Evaluating sensory deterioration of pork stored under modified atmospheres

Microbial spoilage in pork leads to the formation of metabolic volatile organic compounds (VOCs), leading to offensive off-odors. Given that good sensory quality of meat is crucial for consumers, the aim of the study is to investigate the sensory decline of pork in relation to microbial growth and VOCs accumulation in the context of modified atmosphere packaging. In this study, fresh pork was packed under different atmospheres (%O2/CO2/N2: air, 70/0/30, 70/30/0, 5/30/65, 0/30/70, 0/0/100). Spoilage quality for each sample throughout the 4 °C chilled storage was assessed by microbiological, volatolomic and sensory analyses. The results were expressed as the total plate counts (log CFU·g-1), concentrations of VOCs (ppbv) and the rejection percentages according to odor (Rodor%) and appearance (Rapp%). Meat discoloration often occurs due to the myoglobin redox alteration in low-oxygen and/or long-term aerobic storage. However, it has been indicated from the sensory assessments that Rodor% was higher than Rapp% for pork under most atmospheres, suggesting that the off-odor generation can be more useful for spoilage indication. When Rodor% reached 50%, the total bacterial counts were approximately 7 log CFU·g-1 regardless of packaging conditions. In the late storage, the amount of 3-methylbutanal, 2,3-butanedione and sulfur-containing compounds have exceeded the odor thresholds, presumptively leading to panelists’ rejection. Due to high odor thresholds, the detection of most alcohols, ketones and acids should not only rely on sensory perceptions, but also require the implementation of high-sensitivity and -efficiency technologies to monitor their accumulation and thus to indicate spoilage in early or intermediate storage stages