稳定碳、氮同位素在牛肉加工过程中的分馏效应

Fractionation Effect of Stable Carbon and Nitrogen Isotopes During the Beef Processing

为了探究牛肉及副产物中稳定碳、氮同位素在加工过程中的变化规律,确证稳定碳、氮同位素在牛肉加工制品产地溯源中的稳定性和有效性。本试验通过对牛肉进行不同时间的水煮、烤制和油炸3种处理,其中水煮和烤制加工时间分别为5、10、15、20、25和30 min,油炸加工时间分别为1、2、3、4和5 min;采用元素分析仪-稳定同位素比率质谱仪(EA-IRMS)测定脱脂牛肉、粗脂肪及副产物中δ^13C和δ^15N值。结果表明,脱脂牛肉中δ13C值在水煮、烤制和油炸3种加工方式不同加工时间之间均无显著差异,水煮和烤制后粗脂肪中δ13C值无显著变化,油炸后的牛肉粗脂肪δ13C值主要受植物油的影响,加工方式及加工时间对其无显著影响;水煮脱脂牛肉δ15N值在加工25、30 min时与对照组牛肉存在显著差异,但平均差值仅为0.3‰~0.9‰。牛肉稳定碳、氮同位素在不同加工过程中分馏效应较小,可有效用于牛肉加工半成品及成品的原产地溯源。

The aim of this study was to explore the changes of stable carbon and nitrogen isotopes beef and its by-products,and to confirm the stability and effectiveness of stable carbon and nitrogen isotopes in the geographical traceability of beef processing products.The beef was treated by three processing methods,i.e,boiling,roasting and frying for different time.The boiling and roasting time was 5,10,15,20,25 and 30 min respectively,and the frying time was 1,2,3,4 and 5 min respectively.Theδ^13C andδ^15N values in defatted beef,crude fat and residue were determined by Element Analyzer-Isotope Ratio Mass Spectrometry(EA-IRMS).The results showed that theδ13C values in cooked defatted beef of boiling,roasting and frying for different time intervals were not significantly different(P>0.05),and there was no significant change ofδ13C values in the crude fat after boiling and roasting at different time.Theδ13C value in the crude fat of fried beef was mainly affected by the vegetable oil.Theδ15N value of boiling beef was significantly different after 25 min and 30 min,but the average change was only 0.3‰~0.9‰.The stable carbon and nitrogen isotopes of boiled beef were less fractionated during different processing,thus they can be used for the beef geographical origin traceability of semi-finished products and processed products.