Sulfur dioxide generating pads containing different concentrations of sodium metabisulfite maintains postharvest quality of ‘Hicaznar’ pomegranate

Abstract

This study investigated the effects of different sulfur dioxide (SO2) generating pads containing different concentrations of sodium metabisulfite (Na2S2O5) on the storage of ‘Hicaznar’ pomegranate fruit. For this purpose, the pomegranates were harvested at optimal harvest maturity (total soluble solids (TSS): 17.70 %, titratable acidity (TA): 1.57 % citric acid). The first, second and third groups were treated with SO2 generating pads containing different concentrations of Na2S2O5 (1.5, 3.0 and 4.5 g). The fourth group was control which received no treatment. The SO2 generating pads were placed on top of the fruit with butter paper containing holes were kept between the fruit and pads. All the treatments were packaged under modified atmosphere packages (MAP) and stored at 6 °C and 90–95 % relative humidity (RH). The fruit samples for quality analysis were taken at 45, 90, 120, 150 and 180 days (d) of cold storage (CS). Post removal, the samples from each treatment were kept at 20 °C for additional 3 d to determine shelf life (SL) performance of fruit. Extending storage duration showed increase in weight loss, h° values, total flavonoid content, carbon dioxide (CO2) levels and decay index while decrease in L*, C* values, appearance and taste scores, TSS content, TA, total phenolic content, total antioxidant activity, total anthocyanin, ascorbic acid, organic acids (citric, malic, succinic and oxalic acids) contents, phenolic compounds (gallic, protocatechuic and chlorogenic acid), oxygen (O2) levels and SO2 production in MAP. SO2 generating pads reduced weight loss and decay index. The highest taste value was recorded in 3.0 g SO2 generating pads. The highest h° value was in 1.5 g SO2 generating pads while the greatest total anthocyanin content in CS was in 3.0 and 4.5 g with maximum total anthocyanin content in SL was recorded in 1.5 and 4.5 g SO2 generating pads. SO2 generating pads exhibited maximum total phenolic content, total antioxidant activity and gallic acid content as compared to control. There were no SO2 residues in pomegranate arils throughout the storage. It can be concluded that SO2 generating pads can be a potential tool to preserve the postharvest quality of ‘Hicaznar’ pomegranate for 180 d of CS.