Evaluation and Selection of Thermal Processing Conditions for Safety, Flavor Retention, and Shelf-Life Extension of Fermented Pickled Mustard Greens

To address post-acidification, microbial contamination, and quality deterioration in fermented pickled mustard greens after fermentation, this study systematically evaluated the effects of thermal treatment on quality preservation, selected a preferred thermal processing condition from three kinetically designed treatments, and predicted product shelf life. Based on heat penetration curves and the thermal death kinetics of the target heat-resistant microorganism, Bacillus subtilis, three thermal processing conditions were established: 75 °C for 64 min, 85 °C for 19 min, and 95 °C for 17 min. The D-value of B. subtilis spores at 85 °C was 1.37 min, and the corresponding thermal treatments were designed according to a 2D reduction principle. HS-SPME-GC-MS analysis identified 84 volatile compounds, with isothiocyanates representing key contributors to the characteristic pungent aroma of mustard-based pickles. Sensory evaluation showed that the 85 °C treatment group achieved the best observed balance among pungency, refreshing aroma, mellow flavor, color, texture, and overall acceptability, whereas excessive heating at 95 °C promoted isothiocyanate loss and texture deterioration. During accelerated storage, the selected treatment inhibited post-acidification, maintained nitrite at a low level (<1 mg/kg), and delayed microbial and sensory deterioration. Integrating physicochemical indices, microbial populations, and sensory scores, the theoretical shelf life under refrigeration at 4 °C was predicted to be 170 days using the Q10 model. These findings provide practical guidance for selecting thermal processing conditions that balance microbial safety, flavor retention, and shelf-life extension in industrial fermented pickled mustard greens.