Yersinia enterocolitica is a facultative anaerobic bacterium that can survive well in vacuum-packed meat stored at 1 °C; however, in processed meats the addition of potassium or sodium nitrate acts as bactericidal towards Y. enterocolitica.
- gas formation, resulting in an inflated pack
- greening due to:
-sulphmyoglobin formation from reaction with hydrogen sulphide; sulphmyoglobin greening can be associated with growth of Pseudomonas mephitica or Brochothrix thermosphacta, and with poor barrier films which allow small amounts of oxygen into the pack
-the interaction between myoglobin and hydrogen peroxide; hydrogen peroxide greening has been associated with cooked cured meats under aerobic conditions
-'off' odours on opening the bag, such as trace amounts of ammonia from proteolysis
- spots on cured and fermented meats caused by undesirable moulds such as Cladosporium, which causes unsightly, deep-seated black spots on cured hams, or Scopulariopsis, which causes white spots on the skin of hams.