采用比色法检测蔬菜中的亚硝酸盐含量。试验结果表明，不同蔬菜的亚硝酸盐含量在贮藏（常温和4℃冰箱）加工（不同煮沸时间）过程中变化明显，且有"亚硝化峰"现象。两种贮藏温度下，4℃冰箱贮藏可降低蔬菜中亚硝酸盐含量，并使亚硝化峰延迟出现；6种蔬菜中亚硝酸盐含量峰值比较为：菠菜、白菜>芹菜、四季豆>番茄、白萝卜；按蔬菜中亚硝酸盐限量值4.0 mg/kg计，番茄和白萝卜中亚硝酸含量均未超标，而菠菜和白菜中亚硝酸含量均超标。煮沸时间在5 min~20 min内，6种蔬菜中亚硝盐含量均不超过3.5 mg/kg。以菠菜为例，煮熟后室温放置24 h~32 h期间，其亚硝酸盐含量和细菌总数迅速增加，放置至32 h，亚硝酸盐含量达到5.2 mg/kg。%Colorimetric analysis was used to detected nitrite content in vegetables. The result showed that the change of nitrite content in vegetables was obvious under conditions of household storage (room temperature and 4 ℃refrigerator ) and processing (different boiling time). In addition, the nitrite curve showed nitrite peak. Compare with room temperature storage , the nitrite content in vegetables was reduced and nitrite peak was delayed under 4 ℃ refrigerator conditions. The peak sequence of nitrite content in different vegetables were respectively spinach, Chinese cabbage> celery, green beans >tomato, white radish. According to the nitrite content in vegetables limited value of 4 mg/kg , the nitrite content of the tomato and white radish did not exceed the standard. Then, both spinach and cabbage of nitrite content were above the standard. During 5 min-20 minutes of boiling, the nitrite content in six kinds of vegetables was not more than 3.5 mg/kg. Using cooked spinach as an example, the nitrite content and total bacteria increased rapidly during 24 h-32 h at room temperature. Attained 32 h at room temperature, the nitrite content in spinach reached 5.2 mg/kg.
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