[目的]探究不同保存条件和处理方式对生乳样品硫氰酸钠含量的影响.[方法]将生乳样品分别设置不同处理,包括保存条件处理(一20 ℃冷冻保存1、7和30 d,0~6 ℃冷藏保存4、8、24和48 h)、解冻温度处理(冻存24 h后,于25、40、60 ℃ 3个温度下解冻)、解冻次数处理(冻存24 h,于40 ℃水浴分别解冻1、3、5次)、防腐剂(硫氰酸钠、重铬酸钾、叠氮钠、溴硝丙二醇、甲醛)处理,然后进行样品中硫氰酸钠检测,结果通过单因子方差分析、主成分分析和回收率分析,探究不同处理对生乳中硫氰酸钠含量的影响.[结果]冷冻保存1、7和30 d后乳中硫氰酸钠含量无统计学差异(P>0.05),回收率为97.4%~103.1%.冷藏保存4、8、24和48 h后乳中硫氰酸钠含量呈现先降低后升高的趋势,回收率在94.5%~102.1%.冻存24 h后,3个不同解冻温度的乳中硫氰酸钠含量无统计学差异(P>0.05),回收率为97.8%~99.0%.冻存后分别解冻1、3、5次的结果显示,乳中硫氰酸钠含量随解冻次数的增加而降低,检测回收率为95.3%~101.8%,在可接受范围.添加不同防腐剂的乳中硫氰酸钠含量存在显著差异(P<0.05),其中添加硫氰酸钠作为防腐剂会导致结果偏高,添加溴硝丙二醇会导致测定结果偏低,添加甲醛会导致硫氰酸钠未检出.[结论]硫氰酸钠样品采集后在0~6 ℃冷藏保存48 h内,-20 ℃冷冻保存30 d内,解冻温度低于60 ℃,解冻次数少于5次时,不会对生乳中的硫氰酸钠含量产生影响,使用防腐剂保存时可选择叠氮钠或重铬酸钾不会对样品中硫氰酸钠含量产生影响.
[Objective]The aim of this study was to explore the effects of different storage conditions and treatment methods on the content of sodium thiocyanate in raw milk samples.[Method]Raw milk samples were treated differently,including storage conditions(frozen at-20 ℃for 1,7 and 30 days,chilled at 0-6 ℃ for 4,8,24 and 48 h),thawing temperature(thawed at 25,40 and 60 ℃ after being frozen for 24 h),thawing frequency(frozen at 24 h,after thawed in water bath at 40 ℃ for 1,3 and 5 times respectively)and preservatives(sodium thiocyanate,potassium dichromate,sodium azide,propanediol bromide and formaldehyde).Then,sodium thiocyanate was detected in the sample,and the results were analyzed using One-Way ANOVA,principal component analysis,and recovery analysis to explore the impact of different treatments on the content of sodium thiocyanate in raw milk.[Result]After 1,7,and 30 days of frozen storage,there was no statistically significant difference in the content of sodium thiocyanate in milk(P>0.05),with a recovery rate of 97.4%to 103.1%.After being chilled for 4,8,24,and 48 h,the content of sodium thiocyanate in milk showed a trend of first decreasing and then increasing,with a recovery rate of 94.5%to 102.1%.After 24 hours of freezing,there was no statistically significant difference in the content of sodium thiocyanate in milk at three different thawing temperatures(P>0.05),with a recovery rate of 97.8%to 99.0%.The results of thawing 1,3 and 5 times after freezing showed that the content of sodium thiocyanate in milk decreased with the increase of thawing times,and the assay recoveries were 95.3%to 101.8%,which were in the acceptable range.There were significant differences in the content of sodium thiocyanate in milk with the addition of different preservatives(P<0.05),in which the addition of sodium thiocyanate as a preservative led to high results,the addition of bromonitropropanediol led to low assay results,and the addition of formaldehyde led to non-detection of sodium thiocyanate.[Conclusion]When raw milk samples were frozen at-20 ℃ for 30 days,at 0 to 6 ℃ for 48 h,thawing temperature below 60 ℃ and thawing frequency less than 5 times,there was no effect on the content of sodium thiocyanate in raw milk samples.Sodium azide or potassium dichromate did not affect the content of sodium thiocyanate in raw milk samples.