On the Biochemical and Physiological Responses of ‘Crimson Seedless’ Grapes Coated with an Edible Composite of Pectin, Polyphenylene Alcohol, and Salicylic Acid

The ‘Crimson seedless’ grape encountered several difficulties during shelf life, including weight loss, rachis browning, and berry shattering. The effect of exogenous pectin (PE) and polyphenol alcohol (PVA) with supporting salicylic acid (SA) at different concentrations (0, 1, and 2 mM) was applied. The coating was applied to bunches for 5 min and stored at room temperature (26 ± 1 °C and RH 65 ± 3%) for 4 days. In this study, postharvest application of PE + PVA-SA can significantly reduce the cell wall degradation enzyme activities of ‘Crimson seedless’ grape during shelf life. ‘Crimson seedless’ bunches, treated with PE + PVA-SA 2 mmol L−1, had a lowered rachis browning index (RB index), weight loss (WL%), and berry shattering percentage (BS%) and preserved berry color hue angle (ho) compared to untreated bunches during shelf-life duration. Moreover, the PE + PVA-SA 2 mM improved berry firmness (BF) and removal force (BRF). It also improved the soluble solid content (SSC%), titratable acidity (TA%), and SSC: TA-ratio, for assessing berry maturity. The cellular metabolism enzyme activities (CMEAs) of the cell wall such as polygalacturonase (PG), cellulase (CEL), xylanase (XYL), and pectinase (PT) were minimized by applying PE + PVA-SA 2 mM coatings throughout storage duration. The accumulation of malondialdehyde (MDA) and cell wall damage, as well as the electrolyte leakage percentage (EL%), was reduced. PE + PVA-SA 2 mM maintained DPPH radical quenching activities and minimized O2− and H2O2 production rates. Collectively, these findings suggest that PE + PVA with the presence of SA as a coating treatment preserved ‘Crimson seedless’ bunches during shelf life. PE + PVA-SA 2 mM might be at least partially ascribed to the enhancement of bunches’ quality traits as well as inhibiting cell wall damage during the shelf-life period.