Antioxidant activity, antioxidant compounds, antioxidant and hydrolytic enzymes activities of 'Barhee' dates at harvest and during storage as affected by pre-harvest spray of some growth regulators

The response of antioxidant activity, antioxidant compounds concentration and antioxidant and cell wall hydrolytic enzymes activities of Bisir 'Barhee' dates at harvest and during storage (1 C +/- 1 and 90-95 RH) to pre-harvest spray of the plant growth regulators (PGR) naphthalene acetic acid (NM), gibberellic acid (GA(3)), benzyl adenine (BA) and salicylic acid (SA) at 50 and 100 ppm were evaluated. At 3 days before harvest, PGR treatments significantly delayed fruit maturation compared to the control treatment except for, the low rate of SA. PGR decreased total phenols concentration compared to control except for, NM and BA at low rate. PGR increased total flavonoids concentration compared to control except for, NAA at low rate. Antioxidant activity was higher especially at both rates of SA and NAA than control. Peroxidase activity was higher at PGR treatments than control. Catalase activity was higher at low rate of GA(3) and high rate of BA than control. Polygalacturonase activity was higher at both rates of NM and the low rate of GA(3) than other treatments. During storage, NM decreased Rutab percentage compared to other treatments, in contrast to SA and GA(3) at low rate. Rutab and weight loss percentage increased during 50 days of storage. PGR increased vitamin C concentration compared to control. Total phenols concentration was higher at the low rate of BA than other treatments. Total flavonoids concentration was higher at most PGR treatments than control. Soluble tannins concentration was higher at both rates of NM, low rate of GA(3), and high rate of BA than control. Total phenols and vitamin C concentration fluctuated during storage and was lower after 50 days than initial. PGR increased antioxidant activity compared to control. The highest antioxidant activity was at both rates of NM and GA(3). Antioxidant activity fluctuated with a decrease at 50 days of storage. Antioxidant and hydrolytic enzymes activities were inconsistent with dates ripening during cold storage. These enzymes greatly fluctuated but sharply decreased at 50 days of storage except for, xylanase. The possible correlations among these parameters were discussed. (c) 2014 Elsevier B.V. All rights reserved.