木薯製品中總氫氰酸檢驗方法之建立   全文下載

Investigation of Test Method for Total Hydrocyanic Acid in Cassava Products

木薯又稱作樹薯，可作為木薯粉、木薯片等多種加工製品，是開發中國家重要之碳水化合物來源。木薯中含有亞麻苦苷（linamarin），在加工過程可能被內生酵素水解產生丙酮氰醇（acetone cyanohydrin），進一步產生氫氰酸（hydrocyanic acid）。此外，亞麻苦苷也可能經腸道細菌酵素或腸胃道酸鹼環境下水解生成氫氰酸。因此當人們食入因處理不完全而含有氫氰酸或亞麻苦苷殘留的食物時，皆有暴露於氫氰酸中毒的風險。衛生福利部公告之「食品中污染物質及毒素衛生標準」中訂有木薯粉與即食木薯片之總氫氰酸限量為10mg／kg，本研究因應上述標準建立木薯製品中總氫氰酸之檢驗方法。取檢體添加亞麻苦苷酶於38°C作用4小時，透過蒸氣蒸餾以氫氧化鈉收集氫氰酸，以高效離子層析儀進行分析。確效部份，於空白木薯粉中分別添加相當於1、10及40mg／kg氫氰酸之亞麻苦苷，其同日間總氫氰酸之平均回收率分別為94.7、97.2及90.7％，變異係數分別為1.9、1.3及1.1％，異日間添加回收之變異係數為3.2％，皆符合本署之食品化學檢驗方法之確效規範。本方法之定量極限為1mg／kg。以所建立方法檢驗市售6件木薯粉，結果總氫氰酸皆未檢出；20件邊境與後市場抽驗木薯片檢體檢出之總氫氰酸含量介於6.6－104.5mg／kg，計有18件超出法規限量，不合格均已移請相關權責單位進行後續處辦。

Cassava root is an important source of carbohydrates for developing countries. It is not only used as staple food, but also processed into tapioca flour, cassava chips, gari, and so on. Linamarin is a cyanogenic glucoside in cassava. Linamarin may be hydrolyzed by endoenzyme of cassava, and then releases toxic hydrocyanic acid (HCN) during processing. Besides, linamarin can be also hydrolyzed by gut flora enzymes or alkaline /acid environment in the gastrointestinal tract in the human body. Therefore, people are under the risk of cyanide poisoning if consume not fully processed cassava products. Based on the maximum allowed level of total HCN for tapioca starch and ready to eat tapioca chips in ''Sanitation Standard for Contaminants and Toxins in Food'' set by the Ministry of Health and Welfare, Taiwan, this research aims at developing a method to determine the total HCN in cassava products. Besides, a surveillance study was conducted for tapioca starch and ready-to-eat tapioca chips. For sample preparation, the hydrolysis process started from the addition of linamarase into a sample, and then cultivated at 38°C for 4 hours. After steam distillation, HCN was collected in sodium hydroxide, the cyanide in the distillate was determined by ion chromatography coupled with an electrochemical detector. The LOQ of total HCN for this method was assigned to 1 mg/kg. A recovery study for total HCN was conducted by spiking linamarin at the levels of 1, 10 and 40 mg/kg (HCN equ.) to blank tapioca starch samples. The average recoveries were 94.7, 97.2 and 90.7%, respectively, and the coefficients of variation (CV) in repeatability and intermediate precision were 1.1-1.9% and 3.2%, respectively. This method was applied to a market survey. Total HCN in 6 tapioca starch samples were not detected. However, the total HCN in 18 out of 20 ready-to-eat tapioca chip samples were between 6.6 and 104.5 mg/kg. The 18 unconformity products had reported to relative authorities for further administration.