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Study on Preserving Techonology and Mechanism of Sea Urchin Gonads

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Tutor: XueYong
School: Ocean University of China
Course: Aquatic Products Processing and Storage Engineering
Keywords: sea urchin,storage quality,dissolved oxygen concentration,ATP,Chitosan oligosacc
CLC: TS254.4
Type: Master's thesis
Year:  2012
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Sea urchin gonads are highly valued seafood in Japan and other countries for itsedibleness and medicinal efficacy. The product is mainly focused on raw sea urchingonads including chilled sea urchin gonads in table and chilled sea urchin gonads inbags filled with water. This thesis makes a study on effect of dissolved oxygenconcentration to quality changes of sea urchin gonads; the optimizing of conditions,such as temperature, isotonic solution, packaging rate and different antistalingagent,and storage mechanism are also studied; effect of different antistalingagent,temperature and concentration of chitosan oligosaccharide on storage quality of seaurchin gonads is finally studied. This study provides theoretical bases to qualityevaluation and extent of shelf life for sea urchin gonads, it also provides technologicalsupport to the production of it. The main researches in this thesis are listed below:1.To study influence of dissolved oxygen concentration to quality changes of seaurchin (Strongylocentrotus nudus) gonads, they were stored in artificial seawatersaturated with oxygen, nitrogen or air at5±1℃for12days. The sensory acceptabilitylimit was11-12,6-7and7-8days for gonads with oxygen, nitrogen or air packaging,respectively. TVB-N values reached22.60±1.32,32.37±1.37and24.91±1.54mgper100g for gonads with oxygen, nitrogen or air packaging at the points of near to,exceeding and reaching the limit of sensory acceptability, indicating that TVB-Nvalues of about25mg per100g should be regarded as the limit of acceptability forsea urchin gonads. Both pH and APC values showed no significant difference(P>0.05) for gonads with the three treatments.Gonads with oxygen packaging hadlower sensory demerit point (P<0.05) and TVB-N values (P<0.05), higher relativeATP content (P<0.01) and K values (P<0.05) than that with nitrogen or air packagingwith extended shelf life of4-5days during storage in artificial seawater at5±1℃. 2.To optimize the conditions of dissolved oxygen technology, effect oftemperature to quality changes of sea urchin (Glyptocidaris crenularis) gonads inartificial sea water with high oxygen concentration was studied with indicator ofATP%, TVC,TVB-N and pH; isotonic solution was studied with indicator of ATP%and K values; the packaging rate was studied with indicator of OD value; influence of0.1%EDTA、0.1%potassium sorbate and0.1%Nisin to the preservation of sea urchingonads in oxygen packaging was also studied. Degradation rate of ATP:roomtemperature>4±1℃>0℃. Sea urchin gonads stored in0℃had lower TVC、TVB-Nand higher pH values than those of sea urchin gonads stored in4±1℃. Sea urchingonads stored in artificial sea water had higher relative ATP content and lower Kvalues than those of sea urchin gonads stored in3.5%Nacl solution. Dissolved oxygenconcentration of sea urchin gonads filled with oxygen was obviously higher than thatof sea urchin gonads filled with nitrogen and air. The addition of EDTA、 potassiumsorbate and Nisin could restrain the increase of TVC and TVB-N; this effect wasobvious in sea urchin gonads with EDTA and Nisin in the early storage,while it wasobvious in sea urchin gonads with potassium sorbate after5days storage; the pHvalues of sea urchin gonads with potassium sorbate decreased sharply in the earlystorage, and it was lower than that of sea urchin gonads in the other three groups inthe whole storage time; blank group had higher ATP%values and lower K values thanthat of the other three groups with antistaling agent at the early storage time in whichsea urchin gonads were in high freshness status after died. Although EDTA、potassium sorbate and Nisin could improve microbe metabolic and corruption, theymay decrease the preservation of high dissolved oxygen concentration to high ATPlevel.3. Storage mechanism of dissolved oxygen was studied. Effect of different gas toTVC and microbial flora was studied; changes of glycogen and pH of sea urchingonads filled with different gas was also studied. Advantage corruption bacteria wasPseudomonas fluorescens and Kluyvera cryocrescens for sea urchin gonads filled withoxygen, while it was Acinetobacter lwoffii and Shewanella putrefaciens for sea urchingonads filled with nitrogen. Changes of pH correlated well with glycogen during storage.4. To determine the effect of different antistalingagent on storage quality of seaurchin, changes in the quality of Hemicentrous pulcherrimus, processed withChito-oligo saccharide, Trehalose and EDTA-2Na, were evaluated through asystematic study of sensory quality, the total bacterial count, total volatile basenitrogen (TVB-N) and pH during storage in4±1℃. Results indicated that thestorage quality of sea urchin gonads processed with all the three antistalingagentwere improved in varying degree, while sea urchin gonads processed with chitosanoligosaccharide had a harder texture(P<0.05)and better controlled rise of TVC(P<0.01) and TVB-N(P<0.01)values, with extended shelf life of4-5days; thoseprocessed with Trehalose and EDTA-2Na had slightly improved storage quality,with extended shelf life of1-2days.5. To determine the effects of temperature and concentration of chitosanoligosaccharide on storage quality of sea urchin, changes in the quality of sea urchin(Hemicentrous pulcherrimus) gonads processed in four different concentration ofChito-oligo saccharide were evaluated through a systematic study of sensory quality,the total bacterial count, total volatile base nitrogen (TVB-N), pH during storage in0℃. The quality of sea urchin gonads, without processed by chitosanoligosaccharide, stored in both4±1℃and0℃were also determined in the sameway. Results indicated that the degradation of the gonads stored in4±1℃wassignificantly(P<0.05)improved while in0℃, which was then enhanced (P<0.05)by the use of Chitooligo saccharide.However, there were no significantdifferences(P>0.05)during gonads processed in different concentrations ofchitosan oligosaccharide.
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