| In this study, chitosan-citrus essential oil microcapsules were prepared with the following three ingredients at varying concentrations: citrus essential oil 6 g/L, emulsifier 3 ml/L, TPP(Thiamine pyrohphosphate) 2 g/L, and chitosan at 2.5, 5.0, 7.5, 10, 15, or 20 g/L; citrus essential oil 6 g/L, TPP 2 g/L, chitosan 10 g/L, and emulsifier at 0, 3, 6, 9, or 12 ml/L; and citrus essential oil 6 g/L, emulsifier 3 ml/L, chitosan 10 g/L, and TPP at 0.5, 1, 2, 4, or 8 g/L. The particle size, PDI(Poly-dispersible), and zeta potential were used as indicators, and chitosan 10 g/L, citrus essential oil 6 g/L, emulsifier 9 ml/L, and TPP 4 g/L were eventually selected as the final ingredient concentrations for preparing the microcapsules. After soaking Litopenaeus vannamei with 1% (w/v) microcapsule solution for 20 min, the total volatile basic nitrogen (TVB-N) content, SDS-PAGE patterns, thiobarbituric acid (TBA) content, and total viable count (TVC) were analyzed to determine the effectiveness of the chitosan-citrus essential oil microcapsules in preserving the quality of L. vannamei during storage at 4℃. The results showed that the TVB-N level of the experimental group increased slowly (P<0.05), reaching 27.47 mg/100 g on the 22nd day of storage, which was at the secondary freshness level, whereas that of the control group exceeded the secondary freshness level on the 19th day of storage. Likewise, the TBA level of the experimental group increased slowly (P<0.05), reaching 0.789 mg/kg on the 22nd day of storage, which was the same level as that of the control group on the 15th day. The TVC of the experimental group also increased slowly (P<0.05), reaching 5.42 [lg (CFU/g)] on the 19th day of storage, which was at the secondary freshness level, whereas that of the control group exceeded the secondary freshness level on the 13th day of storage. The SDS-PAGE patterns showed that the myosin heavy chain of the experimental group had decomposed more slowly. These results indicated that the chitosan-citrus essential oil microcapsules could effectively inhibit the degeneration of protein, the rancidity of fat, and the growth of microorganisms, thus, hindering the spoilage of L. vannamei and extending its shelf life by 3~4 days compared with that of the control. |
