Foong Sally C C, Gonzalez Glenda L, Dickson James S
Food Safety Research Laboratory, Department of Microbiology, Iowa State University, Ames, Iowa 50011, USA.
J Food Prot. 2004 Jan;67(1):77-82. doi: 10.4315/0362-028x-67.1.77.
A five-strain Listeria monocytogenes culture was inoculated onto six different types of ready-to-eat (RTE) meats (frankfurters, ham, roast beef, bologna, smoked turkey with lactate, and smoked turkey without lactate). The meats were vacuum packed and stored at 4 degrees C for 24 h prior to irradiation. Populations of L. monocytogenes were recovered by surface plating on nonselective and selective media. The margins of safety studied include 3-log (3D) and 5-log (5D) reduction of pathogenic bacteria to achieve an optimal level of reduction while retaining organoleptic qualities of the meats. A 3-log reduction of L. monocytogenes was obtained at 1.5 kGy when nonselective plating medium was used. The dosages for 3-log reduction were 1.5 kGy for bologna, roast beef, and both types of turkey and 2.0 kGy for frankfurters and ham on the basis of use of selective medium. The D10-values ranged from 0.42 to 0.44 kGy. A 5-log reduction of L. monocytogenes was obtained at 2.5 kGy with nonselective medium. With selective medium, the dosages were 2.5 kGy for bologna, roast beef, and both types of turkey and 3.0 kGy for frankfurters and ham. Survival of L. monocytogenes in the same RTE meat types after irradiation was also studied. Meats were inoculated with 5 log L. monocytogenes per g and irradiated at doses of 2.0 and 4.0 kGy. Recovery of the surviving organisms was observed during storage at temperatures of 4 and 10 degrees C for 12 weeks. Preliminary results showed no growth in meats irradiated at 4.0 kGy. Survivors were observed for irradiated meats at 2.0 kGy stored at 10 degrees C after the second week. No growth was observed in samples irradiated at 2.0 kGy stored at 4 degrees C until the fifth week.
将一种五菌株的单核细胞增生李斯特菌培养物接种到六种不同类型的即食（RTE）肉类上（法兰克福香肠、火腿、烤牛肉、博洛尼亚香肠、添加乳酸的烟熏火鸡和未添加乳酸的烟熏火鸡）。这些肉类进行真空包装，并在辐照前于4℃下储存24小时。通过在非选择性和选择性培养基上进行表面平板培养来回收单核细胞增生李斯特菌的菌数。所研究的安全裕度包括将病原菌减少3个对数（3D）和5个对数（5D），以达到最佳的减少水平，同时保持肉类的感官品质。当使用非选择性平板培养基时，在1.5千戈瑞剂量下可实现单核细胞增生李斯特菌减少3个对数。基于选择性培养基的使用，博洛尼亚香肠、烤牛肉和两种火鸡肉实现3个对数减少的剂量为1.5千戈瑞，法兰克福香肠和火腿为2.0千戈瑞。D10值范围为0.42至0.44千戈瑞。使用非选择性培养基时，在2.5千戈瑞剂量下可实现单核细胞增生李斯特菌减少5个对数。对于选择性培养基，博洛尼亚香肠、烤牛肉和两种火鸡肉的剂量为2.5千戈瑞，法兰克福香肠和火腿为3.0千戈瑞。还研究了辐照后单核细胞增生李斯特菌在相同即食肉类类型中的存活情况。将肉类接种每克5个对数的单核细胞增生李斯特菌，并以2.0和4.0千戈瑞的剂量进行辐照。在4℃和10℃下储存12周期间观察存活菌的回收情况。初步结果表明，在4.0千戈瑞辐照的肉类中没有生长。在第二周后，观察到在10℃下储存的2.0千戈瑞辐照肉类中有存活菌。在4℃下储存的2.0千戈瑞辐照样品中直到第五周都没有观察到生长。
