Ethanol Development in Tissues of Spoiling Whole Pink Salmon (Oncorhynchus gorbuscha)

Whole pink salmon, undergoing 4 days of spoilage in elevated temperature (10C) seawater, were dissected to determine ethanol content and changes in the aerobic and facultatively anaerobic bacteria flora. Intestinal tract, viscera, coagulated blood, reproductive organs, skin and muscle were analyzed daily for ethanol content using headspace gas chromatography coupled to mass spectrometry. The intestinal tract contained 32 ppm ethanol initially, increased eightfold on day 1 and reached 314 ppm on day 3. Most other tissues had ethanol concentrations of <100 ppm. Log aerobic plate counts (APC) were determined only for pink salmon skin and belly cavities, and the flora identified. The APC, which include the enumeration of facultatively anaerobic bacteria, were poorly correlated with ethanol production in pink salmon because the APC were low (∼2 log) for the belly cavity where ethanol concentrations were high. Although the APC were higher (∼5 log) in skin, ethanol concentrations were 3–10 times lower for skin than for the intestinal tract. We suggest aerobic and facultatively anaerobic bacteria may not be the primary source of ethanol in spoiling pink salmon. Practical Applications Ethanol is recommended as an indicator of preprocessed fish spoilage before canning. In a previous pink salmon spoilage study, which monitored ethanol incidence in the canned product, we demonstrated that ethanol levels were low when whole pink salmon spoiled on ice (1C) in contrast to higher levels for fish stored in temperature-abused (14C) seawater. The present study established that during whole pink salmon spoilage, the ethanol concentration of different tissues varies widely, and the intestinal tract had significantly higher (P < 0.05) ethanol levels than all other tissues studied. Our findings indicate the need to determine the mechanism of formation of ethanol in fish tissues during bacterial spoilage.