Broccoli (B. oleracea L. var. italica cv. Chaoda No. 1) heads were hand-harvested from a local commercial farm in Nanjing, China. The heads of broccoli were placed on ice and carried back to the laboratory within 4 h of harvest. Broccoli heads were selected for uniform size, colour and absence of mechanical damage, and then randomly divided into three groups of 30 head each and subjected to following treatments