Yuste J, Fung D Y C
Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas 66506, USA.
J Food Prot. 2004 Feb;67(2):371-7. doi: 10.4315/0362-028x-67.2.371.
Pasteurized apple juice with nisin (0, 25, 50, 100, and 200 ppm, wt/vol) and cinnamon (0 and 0.3%, wt/vol) was inoculated with Salmonella Typhimurium and Escherichia coli O157:H7 at 10(4) CFU/ml and stored at 5 and 20 degrees C. Counts on tryptic soy agar (TSA), selective medium (xylose Lysine desoxycholate agar for Salmonella Typhimurium, and MacConkey sorbitol agar for E. coli O157:H7), and thin agar layer (TAL) were determined at 1 h and 1, 3, 7, and 14 days. The TAL method (selective medium overlaid with TSA) was used for recovery of sublethally injured cells. The pathogens were gradually inactivated by the acidic pH of apple juice. Nisin and cinnamon greatly contributed to the inactivation. The killing effect was more marked at 20 degrees C, with counts in all treated samples being undetectable by direct plating in 3 days for Salmonella Typhimurium and 7 days for E. coli O157:H7. Thus, several factors influenced the decrease in counts: low pH, addition of nisin and cinnamon, and storage temperature. The TAL method was as effective as TSA in recovering injured cells of the pathogens. The combination of nisin and cinnamon accelerates death of Salmonella Typhimurium and E. coli O157:H7 in apple juice and so enhances the safety of the product.
将含有乳酸链球菌素（0、25、50、100和200 ppm，重量/体积）和肉桂（0和0.3%，重量/体积）的巴氏杀菌苹果汁接种鼠伤寒沙门氏菌和大肠杆菌O157:H7，接种浓度为10⁴ CFU/ml，并分别在5℃和20℃下储存。在1小时以及1、3、7和14天时，测定胰蛋白胨大豆琼脂（TSA）、选择性培养基（用于鼠伤寒沙门氏菌的木糖赖氨酸脱氧胆酸盐琼脂和用于大肠杆菌O157:H7的麦康凯山梨醇琼脂）以及薄琼脂层（TAL）上的菌落数。采用TAL方法（在TSA上覆盖选择性培养基）来复苏亚致死损伤细胞。病原菌因苹果汁的酸性pH值而逐渐失活。乳酸链球菌素和肉桂对失活有很大作用。在20℃时杀灭效果更显著，对于鼠伤寒沙门氏菌，所有处理样品在3天内通过直接平板计数无法检测到菌落数；对于大肠杆菌O157:H7，在7天内无法检测到。因此，有几个因素影响了菌落数的减少：低pH值、添加乳酸链球菌素和肉桂以及储存温度。TAL方法在复苏病原菌损伤细胞方面与TSA同样有效。乳酸链球菌素和肉桂的组合加速了苹果汁中鼠伤寒沙门氏菌和大肠杆菌O157:H7的死亡，从而提高了产品的安全性。
