EFFECT OF POSTHARVEST PUTRESCINE APPLICATION AND CHITOSAN COATING ON MAINTAINING QUALITY OF TABLE GRAPE CV. “SHAHROUDI” DURING LONG-TERM STORAGE

ABSTRACT The role of postharvest application of putrescine (PUT) alone or in combination with chitosan (CH) on maintaining quality of fresh table grapes (Vitis vinifera) cultivar “Shahroudi” was investigated. The clusters were dipped in an aqueous solution containing different concentrations of PUT (0, 1 and 2 mM). Following PUT treatments, some fruits were coated with 1% w/v CH. After treatment, fruits were stored at 0 ± 1C and 90 ± 5% relative humidity for 60 days and 5 additional days in evaluation room. The general appearance of rachis and berries and some physiological characters were estimated. The combination of 1 mM PUT and 1% CH reduced the weight loss, decay incidence, browning, and berry shattering and cracking. Postharvest PUT-treated berries (1 and 2 mM) exhibited higher total phenolic content, catechin, total quercetin and antioxidant activity and the lower quercetin 3-galactoside as compared with other treatments. PRACTICAL APPLICATIONS Table grape is a nonclimacteric fruit with a low physiological activity, but is subject to serious physiological disorders, water loss and fungal deterioration during postharvest handling. Stem browning and gray mold infection caused by the fungus Botrytis cinerea are the two main factors which reduce table grape postharvest quality. Recently, biologically active natural products have started to become an effective alternative to synthetic fungicides in maintaining fruit quality during storage. Chitosan coating has been reported to enhance disease resistance against many fungal diseases, when applied as either a preharvest or postharvest treatment. Polyamines (PAs) are also biological compounds with low molecular weight that are ubiquitous in living organisms. PAs have been reported as anti-senescence agents, the main effects in fruits being retarded color changes, increased fruit firmness, delayed ethylene and respiration rate emissions, induced mechanical resistance.