## 4 Discussion
The CO-NE-treated liquid-smoked salmon fillets have the least SSOs among the three NE treatments, which may be caused by the later cumulative antimicrobial effect of lengthening the lag phase of bacterial growth. A similar study also showed that NE-loaded natural bioactive extracts delayed the growth of spoilage microorganisms in fish, extending their shelf life [43]. Following the analysis of the microbial activity, lipid oxidation and proteolysis in liquid-smoked salmon storage were investigated, which were indicated by TBARS and TVB-N. The results suggested that CO-NE exhibited a stronger ability to reduce lipid oxidationand protein degradation in salmon fish than ENT-NE and CEO-NE, which was consistent with the DPPH-scavenging activity of NEs. It was reported that NEs incorporating star anise essential oil, polylysine, and nisin had better antioxidant activity than star anise essential oil-loaded NE for meat products [18]. Interestingly, although CEO-NE had better antimicrobial and antioxidant effects compared to ENT-NE, the difference was not obvious when they were applied to liquid-smoked salmon fillets. This phenomenon revealed the fact that the undesirable influence of complex food systems on the activity of active substances in NEs still exists. On day 0, no significant differences (\(p>0.05\)) were found in the odor, taste, color, and appearance of the NE-treated salmon when compared to the control. It was suggested that the NE delivery system could reduce the impact on the color and flavor of the final food product. As the storage time increased, the \(L^{*}\) values of the CO-NE treatment decreased slower, indicating that CO-NE could decrease the reduction in lightness (\(L^{*}\)) due to several factors, such as protein denaturation, pH change, lipid oxidation, and microbial spoilage. Additionally, the fresh salmon covered with active packaging retained its color compared with the blank packaging samples [44]. Moreover, a slight reduction in \(a^{*}\) was observed in this study, corresponding with the results of color protection using anthocyanin-compound chitosan nanoparticle edible films on fresh red sea bream fillets [45]. A decrease in the \(a^{*}\) value was observed in all groups with increasing storage time, which was due to the loss of carotenoids and the oxidation of hemoglobin and myoglobin pigments [46]. The decrease in the texture attributes (hardness, adhesiveness, springiness, and chewiness) can be explained by protein degradation due to the effect of endogenous enzymes and microorganisms, breaking the stable structure of the protein [47]. In this study, CO-NE significantly reduced the decrease in the texture attributes during storage between 28 th-49 th days. The findings of [PERSON] et al. [48] exemplified the effect of the NE with EOs on the texture attributes of fish. A nisin-and-curcumin-loaded nanomat was prepared to enhance the texture of fish in a previous study [49]. The results of the volatiles analysis revealed that the CO-NE-treated salmon fillets exhibited an ideal flavor and fewer unpleasant flavors than the control on the 49 th day. Similar results were also found in the study concerning the effect of active coatings containing \(\varepsilon\)-polysine on the volatile compounds of cultured pufferfish [50]. The results of the sensory evaluation showed that CO-NE had a great effect on the color, texture, taste, and odor of salmon fillets, which was reflected by higher scores for each attribute compared to the control. The higher scores in color were probably due to the increased lightness (\(L^{*}\)) and redness (\(a^{*}\)) found in the CO-NE-treated fillets. The higher texture scores could be attributed to the greater elasticity, cohesion, adhesion, and chewiness caused by the protective effect of CO-NE on the lipids and proteins in salmon. The results of the sensory evaluation of odor were consistent with those of the volatile compounds analyses.