Total phenolics, ascorbic acid, and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder as affected by illumination during storage

摘要

Total phenolics, ascorbic acid, and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder were determined during storage at 24 ℃. After 2 weeks of storage, illuminated noni juice lost 32% of total phenolics, 89% of ascorbic acid, and 46-65% of antioxidant capacity-about 8%, 22%, and 9-15% more than unilluminated juice. Both illuminated and unilluminated juice lost 97% of ascorbic acid by 4 weeks. The difference in antioxidant characteristics between illuminated and unilluminated juice became insignificant at 12 weeks. After 12 weeks, illuminated noni powder lost 21% of total phenolics, 17% of ascorbic acid, and 23-36% of antioxidant capacity-about 13%, 4%, and 7-19% more than the unilluminated powder. Noni powder in brown bottles retained antioxidant characteristics significantly greater than that in clear bottles. Protection from light effectively reduced degradation of antioxidant characteristics of noni juice for only 2 weeks but those of noni powder for at least 3 months.