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Research on Several Crucial Indexs in Quality Evaluation of Dried Sea Cucumber

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Tutor: WangLianZhu
School: Ocean University of China
Course: Aquatic Products Processing and Storage Engineering
Keywords: dried sea cucumber,standard,rates of dry weight after rehydration,exogenous tota
CLC: S968.9
Type: Master's thesis
Year:  2012
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Abstract:
The sea cucumber (Apostichopus japonicus) is a kind of nourishing seafood, but due tothe autolysis of fresh sea cucumber, the sea cucumber for sale are mainly processed into driedones. With the improvement of sea cucumber processing technology and the development ofthe whole sea cucumber processing industry, the demand to overall assess the index of driedsea cucumber and define the national standards is desiderated. This thesis use A. japonicas asresearch object. The whole thesis is consisted of four parts as follow:A detection method was provided for distinguishing the dried sea cucumber added withsugar. An easy and feasible method was applied to extract the exogenous total sugar in driedsea cucumber, and then the total sugar was determined to discriminate if sugar was added. Inthis experiment we confirmed the optimum concentration of extraction solvent, extraction time,temperature, and solid-liquid ratio. The results showed that the optimum scheme is weighting1g dried sea cucumber, water bathing in80%ethanol at40℃for60minutes to extractexogenous total sugar. Then phenol-sulfuric acid method is used to measure the extractedexogenous total sugar. Range of linearity of this method was0-80mg/L; detection limit was1.16μg/mL; test fluid had good stability in1h; the relative standard deviation was less than2%.Using unsalted and salted dried sea cucumber as background, the recovery of standardaddition ranged from82.97%~98.68%, the standard deviation ranged from1.38%~3.45%.Considering the experimental error and processing methods, we suggest to identify the driedsea cucumber containing exogenous total sugar more than3%as sugar added dried seacucumber. This method is simple, stable and precise, which could distinguish dried seacucumber added with sugar effectively.The measuring method of salinity in dried seacucumber was optimized. The results showed ashing method was the first choice to preparethe salinity measuring filter liquor. The method has simple operation and high accuracy and issuitable for determining the salinity in dried sea cucumber. Direct titration has simpleoperation, low cost and satisfying precision and accuracy and meets the common experimentalneeds. Automatic potentiometric titrator judges the titration end point automatically andreduces the operating error and can be applicable to batch determination. But for its high cost and complexity, the automatic potentiometric titrator can hardly be applied to everydayuse. Indirect titration is not recommended for its complexity.The detection method of rates of dry weight after rehydration(RDR) and the relationshipbetween RDR and protein, salinity are studied. The results showed the optimum detectionmethod for RDR is presoaking the dried sea cucumber and cutting it into section about5mm,boiling for1h, rehydrating for24h and then cutting it into piece about5mm×5mm, drying6hbefore weighting.The relevant analysis showed significant positive correlation exsited between RDR andprotein while significant negative correlation exsited between RDR and salinity. Theexperimental results suggest RDR can be used to distinguish salted dired sea cucumber, lightlysalted dried sea cucumber and sugar added dried sea cucumber and judge the quality of driedsea cucumber.The optimum swelling condition for dried sea cucumber was studied; the tenderness,heavy metal and residue of veterinary drug before and after swelling were estimated. Theoptimum swelling procedure was obtained:presoaking the dried sea cucumber for24h to clearthe silt, wiping off the calcareous part around the mouth and peeling the longitudinal fibers,boiling the sea cucumber for30min then store at0-5℃for20h after it cooled. Repeat theprocedure above once for salted dried sea cucumber, twice for unsalted dried sea cucumber.The sea cucumber swelled through the procedure has satisfying resilience and mouth feel.Thetenderness of the sea cucumber decreased with swelling time and the tenderness of salted driedsea cucumber went down faster comparatively. The tenderness ranged from5.72±0.72~8.84±0.59when the sea cucumber was edible, which was similar with sausage(5.71±0.36~8.27±0.81).Some indexs in standard of dried sea cucumber were further explained,including heavymetal content in dried sea cucumber before and after rehydration and residue of veterinarydrug, protein,moistureand silt content.It was found that when the dried sea cucumber wasswelled to ediable status,the heavy metal content decreased substantially. The heavy mentalcontent in dried sea cucumber decreased substantially when it was swelled. The residue ofveterinary drug in dried sea cucumber was low, the contents of chloromycetin, malachite green,total sulfonamides, polychlorinated biphenyl, terramycin,and furan metabolites weredetermined, only furazolidone metabolites were detected but became undetectable after swelling. Reasonable swelling procedure could improve the palatability of dried sea cucumber.Besides, the dried sea cucumber is edible only after swelling, so the heavy metal content andthe residue of veterinary drug should be determined when the dried sea cucumber is swelled toedible state. The measuring method for protein and water content in dried sea cucumber meetsthe detection demand; in this study we detected some samples only to provide some data forthe national standard of dried sea cucumber. In64samples, the protein content ranged from19.8%to72.6%, the water content ranged from1.75%to23.24%. In72samples, the siltcontent ranged from0.31%to7.17%.
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