鲢鱼滑在冻藏过程中的结构变化

为研究鲢鱼滑在-20℃冻藏过程中的结构变化,测定了鲢鱼滑盐溶性蛋白含量、活性巯基含量和Ca²⁺-ATPase活性,并结合圆二色光谱（CD）、扫描电镜（SEM）和低场核磁（LF-NMR）进行分析。结果发现,三个指标随冻藏时间延长逐渐下降,其中盐溶性蛋白含量从新鲜状态的58.2 mg/g降至17.3 mg/g,活性巯基含量从0.598 mol/105g降至0.204 mol/10⁵g,Ca²⁺-ATPase活性从0.214μmol/min·g降至0.051μmol/min·g;CD扫描结果显示,冻藏初期α-螺旋主要向β-折叠转化,后主要转化为无规则结构;SEM结果显示,鲢鱼滑凝胶结构由于失水而逐渐收缩,表面光滑度降低,凝胶网络结构受损;LF-NMR的T₂谱显示-20℃环境下有两种结合水的横向弛豫时间,分别为T₂₁（0.09¹ ms）和T₂₂（1¹0 ms）,随着冻藏时间的延长,T₂₁无明显变化,T₂₂总体呈现下降趋势,可知蛋白内部对水分的束缚力增强。从结构变化角度探究了鲢鱼滑在冻藏过程的品质变化。      

茶多酚-海藻糖脱腥液对白鲢鱼贮藏品质的影响

研究比较了茶多酚、海藻糖以及茶多酚-海藻糖脱腥液对白鲢鱼肉的脱腥效果,并选用脱腥效果最好的茶多酚-海藻糖复合脱腥液应用于白鲢鱼肉的冷藏保鲜。通过感官评价、微生物和理化指标分析,研究复合脱腥液处理对白鲢鱼块在0℃贮藏过程中品质变化及货架期的影响。实验结果表明,经脱腥液处理能有效抑制白鲢鱼块冷藏过程中的细菌生长,减缓鱼肉TVB-N值、TBA值和p H的升高,延缓鱼肉感官评分、硬度和咀嚼度的下降,能够延长白鲢鱼块的货架期6 d左右。      

冻藏对鲢鱼、鲤鱼鱼肉质构影响的比较研究

比较冻藏处理对鲢鱼、鲤鱼鱼肉质质构的影响.采用质构仪对冻藏的鲢鱼、鲤鱼鱼肉进行测定,并与未经冻结的鱼肉指标值进行比较.结果表明,经过冻结的鲤鱼、鲢鱼的硬度、弹性、黏附性、咀嚼性、恢复性等指标值均有所下降,下降幅度不同,与鲤鱼相比较,鲢鱼质构变化明显.     

不同温度对白鲢鱼肉在蒸煮过程中品质的影响

为了研究蒸煮过程中温度对白鲢鱼品质的影响,在常压蒸汽加热下分别测定了温度（20、30、40、50、60、70、80、90℃）对白鲢鱼肉挥发性化合物、蛋白质组分、ATP酶（Ca2+-ATPase）活性、总巯基和活性巯基含量、表面疏水性、失重率、剪切力和p H的影响。结果表明:在60℃时挥发性化合物种类最多为29种,70℃时最少为15种;醇类和烃类物质的含量分别在90和80℃时最高,醛酮类在70℃时最高;水溶性、盐溶性和碱不溶性蛋白、总巯和ATP酶活性随温度的升高而显著（p<0.05）下降。碱溶性蛋白、失重率和p H则随温度的升高而显著（p<0.05）增加。活性巯基和表面疏水性则随温度的增加而先升高后下降,分别在50℃和60℃时达到最大值0.18 mol/g和410.08 So ANS。剪切力在加热初期（20³0℃）显著（p<0.05）降低,到60℃时达到最低值114.39 g。研究结果为白鲢鱼热加工品质控制提供参考。      

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) unwashed and washed mince as related to endogenous proteinases and transglutaminase activities

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) mince and washed mince was investigated with respect to their proteinase and transglutaminase (TGase) activities. Proteinases in sarcoplasmic fluid showed the optimum activity at 65 °C and pH 9, whereas autolytic activity was maximum at 70 °C and pH 10, indicating the presence of heat-stable alkaline proteinases. When mince was washed with three volumes of water twice, TGase and proteinases were mainly removed in the first washing cycle, resulting in a decreased autolytic activity of washed mince. Breaking force of the single washed mince gels was greater than the twice washed mince and the unwashed mince gels (p<0.05). Pre-incubation of mince pastes at 40 °C for 1 h prior to cooking (90 °C/30 min) increased breaking force of all samples, particularly the single washed mince (p<0.05). This coincided with an increase of higher molecular weight polymers observed on SDS-PAGE. Washing did not completely eliminate proteinases as it was evident by an increased trichloroacetic acid (TCA)-soluble oligopeptides of washed gels pre-incubated at 55 °C. Whiteness values of washed mince gels were greater than that of mince gels.     

