污染指数法在乳制品重金属污染评价中的应用研究

The application of contamination index method to evaluate heavy metal contaminations in dairy products

目的了解济南市乳制品中重金属污染物含量分布特征,评价重金属污染状况及程度。方法 2012—2013年对济南市生乳、发酵乳、灭菌乳、婴幼儿配方乳粉和普通乳粉等5种乳制品中的铅(Pb)、汞(Hg)、镉(Cd)、铬(Cr)及类金属元素砷(As)含量进行测定。采用单因子污染指数法和内梅罗综合污染指数法,按农产品质量分级标准,对其污染程度进行分析评价。结果乳制品中5种重金属元素项目检出率分别为Pb 14.0%(21/150)、总As 24.7%(37/150)、总Hg 82.0%(109/133)、Cd 26.3%(35/133)和Cr 72.9%(43/59),生乳中Pb和灭菌乳中Pb、Cd未检出。生乳中总Hg的均值、P75和P95均超过限量值,发酵乳、灭菌乳中总Hg含量和普通乳粉中Cd含量的P95超过限量值。生乳、发酵乳和灭菌乳等液态乳重金属检出率和单因子污染指数均以总Hg最高,其中生乳PHg>1,属重度污染,发酵乳PHg>0.6,属轻度污染;婴幼儿配方乳粉和普通乳粉等固态乳重金属检出率以Cr最高,单因子污染指数以Cd最高,处于安全级别范围内。生乳重金属污染程度最高,综合污染指数Pn=0.754,属轻度污染,婴幼儿配方乳粉最低,综合污染指数排序为生乳>发酵乳>灭菌乳>普通乳粉>婴幼儿配方乳粉。结论济南市4种乳制品达到安全级别,受重金属污染威胁较小。液态乳重金属污染物主要为总Hg,固态乳为Cd。生乳中总Hg单因子污染指数和综合污染指数较高,处于污染状态,应加强生乳中重金属污染物总Hg含量的控制。

Objective To understand the distribution characteristics of heavy metal contamination in dairy products, and to evaluate the status and the extent of heavy metal contamination. Methods The contents of Pb, total-Hg, Cd, Cr and total-As in raw milk, fermented milk, sterilized milk, infant formula and milk powder during 2012-2013 were detected. Single factor contamination index method and comprehensive contamination index method of Nemerow were used to evaluate the contamination level according to the grading standard of agriculture product quality. Results The detection rate of Pb, total-As, total-Hg, Cd and Cr were 14.0% （21/150）, 24.7% （37/150）, 82.0% （109/133）, 26.3% （35/133） and 72.9% （43/59） in dairy products, respectively. Pb in raw milk and Cd in sterilized milk were not detected. The mean, P75 and P95 of total-Hg in raw milk were higher than the limit. The P95 of total-Hg in fermented milk and sterilized milk and Cd in milk powder were higher than the limit. The detection rate and single factor contamination index of total-Hg were the highest in raw milk, fermented milk and sterilized milk, which indicated there was severe contamination in the raw milk （PHg 〉 1 ） and mild contamination in fermented milk （PHg〉 0. 6）. The detection rate of Cr was the highest in infant formula and milk powder, while single factor contamination index of Cd was the highest. The heavy metal contamination in raw milk ranked the first with P = 0. 754, reaching mild level of contamination. The heavy metal contamination in dairy products could be lined in a decreasing order of raw milk, fermented milk, sterilized milk, milk powder and infant formula. Conclusion Four kinds of dairy products were at the safe level of heavy metal contamination. Total-Hg was the dominant heavy metal contamination in liquid milk, while Cd in solid milk. Single factor contamination index and comprehensive contamination index of total-Hg in raw milk indicated that measures should be taken to prevent the contamination.