| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 90 === Abstract
The purpose of this study was to investigate the changes of chemical constituents in the abdominal muscle of female mud crab in relation to short-term salinity acclimation and subsequent air-exposured storage at 15℃.
The crab specimens were acclimated to 25 ppt of sea water for 24 hours (control) and then transferred to 10 and 40 ppt sea water for a period of 4~48 hours. In comparison with control, moisture in 40 ppt sample decreased, but that in 10 ppt sample increased. On contrary, the glycogen showed a inverse trend. Taurine (Tau), glutamine (Gln), proline (Pro), glycine (Gly), alanine (Ala) and arginine (Arg) were dominant free amino acids (FAA) and they together accounted for about 87﹪of the total FAA. Adenosine triphosphate (ATP) and glycinebetaine (GB) were respectively the major component among the ATP-related compounds (ARC) and quternary ammonium bases (QAB) detected. As a whole, the 40 ppt sample was relatively high in levels of the total FAA, total ARC, GB, and homarine (Hom). In addition, the difference in levels of moisture, glycogen, total FAA, total ARC, GB, and Hom between 10 and 40 ppt samples increased with the elongation of acclimation time.
The crab specimens acclimated to 10 ppt, 25 ppt, and 40 ppt sea water and then stored at 15℃ for 12~72 hours. Differences in the moisture and glycogen levels declined after storage. The total FAA in all samples elevated gradually with the storage time and the sample acclimated to higher salinity was more pronounced. The major FAA except for Tau also increased. After storage, the total ARC content was higher in the 40 ppt sample than in other two samples. The ATP decreased with storage time, while its breakdown products accumulated. The GB and Hom contents were higher in the sample acclimated to higher salinity, but their difference between the samples lowered as the storage time increased.
Of the samples acclimated to 10、25, and 40 ppt sea water for 48 hours, their hot-water extracts were prepared and compared by sensory test for taste. Taste intensity of the extracts was higher in the 25 and 40 ppt samples than in the 10 ppt sample. The salt, Na+, and total FAA contents in the hot-water extracts followed the order of 40 ppt > 25 ppt > 10 ppt sample. Levels of glycogen, GB, and Hom were higher in the 25 ppt sample than in the 40 ppt and 10 ppt samples. However, there was no significant difference in the total amounts of ARC between them.
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