Effect of Blanching Time on Total Phenolic, Antioxidant Activities and Mineral Content of Selected Green Leafy Vegetables

Effect of blanching time in hot water (0, 5, 10 and 15 min) was carried out on six green leafy vegetables popularly consumed in Nigeria namely; Cnidoscolus asconitifolius, Talinum triangular, Celosia argentea, Amaranthus hybridus, Vernomia anygdalina, and Telfaria occidentalis. The dry matter, total phenolic content, antioxidant activity and mineral content of the green leafy vegetables were analyzed. Blanching at temperature of 90°C and different times decreased the dry matter content of the vegetables; 5 min blanching significantly (p > 0.05) increased the total phenolic (280.6 – 980.6 mgGAE/100 g db) and antioxidant activity (25.1 – 95.1 mg/100 g Trolox equivalent) in all the vegetables. However, further increase in the blanching time caused a significant reduction in total phenolic content, antioxidant activities and mineral content of all the vegetables. With these results, it could be concluded that blanching time for these vegetables should range between 1 to 5 min to prevent the loss of health benefiting compound present in them.