Juneja Vijay K, Mohr Tim B, Silverman Meryl, Snyder O Peter
U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038.
U.S. Department of Agriculture, Food Safety and Inspection Service, Office of Public Health Science, Science Staff, 530 Center Street N.E., Suite 401, Salem, Oregon 97301.
J Food Prot. 2018 Mar 1;81(3):430-436. doi: 10.4315/0362-028X.JFP-17-397.
The objective of this study was to assess the ability of Bacillus cereus spores to germinate and grow in order to determine a safe cooling rate for cooked rice, beans, and pasta, rice-chicken (4:1), rice-chicken-vegetables (3:1:1), rice-beef (4:1), and rice-beef-vegetables (3:1:1). Samples were inoculated with a cocktail of four strains of heat-shocked (80°C for 10 min) B. cereus spores (NCTC 11143, 935A/74, Brad 1, and Mac 1) to obtain a final spore concentration of approximately 2 log CFU/g. Thereafter, samples were exponentially cooled through the temperature range of 54.5 to 7.2°C in 6, 9, 12, 15, 18, and 21 h. At the end of the cooling period, samples were removed and plated on mannitol egg yolk polymyxin agar. The plates were incubated at 30°C for 24 h. The net B. cereus growth from spores in beans was <1 log after 9 h of cooling, but the pathogen grew faster in rice and pasta. In combination products, the net growth was as follows: 3.05, 3.89, and 4.91 log CFU/g in rice-chicken; 3.49, 4.28, and 4.96 log CFU/g in rice-beef; 3.50, 4.20, and 5.32 CFU/g in rice-chicken-mixed vegetables; and 3.68, 4.44, and 5.25 CFU/g in rice-beef-mixed vegetables after 15, 18, and 21 h of cooling, respectively. This study suggests safe cooling rates for cooling cooked rice, beans, pasta, rice-chicken, rice-chicken-vegetables, rice-beef, and rice-beef-vegetables to guard against the hazards associated with B. cereus.
本研究的目的是评估蜡样芽孢杆菌孢子的萌发和生长能力，以确定米饭、豆类、面食、米鸡（4:1）、米鸡蔬菜（3:1:1）、米牛肉（4:1）和米牛肉蔬菜（3:1:1）的安全冷却速率。将样品接种四种经热激处理（80°C处理10分钟）的蜡样芽孢杆菌孢子菌株（NCTC 11143、935A/74、Brad 1和Mac 1）的混合菌液，以使最终孢子浓度达到约2 log CFU/g。此后，将样品在6、9、12、15、18和21小时内从54.5°C至7.2°C进行指数冷却。冷却期结束后，取出样品并接种于甘露醇卵黄多粘菌素琼脂平板上。平板在30°C下培养24小时。豆类中孢子的蜡样芽孢杆菌净生长在冷却9小时后<1 log，但该病原体在米饭和面食中生长更快。在混合产品中，净生长情况如下：冷却15、18和21小时后，米鸡中分别为3.05、3.89和4.91 log CFU/g；米牛肉中分别为3.49、4.28和4.96 log CFU/g；米鸡混合蔬菜中分别为3.50、4.20和5.32 CFU/g；米牛肉混合蔬菜中分别为3.68、4.44和5.25 CFU/g。本研究提出了将熟米饭、豆类、面食、米鸡、米鸡蔬菜、米牛肉和米牛肉蔬菜冷却至安全温度的冷却速率，以防范与蜡样芽孢杆菌相关的危害。
