Changes of anthocyanins and residual ethylene of table grapes with color promotants treated

Abstract

Different color-promoting treatments were tested on table grape cv. “Flame Seedlees” to evaluate changes on flavonoids such as anthocyanins and the residual ethylene produced. Treatments were spray-applied at the onset of veraison. The control was Ethrel at 250 ppm (ETH), Salicylic Acid at 100 ppm (AS), Melatonin at 25 ppm (MEL) and 1:1 mixtures of ETH+AS, ETH+MEL and AS+MEL. The trials were conducted in triplicate after harvest, measuring Total Soluble Solids (% TSS), total acidity (% tartaric acid), pH, residual ethylene (ppm) and anthocyanin content (mg∙cm-2). It was found that treatments ETH, AS, MEL and ETH+AS reached 16% TSS, standing out with lower values ETH +MEL (14.27%) and AS+MEL (15.17%) (p ≤ 0.05). ETH reached 0.83 ppm of residual ethylene, while a sum effect was appreciated in ETH+AS (0.5 ppm) and ETH+MEL (0.35 ppm), but not beneficial as it did not reflect quality characteristics. Only differences (p ≤ 0.05) in anthocyanin content were recorded between ETH (0.019 mg∙cm-2) and AS+MEL (0.003 mg∙cm-2). The subjective color of the grape bunches in the field made it possible to relate it to the objective results of the analyses performed. This research provides commercially important information on the substitution of Ethrel by natural compounds such as AS and MEL, as they show similar effects on the quality of “Flame Seedless” table grapes. In addition, these compounds do not have an ethylene residual greater than 0.2 mg/kg.