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The changes in nitrate and nitrite content during CA-storage were investigated in two cultivars of carrot (Daucus carota. L), and nitrate reductase activity was assayed to assess the role of the enzyme in the conversion of nitrate to nitrite during storage. After 15 weeks of cold storage, a little amount of nitrate was reduced, whereas, after the same period of CA storage (0% CO₂ + 1 % O₂), nitrate content reduced more than 90%. Nitrite content increased more than 2-fold after 15 weeks of all the storage. But in one cultivar, nitrite content was not different among storage conditions, whereas, in the other, significant differences in nitrite content was observed. The highest amount of nitrite was found in the latter cultivar stored in CA (0% CO₂ + I% O₂) at 0-1℃. However, the activity of endogenous nitrate reductase reduced sharply during cold storage. The enzyme activity was a little higher in CA-stored carrots than cold-stored carrots but still much lower than the activity at harvest. No clear relationship was shown between nitrate-nitrite conversion and the enzyme activity during storage and among different CA conditions. These results suggest that most conversion of nitrate to nitrite might be generally monitored by the anaerobic microbial action, not by endogenous nitrate reductase during storage.
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