Comparative study of hot-air, freeze, and supercritical carbon dioxide drying on the physicochemical, microbiological, and sensory quality of shrimp (Metapenaeus spp.)

This study evaluates the application of supercritical CO2 drying on shrimp (Metapenaeus spp.) as a combined dehydration and decontamination strategy, comparing it to conventional hot-air drying (AD) and freeze-drying (FD). Two complementary storage assessments were performed over 4 months: microbiological stability under ambient storage conditions at 20 ± 1 °C, and physicochemical, structural, and volatile quality retention under refrigerated storage conditions at 4 ± 1 °C. All three treatments reached a comparable target water activity of approximately 0.55, achieved in 6.5 h (AD), 15 h (scCO2), and 104 h (FD). Microbiologically, scCO2 drying demonstrated the highest efficacy, maintaining natural spoilage flora at or near the detection limits throughout storage. A small-scale challenge test performed on scCO2-dried samples achieved >4 Log CFU/g reductions for surrogate pathogens (Listeria innocua and Enterococcus faecium), confirming the antimicrobial potential of this technology. Moreover, physicochemical analyses of samples under refrigerated storage conditions at 4 ± 1 °C revealed that scCO2 exhibited intermediate color preservation and rehydration capacity (rehydration ratio > 4 g/g), closer to FD than to AD, while maintaining a more stable volatile organic compound (VOC) profile. However, instrumental and sensory texture evaluations indicated that scCO2-dried shrimp exhibited a firmer texture and a whitish appearance, both negatively perceived by consumers, resulting in consumer liking scores comparable to AD but lower than the highly porous FD samples. Overall, scCO2 drying showed excellent microbiological safety under ambient storage conditions at 20 ± 1 °C and favorable physicochemical stability under refrigerated storage at 4 ± 1 °C, however further optimization is required to enhance its structural and sensory acceptance.