【作者】 余萃；

【导师】 曾德芳； 黄敏；

【作者基本信息】 武汉理工大学 ， 环境工程， 2010， 硕士

【摘要】 近年来,由于农药、化肥的不合理施用及工业“三废”的排放等导致农产品污染突出,主要表现为农产品中硝酸盐、农药残留、重金属等含量不同程度超过标准规定范围。武汉市城市常住人口超过890万,是重要的蔬菜流通和消费市场,硝酸盐作为蔬菜重要的不良品质指标值得关注。本研究基于对蔬菜硝酸盐采取农艺削减措施的前提下,通过市场取样和室内模拟相结合的方法,揭示了武汉市典型蔬菜硝酸盐和亚硝酸盐的污染状况,探讨了储放环境条件对蔬菜硝酸盐含量的影响,明确了几种实用的食前处理方式去除蔬菜硝酸盐的效果。主要结果如下：(1)武汉城区市售蔬菜硝酸盐污染问题突出,尤其是叶菜类蔬菜,其硝酸盐含量平均为3482.2mg·kg-1；不同类型蔬菜硝酸盐含量差异明显,其顺序从大到小依次为叶菜类、根茎类、瓜果类、豆类。在所调查的81个蔬菜样品中,硝酸盐含量达到严重污染等级的占35.8%、重度污染占8.6%、中度污染占9.9%、轻度污染占45.7%,其中超过严重污染等级的全部为叶菜类,占全部叶菜类样品数的58.3%。市售蔬菜亚硝酸盐含量均小于4mg·kg-1,在食用安全范围内。(2)温度条件对叶菜类和根茎类的蔬菜硝酸盐含量影响明显。在4d储放时间内,小白菜硝酸盐含量在0-5℃、10-15℃和20～25℃条件下分别在2350.4-3386.6mg·kg-1、2725.9-4068.9mg·kg-1和3138.2-6663.5mg·kg-1范围内波动；初始含量为1695.4mg·kg-1的白萝卜随储放时间延长硝酸盐含量持续上升,0-5℃、10-15℃和20-25℃条件下分别增加到2071.5mg·kg-1、1941.5mg·kg-1和1792.3mg·kg-1。在上述三种储放条件下,小白菜和白萝卜的亚硝酸盐含量均不超过lmg.kg-1,低于对人畜安全的含量标准。(3)湿度条件对叶菜类和根茎类蔬菜硝酸盐含量的影响规律存在差异。大白菜在10～15℃条件下储放1d后,70%-75%、80%-85%和90%-95%三种湿度环境下硝酸盐含量分别增加33.2%、13.2%和0.6%；70%-75湿度条件下储放2-5d内,其硝酸盐含量持续增加,到第5d增加了41.0%,而80%-85%湿度条件下第5d增加了13.0%；在90%-95%湿度条件下2-4d内硝酸盐含量呈上升趋势,到第5d却降低了15.8%。白萝卜在10～15℃条件下储放5d,70%～75%湿度条件下,第5d其硝酸盐含量持续增加了56.6%；80%-85%湿度条件下,储放1d后硝酸盐含量降低6.6%,而2-5d一直高于储放前的含量,增加率最高达20.0%；90%-95%湿度条件下前4d内硝酸盐含量变化平缓,第5d却降低19.3%。(4)淘米水、食盐水、食用白醋和果蔬洗涤剂均能不同程度地降低蔬菜硝酸盐含量。小白菜的优化清洗方式为在4%食用白醋溶液中浸泡l0min,该处理可降低23.4%的硝酸盐；降低小白菜硝酸盐的各洗涤因素作用从大到小依次为：洗涤剂种类、浸泡时间、洗涤剂浓度。进一步优化正交试验,各因素的作用从大到小依次则为：蔬菜类型、洗涤剂种类与其浓度的交互作用、洗涤剂种类、洗涤剂浓度、洗涤剂种类与浸泡时间的交互作用、浸泡时间；就去除硝酸盐的最佳效果而言,小白菜在1‰食盐水浸泡30min,其降低率达32.5%；菠菜在2‰食盐水浸泡60min,其降低率达23.7%；洗涤方式对白萝卜硝酸盐的去除效果不明显。(5)食前对叶菜类蔬菜进行短时间漂烫能有效降低其硝酸盐含量。比较0.5min、1.0min和2.0min三种漂烫处理结果,0.5min漂烫去除蔬菜硝酸盐的效果最佳,该处理可使小白菜和菠菜中硝酸盐含量分别降低26.9%和14.5%。蔬菜经三种漂烫处理后亚硝酸盐可增加6.2～11.6倍,但含量均低于1mg·kg-1。(6)去皮处理可降低根茎类和瓜果类蔬菜中硝酸盐含量或亚硝酸盐含量。去皮可使白萝卜硝酸盐含量降低3.0%-9.4%,使黄瓜硝酸盐含量降低10.4%-30.7%,使茄子亚硝酸盐含量降低3.6%～75.0%。更多还原

