Greer G G, Dilts B D
Agriculture and Agri-Food Canada, Lacombe Research Station, Alberta, Canada.
Int J Food Microbiol. 1995 Apr;25(2):141-51. doi: 10.1016/0168-1605(94)00088-n.
The antibacterial effects of a 3% solution of lactic acid at 55 degrees C were assessed, by examining aerobic bacterial growth on artificially-inoculated pork fat and lean tissue. Discs of fat or lean tissues, each of 10 cm2 surface area, were aseptically excised from pork Longissimus dorsi muscle and inoculated with the cold tolerant pathogens Listeria monocytogenes 4b Scott A no. 3, Yersinia enterocolitica 0:4,32 or Aeromonas hydrophila ATCC 7966, or with the wild type spoilage bacteria Pseudomonas fragi or Brochothrix thermosphacta. After inoculation, each meat disc was immersed in water or lactic acid for 15 s and aerobic bacterial growth followed during 15 days of storage at 4 degrees C. P. fragi and B. thermosphacta grew on both fat and lean, but the pathogens grew on fat tissue only and A. hydrophila did not survive on lean. Lactic acid reduced all test bacteria on fat to below detectable levels within 4 days of treatment and no bacteria could be recovered from acid-treated fat surfaces for the remainder of the 15-day storage interval. Bacteria attached to lean were generally more resistant to lactic acid. In some instances the acid was bacteriostatic (P. fragi, L. monocytogenes) while in others the population declined at a greatly reduced rate as compared with a similar population on fat (B. thermosphacta, Y. enterocolitica). A. hydrophila was equally sensitive to lactic acid on lean and fat. Depending upon the tested strain, tissue type and storage time, maximum reductions in the number of bacteria recovered from acid treated pork ranged from 1 to 8 log cycles. The high bactericidal efficacy of lactic acid applied to pork fat was attributable to a low tissue pH, which varied from 3.49 to 4.41 during the 15 days of aerobic storage.
通过检测人工接种的猪脂肪和瘦肉组织上需氧菌的生长情况，评估了55摄氏度下3%乳酸溶液的抗菌效果。从猪背最长肌无菌切下表面积为10平方厘米的脂肪或瘦肉组织片，接种耐冷病原体单核细胞增生李斯特菌4b Scott A 3号菌株、小肠结肠炎耶尔森菌0:4,32或嗜水气单胞菌ATCC 7966，或接种野生型腐败菌脆弱拟杆菌或热杀索丝菌。接种后，将每个肉组织片在水或乳酸中浸泡15秒，并在4摄氏度下储存15天期间跟踪需氧菌的生长情况。脆弱拟杆菌和热杀索丝菌在脂肪和瘦肉上均能生长，但病原体仅在脂肪组织上生长，嗜水气单胞菌在瘦肉上无法存活。乳酸在处理后4天内将脂肪上的所有测试细菌数量降至可检测水平以下，在15天储存期的剩余时间内，酸处理过的脂肪表面未检测到细菌。附着在瘦肉上的细菌通常对乳酸更具抗性。在某些情况下，酸具有抑菌作用（脆弱拟杆菌、单核细胞增生李斯特菌），而在其他情况下，与脂肪上的类似菌量相比，菌量下降速度大幅降低（热杀索丝菌、小肠结肠炎耶尔森菌）。嗜水气单胞菌在瘦肉和脂肪上对乳酸的敏感性相同。根据测试菌株、组织类型和储存时间的不同，从酸处理猪肉中回收的细菌数量最多可减少1至8个对数周期。应用于猪脂肪的乳酸具有高杀菌效力，这归因于较低的组织pH值，在需氧储存的15天内，pH值在3.49至4.41之间变化。
