【作者】 杨文鸽；

【导师】 薛长湖；

【作者基本信息】 中国海洋大学 ， 水产品加工及贮藏工程， 2007， 博士

【摘要】 近年来,我国海水养殖产业发展迅速,以鲜活销售为主的方式已不能适应其产量快速增长的状况。利用冰藏或冻藏进行海水养殖鱼贝类的保鲜,意义重大。然而鱼贝类在低温贮藏期间仍会发生一系列的变化,这些变化严重影响着鱼贝肉的鲜度和食用品质。本文以养殖大黄鱼、美国红鱼、鲻鱼、缢蛏为研究对象,以肌原纤维盐溶性蛋白含量、巯基含量、ATPase活性,ATP及其关联物,糖原,甜菜碱,游离氨基酸含量,挥发性盐基氮等作为指标,对其低温贮藏生化特性的变化及其鲜度进行评价。主要研究内容和结论如下:1)以养殖大黄鱼为对象,利用HPLC对冰藏期间鱼肉ATP关联物含量进行分析,结合K值、T-VBN和感官性状的变化评价其鲜度。结果表明:冰藏1d内大黄鱼ATP、ADP含量快速下降,此后变化平缓;AMP含量一直维持在一个低水平;IMP含量在冰藏1d时达到最大值,随后维持在一个较高水平,8d后下降速度加快;HxR含量在冰藏1d内快速上升,随后呈下降趋势;Hx量在冰藏前8d内上升速度缓慢,8d后上升趋势加剧,由8d时的0.97μmol/g上升到13d时的3.10μmol/g;冰藏期间大黄鱼鱼肉的K值和T-VBN含量一直呈现上升趋势。结合感官评定结果,在冰藏4d内大黄鱼处于一级鲜度范围,冰藏11d后鱼肉出现腐败。大黄鱼的冰藏期限为10～11d。2)采用冰藏、-20℃冻藏,以肌原纤维盐溶性蛋白含量、巯基含量和ATPase活性,ATP及其关联物含量,T-VBN,pH值和感官评定为指标,考察美国红鱼在低温贮藏过程中生化特性的变化,同时分析对比抗冻剂或低温速冻处理对抑制蛋白质冷冻变性的效果。结果表明:冰藏期间,美国红鱼肉盐溶性蛋白、巯基含量和ATPase活性均呈下降趋势,IMP含量始终保持在较高的水平,K值上升速度缓慢,冰藏13d后K值只有22.42%,但此时美国红鱼已处于初期腐败状态,用推荐的K值范围评价红鱼肉鲜度并不合适。初步确定K值6%和12%或Hx达0.3μmol/g和0.6μmol/g作为美国红鱼一级鲜度和二级鲜度的评价界限,结合T-VBN值和感官评价,冰藏条件下美国红鱼一级和二级鲜度的保藏期限分别是4～5d和8d。-20℃冻藏过程中,美国红鱼肉肌动球蛋白的溶出量、巯基含量、Ca²⁺-ATPase活性均呈下降趋势,但低温速冻处理后冻藏时Ca²⁺-Mg²⁺-ATPase和Mg²⁺-EGTA-ATPas活性均先上升,2周后开始下降,而其余组样品则一直处于下降通道。尽管低温速冻处理或抗冻剂处理均不能停止肌肉蛋白质冷冻变性,但能延缓鱼肉盐溶性蛋白量、Ca²⁺-ATPase活性的下降速度;与添加抗冻剂处理相比,在冻藏12周内低温速冻处理更能有效抑制鱼肉蛋白质冷冻变性,有助于提高鱼肉持水力和感官评分。3)以鲻鱼为原料,采用冰藏、-20℃和-40℃冻藏的方法,研究鲻鱼在不同贮藏温度下的生化特性变化,考察低温速冻处理对鱼肉蛋白质变性的影响。结果表明:冰藏时鲻鱼肌原纤维的盐溶性蛋白和巯基含量下降,利用T-VBN值、感官评分和K值进行鲜度评价,具有良好的一致性,认为K值以20%和40%作为一级和二级鲜度的判断指标,得出鲻鱼一级和二级鲜度的冰藏保鲜期限分别为5d和9d,冰藏11d后鲻鱼已不能食用。与直接冻结相比,低温冻结处理能延缓鲻鱼肌原纤维蛋白质冷冻变性速度,与-40℃冻藏相比,-20℃冻藏前低温冻结处理的优势更加突出。采用同样的冻结方式,冻藏温度越低,蛋白质冷冻变性越慢。4)以缢蛏为研究对象,对缢蛏冰藏保活期间糖原、甜菜碱、ATP及其关联物、游离氨基酸组成和感官评定变化进行分析,同时研究缢蛏在冻藏过程中蛋白质冷冻变性和其它相关物质的变化,对缢蛏鲜度进行评价。结果表明:缢蛏冰藏13d后存活率达80%,冰藏第8d缢蛏肉ATP含量达到最大值1.89μmol/g,AMP含量较高且变化平缓,而IMP含量较低。缢蛏糖原初始含量较高,冰藏1d内迅速下降到9.86mg/g,随后变化缓慢,游离氨基酸以Ala、Ser、Glu和Arg为主。冰藏期间糖原、甜菜碱、游离氨基酸、AMP对缢蛏鲜美的风味起着重要作用。-20℃冻藏时,缢蛏AMP含量保持在一个较高水平,而IMP含量一直处于低水平,冻藏前14周HxR和Hx含量一直处在上升通道之中。在评价缢蛏肉鲜度时,K值比Ki值更有说服力。在-20℃贮藏10周后,T-VBN、HxR和Hx、游离脂肪酸含量等开始快速增加,而肌原纤维蛋白溶出量及巯基含量开始迅速下降,使得缢蛏肉品质在贮藏后期快速下降。综合感官评定和T-VBN值,认为缢蛏在-20℃下可贮藏4个月。更多还原

【Abstract】 In recent years,maricultured fisheries have developed rapidly in china,and taking the fresh or live sale as the main way can not adapt to the condition that the yield of fish and shellfishes quickly increase.It is very important to keep the freshness of the maricultured fish molluscs by iced or frozen storage.However,a series of changes which effect seriously the freshness and edible quilities of the maricultured fish molluscs occur at low temperature storage.Using the salt-solubility of actomyosin,-SH content,ATPase activities,the contents of ATP-related compounds, glycogen,glycine betaine,free fatty acids and total volatile basic nitrogen（T-VBN） as assessment indexes,changes of biochemical properties and freshness from Pseudosciaena crocea,Scianeops ocellatus and Mugil cephalus as well as Sinonovacula constricta during low temperature storage were studied respectively. The main research contents and conclusions are as follows:1) The contents of ATP-related compounds in Pseudosciaena crocea