Effect of silver carp (Hypophthalmichthys molitrix) muscle hydrolysates and fish skin hydrolysates on the quality of common carp (Cyprinus carpio) during 4 °C storage

Silver carp (Hypophthalmichthys molitrix) skin and muscle were hydrolysed, respectively, and then used as part of an edible coating to preserve fish. The effects of muscle and skin hydrolysates as edible coatings for shelf life extension of common carp (Cyprinus carpio) were evaluated over 18 days at 4 °C, by comparing these two treatments, a chitosan coating with muscle hydrolysate, chitosan alone, and an untreated control. All coatings were made up with 5% glycerol. The quality of the carp was assessed by using total volatile basic nitrogen (TVB‐N), total viable counts (TVC), thiobarbituric acid (TBA) and K value. Compared with the control group, the rate of increase in TVB‐N, TVC, TBA and K value of carp coated with fish skin hydrolysates, fish muscle hydrolysates and chitosan added to fish muscle hydrolysates were lower. According to the total viable counts, the storage life of fish with fish skin hydrolysates coatings and chitosan added fish muscle hydrolysates coatings were 16 days, 2 days longer than those with the chitosan coatings and twice as long as the control group.     

鲫鱼、鲢鱼和乌鱼的元素分布分析

为了解鲫鱼、鲢鱼和乌鱼的元素分布情况,将其可食部位中污染元素和矿物质元素分别进行测定。结果表明,各种元素在鱼的可食部位蓄积量存在明显的差异。鲫鱼内膜的铝（Al）、铬（Cr）、砷（As）、镉（Cd）、铅（Pb）含量显著高于鲫鱼的其他可食部位（P＜0.05）,而鲫鱼鱼头的钙（Ca）、磷（P）、镁（Mg）含量显著高于鲫鱼的其他可食部位（P＜0.05）;鲢鱼内膜的Cr、As、Cd含量显著高于鲢鱼的其他可食部位（P＜0.05）,总As含量（1.81 mg/kg）也显著高于鲫鱼和乌鱼的各个可食部位（P＜0.05）,而鲢鱼鱼头的Ca、P、Mg、Fe含量显著高于鲢鱼的其他可食部位（P＜0.05）;乌鱼鱼头富集Cd很严重,在这3种鱼的可食部位中其含量（0.006 14 mg/kg）是最高的,但乌鱼鱼头同时也富含Mg、Fe、铜（Cu）、Ca、P等营养元素。     

鲢鱼组织蛋白酶活性影响因素的研究

对鲢鱼中组织蛋白酶活性影响因素进行了研究,结果表明:组织蛋白酶对热的耐受性较强,温度超过65℃组织蛋白酶活性下降很快,到85℃基本失活;组织蛋白酶活性的最适pH5~7之间;漂洗和加盐擂溃可以有效地降低3种组织蛋白酶的活性,试验证明NaHCO3溶液是较理想的漂洗溶液;添加非肌肉蛋白和E64都可以显著地降低鱼肉中组织蛋白酶的活性。     

不同气调包装对冷藏白鲢鱼片质量的影响

用不同的气调成分(50%O2/50%CO2、50%N2/50%CO2、50%CO/50%CO2)及空气(对照组)分别包装鲢鱼片,并在冷藏(4±2℃)条件下贮藏,研究不同的气调包装处理对鲢鱼片理化及微生物的影响。结果显示,随贮存期增加,气调包装能有效抑制需氧菌数、嗜冷性细菌及大肠菌群的生长;气调包装处理的pH比控制组低,但其汁液流失量较控制组高;所有包装的TVBN值及TBA值随贮存时间增加而上升,色泽则逐渐衰减。     

