Food Hygienic Studies on the Storage and Cooking of Vegetables, with Special Reference to Changes in Nitrite and Nitrate Contents and Possible Formation of N-Nitroso Compounds

Abstract

On quantitative analyses of nitrite (NO-2) and nitrate (NO-3) in vegetables, a comparative study has been undertaken between the method modified by Mori et al. and that by Nagata et al. In addition, the effect of reducing agents, viz. ascorbic acid (AsA) and FeCl2, on the determination of NO-2 by the above-mentioned methods have been examined. The results obtained may be summarized as follows:1. As to the recoveries of NO-2 being added to raw vegetable samples, it was found that Mori et al's method is superior to Nagata et al's in points of higher recovery, giving clear and colorless test solution, etc.2. Almost no appreciable effect could be observed in measuring NO-2 when AsA was added to raw vegetable samples.3. The addition of FeCl2 to a certain species of vegetables resulted in a marked decrease of NO-2 contents, while no appreciable effect was observed in other vegetables when determined by Mori et al's method.4. During the process of boiling vegetable samples, changes in NO-2, NO-3 and NH3-N contents were observed. It was found that either NO-2 or NH3-N apparently increased, while NO-3 rapidly decreased. However, there were no quantitative relationships among these values.