CHANGES IN ANTIOXIDANT ACTIVITY OF FERMENTED FISH SAUCE (NAM PLA-RA) FROM OSTEOCHILUS HASSELTII DURING FERMENTATION

The objective of this study was to determine the changes in antioxidative activities of fermented fish sauce (Nam Pla-ra) from Osteochilus hasseltii at various fermentation times. A 5 kg of fish was mixed with salt at a ratio of salt to fish of 1:4 (w/w) and packed in a plastic bag. After 1 day of fermentation, rice bran (4%) was added to the mixture and fermented under ambient conditions in a plastic bag for up to 12 months. Samples were collected at 0, 6, 9, and 12 months for antioxidant activity and chemical composition analysis. The results showed that protein content of Nam Pla-ra at 12 months of fermentation had the highest, followed by Nam Pla-ra at 9 months with protein levels of 7.82 +/- 0.72% and 6.94 +/- 0.61%, respectively. The ABTS radical scavenging activity of Nam Pla-ra at 9- and 12-months were comparable but higher than that at 6-months. The 12 month-old Nam Pla-ra exhibited the highest ferric reducing antioxidant power (FRAP) value of 1.02 +/- 0.068 mg Trolox equivalents/ml sample. The highest metal chelating activity was observed in the 9-month-old Nam Pla-ra (0.17 +/- 0.014 mg EDTA equivalents/ml sample). While 6- and 9-month old Nam Pla-ra showed the highest hydroxyl radical scavenging activity. Nam Pla-ra at 9-months fermentation time contained peptides with molecular weights of around 1,537-579 and 410 Dalton. Based on these results, it is recommended that people consume Nam Pla-ra from Osteochilus hasseltii at a 9-month fermentation time because of its high nutrition and antioxidant properties.