Hydrothermal treatment minimizes the effects of refrigeration in okra fruits

ABSTRACT This study evaluated the involvement of peroxidase and polyphenoloxidase on the enzymatic browning of okra and the role of catalase in the appearance of chilling injury in cultivars Amarelinho and Mammoth Spineless treated with hot water. Okra fruits from two cultivars were immersed in water at 40°C, during 15 and 30 minutes. The control treatment was not immersed, and all fruits were stored at 5°C. Visual analysis of fruits was carried out and total chlorophyll content and total phenolic compounds were determined. The activity of the enzymes catalase, peroxidase and polyphenoloxidase was analyzed. In all treatments, the cultivar Mammoth Spineless showed higher values of chlorophyll content and soluble phenolic compounds compared to cultivar Amarelinho. For both cultivars, catalase activity was higher at the last days of storage, regardless if the fruits were immersed or not in hot water. However, the catalase activity was higher in ‘Mammoth Spineless’, which presented the higher tolerance to chilling injury. The fruit skin browning was coincident with the increase on polyphenoloxidase activity and phenolic compounds content. This relationship was not observed for the peroxidase activity. The heat treatment during 15 minutes increased the length of storage of cultivar Amarelinho, and for 30 minutes of the cultivar Mammoth Spineless.