新西兰南岛生牛乳中硫氰酸根残留水平检测及影响因素分析

Determination of Endogenous Thiocyanate and Analysis of Influencing Factors in Raw Dairy Milk from South Island,New Zealand

[目的]了解和掌握新西兰生牛乳中硫氰酸根的本底含量、分布情况及影响因素,为生牛乳硫氰酸根残留的风险评估和限量标准制定提供参考。[方法]从新西兰南岛选取50个牧场,于2022年8月—2023年5月,连续逐月采集生牛乳样品800份(6—7月为当地奶牛干奶期,未采集样品);利用离子色谱法检测生牛乳样品中硫氰酸根含量,计算检出率,分析检测结果分布情况;探讨不同采样月份和采样牧场对生牛乳样品中硫氰酸根含量的影响。[结果]800份生牛乳样品中,有798份检出硫氰酸根,检出率为99.75%;检出范围0~10.62 mg/kg,平均值为6.25 mg/kg,中位数为6.21 mg/kg,1.13%的样品硫氰酸根含量在0~2.00 mg/kg,36.62%的样品硫氰酸根含量在4.00~6.00 mg/kg,50.50%的样品硫氰酸根含量在6.00~8.00 mg/kg,仅有0.75%的样品硫氰酸根含量大于10.00 mg/kg。2022年9—11月采集的生牛乳样品中硫氰酸根含量呈逐月上升趋势,2022年12月—2023年5月采集的生牛乳样品中硫氰酸根含量总体呈逐月上升趋势;2023年1—5月采集的生牛乳样品中硫氰酸根含量高于2022年8—12月采集的生牛乳样品中硫氰酸根含量;2023年5月采集的生牛乳样品中硫氰酸根含量平均值最高,为7.02 mg/kg;2022年9月采集的生牛乳样品中硫氰酸根含量平均值最低,为2.95 mg/kg。随机选取的2家牧场2023年1—5月采集的生牛乳样品中硫氰酸根含量变化趋势与800份生牛乳样品中硫氰酸根含量同期变化趋势一致,并且2家牧场的生牛乳样品中硫氰酸根含量无显著(P>0.05)差异。[结论]新西兰南岛牧场生牛乳中普遍存在硫氰酸根残留,主要来源于本底,外源添加的可能性极低。当地生牛乳中硫氰酸根含量存在季节性变化。

[Objective]The aims of this study were to assess the content,distribution and influencing factors of endogenous thiocyanate in raw dairy milk in New Zealand,and to provide references for risk evaluation and limit standard establishment of thiocyanate residue in raw dairy milk.[Method]From August 2022 to May 2023,a total of 800 raw milk samples were monthly collected from 50 dairy farms in South Island,New Zealand(no samples were collected in June and July due to the dry milk period of local dairy cows).The contents of thiocyanate in raw milk samples were determined by using ion chromatography.The detection rate was calculated and the distribution of detection result was characterized.The influence of different sampling months and pastures on endogenous thiocyanate levels in raw milk was analyzed.[Result]A total of 798 raw milk samples were positive for thiocyanate,with an overall detection rate of 99.75%.The contents of thiocyanate in the tested samples ranged from 0 to 10.62 mg/kg,and the mean and median were 6.25 mg/kg and 6.21 mg/kg,respectively.The samples containing 0-2.00 mg/kg,4.00-6.00 mg/kg and 6.00-8.00 mg/kg of thiocyanate accounted for 1.13%,36.62%and 50.50%of all the tested samples,respectively,while the samples with thiocyanate content exceeded 10.00 mg/kg only accounted for 0.75%.The contents of thiocyanate in the samples collected from September to November 2022 increased monthly,and the contents of thiocyanate in the samples collected from December 2022 to May 2023 generally exhibited an increasing trend month by month.The samples collected from January to May 2023 had higher contents of thiocyanate than those collected from August to December 2022.The highest average content(7.02 mg/kg)of thiocyanate was observed in the samples collected in May 2023,while the lowest average content(2.95 mg/kg)was observed in the samples collected in September 2022.The change trend of thiocyanate contents in the samples collected from 2 randomly selected dairy farms from January to May 2023 was consistent with that of thiocyanate contents in the 800 samples collected during the same period.There was no significant(P>0.05)difference in thiocyanate content between the samples collected from the 2 dairy farms.[Conclusion]Thiocyanate was commonly observed in raw dairy milk in South Island,New Zealand.It was attributed to the endogenous factor,and the possibility of exogenous addition was extremely minor.There were seasonal variations in thiocyanate content in local raw dairy milk.