Ariyapitipun T, Mustapha A, Clarke A D
Department of Food Science and Human Nutrition, University of Missouri-Columbia, 65211, USA.
J Food Prot. 1999 Aug;62(8):913-20. doi: 10.4315/0362-028x-62.8.913.
The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control, water, or nisin alone (P < or = 0.05).
测定了聚乳酸、乳酸、乳酸链球菌素以及酸与乳酸链球菌素组合对延长生牛肉货架期的效果。将新鲜牛肉块（5×5×2.5厘米）浸入2%低分子量聚乳酸（LMW-PLA）溶液、2%乳酸（LA）溶液、每毫升含200国际单位乳酸链球菌素的溶液，或乳酸链球菌素与2% LMW-PLA或2% LA的组合溶液中。然后将样品沥干、真空包装，并在4℃下储存长达56天。在56天内每周测定牛肉表面的pH值以及嗜冷需氧菌、嗜冷和嗜温肠杆菌科、假单胞菌和乳酸杆菌的数量。用2% LMW-PLA或每毫升含200国际单位乳酸链球菌素与2% LMW-PLA的组合处理的牛肉样品，在第0天的平均表面pH值分别显著降至5.19和5.17（P≤0.05），而用2% LA或每毫升含200国际单位乳酸链球菌素的2% LA溶液去污处理的样品，其表面pH值分别从5.62显著降至4.98和4.96。2% LMW-PLA、2% LA或每种酸与乳酸链球菌素的组合对新鲜牛肉上的嗜冷需氧菌（分别减少1.94、2.36、2.59和1.76个对数级）、嗜冷肠杆菌科（分别减少1.37、1.86、1.77和1.35个对数级）、嗜温肠杆菌科（分别减少1.00、1.00、0.82和0.68个对数级）以及假单胞菌（分别减少1.77、1.57、1.76和1.41个对数级）均表现出即时抑制作用（P≤0.05）。从肠杆菌科和假单胞菌的数量来看，这种减少在长达56天内都很明显（P≤0.05）。由于处理与储存时间之间没有相互作用，所以将每个时期的数据合并，并呈现为处理对新鲜牛肉总体微生物数量的影响。结果发现，与未处理的对照、水或单独的乳酸链球菌素相比，2% LMW-PLA、2% LA以及每种酸与乳酸链球菌素的组合均显著降低了上述微生物的数量（P≤0.05）。
