Effect of cooking methods on total phenolic and carotenoid amounts and DPPH radical scavenging activity of fresh and frozen sweet corn (Zea mays) kernels

We evaluated the effect of three different cooking methods on antioxidant content and radical scavenging activity of sweet corn. Both fresh and frozen sweet corn kernels were boiled, microwaved, and stir-fried for 1, 3, and 5 min, respectively, then total phenolic (TP) and total carotenoid (TC) contents were determined by spectrophotometric methods. The free radical scavenging activity of the samples was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The results showed that there was a significant increase in TP (1.2-1.9 times) and TC (1.1 to 1.8 times) content of fresh sweet corn after each cooking session for 1, 3, and 5 min, the same treatment of frozen corn resulted in 47-80% losses of TP and 10 to 39% losses of TC content. The free radical scavenging activity (RSA) exhibited by cooked fresh and frozen sweet corns was found to be different, neither of them was very high, in the range of 70.2-78.6%, and the fresh cooked ones had higher values of RSA.