The effects of photodynamically activated curcumin on the preservation of low alum treated ready-to-eat jellyfish

Abstract

Residual aluminum in jellyfish is largely due to the use of alum as a firming agent. Simply lowering the usage of alum during jellyfish dehydration may not only affect its texture, but also increase its susceptibility to foodborne pathogens and spoilage bacteria. In this study, the antibacterial effects of curcumin-mediated photodynamic treatment on jellyfish were investigated. The ready-to-eat flame jellyfish was dehydrated by brine prepared by a NaCl salt containing 3.5% alum followed by curcumin-mediated photodynamic treatment. The jellyfish samples were analysed for total bacterial count; aluminum residuals; total volatile basic nitrogen content; proximate composition (water, lipid, protein, carbohydrates, and ash contents); texture (hardness, cohesiveness, springiness, chewiness) and sensory quality (texture, colour, odour and overall acceptability). The data showed that decreasing alum usage significantly lowered the residual aluminum compared to jellyfish dehydrated by brine prepared by salt mix containing 10% alum. In addition, photo-irradiating the jellyfish with curcumin at 50 μM by blue LED light (16 mW/cm2) for 15 min presented desirable preserving effects. Moreover, jellyfish after this antimicrobial photodynamic treatment also showed acceptable sensory scores. Together, these findings suggest that photodynamic treatment is a promising method suitable to be used for the preservation of low-alum treated ready-to-eat jellyfish.