Evaluation of clove, cassia, tea polyphenols, rosemary extract, lysozyme, and nisin in inhibiting fat oxidation and microbial growth in salted and dried Spanish mackerel fillet during storage and subsequent shelf-life model development

Salted and dried Spanish mackerel (SDSM) is highly susceptible to lipid oxidation and microbial spoilage during storage, compromising its sensory and nutritional quality. The purpose of this study was to investigate the efficacy of natural additives—clove, cassia, tea polyphenols, rosemary extract, lysozyme, and nisin—in inhibiting fat oxidation and microbial growth in SDSM and to develop a predictive shelf-life model under different storage conditions. The 0.3% tea polyphenols + rosemary extract treatment group had the lowest peroxide value (POV) and thiobarbituric acid (TBA) values, with the best sensory score of 4 as the reference point. The POV content increased from 0.702 to 3.145 meq/kg before decreasing to 0.848 meq/kg, and the TBA value increased from 0.024 to 0.324 mg/kg. This group also demonstrated the most significant inhibition of fat oxidation, along with the highest sensory scores and longest shelf life. Although the 0.3% lysozyme-treated group demonstrated the greatest bacteriostasis, it had the lowest polyunsaturated (10.89%) and highest saturated (45.43%) fatty acid content. Furthermore, SDSM shelf life could be extended to 12 weeks by reducing additive levels and using vacuum packaging. Finally, an SDSM shelf-life prediction model was developed using TBA values as the criteria, with relative errors ranging from 2% to 10.8%. This study is the first to report the inhibition of fat oxidation in SDSM by the addition of natural bacteriostatic and antioxidant agents. Thus, these findings fill a critical gap in SDSM preservation research by demonstrating the potential of natural preservatives and providing a theoretical foundation for SDSM preservation.