Yuste J, Fung D Y C
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600, USA.
J Food Prot. 2002 Oct;65(10):1663-6. doi: 10.4315/0362-028x-65.10.1663.
Normal (pH 3.7) and adjusted (pH 5.0) pasteurized apple juice containing cinnamon (0, 0.1, 0.2, and 0.3%) was inoculated with Listeria monocytogenes Scott A 49594 at 10(4) CFU/ml and stored at 5 and 20 degrees C for 7 days. Counts on tryptic soy agar (TSA), modified Oxford (MOX) medium, and thin agar layer (TAL) were determined at 1 h and 1, 3, and 7 days. The TAL method (MOX medium overlaid with TSA) was used for the recovery of injured cells. In apple juice, both at normal and adjusted pH, with any doses of cinnamon, no L. monocytogenes (a 4.6-log CFU/ml reduction) was detected after 1 h of storage at both temperatures, and no growth occurred at any points of storage. Therefore, cinnamon by itself (regardless of pH) had a pronounced killing effect. A further enrichment step with brain heart infusion agar showed that L monocytogenes was completely inactivated in apple juice stored at 20 degrees C, except in pH 5.0 samples with 0.1% of cinnamon. The TAL method was as effective as TSA in recovering injured cells of L. monocytogenes. Cinnamon considerably inactivates L. monocytogenes in apple juice and thus enhances the safety of this product.
将含有肉桂（0%、0.1%、0.2%和0.3%）的正常（pH 3.7）和调节后（pH 5.0）的巴氏杀菌苹果汁接种单核细胞增生李斯特菌Scott A 49594，使其浓度达到10⁴CFU/ml，并在5℃和20℃下储存7天。在1小时以及1、3和7天时，测定胰蛋白胨大豆琼脂（TSA）、改良牛津（MOX）培养基和薄琼脂层（TAL）上的菌落数。TAL方法（在TSA上覆盖MOX培养基）用于复苏受损细胞。在苹果汁中，无论正常pH还是调节后的pH，无论肉桂剂量如何，在两个温度下储存1小时后均未检测到单核细胞增生李斯特菌（减少4.6个对数CFU/ml），且在储存的任何时间点均未生长。因此，肉桂本身（无论pH值如何）具有显著的杀菌作用。用脑心浸液琼脂进行进一步富集培养表明，除了含0.1%肉桂的pH 5.0样品外，在20℃储存的苹果汁中，单核细胞增生李斯特菌完全失活。TAL方法在复苏单核细胞增生李斯特菌受损细胞方面与TSA同样有效。肉桂能使苹果汁中的单核细胞增生李斯特菌大量失活，从而提高该产品的安全性。
