100A-33 |
Reduction of spoilage and pathogenic bacteria on fresh beef by low molecular weight polylactic acid and vacuum-packaging |
K. W. LIM and A. Mustapha. Food Science, University of Missouri-Columbia, 256 William C. Stringer Wing, Columbia, MO 65211 The efficacy of low molecular weight polylactic acid (LMW PLA) at extending the shelf life of raw beef was determined. Fresh beef pieces (2.5 by 2.5 by 2.5 cm) inoculated with Escherichia coli O157:H7 505 B or Lactobacillus plantarum ATCC 8014 were dipped in PLA solutions directly or placed into packaging films sprayed with 2% MW 240 PLA, 2% MW 360 PLA, an equal mix of the two, water, or 1% Tween 20, with an exception of one set of control beef samples without treatment. Beef samples were then vacuum-packaged and stored at 4oC. Beef surface pH values and numbers of E. coli O157:H7 and L. plantarum were determined weekly. Throughout storage, samples of beef treated with 2% MW 360 PLA maintained a significantly lower pH compared to the untreated, water, and Tween 20 treated controls. At day 0, dip treatment with 2% MW 360 PLA and equal mix of 2% MW 240 and 360 PLA reduced surface pH values of the beef samples inoculated with E. coli O157:H7 by 4.74 and 4.77, respectively, from 5.62. Two percent MW 360 PLA reduced the population of E. coli O157:H7 and L. plantarum by 5.76 and 6.50 log CFU/cm2 from the initial numbers of 6.67 and 7.58 log CFU/cm2, respectively. Spraying on the film used for packaging raw beef with polylactic acid, demonstrated a 7.29 log reduction of E. coli O157:H7 and 1.26 log reduction of L. plantarum numbers, respectively, over a storage time of 3 weeks. Data from this study demonstrate that LMW PLA treatments followed by vacuum packaging under refrigerated conditions could increase the shelf life and safety of fresh beef by suppressing or inhibiting the growth of pathogenic bacteria such as E. coli O157:H7 and spoilage bacteria such as L. plantarum.
Session 100A, Food Microbiology: General II
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