Kasrazadeh M, Genigeorgis C
Department of Epidemiology and Preventive Medicine, School of Veterinary Medicine, University of California-Davis 95616, USA.
Int J Food Microbiol. 1995 May;25(3):289-300. doi: 10.1016/0168-1605(94)00089-o.
This study examined growth and control of two enterohemorrhagic Escherichia coli serotype O157:H7 strains in a soft Hispanic type cheese (Queso Fresco). Cheese was made in the laboratory using a commercial procedure and after inoculation it was stored under vacuum at temperatures ranging from 8 to 30 degrees C. The minimum temperature that allowed growth of E. coli in the unmodified normal cheese (pH 6.6) was 10 degrees C. No growth of either strains was observed during a 2 month storage period at 8 degrees C. Accumulated data from the growth studies were used for development of models relating square root of 1/LT (LT = lag time) and specific growth rate, to temperature. The effect of selected antimicrobials (potassium sorbate, sodium benzoate, and sodium lactate) added to milk or cheese on the growth and survival of these pathogens at various storage temperatures was also evaluated. Addition of sodium benzoate (0.3%) to cheese (pH 6.6) or addition of potassium sorbate (0.3%) to cheese (pH 6) made from milk acidified to pH 5.9 with propionic acid, had a significant impact on delaying or preventing growth of the pathogens.
本研究检测了两种肠出血性大肠杆菌O157:H7菌株在一种西班牙软质奶酪（新鲜奶酪）中的生长及控制情况。奶酪在实验室采用商业流程制作，接种后在8至30摄氏度的温度下真空储存。在未改良的普通奶酪（pH 6.6）中，大肠杆菌生长的最低温度为10摄氏度。在8摄氏度下储存2个月期间，未观察到任何一种菌株生长。生长研究积累的数据用于建立将1/LT的平方根（LT = 延滞期）和比生长速率与温度相关联的模型。还评估了添加到牛奶或奶酪中的选定抗菌剂（山梨酸钾、苯甲酸钠和乳酸钠）在不同储存温度下对这些病原体生长和存活的影响。向奶酪（pH 6.6）中添加苯甲酸钠（0.3%），或向用丙酸酸化至pH 5.9的牛奶制成的奶酪（pH 6）中添加山梨酸钾（0.3%），对延迟或防止病原体生长有显著影响。
