食品中乳酮糖之檢驗方法研究   全文下載

Development of an Analytical Method for Lactulose in Foods

乳酮糖（Lactulose）係由半乳糖及果糖以β-1,4鍵組成之雙糖，多用於特殊營養食品或保健食品中，可做為供雙歧桿菌（Bifidobacterium spp.）及乳酸桿菌（Lactobacillus spp.）等腸道菌使用之益生質，促進宿主健康。衛生福利部於107年公告修正營養添加劑「乳酮糖」可用於特殊營養食品及標有每日食用限量之食品，其每日乳酮糖食用總量不得高於10 g，故為配合行政管理，爰建立食品中乳酮糖之檢驗方法。本研究將均質檢體以50%乙醇溶液以超音波振盪萃取，加入carrez I、II溶液及乙腈溶液沉澱非糖類成分，檢液以高效液相層析儀搭配折射率檢出器（UPLC-RID）進行分析。採用ACQUITY BEH Amide（1.7μm，2.1 mm × 10 cm）管柱搭配含0.2%TEA之80%乙腈溶液移動相，於流速0.25 mL/min進行沖堤，可於10分鐘內完成分析。於特殊營養食品及益生菌粉檢體中分別添加乳酮糖0.25及1.25 g/100 g進行確效試驗，結果顯示同日間之平均回收率分別介於94-100%及96-106%，變異係數分別為2.5-5.3%及0.9-1.1%，異日間平均回收率分別介於92-102%及95-107%，變異係數分別為3.3-5.0%及1.6%，符合「食品化學檢驗方法之確效規範」要求。以此方法進行5件市售產品中乳酮糖之含量檢測，檢測值介於0.48-10.2 g/100 g，其中1件檢體未標示每日建議食用量僅標示乳酮糖含量，其檢測值大於標示值之80%，符合「包裝食品營養標示應遵行事項」規定，其餘4件檢體之乳酮糖每日建議食用量均未超出法規訂定之每日食用限量。

Lactulose, a disaccharide composed of β-1,4-linked galactose and fructose, is commonly used in special dietary food and functional foods. It's prebiotic property can stimulate bacteria growth in the gastrointestinal tract, such as Bifidobacterium spp. and Lactobacillus spp., and thus improves the host health. There is a daily consumption limit of 10 g for lactulose in special dietary foods and products labeled with daily limit of lactulose, regulated by Ministry of Health and Welfare. In this study, we coordinated the implementation of administrative management to establish the analytical method for lactulose in foods. The sample was extracted with 50% ethanol in an ultrasonic bath and precipitated by Carrez reagent and acetonitrile. After filtering, the filtrate was analyzed by the ultra-high performance liquid chromatographic system with an ACQUITY BEH Amide (1.7μm, 2.1 × 10 cm) column and refractive index detector at 0.25 mL/min isocratic elution with acetonitrile and water (80:20, v/v) solution containing 0.2% TEA. The method was validated by spiking lactulose at the levels of 0.25 and 1.25 g/100 g into infant formula and probiotics powder, respectively. The average recoveries of lactulose in intra-day were in the range of 94-100% and 96-106%, and their coefficients of variation were 2.5-5.3% and 0.9-1.1%, respectively. The average recoveries of lactulose in inter-day were in the range of 92-102% and 95- 107%, and their coefficients of variation were 3.3-5.0% and 1.6%, respectively. All results showed that the method offered good precision and accuracy. The market survey results of five commercial products were as follows: The detected values of lactulose ranged between 0.48 and 10.2 g/100 g. One of 5 samples contained more than 80% of the labeled value of lactulose, but the labeling of daily recommended consumption value was missed. The recommended daily consumption values of lactulose in other 4 samples were found not exceed the daily consumption limit of lactulose set by the regulation.