Antioxidant and Antibacterial Effects of Vitamins C and E Alone or a Combination on Microalgae (Nannochloropsis oculata) Paste Quality during Cold Storage

Vitamins C and E are natural antioxidants and antibacterial that can be added to algae paste without any side effects on humans. The present study examined a method of producing microalgae paste from Nannochloropsis oculata and adding vitamins C and E in order to improve shelf life during storage at 4 degrees C. Microalgae were grown in logarithmic phase in Conway culture medium with 3.2 x 10(7) cells/ml concentration. The microalgae paste was then treated with vitamins C, E, or a mixture of them (0.1% weight/weight), and refrigerated for 12 weeks. The initial density of the algae paste was 1.8 x 10(10) cells/ml. The results showed that adding vitamins C and/or E to pastes increased cell viability in comparison to the control samples, indicating a positive effect of the vitamins (P < .05). While a significant increase in saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) was observed, polyunsaturated fatty acids (PUFA) significantly decreased during storage (P < .05). Total viable bacterial counts (TVBC), total psychrotrophic bacterial counts (TPBC), and total marine bacterial counts (TMBC) after the third week in control was significantly higher than other treated samples (P < .05). Total volatile base nitrogen (TVB-N) levels in the vitamin C treated samples were lower (P < .05) than control samples after the fifth week. Vitamin E was the most effective treatment for reducing the thiobarbituric acid reactive substances values (TBARS) and hence oxidative rancidity after the sixth week. In summary, vitamins C or E proved to be suitable preservatives for this microalgae paste individually but not in combination.