Postharvest trans-resveratrol and glycine betaine treatments affect quality, antioxidant capacity, antioxidant compounds and enzymes activities of 'El-Bayadi' table grapes after storage and shelf life

The effect of exogenous trans-resveratrol (1.6 x 10(-5) M, 1.6 x 10(-4) M and 1.6 x 10(-3) M) and glycine betaine (GB) (10, 15 and 20 mM/L) treatments on quality, antioxidant capacity, antioxidant compounds and enzymes activities of 'El-Bayadi' table grapes after 30 days of cold storage plus 2 days of shelf life were evaluated. trans-resveratrol especially at medium and high rates decreased decay after storage compared to control. GB, only at the high rate, decreased decay. Weight loss was higher at the low rate of trans-resveratrol than control. However, GB had no effect on weight loss. TSS, acidity and pH slightly changed during storage and were not affected by trans-resveratrol and GB. Firmness decreased after storage compared to initial, but was higher at trans-resveratrol and GB treatments than control. Both trans-resveratrol and GB retained higher total phenols concentration after storage than control. The high rate of trans-resveratrol and GB retained higher total flavonoids concentration than control. Vitamin C concentration was not affected by the applied treatments. Both trans-resveratrol and GB increased peroxidase (POD) and polyphenoloxidase (PPO) activities compared to control. Polygalacturonase (PG) activity greatly decreased by trans-resveratrol treatments. Xylanase activity increased by the medium rate of trans-resveratrol and the high rate of GB. Antioxidant capacity measured by DPPH assay decreased after storage in control compared to initial, but was higher at trans-resveratrol than other treatments. GB at low rate showed higher antioxidant activity than control. Also, antioxidant capacity measured by ABTS assay decreased after storage in control compared to initial, but was higher at the high rate of trans-resveratrol than other treatments. It is concluded that exogenous trans-resveratrol and GB treatments retained quality of 'El-Bayadi' table grapes after cold storage and shelf life and being suggested as natural alternatives to synthetic chemicals. (C) 2015 Elsevier B.V. All rights reserved.