清洗條件對截切萵苣品質之影響

中文摘要隨著工商資訊社會之快速發展，外食人口膨脹，截切蔬菜之市場需求量迅速增加，截切蔬菜最近幾年中已成為超商販賣之熱門產品之一。即食工廠生鮮蔬菜的微生物品質會影響其後續之清洗條件及產品架售期，如何延長截切蔬菜架售期（shelf life）為業者努力的方向。本研究探討即食工廠進貨各類蔬菜原料的微生物品質，及清洗條件包括：以不同的菜量與水量比例、浸泡時間及清洗藥劑（次氯酸鈉、二氧化氯）的濃度等對結球萵苣微生物品質及藥劑殘留等情形作探討，以供即食工廠作業人員設計作業流程之參考。結果顯示原料所含初始菌數因種類不同而有所差異。葉菜類（芥蘭菜、青江菜、油菜、龍鬚菜）的生菌數約為104~106 CFU/g，大腸桿菌群約為102~103 CFU/g；結球類（萵苣、高麗菜）生菌數約為102~106 CFU/g，大腸桿菌群約為101~103 CFU/g；以葉菜類的生菌數及大腸桿菌群較偏高。氯系溶液(次氯酸鈉及二氧化氯)清洗截切萵苣效果，以濃度為200 ppm，浸泡時間為10分鐘及20分鐘，其清洗消毒效果可達沙拉用生菜之國家衛生標準要求。清洗浸泡過程中，次氯酸鈉與二氧化氯溶液對總生菌數及大腸桿菌群的殺菌效果相同，但在貯存試驗中發現以200 ppm氯系溶液清洗後之截切萵苣，貯存於環境22℃下24小時後，以二氧化氯抑菌效果較次氯酸鈉溶液為佳。其總生菌數比次氯酸鈉溶液組低約1.09 log CFU/g，在大腸桿菌群方面則比次氯酸鈉組低約1.12 log CFU/g，顯示以二氧化氯溶液當清洗殺菌劑在微生物品質之控制上是較有幫助。隨著氯系溶液濃度增加其殺菌效果亦增加，截切萵苣中大腸桿菌群的減少量與浸泡氯系溶液的濃度呈線性相關(r2=0.72~0.95)由其迴歸方程式可得知，當次氯酸鈉溶液提高至185.34 ppm以上或二氧化氯溶液提高至205.74 ppm以上，浸泡20分鐘即可有效將截切萵苣的大腸桿菌群減少4 log CFU/g以上。以200 ppm二氧化氯溶液清洗浸泡截切萵苣20分鐘後，於0、2及4小時連續檢測其殘留餘氯，結果顯示並無殘留情形，而以200 ppm次氯酸鈉溶液清洗浸泡組其殘氯值於0、2、4小時後分為0.1 、0.08 、0.08 ppm，均符合飲用水標準（1.0ppm以下）。

關鍵字

截切蔬菜；二氧化氯；次氯酸鈉

並列摘要

ABSTRACT The amount of population eating out is getting bigger and bigger with the fast development of today`s society. Meanwhile, the demands of shredded vegetables, which has been one of the best sellers in supermarkets in recent years, increase rapidly. Because the microorganism quality of raw vegetables in fresh-to-eat factories will affect the following washing conditions and shelf life, it is important to extend the shelf life of shredded vegetables. The objective of this study is to explore the microorganism quality and washing conditions of raw vegetables in fresh-to-eat factories. In this study, we intend to evaluate the microorganism quality of different kinds of vegetables form fresh-to-eat factories. How many disinfectants are left in lettuce, by using different proportions of water and vegetables, soaking time, and concentration of disinfectants (sodium hypochlorite solution and chlorine dioxide). The results could be referenced by the fresh-to-eat factories to design the progress of work. The result shows that the original bacterial counts of materials are different from their categories. In（chinese broccoli、green cabbage、pak-choi、sauash seeding）, the total plate count(TPC) is about 104~106 CFU/g, and the coliform count is about 102~103 CFU/g. In （lettuce and cabbage）, the TPC is about 102~106 CFU/g, and the coliform count is about 101~103 CFU/g. The TPC and coliform count of vegetables are higher. Shredded lettuce washed and soaked with 200 ppm chlorine solution (sodium hypochlorite solution and chlorine dioxide), and soaking in 10 and 20 min, can reach the National Hygiene Standard of shredded vegetables. During the progress of washing and soaking, the effects of sodium hypochlorite solution and chlorine dioxide sanitizing total bacterial count and coliform count are the same. But in storage tests, we find that washing shredded lettuce treated with 200 ppm chlorine solution, storage at 22℃ during 24hours, the chlorine dioxide is found to be more effective in disinfecting than sodium hypochlorite solution. The TPC of shreeded lettuce treated with 200 ppm chlorine solution is lower than treated with sodium hypochlorite solution by about 1.09 log CFU/g. The coliform count treated with 200 ppm chlorine solution is lower than treated with sodium hypochlorite solution by about 1.12 log CFU/g. The result shows that using chlorine solution as a washing disinfectant is beneficial to control the microorganism quality. The concentration of chlorine solution is increasing, the more effective to sanitize is increasing. The coliform reduction of shredded lettuce is linear relative with the concentration of soaking chlorine solution(r2=0.72~0.95). According to the regression formula, if treated with 185.34 ppm or higher concentration sodium hypochlorite solution, or treated with higher than 205.74 ppm chlorine dioxide, after 20 min soaking, the coliform count of shredded lettuce is effectively reduced to more than 4 log CFU/g. After washing shredded lettuce soaked in 200 ppm chlorine dioxide in 20 min, we test the left chlorine in 0, 2 and 4 hours. The result shows there`s no free residual chlorine. After washing shredded lettuce soaked in 200 ppm sodium hypochlorite solution, we test the left chlorine of shredded lettuce in 2 and 4 hours. The left chlorine is 0.1, 0.08, 0.08 ppm, respectively, which is acceptable by the standard of drinking water(under 1.0 ppm).