Tamminga S K, Beumer R R, Kampelmacher E H
J Hyg (Lond). 1982 Feb;88(1):125-42. doi: 10.1017/s0022172400069989.
One hundred and eighty-two raw, 112 pre-cooked and 750 cooked hamburgers composed mainly of beef or beef and pork were subjected to microbiological examination.Raw hamburgers gave total bacterial counts from 10(6) to 10(8) per g, counts of Enterobacteriaceae from 10(4) to 10(6) per g, of Escherichia coli from 10(3) to 10(5), of group D streptococci from 10(2) to 10(4), of Staphylococcus aureus from 3 to 10(2) and of Clostridium perfringens less than 10 bacteria per g. Of the samples, 32% contained salmonellas; the highest most probable number was 10(2) per g but most estimates were below 1 per g. Corresponding figures for the pre-cooked samples were 2-3 log cycles lower, and only one sample contained salmonella. Yersinia enterocolitica was not isolated from any raw or pre-cooked sample.Three hundred and ninety-five of the cooked hamburgers were prepared by grilling raw hamburgers for between 2 and 5.5 min. These gave total bacterial counts from 10(5) to 10(7) per g, and counts of Enterobacteriaceae from 10(2) to 10(5) per g. Of the samples, 9.4% contained salmonellas, always in numbers below 1 per g. The remaining 355 cooked hamburgers were prepared from samples pre-cooked for 10 min at 80 degrees C. Some were grilled and some fat fried. The total bacterial counts were from 10(3) to 10(5) per g, and counts of Enterobacteriaceae below 10(2) per g. Salmonellae, again in small numbers only, were recovered from 3.5% of samples.When hamburgers were artificially contaminated with Salmonella typhimurium it took 5.5 min on a commercial grill, 2.25 min frying in a frying pan and 1.75 min on a household grill to reliably reduce the salmonella count one hundredfold. This means that at many vending places hamburgers are often cooked for too short a time.D-values were determined for S. typhimurium in hamburger meat at 50, 55, 60, 65 and 70 degrees C, these values were 7.1, 5.1, 1.2, 0.9 and 0.6 min respectively. It can be concluded that the heating action in the centre of the hamburgers will take place more slowly than in the hamburger as a whole, and that the time between cooking and consumption is very important in reducing the microbial load to acceptable levels.Pre-cooking (10 min at 80 degrees C in a water bath) gives a reduction in the numbers of salmonella of about 4 x 10(3), after which cooking gives a further reduction as mentioned above.
对182个生的、112个预煮的和750个主要由牛肉或牛肉与猪肉制成的熟汉堡进行了微生物检验。生汉堡每克的总细菌数为10⁶至10⁸，肠杆菌科细菌数为10⁴至10⁶，大肠杆菌数为10³至10⁵，D群链球菌数为10²至10⁴，金黄色葡萄球菌数为3至10²，产气荚膜梭菌数每克少于10个。在这些样本中，32%含有沙门氏菌；最高的最可能数为每克10²，但大多数估计值低于每克1个。预煮样本的相应数字低2至3个对数周期，且只有一个样本含有沙门氏菌。未从任何生的或预煮的样本中分离出小肠结肠炎耶尔森氏菌。
750个熟汉堡中有395个是通过将生汉堡在烤架上烤2至5.5分钟制成的。这些熟汉堡每克的总细菌数为10⁵至10⁷，肠杆菌科细菌数为10²至10⁵。在这些样本中，9.4%含有沙门氏菌，数量始终低于每克1个。其余355个熟汉堡是由在80℃预煮10分钟的样本制成的。有些是烤的，有些是油炸的。总细菌数为每克10³至10⁵，肠杆菌科细菌数低于每克10²。沙门氏菌同样仅在少数样本中检出，占样本的3.5%。
当汉堡被鼠伤寒沙门氏菌人工污染后，在商业烤架上烤5.5分钟、在平底锅中煎2.25分钟以及在家庭烤架上烤1.75分钟才能可靠地将沙门氏菌数量减少100倍。这意味着在许多售货场所，汉堡的烹饪时间往往过短。
测定了鼠伤寒沙门氏菌在汉堡肉中50℃、55℃、60℃、65℃和70℃时的D值，这些值分别为7.1分钟、5.1分钟、1.2分钟、0.9分钟和0.6分钟。可以得出结论，汉堡中心的加热作用比整个汉堡的加热作用进行得更慢，并且烹饪和食用之间的时间对于将微生物负荷降低到可接受水平非常重要。预煮（在水浴中80℃煮10分钟）可使沙门氏菌数量减少约4×10³，之后如上述烹饪可进一步减少。
