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.