Structure (micro, ultra, nano), color and mechanical properties of Vitis labrusca L. (grape berry) fruits treated by hydrogen peroxide, UV–C irradiation and ultrasound

Abstract

Main structural (micro, ultra, and nano) alterations occurred in the outer tangential epidermal cell wall of Vitis labrusca L. fruits (grape berry) due to hydrogen peroxide, UV–C irradiation and ultrasound treatments were examined, and described using light microscopy, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Changes in mechanical properties and surface color were also evaluated. In general, decontamination treatments caused epicuticular wax pattern alteration, epicarp disruptions, cell plasmolysis, and mesocarp collapse. Major observed ultrastructural and nanostructural changes were increased demarcation between cellulose layer and cuticular membrane, alteration of cellulose aggregates pattern, and presence of nanofractures, variables in shape and size. All treatments, mainly ultrasound, provoked significant but small differences in color parameters compared to untreated fruit. On contrast, mechanical properties determined by puncture test did not vary.