開發微流體蒸餾晶片以輔助食品中丙酸的檢測

食品添加劑是為了保持味道或增強口感、改善外觀而添加到食物中的物質，其定義可參考食品安全衛生管理法第3條之三規定：「食品添加物」係指為食品著色、調味、防腐、漂白、乳化、增加香味、安定品質、促進發酵、增加稠度、強化營養、防止氧化或其他必要目的，加入、接觸於食品之單方或複方物質。目前合法添加劑大致可分為十八類，其種類與用量限制須遵照衛生福利部食品藥物管理署公布之正面表列內的規定。丙酸(Propionic acid)廣泛用於化學，製藥，食品等行業，在食品領域中常以無機鹽形式使用，以增加儲放與使用的便利性。在台灣「食品添加物使用範圍及限量暨規格標準」中，對丙酸及其鹽類用量有明確規範，用量以丙酸計為2.5 g/kg以下。　　食品用防腐劑作為一種食品添加劑，其用途為延遲微生物生長或化學變化引起的食品腐敗和變質，從而達到延長其保存期限之效果。隨著市場需求的變動及飲食型態的變遷，食品安全是消費者重視身體健康的關鍵因素。若懷疑食品中非法添加了某些防腐劑或超出了規定的限制，需進行定期查驗，衛生福利部食品藥物管理署有提供針對不同添加物的規範與檢測方法。　　本研究以實驗室晶片(Lab on a Chip, LOC)的概念，與公告方法中食品添加物丙酸檢測蒸餾前處理為基礎，嘗試開發出一套簡易、方便且完善的快速前處理系統。本研究包含二部分，壓克力蒸餾晶片製作及檢體餾出液檢測。實驗設計分為標準品與真實樣品兩大類，標準品包含1000 ppm丙酸水溶液製成的檢體，與公告方法中所需的蒸餾水、磷酸調和製成的檢液。真實樣品的實驗則以吐司及自製高油脂含量餅乾為烘焙產品代表，取0.1克樣品依實驗設計添加不同濃度丙酸作為檢體，利用同樣條件進行實驗。餾出液檢測使用高效能液相層析儀(High performance liquid chromatograph, HPLC)，參考公告方法之條件進行分析檢測。　　實驗過程中利用不與檢體溶液反應的氮氣通過晶片內空間，使系統中的丙酸能流暢的溶於水蒸氣中被帶出，最後冷凝流出晶片以利收集，在加熱區域對蒸餾水和檢體溶液進行加溫達到水蒸氣蒸餾的效果，產生帶有檢體丙酸的水蒸氣。最後用通過冷卻水的冷凝區模擬傳統蒸餾設備中的冷凝管，使帶有丙酸的蒸氣冷凝，收集後經由HPLC檢測。　　從結果中可觀察到，利用微型蒸餾晶片進行丙酸檢測前處理時，會受到氣體流速，加熱及冷凝溫度調控，冷凝通道之寬度與長度，樣品蒸餾區之面積，水蒸氣通道設計和餾出液保存等多元因子影響。蒸餾區域過小會限制檢液含量，在檢體含水量低的情況下使丙酸含量高於溶液飽和濃度，同時使沸騰之檢液溢出加熱區流進冷凝管道中影響實驗進行；蒸餾區域過大則會降低晶片之便捷性違反實驗目的。在傳統實驗方法的結果中回收率約為100%，最終蒸餾晶片結果回收率大約介於93 % 到101 % 之間，然而實驗時間卻可減少約5/6，試劑用量減少約250倍。所開發之蒸餾晶片能提升檢測過程，達到快速便捷、成本低廉、攜帶方便等優勢。在相關食品檢測領域具有發展研究的潛力。

關鍵字

丙酸；晶片實驗室；蒸餾；高效能液相層析儀

並列摘要

Food additives are substances added to food in order to maintain the taste, enhance the taste, and improve the appearance. The term "food additives", according to the definition in Article 3 of “Act Governing Food Safety and Sanitation”, shall mean a single substance or combination of substances that are added to or brought into contact with foods for the purpose of coloring, seasoning, preserving, bleaching, emulsifying, flavoring, stabilizing quality, enhancing fermentation, increasing viscosity, enriching nutritional value, preventing oxidation or other necessary purpose. At present, legal additives can be roughly divided into eighteen categories, and their types and dosage restrictions must comply with the regulations in the positive list published by the Food and Drug Administration of the Ministry of Health and Welfare. 　　Propionic acid has been widely used in the chemical, pharmaceutical, food and other industries. It is often used in the form of inorganic salts in the food fields to increase the convenience of storage and use. In Taiwan's "Standards for Specification, Scope, Application and Limitation of Food Additives ", there are clear regulations on the amount of propionic acid and its salts, and the dosage is 2.5 g/kg or less based on propionic acid. 　　As a food additive, food preservatives are used to delay food spoilage and deterioration caused by microbial growth or chemical changes, with the purpose of achieving the effect of extending its shelf life. With changes in market demand and alterations in dietary patterns, food safety is a crucial factor for consumers to value their health. If it is suspected that certain preservatives have been illegally added to food or exceed the prescribed limits, regular inspections are required. The Food and Drug Administration of the Ministry of Health and Welfare, provides specifications and testing methods for different additives. 　　This research is based on the concept of Lab on a Chip (LOC), and the distillation as pre-treatment of the food additive propionic acid detection, in the official method. We have tried to develop a simple, convenient and complete rapid pre-treatment system. This research consists of two parts, acrylic distillation wafer production and sample distillate analysis. The experimental design is divided into two categories: standard products and real food samples. The standard product contains a sample made of 1000 ppm propionic acid aqueous solution and a test solution prepared by mixing distilled water and phosphoric acid required in the official method. The real food sample experiment used toast and homemade high-fat biscuits as representative baked products. A 0.1 gram sample was added with different concentrations of propionic acid according to the experimental design, and the experiment was carried out under the same conditions. Distillate was analyzed via high performance liquid chromatograph (HPLC), referring to the conditions listed in official method. 　　During the experiment, nitrogen that does not react with the sample solution is used to pass through the internal space of the wafer, so that the propionic acid in the system can smoothly dissolve in the water vapor to be taken out, and finally condenses out of the wafer to facilitate collection. The distilled water and sample solution are heated in the heating area to achieve the effect of steam distillation and produce steam with sample propionic acid. Finally, the condensing zone through the cooling water is used to simulate the condenser tube in the traditional distillation equipment, to condense the vapor with propionic acid, which is collected and assayed by HPLC. 　　It can be observed from the results that when using the micro-distillation wafer for propionic acid detection pretreatment, it will be affected by the gas flow rate, heating and condensation temperature, the width and length of the condensation channel, the area of the sample distillation zone, the design of the water vapor channel, the storage of distillate, etc. If the distillation area is too small, the content of the test liquid will be restricted. If the sample contains low water content, the content of propionic acid might go higher than the saturation concentration. At the same time, the boiling test liquid could overflow the heating zone and flow into the condensing channel, which certainly affect the experiment. Excessive distillation area would reduce the convenience of the wafer, which violates the purpose of the experiment design. The recoveries of traditional distillation method were about 100%, yet the recoveries via distillation wafer of final design were between 93% and 101%. However, the experiment time can be reduced by about 5/6, and the amount of reagents consumed by about 250 times. The developed distillation wafer can improve the inspection process, and achieve the advantages as fast and convenient, low cost, and convenient to carry. It has the potential for research and development in the field of food testing.