- 期刊
Bacteriological Analysis of Alfalfa Seeds and Sprouts Using Disinfectants for Sanitization
使用消毒劑清洗對於苜蓿種子和苜蓿芽細菌殺菌之影響
摘要
苜蓿芽為即食性沙拉用生菜之重要芽菜之一，此類型食品常因種子污染和出芽時衛生狀況不良，造成高風險的食品中毒事件。由於種子本身就有微生物附著，培育過程中提供充足之水分與最適微生物生長之溫度，促使種子出芽與成長為苜蓿芽。因此本研究採樣分析超市販賣之冷藏苜蓿芽，雖然並未檢出含有四種病原菌，但是生菌數和大腸桿菌群皆高於7 log CFU/g和4 log CFU/g。因此，研究以消毒試劑(0.5% H2O2, 100 ppm available chlorine，100 ppm Clean Good (ClO2), 75% ethanol)與50℃和70℃無菌水清洗苜蓿種子5分鐘，75% ethanol和50℃ 0.5% H2O2會影響種子出芽率。除50℃，70℃和100 ppm Clean Good (ClO2)外，其餘都能降低生菌數1.5 log CFU/g以上。在出芽成長的過程中，苜蓿芽生菌數與大腸桿菌群會增加3-4 log CFU/g。剛採收的苜蓿芽之生菌數平均高達8.8 log CFU/g，大腸桿菌群為6.6 log CFU/g，用單一之化學試劑清洗60 ppm ClO2 (Clean Good)+1% citric acid，Clean Good (ClO2) 60 ppm，available chlorine 50 ppm 和H2O2 50 ppm，大約只能降低生菌數0.9-2.2 log CFU/g，降低大腸桿菌群0.2-1.0 log CFU/g。探討苜蓿芽不易清洗的原因，苜蓿芽的種皮不易清洗，含的菌數最高，清洗無法完全去除。若以連續的化學試劑（次氯酸鈉→Clean Good→酸性電解水）配合超音波清洗，能降低生菌數可達4.5 log CFU/g，降低大腸桿菌群3.5 log CFU/g，並且能使接種3.0 log CFU/g之Salmonella typhimurium, Escherichia coli O157：H7和Listeria monocytogenes完全殺死，效果非常顯著。
並列摘要
Alfalfa sprouts are an important element in ready-to-eat vegetables for making a salad. This food item poses a potential and relatively high risk of food-borne illnesses due to the fact that it is ready to be used, and its exposure to poor sanitary conditions during both seed and sprout production. In addition, the conditions for seed germination as well as for sprouting are characterized by warm temperature, high humidity, and readily available nutrients. All of these conditions facilitate the growth of the microorganisms adhering to the seeds. In this study, refrigerated alfalfa sprouts from some domestic supermarkets in northern Taiwan were sampled; and the microbiological analysis showed these food samples to be negative for three types of pathogenic bacteria, while the total plate count (TPC) and coliform count were higher than 8 and 5 log CFU/g, respectively. In the experiments of chemical disinfectants including 0.5% H2O2, 100ppm available chlorine (NaOCl), 100 ppm ClO2 (Clean Good), and 75% ethanol as well as 50 and 70℃ sterile water, their effects on the bacterial load of alfalfa sprouts and on the germination rate of alfalfa seeds were tested. Among the chemicals, 100 ppm available chlorine, 75% ethanol, and 0.5% H2O2 could effectively reduce TPC by ＞1.5 log CFU/g of alfalfa seeds, while both 75% ethanol at 70℃ and 0.5% H2O2 at 50℃ displayed a negative impact on the germination rate of alfalfa seeds. During the process of seed germination and sprouting, both the TPC and the coliform count increased 3-4 log CFU/g of alfalfa sprouts. For freshly harvested alfalfa sprouts on which the TPC and the coliform count were initially 8.8 and 6.6 log CFU/g, respectively, a single chemical disinfection with acidified 60 ppm ClO2 (Clean Good), 60 ppm ClO2, 50 ppm available chlorine, or 50 ppm H2O2 reduced the TPC and the coliform count by only 0.9-2.2 and 0.2-1.0 log CFU/g, respectively. The cause of the poor efficacy of chemical disinfectants was due to the fact that a washing procedure with any single disinfectant could not completely sanitize or get rid of the alfalfa seed coating of bacterial contamination. In contrast, a three-stage washing treatments in a manner of sequential disinfection (NaOCl→Clean Good→electrolyzed oxidizing water) under ultrasonic enhancement could reduce 4.5 log CFU/g for TPC and 3.5 log CFU/g for coliform count, and eliminated Salmonella typhimurium, Escherichia coli O157: H7, and Listeria monocytogenes (at 3.0 log CFU/g each) inoculated onto alfalfa sprouts.