醬油中果糖酸之檢驗方法建立   全文下載

Development of an Analytical Method for Levulinic Acid in Soy Sauce

速釀法製造醬油是在高溫100-130℃下，以鹽酸水解黃豆粉或黃豆片等植物蛋白，在水解過程中，原料中的醣類與酸反應會產生果糖酸。釀造醬油是利用微生物發酵，不會產生果糖酸，因此果糖酸之存在與否可用來判斷釀造醬油是否摻雜速釀醬油。本研究利用氣相層析儀搭配火焰離子偵檢器進行分析，層析管柱使用DB-FATWAX UI毛細管柱（內膜厚度0.25μm，內徑0.25 mm × 30 m），載氣為氦氣，流速1.8 mL/min，注射器溫度240℃，偵檢器溫度260℃，分流比10：1。以庚酸作為內部標準品，前處理以乙醚為萃取溶劑，乙醚萃取液濃縮後以乙腈定容。確效結果：添加低、高濃度分別為0.025及0.05%，在同日間之平均回收率分別為102.3及102.1%，變異係數為0.3及0.5%；異日間之平均回收率分別為100.1及97.5%，變異係數為0.2及0.3%，定量極限為0.0025%，符合食品化學檢驗方法之確效規範。以本研究方法執行市售醬油產品中果糖酸含量調查，24件檢體中有22件標示為釀造醬油，2件未標示釀造醬油之檢體中，1件檢出果糖酸含量0.64%，其餘檢體均未檢出果糖酸。

Chemical soy sauce is produced by hydrolyzing the vegetable protein with hydrogen chloride at a high temperature of 100 - 130℃. During hydrolysis, levulinic acid is generated from the reaction of sugar and acid. The presence of levulinic acid in soy sauces indicates adulteration by chemical soy sauce. Gas chromatography was performed on a capillary column, DB-FATWAX UI (30 m×0.25 mm i.d., 0.25μm film thickness) using helium as the carrier gas with flow rate of 1.8 mL min^(-1). Injector temperature was set at 240°C with a split injection of 10:1. Detector temperature was set at 260°C. Levulinic acid in sample was extracted with ether, then diluted with acetonitrile after concentration. Heptanoic acid was selected as an internal standard for the accurate quantification of levulinic acid in samples. Accuracy was conducted by spiking 0.025% and 0.05% levulinic acid into blank samples. The average recoveries were 102.3 and 102.1%, and the coefficients of variation were 0.3 and 0.5%, respectively. The limit of quantification was estimated to be 0.0025%. The market survey results of 24 soy sauce samples (22 labeled fermented soy sauce, 2 not claimed) were as follows: one not claimed fermented soy sauce was found containing 0.64% levulinic acid, and the others were not detected.