Effects of chitosan-zinc oxide nano coating supplemented with bergamot essential oil on postharvest shelf life of table grapes (Vitisvinifera L., Red Globe)

Abstract

In current study, the effect of various coating formulations such as control (glycerol+acetic acid+distilled water); chitosan (CH) (glycerol+acetic acid+CH 1%); CH-Nano-ZnO (chitosan+Nano-ZnO (1%)); CH-Nano ZnO-EOs (Essential oils) (CH-Nano-ZnO+EOs (1%)) were investigated on postharvest physiological characteristics such as weight loss, browning index, enzymatic activity, microbiological, phenolic acid and total phenols of table grape fruits during the storage at 25 °C with an RH of 40–60% for 16 days. The effects of coating treatments were performed at 0, 4, 7, 14 and 16 days of storage. The application of CH-Nano ZnO-EOs coating was most significant to retarded the weight loss (6.12%), least browning (1.37). O2 concentrations in the control samples decreased slightly (8.45 kPa), Chitosan reached (11.01 kPa), CH-Nano ZnO was (11.07 kPa), and CH-Nano ZnO-EOs was (12.35 kPa). CH-Nano ZnO-EOs samples reached (14.88 mg CO2 · kg−1h−1) then CH-Nano ZnO-EOs showed the lowest values (11.35 mg CO2 · kg−1h−1) on 16 days of storage. Chitosan treatment did not effectively enhance the antimicrobial activities compared with nano-coatings. The lowest count for mold and yeast was detected in the CH-Nano ZnO-EOs coating treatment (49.45 CFU/ml). CH-Nano ZnO-EOs treatment recorded the highest phenolic acid contents; 9.98 μg−1FW for P-Coumaric Acid, 3.96 μg−1FW for Ferulic Acid, 5.70 μg−1FW for Gallic Acid, 1.35 μg−1FW for Coffeic Acid, and 11.73 μg−1FW for Reseratrol. The highest total phenol value was for CH-Nano ZnO-EOs 2.15 mg g−1FW followed by CH-Nano ZnO 2.05 mg g−1FW. The results showed that the nano-coating film with the addition of essential oil can extend the shelf life.