Free-radical-scavenging activity and total phenols of noni (Morinda citrifolia L.) juice and powder in processing and storage

The fresh juice of nom (Morinda citrifolia L.), a tropical plant used as a folk medicine in Pacific islands, possessed free-radical-scavenging activity (RSA), 1,1-diphenyl-2-picrylhydrazyl (DPPH), at 140 mg equivalent ascorbic acid/100 ml and total phenols at 210 mg gallic acid/100 ml. Fermentation of nom fruit for 3 months resulted in a loss of more than 90% of RSA. Dehydration at 50 degrees C produced a loss of 20% of RSA. Storage of fresh noni juice at 24 degrees C for 3 months reduced RSA more than 90%. Storage of nom juice or powder at -18 degrees C and 4 degrees C for 3 months decreased RSA by 10-55%. The reduction of RSA of nom Juice or puree during heat treatment or dehydration was much greater than reduction of total phenols. For maintenance of the substantial antioxidant properties of noni products, processing of nom powder or fresh frozen noni juice rather than fermented noni juice is recommended. (c) 2006 Elsevier Ltd. All rights reserved.