Abstract: This study compared the quality characteristics of lightly preserved cooked mackerel and raw mackerel. Quality changes and safety of cooked mackerel were analyzed during the examination of commercial sterilization. The spoilage bacteria causing swollen bags were identified by Biolog and 16S rDNA gene sequencing. The results showed that the salt content and pH of raw mackerel increased significantly after processing, and the water content, water activity (aw) and total viable count (TVC) decreased significantly. Sensory scores for odor, appearance, elasticity and taste were not significantly different between samples collected at the beginning (A0) and the end (A1; unswollen) of the 10-day period storage (P > 0.05). TVC values were less than 2 (lg(CFU/g)) in A0 and A1 and were in the range of 4 to 6 (lg(CFU/g)) in swollen samples B1, B2, B3 and B4 (on day 2, 3, 6 and 7, respectively), exceeding the safety limit. Bacillus licheniformis, Bacillus subtilis, Bacillus sonorensis and Brevibacterium sp. were isolated from the swollen samples. The pH of A0 and A1 was higher than that of B1, B2, B3 and B4; the pH of A0, A1, B1, B2 and B3 decreased in that order, while that of B4 slightly increased as compared to B3. There was a significant difference in total volatile basic nitrogen (TVB-N) content between the swollen (except B2) and unswollen samples (P < 0.05). The histamine contents of A0 and A1 were both lower than the detection limit (5 mg/100 g). This study provides support for the optimization of lightly cooked mackerel products to control product quality and safety.

Key words: lightly preserved cooked mackerel, quality characteristics, residual bacteria, histamine