Applying pectin coatings enriched with antioxidant compounds as pre-treatment for kiwi ( Actinidia deliciosa ) drying process

One of the main drawbacks of drying fruits is the degradation of their quality by oxidative processes. In this study, antioxidant pectin coatings were prepared and applied onto kiwi slices before the drying process to evaluate their effect on drying kinetics, on maintaining nutritional quality and antioxidant capacity of the cut fruit, and during 31 days of storage. Pectin antioxidant coating formulations have been developed by adding antioxidant extracts from fruits or antioxidant acids. Uncoated dehydrated fruits and those coated with pectin without antioxidants were used as control. Convective drying was carried out, desorption isotherms (30, 50 and 60°C) and drying kinetics (50 and 60°C) were analyzed, and the obtained experimental data were adjusted to the GAB and Page models, respectively. The dried kiwi slices were evaluated for their retention of antioxidants (vitamin C and phenolic compounds), total antioxidant activity (DPPH), mechanical properties, and color. The coatings had a slight influence on the isotherms and drying kinetics at the studied temperatures, mainly for the one performed at 30°C. However, the drying rate at 60°C decreased more rapidly and the Page model fit well with the experimental data. The antioxidant coatings preserved the thermosensitive compounds during drying, and formulations with the acerola extract and antioxidant acids may be highlighted since, in addition to the antioxidant effect, they also nutritionally enriched the kiwi slices. Thus, the proposed methodology is a promising technique to reduce the oxidative effects inherent in the drying and storage processes.