The effect of temperature and time on the quality of naturally fermented marula (Sclerocarya birrea subsp Caffra) juice

This paper presents the effects of fermentation on the retention of vitamin C, total polyphenols and antioxidant activity in the naturally fermented marula juice. The fermentation conditions have been varied: temperature ranged between 20 and 40 degrees C and fermentation time from 1 to 8 days. Marula juice fermented at higher temperatures ranged between 30 and 40 degrees C for 6 to 4 days retained high antioxidant activities, and they were positively correlated to its ascorbic acid and phenolic content. The values obtained ranged between 0.0239 +/- 0.0051 and 0.029 +/- 0.0038 mu mol/mg for Trolox Equivalence Antioxidant Capacity, 870 +/- 80 and 960 +/- 130 mg/100 ml for total phenolic content and 90 +/- 6 and 159 +/- 15 mg/100 ml for ascorbic acid. Overall, fermented manila juice can be used as a good source for natural antioxidants. (C) 2013 Elsevier Ltd. All rights reserved.