Bacteriology of Prepacked Pork with Reference to the Gas Composition within the Pack

Abstract

Bncteriological changes in pork stored a t 16 and 2" under gas permeable and gas impermeable films and 'aerobic' conditions have been studied. The concentrations of CO,, 0, and N, in the atmosphere within the packs were also determined. The groups of bacteria isolated from prepaclred pork were Pseudomonas-Achronaobacter spp., Rzuthia spp., Microbacterium thermosphactum, Enterobacter-Hafnia spp. and lactobacilli. Their importance is discussed in relation t,o storage temperature and gas composition within the packs.

Effect of oxygen concentration on the shelf-life of fresh pork packed in a modified atmosphere

“…The initial pH of the sample was 6.33 ± 0.02 when collected from the slaughterer. In aerobic spoilage at refrigerated conditions, Pseudomonas is the major microorganism of interest 19,20 and it is inhibited at higher O 2 levels. 21 Thus, this could be the reason for lower TVBN at 45% and 55% O 2 .…”

Microbiological, physical and chemical studies on fresh red meats packaged under different modified gas atmospheres

“…For example, it has been reported that CO2 had little effect on the facultative anaerobe EnterobacterHafnia spp. and B. thermosphactum (Gardner et al, 1967). noted that B. thermosphacta on beef increased at the same rate as total counts in air, vacuum, and in a 20%C02/2%02/78%N2 mixture.…”

“…Pseudomonas-Achromobacter spp. and other related psychrotrophs which grow rapidly and produce off-odors and flavors in raw meats are selectively inhibited by CO2 (Gardner et al, 1967;.…”

“…They include the initial concentrations of the gases in the atmosphere in which the meat is stored, the amount of headspace in the package, and the use of reducing substances . The concentrations of the primary gases in the headspace influence the rate of growth of microorganisms and the type of species of microorganisms which might be present on the surface of the fresh meat (Beebe et al, 1976;Blickstad et ai., 1981 ;Christopher et ai., 1979;Enfors et al, 1979;Gardner et al, 1967;. This is because individual bacterial species present initially on the food show different responses to the O2 and CO2 contents of the atmosphere in which the meat is stored .…”

“…Brown and Hugget (1968) studied the effect of various partial pressures of O2 on microbial growth and concluded that O2 was toxic for many forms of life. According to Gardner et al (1967), O2 must be drastically reduced to affect aerobic bacterial growth.…”