Department Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409, USA.
J Food Prot. 2005 Aug;68(8):1587-92. doi: 10.4315/0362-028x-68.8.1587.
Studies were conducted to determine whether four strains of lactic acid bacteria (LAB) inhibited Escherichia coli O157: H7 and Salmonella in ground beef at 5 degrees C and whether these bacteria had an impact on the sensory properties of the beef. The LAB consisted of frozen concentrated cultures of four Lactobacillus strains, and a cocktail mixture of streptomycin-resistant E. coli O157:H7 and Salmonella were used as pathogens. Individual LAB isolates at 10(7) CFU/ml were added to tryptic soy broth containing a pathogen concentration of 10(5) CFU/ml. Samples were stored at 5 degrees C, and pathogen populations were determined on days 0, 4, 8, and 12. After 4 days of storage, there were significant differences in numbers of both pathogens exposed to LAB isolates NP 35 and NP 3. After 8 and 12 days of storage, all LAB reduced populations of both pathogens by an average of 3 to 5 log cycles. A second study was conducted in vacuum-packaged fresh ground beef. The individual LAB isolates resulted in an average difference of 1.5 log cycles of E. coli O157:H7 after 12 days of storage, and Salmonella populations were reduced by an average of 3 log cycles. Following this study, a mixed concentrated culture was prepared from all four LAB and added to ground beef inoculated with pathogen at 10(8) CFU/g. After 3 days of storage, the mixed culture resulted in a 2.0-log reduction in E. coli O157:H7 compared with the control, whereas after 5 days of storage, a 3-log reduction was noted. Salmonella was reduced to nondetectable levels after day 5. Sensory studies on noninoculated samples that contained LAB indicated that there were no adverse effects of LAB on the sensory properties of the ground beef. This study indicates that adding LAB to raw ground beef stored at refrigeration temperatures may be an important intervention for controlling foodborne pathogens.
研究旨在确定四种乳酸菌（LAB）是否能抑制 5°C 下碎牛肉中的大肠杆菌 O157:H7 和沙门氏菌，以及这些细菌是否会影响牛肉的感官特性。LAB 由四种乳酸菌的冷冻浓缩培养物组成，而耐链霉素的大肠杆菌 O157:H7 和沙门氏菌的鸡尾酒混合物则被用作病原体。将 10（7）CFU/ml 的单个 LAB 分离物添加到含有 10（5）CFU/ml 病原体浓度的胰蛋白酶大豆肉汤中。样品储存在 5°C 下，在 0、4、8 和 12 天测定病原体种群。在储存 4 天后，暴露于 LAB 分离物 NP 35 和 NP 3 的两种病原体数量存在显著差异。在储存 8 和 12 天后，所有 LAB 均使两种病原体的种群数量平均减少了 3 到 5 个对数周期。第二项研究在真空包装的新鲜碎牛肉中进行。在 12 天的储存后，单个 LAB 分离物导致大肠杆菌 O157:H7 的平均差异为 1.5 个对数周期，沙门氏菌种群减少了平均 3 个对数周期。在这项研究之后，从所有四种 LAB 中制备了混合浓缩培养物，并添加到接种有 10（8）CFU/g 病原体的碎牛肉中。在储存 3 天后，与对照相比，混合培养物使大肠杆菌 O157:H7 的数量减少了 2.0 个对数，而在储存 5 天后，数量减少了 3 个对数。沙门氏菌在第 5 天后降至无法检测的水平。对含有 LAB 的未接种样品进行的感官研究表明，LAB 对碎牛肉的感官特性没有不良影响。这项研究表明，在冷藏温度下储存生碎牛肉时添加 LAB 可能是控制食源性病原体的重要干预措施。
