| The sea cucumber Apostichopus japonicus, which contains many biologicalactivity substances, was known as its tender texture and nice flavor, and was wellreceived by consumers. In this paper, the dried A. japonicus grown in Russia waschosen and the following researches were carried out.Firstly, the changes in tissue structure and rheological properties of raw andreconstituted A. japonicus were studied. The results showed that, the tissue structure,rheological properties and TPA in samples greatly changed during heating. Withincreasing of heating temperature, collagen fibers in heated samples shrank andsubsequently reassembled, and the voids among fibers tended to expand. Rheologicalproperties (E0, rupture strength) and TPA parameters suggested that heated sampleswere more flexible and tender while less hardness than that of raw sample. Meanwhilethe correlations between rheological properties and structural characteristic valueswere confirmed.Compared with raw sample, collagen fibers in reconstituted samples were thinner,looser, and voids among fibers were bigger. Rheological properties and TPAsuggested that reconstituted samples have more springiness and viscosity, lesshardness than that of raw sample. The tissue structures between different reconstitutedsamples were diversity. Collagen fibers in Russian japonicas were slender and voidsamong fibers were smaller than those in Japanese japonicas, and last the sensoryevaluation indicated that the former have a better taste than the latter.Secondly, the changes in quality and rheological properties of reconstitutedRussian A. japonicas during controlled freezing-point storage were studied, while thesamples were respectively stored under-1.0°C and4℃. Freshness indicators (the totalnumber of bacteria, auto-enzyme activity, T-VBN value, drip loss), tissue structures,texture profile analysis, sensory evaluation and rheological properties (E, τ, η, rupturestrength) were determined the quality variation. It were found that, with the extension of storage time, the total number of bacteria, auto-enzyme activity, T-VBN value andthe drip loss indicators gradually increased, while sensory evaluation scores decreased;the collagen fibers in the muscle tissue tended to smaller fragment, and tissuestructure deteriorated with storage time; rheological properties (E0, rupture strength)and TPA parameters gradually decreased, while relaxation time τ1and viscousmodulus η1changed irregular.Compared with refrigerated samples, the indicators’ changes speed of controlledfreezing-point storage samples were declined and shelf life of up to18d, while therefrigerated samples only kept6d. It suggested that controlled freezing couldeffectively inhibit the activity of enzymes in reconstituted samples and the growth ofmicroorganisms. As a result, controlled freezing-point storage is an effective methodto extend the storage time of reconstituted samples.Thirdly, the changes in quality and rheological properties of dried Russianjaponicas stored under vacuum packaging at4℃and20℃were studied, while thesamples were packaged in PET/PE compound bag. Freshness indicators (the totalnumber of bacteria, T-VBN value and drip loss), rehydration rate and rheologicalproperties (E, τ, η, rupture strength) of reconstituted samples were determined. Theresults showed that, with the extension of storage time, the total number of bacteria,T-VBN value, and drip loss gradually increased, while crude protein contentdecreased. Area of mold expanded, thorns collapsed and surface of samples becomesticky. Meanwhile, the rehydration rate changed irregular; elastic modulus E0andrupture strength of stored samples tended to less.Compared with20°C samples, the indicators’ change speed of4°C storagesamples were significantly declined. It suggested that4℃could effectively inhibitthe growth of mold, the decline of rheological properties of dried samples undervacuum packaging. As a result, controlled vacuum packaging stored at4℃is aneffective method to kept the quality. |
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