A Study on Structure (Micro, Ultra, Nano), Mechanical, and Color Changes of Solanum lycopersicum L. (Cherry Tomato) Fruits Induced by Hydrogen Peroxide and Ultrasound

Changes in the epidermis structure (micro, ultra, and nano), mechanical properties, and surface color of Solanum licopersicum L. fruits (cherry tomatoes) due to hydrogen peroxide (HP) and high-power ultrasound (US) treatments were examined. Both treatments induced small alterations in the epicuticular waxes, the cuticular membrane, and the epidermal and subepidermal cells. Plasmolysis of subepidermal cells, slight epicarp compression, and dense cellulose microfibrils pattern in the non cutinized cellulose layer were documented after US. Looser cellulose microfibrils pattern in the cutinized and non cutinized cellulose layer was detected after HP exposure. Main nanostructure alterations in the cellulose domain affected the morphology and size of cellulose aggregates and nanofractures of cellulose layer in treated fruits. US treatment decreased a*, b*, and chroma values by 10, 5, and 7% and increased L* and hue angle by 2.5 and 3%, respectively, as compared to raw fruits. These small but significant differences were attributed to the disruption of the wax layer; color became brighter, more vivid, and more orange. Treatments slightly affected puncture parameters; the rupture force decreased from 14.8 N to 14.1 N and 13.8 N; the penetration probe at the rupture point increased from 7.6 mm to 7.7 mm and 8.0 mm and the mechanical work decreased from 48.7 mJ to 48.3 mJ and 44.4 mJ in raw fruits and after HP and US exposure, respectively. The mechanical response could be partially explained by the alterations in the micro, ultra, and nanostructure of the tissues. The low impact of US and HP treatments on mechanical and color characteristics would indicate their potential for cherry tomatoes decontamination.