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首页> 外文学位 >Lactic acid, low molecular weight polylactic acid, and nisin for reduction of spoilage and pathogenic bacteria on vacuum-packaged fresh raw beef.
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Lactic acid, low molecular weight polylactic acid, and nisin for reduction of spoilage and pathogenic bacteria on vacuum-packaged fresh raw beef.

机译：乳酸，低分子量聚乳酸和乳链菌肽，可减少真空包装的新鲜生牛肉上的腐败和致病菌。

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摘要

The efficacy of 2% lactic acid (LA) and 2% low molecular weight polylactic acid (LMW PLA) against spoilage and pathogenic bacteria on vacuum-packaged fresh raw beef stored at refrigeration temperature was investigated. Nisin was tested as an additional hurdle to microbial growth. In the first experiment, raw beef cubes were dipped in a solution of 2% LA, 2% LMW PLA, 200 IU Nisaplin(TM)/mL, 200 IU Nisaplin(TM)/mL in 2% LA (2%NLA) or 200 IU· Nisaplin(TM)/mL in 2% PLA (2%NPLA) for 5 minutes. The beef cubes were drip-dried for 15 minutes, vacuum-packaged, and stored at 4°C for up to 56 days. The surface pH values and population reduction of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were investigated at days 0, 7, 14, 21, 28, 42, and 56. Compared to control, 2% LA significantly reduced surface pH values of the beef samples by approximately 0.6 units while 2% LMW PLA only reduced them by approximately 0.4 units at day 0 (P 0.05). Efficacy of 2% LA at lowering the surface pH of raw beef at day 0 was significantly greater than 2% LMW PLA (P 0.05). However, neither 2% LA nor 2% LMW PLA maintained a low pH on the meat surface beyond 7 days. The 2% LA and 2% LMW PLA showed immediate inhibitory effects on psychrotrophic aerobic bacteria (2.36 and 1.94 log10 reduction), psychrotrophic Enterobacteriaceae (1.86 and 1.37 log10 reduction), mesophilic Enterobacteriaceae (1.00 and 1.00 log10 reduction) and Pseudomonas (1.57 and 1.77 log10 reduction) on fresh raw beef ( P 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P 0.05). In the second experiment, inoculated beef cubes were treated with a solution of 2% LA, 2% LMW PLA, 400 IU Nisaplin(TM)/mL, 2% NLA, or 2% NPLA as described above. These five treatments showed immediate bactericidal effects on Listeria monocytogenes Scott A (1.56, 1.22, 1.57, 1.64, and 1.94 log10 reduction, respectively) (P 0.05). The reductions of Escherichia coli O15:H7 numbers by 2% LA, 2% LMW PLA, 2% NLA, and 2% NPLA were only 0.95, 0.89, 1.07, and 0.80 log10, respectively (P 0.05). These treatments, combined with vacuum-packaging and refrigeration temperature, succeeded more in inhibiting the growth of L. monocytogenes Scott A than E. coli 0157:H7· during storage. These findings suggested that bactericidal and bacteriostatic effects of 2% LA and 2% LWM PLA against spoilage microflora, E. coli O157:H7· and L. monocytogenes Scott A were not significantly different. Furthermore, low concentrations of nisin solutions (200 or 400 IU Nisaplin(TM) per mL) did not have efficacy at enhancing 2% LA and 2% LMW PLA against these four groups of spoilage bacteria or E. coli O157:H7 during storage.
机译：研究了2％乳酸（LA）和2％低分子量聚乳酸（LMW PLA）对在冷藏温度下真空包装的新鲜生牛肉的变质和致病菌的功效。 Nisin被测试为微生物生长的另一个障碍。在第一个实验中，将生牛肉块浸入2％LA（2％NLA）的2％LA，2％LMW PLA，200 IU Nisaplin™/ mL，200 IU Nisaplin™/ mL的溶液中。在2％PLA（2％NPLA）中的200 IU·NisaplinTM / mL，持续5分钟。将牛肉块滴干15分钟，真空包装，并在4°C下保存最多56天。在第0、7、14、21、28、42和56天研究了精神营养性需氧细菌，精神营养性和中温肠杆菌科，假单胞菌和乳杆菌的表面pH值和种群减少。与对照组相比，2％的LA明显减少了表面牛肉样品的pH值约0.6单位，而2％LMW PLA仅在第0天将其pH值降低约0.4单位（P <0.05）。在第0天2％的LA降低生牛肉表面pH的功效显着大于2％的LMW PLA（P <0.05）。但是，超过7天，无论是2％的LA还是2％的LMW PLA都不会在肉类表面保持较低的pH值。 2％的LA和2％的LMW PLA表现出对精神营养性好氧细菌（2.36和1.94 log10 log10减少），精神营养性肠杆菌科细菌（1.86和1.37 log10 log10减少），中温肠杆菌科细菌（1.00和1.00 log10减少10）和假单胞菌（1.57和1.77）的立即抑制作用。鲜生牛肉上的log10降低（P <0.05）。从肠杆菌科和假单胞菌的数量可以看出，在长达56天的时间内，这种减少是明显的（P <0.05）。在第二个实验中，如上所述，将接种的牛肉块用2％LA，2％LMW PLA，400 IU NisaplinTM / mL，2％NLA或2％NPLA的溶液处理。这五种处理方法均显示出对单核细胞增生李斯特菌Scott A的即时杀菌作用（分别降低1.56、1.22、1.57、1.64和1.94 log10）（P <0.05）。 2％LA，2％LMW PLA，2％NLA和2％NPLA降低的大肠杆菌O15：H7值分别仅为0.95、0.89、1.07和0.80 log10（P <0.05）。这些处理方法与真空包装和冷藏温度相结合，比大肠杆菌0157：H7·在储存过程中更能成功地抑制单核细胞增生李斯特菌Scott A的生长。这些发现表明，2％LA和2％LWM PLA对腐败菌群，大肠杆菌O157：H7·和单核细胞增生李斯特菌Scott A的杀菌作用和抑菌作用没有显着差异。此外，低浓度的乳链菌肽溶液（每毫升200或400 IU Nisaplin TM）在储存过程中对这四类腐败细菌或大肠杆菌O157：H7没有增强2％LA和2％LMW PLA的功效。

著录项

  • 作者

    Ariyapitipun, Tipayanate.;

  • 作者单位

    University of Missouri - Columbia.;

  • 授予单位 University of Missouri - Columbia.;
  • 学科 Agriculture Food Science and Technology.; Biology Microbiology.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 237 p.
  • 总页数 237
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 农产品收获、加工及贮藏;微生物学;
  • 关键词

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