meat were determined by HPLC,and the freshness of Pseudosciaena crocea meat during iced storage were assessed using K value,T-VBN level and sensory scores.Results showed that the contents of ATP and ADP decline rapidly on the first day of storage and thereafter change slowly.AMP didn’t accumulate and its content was low duing storage.On the other hand,IMP content was present at high level.After the first day of storage,IMP content reached a maximum value of 9.12μmol/g and remained at higher level until the 8th day,and then decreased.The content of HxR increased fastly on the first day of storage,then decreased as storage progressed.Hx content increased slightly until the 8th day and then increased fastly from 0.97μmol/g on the 8th day to 3.10μmol/g on the 13th day.Both K and T-VBN values increased during iced storage. Combined with the sensory scores,Pseudosciaena Crocea meat was in the first grade of freshness until the 4th day of storage,and reached the initial decomposition stage after 11 days storage.The limit time for sensory acceptability of Pseudosciaena Crocea meat stored in ice was 10 or 11 days.2) Changes of biochemical properties from Sciaenops ocellatus during iced and -20℃forzen storage were analyzed by measuring the salt-solubility of myofibrillar proteins,-SH content,ATPase activities and freshness indexes such as pH value、sensory scores and T-VBN.At the same time,the effects of ultra rapid-deep-freezing and antistaling agents on the protecting myofibrillar proteins from denaturation were compared.The results indicated:During iced storage,the salt-solubility of myofibrillar proteins,-SH content and ATPase activities of Sciaenops ocellatus all decreased.IMP content was present at high level,and K values increased slowly as storage progressed.K value got to 22.42%after 13 days of storage,but at the same time the sensory scores indicated that Sciaenops ocellatus meat was in the early corrupt appearance.It was not fit to use the recommended K values to evaluate the fresh-degree in Sciaenops ocellatus.It was suggested that K values of 6%and 12%,or Hx contents of 0.3μmol/g and 0.6μmol/g in the Sciaenops ocellatus meat were boundary of first and second grade freshness. Combined with the T-VBN value and sensory scores,the limit time for the first and second grade freshdegree of Sciaenops ocellatus meat stored in ice were 4～5 and 8 days,respectively.During frozen storage at -20℃,the salt-solubility of myofibrillar proteins,-SH content and Ca²⁺-ATPase activities in Sciaenops ocellatus all decreased.However,the Ca²⁺-Mg²⁺-ATPase and Mg²⁺-EDTA-ATPase activities of Sciaenops ocellatus by ultra rapid-deep-freezing increased at the first two-weeks of storage,then decreased as storage progressed.Although the myofibrillar-protein denaturation in Scianeops ocellatus meat was not stoped by ultra rapid-deep-freezing or antistaling agents,the denaturation could be delayed.Compared with the antistaling agents group,ultra rapid-deep-freezing was more effectual on the reducing myofibrillar protein denaturation and helpful to increase the water binding capacity and sensory scores in the 12 week’s frozen storage at -20℃. 