Abstract
The effects of helium and argon plasma treatments on inactivation of both pure bacterial cultures inoculated onto the surface of agarized media and the surface microbiota of meat were investigated. Cold plasmas were generated by high voltage discharge at low pressure (20 kPa) for 2, 5, and 10 min. The number of viable microorganisms was determined using a plate count method. Morphological changes were observed using scanning electron microscopy (SEM). Microbial log reduction depended on time of exposure and type of gas used. After a 10-min treatment with helium plasma, the total number of microorganisms, yeasts and molds, and psychrotrophic microorganisms was reduced in the range of 1.14–1.48 log cycles for pork and 0.98–2.09 log cycles for beef. A significant reduction of 2.00 log for Bacillus subtilis and Yersinia enterocolitica was achieved within 2 min of helium plasma treatment. Similar results were obtained for Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens after 5 min and 10 min of exposure. SEM revealed disruption and lysis of E. coli cells treated with helium plasma for 10 min, suggesting a bactericidal effect.
Highlights
IntroductionMeat spoilage is caused by three basic mechanisms: microbial growth, lipid oxidation and enzymatic autolysis (Dave and Ghaly 2011)
Microbial hazards are one of the most important issues in the food industry
Meat may be contaminated by bacterial pathogens, including Salmonella spp., Campylobacter jejuni/coli, Escherichia coli, Listeria monocytogenes, Staphylocccus aureus, Yersinia enterocolitica/ pseudotuberculosis, Bacillus cereus, Clostridium perfringens and Clostridium botulinum (Sofos 1994; Borch et al 1996)
Summary
Meat spoilage is caused by three basic mechanisms: microbial growth, lipid oxidation and enzymatic autolysis (Dave and Ghaly 2011). Those result in discoloration, slime formation, undesirable odors and flavors, and texture softening and make the product unacceptable to consumers. The most common sources of carcass meat contamination are Pseudomonas spp., Moraxella spp., Acinetobacter spp., Alcaligenes spp., Flavobacterium spp., Aeromonas spp., Staphylococcus spp., Micrococcus spp., coryneforms and Enterobacteriaceae. The most common spoilage microorganism of fresh chilled meat is Pseudomonas spp. These bacteria produce putrefactive odors and slime when their population exceeds 107 CFU/cm (Sofos 1994)
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