以元素分析儀串聯同位素比值質譜儀進行蜂蜜C4糖之檢驗

Detection of Honey Adulteration by Measuring C4 Sugar via Elemental Analysis-Isotope Ratio Mass Spectrometry

蜜蜂採蜜以C3植物為主，因此利用C3和C4植物糖之碳同位素比值不同的特性，可分析蜂蜜所含C4植物糖之含量來區別摻偽。本研究利用元素分析／同位素比值質譜儀（elemental analyzer／isotope ratio mass spectrometer，EA-IRMS）分析蜂蜜之碳同位素，以協助釐清是否有混摻C4植物糖之行為。分析中以參考物質（USGS-40）及fructose、maltotriose、melezitose、turanose、raffinose、maltose、glucose及sucrose等糖類確認數據之品質，同日內或異日間精密度及準確度測試之標準偏差均小於千分之0.3，準確度達99.93％以上。蜂蜜於室溫下貯放1、7、14及30天進行穩定性試驗，結果δ^（13）C值在-25.83－千分之-25.89之間，並無明顯差異。將不同比例果糖添加於蜂蜜後進行碳同位素分析，結果當C4果糖添加量為10％時，其C4糖含量分析值為12.92％（大於7％），可判定為摻混。添加C3果糖者則無法藉此方法看出差異。以上述方法進行台灣養蜂協會提供蜂蜜檢體211件及食藥署北區管理中心抽驗市售蜂蜜檢體83件之碳同位素分析，檢驗結果養蜂協會211件蜂蜜檢體之δ^（13）C_H值分布於-29.53-千分之-18.18，平均值為千分之-25.66，其中9件檢體δ^（13）C_H值大於千分之-24，且C4糖含量大於7％。北區管理中心83件蜂蜜檢體之δ^（13）C_H值分布於-26.80-千分-12.04，平均值為千分之-24.23，其中19件檢體δ^（13）C_H值大於千分之-24，且C4糖含量大於7％。以台灣地區取得之蜂蜜檢驗結果進行分析，δ^（13）C_H值大於千分之-24.00者與C4糖含量之相關性迴歸分析，所得線性迴歸係數R^2為0.8263，顯示兩者具有顯著相關性。本研究將持續累積蜂蜜檢測資料庫，俾憑評估建立本土蜂蜜摻偽判定模式之可行性。 In this study, the elemental analysis-isotope ratio mass spectrometry (EA-IRMS) was employed for the stable carbon isotopes ratio analysis in honey samples. The data quality was validated by reference material USGS-40 and standard compounds including fructose, maltotriose, melezitose, turanose, raffinose, maltose, glucose and sucrose. The intra- and inter-day precision test gave a standard deviation less than 0.3 per mille. The accuracy was tested to be 99.93%. A honey sample was stored at room temperature for 1, 7, 14 and 30 days for the stability test. Theδ^(13)C value was analyzed after storages. The results ranged between -25.83 and -25.89 per mille with no significant difference. The adulteration test was carried out by spiking different proportions of fructose from C4 source into pure honey. The preliminary testing indicated that the adulterated sample could be detected if more than 10% exogenous C4 fructose was added. In this case the test value of C4 sugar was 12.92% (more than 7%). Two hundred and eleven honey samples from Taiwan Beekeeping Association and 83 commercial honey samples from Northern Center of TFDA were surveyed for δ^(13)C. The results showed that δ^(13)C_H values of 211 honey samples from Taiwan Beekeeping Association ranged from -29.53 to -18.18 per mille with an average value of -25.66 per mille. Among them, the δ^(13)C_H values of 9 samples were greater than -24 per mille, which indicated the content of C4 sugar was more than 7%. The δ^(13)C_H values of 83 samples of honey from Northern Center of TFDA ranged between -26.80 and -12.04 per mille with an average of -24.23 per mille. The δ^(13)C_H values of 19 samples were greater than -24 per mille. The correlation between honey specimens with δ^(13)C_H greater than -24.00 per mille and their C4 sugar content was calculated, with a linear regression coefficient R^2 of 0.8263, indicating a significant correlation. This study will keep accumulating the testing database of honey in order to assess the feasibility of establishing a decision mode for local honey adulteration.