3) Changes of biochemical properties from Mugil cephalus at different storage temperature were studied.Meantime the effects of ultra rapid-deep-freezing on the denaturation of myofibrillar protein were analyed.Results showed that:During iced storage,the actomyosin salt-solubility and -SH content of Mugil cephalus decreased.It had good relativity to make use of T-VBN value,sensory scores and K value as freshness evaluation indexes.It was suggested that K values of 20%and 40%in the Mugil cephalus meat were boundary of first and second grade freshdegree.The limit time for the first and second grade freshness of Mugil cephalus meat stored in ice were 5 and 9 days,respectively.The limit time for sensory acceptability of Mugil cephalus meat stored in ice was 11 days.Compared with the direct freezing,ultra rapid-deep-freezing could defer the myofibrillar protein denaturation particularly at -20℃frozen storage.Using the same freezing method,the lower storage temperature,the slower protein denaturation.4) During keeping alive at 0℃,the contents of glycogen,glycine betaine and ATP-related compounds,the composition of free amino acids and sensory assessment of Sinonovacula constricta were determined.Moreover,based on the study of myofibrillar protein denaturation and changes of other related-compounds,the freshness of Sinonovacula constricta during -20℃frozen storage were evaluated.The results showed that:During iced storage,the survival rate of Sinonovacula constricta amounted to 80%.ATP contents reached a maximum value of 1.89μmol/g on the 8th day.The content of AMP was in higher level and changed slowly.On the contrary,IMP content was lower during storage.The original contents of glycogen in Sinonovacula constricta was higher and decreased quickly on the first day of storage,then descended slowly.The free amino acids of Sinonovacula constricta included mainly Ala,Ser and Glu as well as Arg.During iced storage,glycogen,glycine betaine,AMP and free amino acids with sweet-fresh flavor played the important role in the delicious taste of Sinonovacula constricta.During frozen storage at -20℃,the content of AMP was higher obviously in comparison with IMP.The content of HxR and Hx increased on the 14 weeks of storage.To evaluate the freshness of Sinonovacula constricta,the K value was more fitter than the Ki value.After 10 weeks of frozen storage at -20℃,the contents of T-VBN,HxR and Hx as well as free fatty acids increased quickly,but the actomyosin salt-solubility and -SH content decreased rapidly.For the above reasons,the quality of Sinonovacula constricta descended quickly in the late frozen storage.Combined with the results of sensory assessment and T-VBN values,the keeping time of Sinonovacula constricta frozen at -20℃was about 4 mouths.更多还原