【Abstract】 Recently, irrational pesticides, unbalanced fertilizers, and emission of industrial wastes have caused agricultural products to be polluted seriously, including that the contents of nitrate, pesticide residues and heavy metals in agricultural products have exceeded corresponding standards to a certain extent. Wuhan is an important vegetable circulation and consumer market with more than 890 million permanent residents. Nitrate which was the significant harmful factor of vegetable quality is worthy paying close attention. In this paper, based on agronomic reduction measures, it was shown that the pollution status of nitrate and nitrite in typical vegetable in Wuhan City, discussed that the influence of storage conditions on the contents of nitrate in vegetables, and definited that effect of reducing nitrate in vegetables by some handling process after collection with the method of combining market sampling and laboratory simulation. Main results were summarized as follows:(1) The present pollution status of nitrate in vegetables were serious in Wuhan City, especially in leaf vegetables, whose average concentration was 3482.2mg·kg-1; the nitrate contents varied significantly in different types vegetables, and the descending sequence was:leaf vegetables, root vegetables, melon and fruit vegetables, beans. Among 81 investigated vegetable samples, the proportion which nitrate contents reached a severe pollution grade which accounted for 35.8%, heavy pollution for 8.6%, moderate pollution for 9.9%, and mild pollution for 45.7%, respectively, and most serious in leaf vegetables, moreover, the vegetables which exceeded the severe pollution grade were all leaf vegetables, and the proportion which nitrate contents exceeded the severe pollution grade accounted for 58.3% in leaf vegetables. All the vegetables were lower than 4mg·kg-1 in nitrite contents in Wuhan City, which were lower than in corresponding hygienic criterion.(2) Temperature conditions influenced the nitrate contents of leafy vegetables and root vegetables significantly. Under the conditions of 0～5℃,10～15℃or 20～25℃, nitrate contents in pakchoi were within 2350.4-3386.6mg·kg-1, 2725.9～4068.9mg·kg-1 and 3188.2～6663.5mg·kg-1, respectively, during four days storage period. The nitrate content of white radish in which initial value was 1695.4mg·kg-1 showed a pesistent ascending trend, nitrate content of white radish were reached 2071.5mg·kg-1,1941.5mg·kg-1 and 1792.3mg·kg-1, respectively, under the conditions of 0～5℃,10～15℃and 20～25℃. Under above three kinds of storage temperature, nitrite contents of both pakchoi and white radish were below 1mg·kg-1, which were below safety standards and will not cause harm to people and livestoke.(3) Under three humidity conditions, the dynamic laws of the nitrate contents in leafy vegetables differed from in root vegetables under the condition of 10～15℃. During the storage period, cabbages were stored under conditions of RH70%～75%, RH80%～85% or RH90%～95% for one day, whose nitrate contents increased by 33.2%,13.2% and 0.6%, respectively; under condition of RH70%～75%, nitrate contents were increased continuous in day 2～5, and increased by 41.0% on day 5, while increased by 13.0% under condition of RH80%～85%; under condition of RH90%-95%, nitrate contents were increased in day 2～4, but decreased by 15.8% on day 5. Under the condition of 10～15℃, white radish were stored for 5 days under the condition of RH70%～75%, whose nitrate contents were increased by 56.6% on day 5; under the condition of RH80%～85%, nitrate contents of white radish were decreased by 6.6% after one day, and which were more than initial value in day 2～5, and the highest yield can reach to 20.0%; nitrate contents kept stable in day 1～4 under condition of RH90%～95%, and which were decreased by 19.3%.(4) Rice washing water, salt solution, vinegar solution and detergent can reduce nitrate contents in vegetables in varying degrees. The optimal treatment decreasing nitrate contents in pakchoi was immersed for 10 minutes in 4%white vinegar solution, which can decrease nitrate contents by 23.4%. The descending sequence of various influencing factors on pakchoi was as follows:detergent types, immersion time, detergent concentration. To optimize experimental factors and levels furtherly, the descending sequence of various factors was as follows:vegetable types, interaction of detergent types and its concentration, detergent types, detergent concentration, interaction of detergent types and immersion time, immersion time. Considering the preferably treatment for decreasing nitrate contents, the treatment for pakchoi was immersed for 30 minutes in 1‰salt solution, whose reduction rate was 32.5%; the treatment for spinach was immersed for 60 minutes in 2‰salt solution, whose reduction rate was 23.7%; however, all above treatments were useless to reduce nitrate contents in white radish.(5) Scalding treatment for a short time can reduce nitrate contents in leafy vegetables just before serving. Results of scalding for 0.5minute, 1.0minute or 2.0minute showed that the effect of 0.5 minute scalding was the best to reduce nitrate contents in vegetables, and through 0.5 minute scalding treatment, nitrate contents of pakchoi and spinach were reduced by 26.9% and 14.5%, respectively. Moreover, nitrite content in scalding vegetables were increased by 6.2-11.6 times, while the amount is no more than 1mg·kg-1.(6) Peeling treatment could be helpful to reduce nitrate or nitrite contents in root vegetables, melon and fruit vegetables. It could reduce the nitrate contents by 3.0%～9.4% for white radishes,10.4%～30.7% for cucumbers. And the nitrite contents could be reduced by 3.6%～75.0% for eggplant.更多还原