微生物抑制法快速检测鲜牛乳中红霉素残留

Research on microbial inhibition method for rapid detection of erythromycin in raw milk

目的利用微生物抑制法快速检测鲜牛乳中红霉素残留。方法将待测的牛奶样品和空白样品经杀菌后接入乳酸菌,经过相同时间发酵后,计算待测牛奶样品发酵前后的pH变化差值与空白样品发酵前后的pH变化差值,从而判断鲜牛奶中红霉素残留的含量。结果经过单因素及正交实验,确定乳酸菌发酵产酸条件如下:接种量0.15 U/L、发酵温度40℃、菌粉溶解时间25 min、发酵时间3.5 h,利用乳酸菌发酵产酸建立了检测鲜牛奶中红霉素残留的标准曲线Y=0.024X-0.013(其中,Y为△pH,X为鲜牛乳样品中的红霉素浓度),线性相关系数R^2=0.9949,检测的灵敏度IC_(50)为29.71μg/L,检测的线性范围为0~50μg/L,加标回收率为103.54%~124.58%,同一批次内检测的变异系数为4.39%~16.46%。结论建立的检测方法可用于筛选鲜牛乳中是否有抗生素残留并进行定量检测。

ABSTRACT:Objective To determine the concentration of erythromycin in raw milk by microbial inhibition method. Methods After sterilized and cooled the raw milk, erythromycin was added into raw milk samples with Lactobacillus, and the blank control was set. After fermented for some time, the pH of the fresh milk sam-ples before and after fermentation was detected for testing the difference of pH of raw milk samples while the blank control was set. Results After single factor and orthogonal experiment, the optimum experimental con-ditions for Lactobacillus fermentation were established as follows: inoculum concentration of Lactobacillus CH-1 was 0.15 U/L, fermentation temperature was 40℃, fermentation time was 3.5 h and the dissolution time of CH-1 lactobacillus powder was 25 min. According to the relationship between doxycycline concentration and difference of pH value, the standard curve was established. The standard curve equation was as follows:Y=0.024X-0.013 (Y was the concentration of erythromycin in raw milk samples, X was the ΔpH). The linear correlation coefficient R2 was 0.9949. The detection range of the standard cure was 0~50μg/L. The microbial inhibition method showed that the sensitivity IC50 was 29.71μg/L for erythromycin. The assay showed a mean recovery ranged from 103.54%~124.58%, and the coefficients of variations for the inter-assay was 4.39%~16.46%. Conclusion It could be used to detect the erythromycin residual concentration in raw milk.