Studies On The Superchilling Technology Of Hairtail (Trichiurus Haumela)

Effect of superchilling (-3?) and other two low-temperature preservations (4?, and -18 C) on the quality of hairtail was investigated. Light microscope was used to observe the microstructure of hairtail during storage at different temperatures. Effect of superchilling and freezing on the biochemical character of hairtail protein was also studied. The physicochemical properties and molecular structure of myofibrillar protein were determined. Fianlly, physicochemical properties, such as pH value, conductivity, TVB-N, TBA, K value, total bacteria count and sensory attribute, were investigated for fresh-keeping effects of biopreservatives in hairtail under the superchilling storage. The main results were as follows:1. The proximate composition of hairtail which captured in October from Zhoushan coast near East China Sea showed to be water of 78.12%, crude protein of 14.98%, fat of 4.76%, ash of 1.21% and others of 0.93%.2. The freezing point of hairtail was detected to be -1.9?. Therefore the superchilling temperature was set to be -3.0±0.5?3. Effect of low-temperature preservation on the quality of hairtail was investigated. Hairtail was stored at 4?,-3? and -18?, the physicochemical properties of the samples, such as pH value, conductivity, TBA, TVB-N, salt soluble protein content and Ca2+ -ATPase activity were determined, combined with TPA and sensory attribute. The results showed that with the extension of storage time, the pH value decreased first, then increased. While conductivity, TBA and TVB-N increased with the salt soluble protein content. Ca2+-ATPase activity, TPA (hardness, springiness, chewiness) and sensory attribute decreased gradually. The results indicated that-18? was the best of the three tested methods for the maintenance of the quality of hairtail, followed by that of?-3?. The quality of hairtail decreased most quickly at 4?, compared with the other two methods.4. Effect of superchilling and freezing on the biochemical character of hairtail protein was also studied. Myofibrillar protein content, total sulfhydryl, disulfide bond and surface hydrophobicity were determined, combined with UV spectra and intrinsic fluorescence spectrum of myofibrillar protein. The results showed that with the extension of storage time, myofibrillar protein content and total sulfhydryl decreased gradually, the lower storage temperature was the slower decline. Disulfide bond and surface hydrophobicity of myofibrillar protein increased with prolonged storage, the lower storage temperature was, the slower increase. The maximum absorption in ultraviolet (UV) spectra and intrinsic fluorescence intensity decreased with prolonged storage. Changes of biochemical character of hairtail protein indicated the denaturation of myofibrillar protein under the two storage temperatures, and?-18? was better in the two low-temperature preservation methods for maintenance of the biochemical character of hairtail.5. Microstructure observation by light microscope of hairtail during storage at different temperatures showed that fresh fillets had compact texture, intact cells and no destruction by ice crystals, and cell integrity was the best when stored at?-3? during short term storage, while it was the best at?-18? during long term storage.6. The pH value, conductivity, TVB-N, TBA, K value, total bacteria count and sensory attribute, were investigated for fresh-keeping effects of different concentrations tea polyphenols in hairtail under the superchilling storage. Results showed that with the extension of storage time, the pH value decreased first, then increased. While conductivity, TBA, TVB-N, K value and total bacteria count increased with the sensory attribute decreased gradually. The quality of samples without tea polyphenols declined faster, while it reached the best value as the concentration of tea polyphenols was 6.0g/L.7. The pH value, conductivity, TVB-N, TBA, K value, total bacteria count and sensory attribute, were investigated for fresh-keeping effects of 6g/L concentration of tea polyphenols combined with different concentrations citric acid in hairtail under the superchilling storage. Results showed that with the extension of storage time, the pH value decreased first, then increased. While conductivity, TBA, TVB-N, K value and total bacteria count ncreased with the sensory attribute decreased gradually. The quality of samples without any biopreservatives declined faster, while it was the best as 6.0g/L concentration of TP combined with 5.0g/L citric acid.