Fresh meat stored aerobically at refrigeration temperatures develops a characteristic spoilage microbiota dominated by Pseudomonas species (P. fragi, P. fluorescens, P. lundensis). These organisms metabolize glucose, lactate, and amino acids, producing volatile compounds including ethyl esters (fruity odors), sulfur compounds (H₂S, dimethyl sulfide), and ammonia. Once glucose is depleted, Pseudomonas begins metabolizing amino acids, leading to the production of putrescine, cadaverine, and other biogenic amines associated with putrefaction. Brochothrix thermosphacta also grows under aerobic conditions, producing acetoin and diacetyl that contribute sour, dairy-like off-odors.
Under vacuum packaging, the depletion of oxygen selects for facultative and obligate anaerobes. Lactic acid bacteria (Lactobacillus sakei, Lactobacillus curvatus, Leuconostoc) dominate and produce lactic acid, causing a sour, acid odor. Brochothrix thermosphacta also grows well under vacuum, especially if residual oxygen is present. Enterobacteriaceae (including Hafnia alvei and Serratia liquefaciens) can grow in vacuum-packaged meat, particularly at temperature abuse, producing putrescine, cadaverine, and H₂S that cause sulfidic, putrid odors. Color changes in red meat are driven by myoglobin oxidation: oxymyoglobin (bright red) converts to metmyoglobin (brown) as oxygen is depleted.
Seafood spoilage proceeds differently due to the presence of trimethylamine N-oxide (TMAO), an osmolyte found in marine fish. Psychrotolerant Gram-negative bacteria, particularly Shewanella putrefaciens and Photobacterium phosphoreum, reduce TMAO to trimethylamine (TMA), which is responsible for the characteristic “fishy” odor. Pseudomonas also contributes to seafood spoilage, producing volatile sulfides and hypoxanthine from ATP degradation. Histamine fish poisoning (scombroid poisoning) results from the decarboxylation of histidine to histamine by Morganella morganii, Proteus, and Hafnia species in fish stored at temperatures above 4-5°C.
Biogenic amines (histamine, putrescine, cadaverine, tyramine, spermine, spermidine) serve as spoilage indicators in both meat and seafood. They are produced by bacterial decarboxylation of amino acids and their accumulation correlates strongly with microbial growth and sensory rejection. HPLC and LC-MS/MS methods are used for quantitative determination of biogenic amines. Control of spoilage in muscle foods relies on rapid chilling, strict temperature control throughout the cold chain, hygienic slaughter and processing, and packaging technologies including vacuum packaging and modified atmosphere packaging (high CO₂, low O₂) to inhibit the growth of aerobic spoilage organisms. Meat spoilage involves psychrotrophic organisms that produce off-odors and slime. Biogenic amines such as histamine are safety hazards in seafood. Modified atmosphere packaging extends shelf-life by inhibiting aerobic spoilage bacteria.
