不同处理方法对小白菜硝酸盐含量的影响

在不同氮水平条件下（5，10，15，20mmol／L4个氮浓度梯度，分别用N1、N2、N3和N4表示），采用水培方法研究新鲜和漂烫的小白菜在室温和冷藏条件下的硝酸盐含量变化。结果表明：①低氮水平N1和N2，在室温条件下，新鲜小白菜硝酸盐含量随放置时间基本不变，而冷藏条件下，有所增加；高氮水平N3和N4条件下，无论是室温还是冷藏，新鲜小白菜硝酸盐含量均呈先微增后下降的变化趋势。当室温放置48h时，N3、N4处理的硝酸盐含量分别下降16．8％和23．0％，而冷藏放置48h时，分别下降21．2％和18．0％。②低氮水平N1和N2条件下，无论在室温还是冷藏漂烫小白菜硝酸盐含量基本不随放置时间而变化；高氮水平N3和N4条件下，其含量总体呈下降趋势，室温放置48h时，N3、N4处理的硝酸盐含量分别下降5．2％和33．1％，而冷藏48h时，分别下降10．0％和27．9％。③冷藏新鲜和漂烫小白菜硝酸盐含量均高于室温含量。④在N4、N3、N2、N1处理中，新鲜小白菜硝酸盐含量分别是漂烫小白菜的2．43倍、3．08倍、10．04倍、2．78倍。漂烫可显著减少小白菜的硝酸盐含量。

Influence of Different Treatments on Nitrate Contents of Chinese Cabbage

The change of nitrate eontent of Chinese cabbage was studied by water culture under different nitrogen treatments （5,10,15,20 mmol/L 4 nitrogen concentration gradient, which was showed by N1, N2,N3,N4 respectively） of the fresh and blanching condition at ambient temperature and cold storage. The results showed that：①At lower nitrogen level N1 and N2, the nitrate content of the fresh Chinese cabbage was not changed at ambient temperature, but increased at cold storage;at higher nitrogen level N3 and N4,the nitrate content was decreased both at ambient temperature and cold storage. After 48h,the nitrate content of N3 and N4 was decreased by 16.8% and 23.0% ,respectively under ambient temperature;the nitrate content of N3 and N4 was decreased by 21.2% and 18.0%, respectively under cold storage. ②At lower nitrogen level N1 and N2, the nitrate content of the blanching Chinese cabbage was not changed both under ambient temperature and cold storage; but at higher nitrogen level N3 and N4,the nitrate content was decreased. After 48 h, the nitrate content of N3 and N4 at ambient temperature was decreased by 5.2%and 33. 1%, respectively. Under cold storage, the nitrate content was decreased by 10. 0% and 27.9%, respectively.③Under cold storage, the nitrate content of Chinese cabbage under the fresh and blanching treatments was both higher than that of the ambient temperature condition. ④Under the nitrogen level of N4, N3, N2 and N1, the nitrate content of the fresh Chinese cabbage was 2.43,3.08,10.04 and 2.78 times, respectively, compared with the blanching Chinese cabbage. The reduce nitrate content could be reduced remarkably with blanching method.