冷藏对蔬菜中亚硝酸盐及硝酸盐含量的影响

目的 探索冰箱冷藏(4℃)条件下蔬菜中硝酸盐和亚硝酸盐含量随时间的变化,对冷藏食品的安全性进行评价.方法 分别采用重氮偶合分光光度法和麝香草酚分光光度法对生菜、菠菜、油麦菜及苦苣4种常用蔬菜在冷藏条件下其亚硝酸盐及硝酸盐的含量变化进行测定.结果 1～4d内,生菜、苦苣中的亚硝酸盐含量随着时间的延长逐渐增加；菠菜、油麦菜中亚硝酸盐含量分别在第2天和第3天达到最大,之后逐渐降低,而菠菜中亚硝酸盐含量在第4天又出现上升趋势.4种蔬菜中亚硝酸盐含量4d中最大值仅为0.419 4 mg/kg(生菜),均＜4 mg/kg的限量值.苦苣和油麦菜中硝酸盐含量在1～4d内逐渐上升.菠菜中硝酸盐含量第2天达到418.48 mg/kg,之后又降低至20.83 mg/kg.生菜中硝酸盐含量在第3天达到最大值317.26 mg/kg,之后逐渐下降,但均在安全范围内(432 mg/kg).结论 在4℃下冷藏4d后,4种常见蔬菜均可安全食用.可见,冷藏能有效减缓亚硝酸盐和硝酸盐含量的升高.

Effects of cold storage on nitrite and nitrate contents in vegetables

Objective In order to obtain the effects of cold storage on the nitrite and nitrate contents of four kinds of green vegetables and evaluate the safety of cold storage processing. Methods Diazotization-coupling reaction spectrophotometer and tnymol spectrophotometer method were used to analysis the nitrite and nitrate contents in four kinds of green vegetables include lettuce, spinach, leaf lettuce and endive in four days stored at 4 oC. Results The results indicate that nitrite content in lettuce and endive was rising with storage time. The nitrite content in spinach and leaf lettuce reached the maximum in the second and third day, respectively. Later, the content began to decrease. However, it would rise in the fourth day in spinach. The biggest content of nitrite in four vegetables in four days was 0.4194mg/kg (in cucumber) which far less than the limited value of 4mg/kg. Nitrate content in endive and leaf lettuce was gradually increasing in four days. The nitrate content in spinach reached to 418.48mg/kg in the second day, but decreased to 20.83 mg/kg a few days later. The nitrate content in lettuce reached to 317.26 mg/kg, while it decreased in the later days. The contents of nitrate in four vegetables were within the safety range (432mg/kg). Conclusion Compared with nitrite, four vegetables have more nitrates in four days. Fortunately, contents of nitrate were all in the safety range. Cold storage can effectively slow down the increase of nitrite and nitrate contents in vegetables.