| The thesis is focused on the influences of biopreservative and modified atmosphere packaging ( MAP ) on the shelf-life of Trichiutus haumela stored at ( 4±1 )℃, and the sensory evaluation values, total viable count ( TVC ), total volatile base nitrogen ( TVB-N ), pH value, the 2-thiobarbituric acid ( TBA ) and the drip loss of Trichiutus haumela were used to evaluate the fish quality during the cold storage at ( 4±1 )℃. The results were summarized as follows:1. The initial fresh quality of aquatic products market-purchased Trichiutus haumela can meet the first class standard issued by Ministry of Agriculture.2. The effects of different concentrations chitosan on the quality changes of Trichiutus haumela in cold storage at (4±1)℃were investigated. The result indicated that the total bacterial count, TVB-N, pH value and TBA of samples coated with chitosan could be kept in good values significantly, and sensory evaluation values decreased slowly as well. The shelf-life of the coated samples were 7-8 days, prolonged 2-3days with the first fresh grade freshness and the shelf-life of the second fresh grade compared with that of samples under cold storage of (4±1)℃were 11 days, prolonged 6-7days.3. In order to extend the shelf life of Trichiutus haumela under cold storage at (4±1)℃, the preservation effects of 1.0% concentration of chitosan combined with different concentrations Tea Polyphenols (TP) on Trichiutus haumela were studied. The results showed that the Trichiutus haumela coated with chitosan and tea polyphenols was significantly better than the blank group, it could effectively retard the increase in total bacteria count, total volatile base nitrogen and the 2-thiobarbituric acid. Under cold storage of (4±1)℃, 1.0% concentration of chitosan combined with 0.4% TP applied to Trichiutus haumela could extend the shelf life of hairtail from 4-5d to 12-13d.4. Trichiutus haumela packaged in vacuum-packaging (VP) or a controlled atmosphere with 50% CO2+50% N2, 50% CO2+10% O2+40% N2 and 50% CO2+20% O2+30% N2 were stored at (4±1)℃to study the effect of atmosphere composition on its physicochemical properties, such as total viable count and sensory evaluation values every 2 days over a period of 14 days. It was shown that vacuum packaged (VP) had low TBA values, high TVB-N values and total viable count. When the initial CO2 concentration remained 50%, the shelf-life of the Trichiutus haumela could be extended with the O2 concentration increased. The TBA of the sample packaged with 50% CO2+20% O2+30% N2 was high, but the TVB-N values and total viable count were low, and had significant fresh-keeping effect during the 14 days under (4±1)℃.5. Trichiutus haumela packaged in controlled atmosphere with 40% CO2+10% O2+50% N2, 60% CO2+10% O2+30% N2, 80% CO2+10% O2+10% N2 were stored at (4±1)℃. The sensory evaluation values, total bacteria count, total volatile base nitrogen (TVB-N), pH value, the 2-thiobarbituric acid (TBA) and drip loss were used to evaluate the Trichiutus haumela quality during the cold storage. It was showed that samples in MAP had lower total bacteria count and total volatile base nitrogen than those of samples in air for Trichiutus haumela, 80% CO2+10% O2+10% N2 could extent the shelf-life of Trichiutus haumela to 14 days, but the drip loss and the TBA values of samples in MAP was higher than those in air during storage.6. The influences of compound biopreservative and biopreservative combined with modified atmosphere packaging on the shelf-life of Trichiutus haumela stored at (4±1)℃were studied with air packaged product as controls. The results showed that mixing biopreservative (1.0% Chitosan+0.4% Tea Polyphenols) had a significant bacteriostatic activity . The compound biopreservative combined with modified atmosphere packaging with 60% CO2+10% O2+30% N2 had the best fresh-keeping effect that after the Trichiutus haumela storaged at (4±1)℃for 20 days, the values of TVC and TVB-N of Trichiutus haumela were 5.59 lg CFU/g and 19.39 mg/100g, respectively, which meant the sample was still at the secondary freshness and that the shelf-life could be entended to 20days, 4 times loner than the blank. |
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