Spoilage association of chicken leg muscle

The microbiology of DFD fresh meats: A review

Muscle which is deficient in glycogen because of exercise or stress prior to slaughter produces dark, firm, dry (DFD) meat. Such meat is characterized by a high ultimate pH (>6·0) and deficiencies in glucose and glycolytic intermediates. These factors can result in bacterial spoilage becoming evident at an early stage of growth of the meat flora. Spoilage becomes apparent when bacteria attack amino acids. This does not occur under aerobic conditions until bacteria exhaust the glucose at the meat surface. However, since glucose is absent in DFD meat, amino acids are utilised without delay and spoilage becomes evident at lower cell densities than in normal meat. The absence of glucose also allows the anaerobic flora to produce spoilage odours at an early stage. Additionally, the high pH of DFD meat allows growth of potent spoilage organisms which are inhibited at the usual ultimate pH of meat. Early aerobic spoilage can be prevented by the addition of glucose, but prevention of early anaerobic spoilage requires the addition of a citrate buffer which reduces the surface pH, as well as providing a carbohydrate substrate which is utilised in preference to amino acids. Comparisons can be made between spoilage of DFD red meat and spoilage of white meats from poultry and fish, which normally have a high ultimate pH.

Spoilage Microflora of Broiler Carcasses Washed with Electrolyzed Oxidizing or Chlorinated Water Using an Inside-Outside Bird Washer

The effect of acidic, electrolyzed oxidizing (EO) water and chlorinated water on the spoilage microflora of processed broiler carcasses was examined. Carcasses were sprayed for 5 s at 80 psi with tap, chlorinated, or EO water in an inside-outside bird washer. Treated carcasses were then stored at 4 degrees C for 0, 3, 7, or 14 d, and the microbial flora of the carcasses was sampled using the whole-carcass rinse procedure. Populations of psychrotrophic bacteria and yeasts in the carcass rinsates were enumerated. Results indicated that immediately after spraying the carcasses, significantly fewer psychrotrophic bacteria were recovered from carcasses sprayed with chlorinated or EO water than from carcasses sprayed with tap water. Furthermore, significantly fewer yeasts were recovered from carcasses sprayed with EO water than from carcasses sprayed with tap or chlorinated water. The population of psychrotrophic bacteria and yeasts increased on all carcasses during refrigerated storage. However, after 14 d of storage, significantly fewer psychrotrophic bacteria and yeasts were recovered from carcasses sprayed with EO water than from carcasses sprayed with tap or chlorinated water, and significantly fewer microorganisms were recovered from carcasses sprayed with chlorinated water than from carcasses sprayed with tap water. Pseudomonas spp. and Candida spp. were the primary microbial isolates recovered from the broiler carcasses. Findings from the present study indicate that EO water can effectively be used in inside-outside bird washers to decrease the population of spoilage bacteria and yeasts on processed broiler carcasses.

Incidence, radioresistance, and behavior of Psychrobacter spp. in rabbit meat

The relative incidence of Psychrobacter spp. in rabbit meat, the radioresistance of these bacteria, and the growth of nonirradiated and irradiated psychrobacter isolates, alone and in coculture, during chilled storage of inoculated sterile rabbit meat was investigated. Psychrobacter spp. accounted for 4.2% of the storage psychrotrophic flora of 30 rabbit carcasses. The radiation D10-values of 10 Psychrobacter isolates, irradiated at 4 degrees C in minced rabbit meat, ranged from 0.8 to 2.0 kGy, with significant (P < 0.05) differences among strains. Over 12 days of storage at 4 degrees C, pure cultures of two nonirradiated psychrobacter strains (D10 = 2 kGy) were capable of substantial increases (up to 3 log CFU/g) in sterile rabbit meat, but when the fastest growing strain was cocultured with Pseudomonas fluorescens and Brochothrix thermosphacta isolates, maximum cell densities and growth rates were significantly (P < 0.01) lower. After irradiation (2.5 kGy) of pure cultures in sterile rabbit meat, surviving cells of both Psychrobacter strains decreased for a period of 5 to 7 days and then resumed multiplication that, at day 12, resulted in a similar increase (1.6 to 1.7 log CFU/g) over initial survivor numbers. When irradiated in combination with the spoilage bacteria, one of the strains required 12 days to reach initial numbers. In conclusion, Psychrobacter spp. are radioresistant nonsporeforming bacteria with a low relative incidence among the storage flora of rabbit meat, unable to compete with food spoilage bacteria in this ecosystem and apparently not a major contributor to the spoilage of rabbit meat after irradiation.

Storage of poultry meat under modified atmospheres or vacuum packs: possible role of microbial metabolites as indicator of spoilage

The effect of carbon dioxide (100%), nitrogen (100%), carbon dioxide/oxygen (20%:80%) or vacuum pack at 3 and 10 degrees C was studied on the microbial flora, in skinless poultry breast fillets or thigh meat. Lactic acid bacteria and Brochothrix thermosphacta were the predominant organisms in samples stored in vacuum packs, carbon dioxide and nitrogen. Pseudomonads grew only in oxygen/carbon dioxide packaging systems. The concentration of lactate diminished in both thigh and breast meat during storage at 3 and 10 degrees C. This decrease was more pronounced in thigh meat stored under 20%:80% carbon dioxide/oxygen. Acetate increased to varying degrees in all samples regardless of the storage conditions.

Identification of volatile organic compounds produced by fluorescent pseudomonads on chicken breast muscle

Four different fluorescent pseudomonads were isolated from spoiled, uncooked chicken breasts and were grown in pure culture on initially sterile chicken breast muscle at 2 to 6 degrees C for 14 days. The volatile compounds produced by each culture were concentrated on a porous polymer precolumn and separated and identified by high-resolution gas chromatography-mass spectrometry.

Spoilage of chicken skin at 2 degrees C: electron microscopic study

Microscopic techniques were used in conjunction with normal microbiological procedures to examine the development of the spoilage microflora on the skin of chicken carcasses held at 2 degrees C. Pigmented and nonpigmented psychrotrophic pseudomonads were the major spoilage bacteria isolated at all stages of storage examined. The spoilage microflora grow within a liquid film covering the skin surface, as well as in feather follicle shafts. Penetration and disruption of skin tissue were not observed even after onset of organoleptic spoilage. Bacteria were not attached to the skin by extracellular bridging substances. These data suggest a nonspecific histological-microbiological relationship between he spoilage association and the skin substrate.

Spoilage association of chicken skin

The bacterial succession on the skin of broiler chicken carcasses stored at 2 degrees C was traced, and the ability of representative isolates to produce off-odors was determined by using sterile leg and breast muscle sections. Off-odors were identified by olfactory and chemical means. The inability of peptone-iron agar to detect sulfide-producing strains was noted.

Detection of volatile sulfide-producing bacteria isolated from poultry-processing plants

A technique using filter paper strips impregnated with 5-5'-dithiobis-nitrobenzoic acid was developed to allow the detection of bacteria (isolated from poultry-processing environs) which produced volatile sulfides (H2S, CH3SH, [CH3]2S). The technique is preferred to conventional methods in that it allows the detection of volatile organic sulfides in addition to hydrogen sulfide.