: convective drying, freeze-drying, infrared-radiation drying, and solar drying, on the properties of pectin fractions obtained from pisco grape pomace. Freeze-drying and convection drying reported the highest extraction yields. The drying of grape pomace by all the methods evaluated decreased the degree of esterification on the pectins. The highest reducing sugar content (19.8%) and antioxidant capacity (7238 µmol TE/100 g d.m.) were obtained from freeze-drying pretreatment. The highest galacturonic acid content (28.4%) and molecular weight (63.3 kDa) were found in the pectin obtained from the convective drying pretreatment. Thus, each drying method evaluated affects the pectin’s physicochemical properties differently. Also, pectin fractions with a high degree of methoxylation and a high antioxidant capacity were obtained from pisco grape pomace. This study provides information about the effect of drying as a pretreatment of pisco grape pomace on the properties of the pectin obtained from it.