鲢鱼鱼丸最佳配方及工艺的研究

研究了鲢鱼鱼丸的加工工艺,通过流变学特性和感官特性的综合评定,确定了鲢鱼鱼丸的最适配方,并对鱼丸的理化和微生物指标进行了测定。     

鲢鱼酶解产物在冷冻鱼糜中的抗冻性能研究

分别利用复合蛋白酶和碱性蛋白酶酶解鲢鱼,获得复合蛋白酶酶解产物(protamex hydrolysates,PH)和碱性蛋白酶酶解产物(alcalase hydrolysates,AH),将PH和AH分别加入冷冻鲢鱼鱼糜中,研究其对鱼糜色泽和凝胶结构的影响,并与工业上常用的抗冻剂(蔗糖—山梨醇)进行比较。结果表明:PH相比AH具有较高含量的天冬氨酸、赖氨酸及游离氨基酸(P0.05);PH比AH中包含较多的较大分子质量的组分;在-20℃冻藏4周的情况下,2%PH添加组和蔗糖—山梨醇添加组的凝胶强度和硬度有一定提高;各组样品的弹性均略有降低;冻藏条件对各鱼糜样品的色泽影响较小;各组样品均出现了鱼蛋白分子聚集现象,而2%PH添加组和蔗糖—山梨醇添加组的鱼糜样品表面较为均匀、鱼糜孔隙较小。该研究表明PH有助于稳定鱼糜在冷冻过程中的凝胶结构,为鲢鱼酶解产物作为一种可能的新型鱼糜抗冻剂提供了依据。     

鲢鱼酶解物对冻融鱼糜制品品质及其蛋白质体外消化率的影响

选择复合蛋白酶水解鲢鱼制酶解产物,以添加了商业抗冻剂(商抗,4%蔗糖+4%山梨醇)的鱼糜制品作对照,综合评价添加了鲢鱼酶解产物的鱼糜制品冻融前后品质及其蛋白质体外消化率的变化。试验结果表明:冻融后,鱼糜制品中添加2%的酶解产物可以增加鱼糜凝胶持水性,降低蒸煮损失,并且不会导致鱼糜制品带上酶解产物本身的淡黄色;同时,2%酶解产物添加组能有效减缓鱼糜制品凝胶强度、硬度和弹性的降低及其蛋白质消化率的下降程度;2%酶解产物添加组在冻融前后感官评分均较高,酶解产物的添加避免了商业抗冻剂给产品带来的明显甜味。研究表明,鲢鱼酶解产物可作为潜在的抗冻剂应用于鱼糜及其制品的工业化生产。     

Structural stability of myosin rod from silver carp as affected by season

Chymotrypsin digestion and Circular dichroism (CD) spectroscopy were used to study the structural stability of myosin rods prepared from silver carp in summer and winter. Differences in the thermal stability were clearly demonstrated by the chymotryptic digestion patterns and CD data obtained at pH 7.5 in 0.5 M KCl for myosin rods in both seasons, indicating the structural properties differed seasonally. In winter, the myosin rods were more susceptible to be cleaved into short (40 kDa) subfragments when digested at high temperature (30 °C). The major peaks in unfolding profiles showed that transition temperatures for the rods were 35 °C in winter, and 36 and 41 °C in summer. Rod subfragments (S-2 and LMM) were isolated and further analyzed by CD. In both winter and summer, the LMM fragments showed an unfolding transition at around 35.5 °C, but the S-2 fragments showed large seasonal difference; in winter, they showed a major unfolding peak around 35 °C and a minor peak at 40.5 °C, while in summer, they unfolded mostly at 44.5 °C, which was 8 °C higher than that for the LMM fragments. Short (40 kDa) S-2 subfragments isolated from winter rods gave a single unfolding transition at 41 °C. These results suggest that differences in the thermal stability of myosin rods between winter and summer were due to differences in the stability of S-2 region. PRACTICAL APPLICATION: The aim of this study was to detect the differences in the structure thermal stability of myosin rods between summer and winter, which is a very important portion for gel formation. The information will be very useful for producing surimi from freshwater fish species in different seasons.     

Changes in biogenic amines of silver carp (Hypophthalmichthys molitrix) fillets stored at different temperatures and their relation to total volatile base nitrogen,microbiological and sensory score

BACKGROUND: Biogenic amines have received considerable attention owing to their undesirable effects in humans. There are few studies of changes in biogenic amine contents related to freshwater fish. Silver carp is an important freshwater fish species in China. This study aimed to investigate the changes in biogenic amines and their relation to total volatile base nitrogen (TVB‐N), microbiological and sensory score of silver carp fillets stored at 0, 3 and 15 °C. RESULTS: The total biogenic amine contents of all silver carp fillets (regardless of storage time and temperature) ranged from 13.05 to 318.10 mg kg^?1. Putrescine and histamine were the main biogenic amines in silver carp fillets during storage. Cadaverine was only detected after 12 days at 3 °C and after 2 days at 15 °C. Spermidine and spermine contents increased during the early storage period and then slightly decreased. CONCLUSION: Low temperature could control the quality of silver carp fillets by inhibiting the contents of biogenic amines. Putrescine showed significant correlation with TVB‐N, total aerobic content, sensory score, tryptamine and phenylethylamine. Putrescine was a good quality marker of silver carp fillets in the cold chain. Copyright © 2012 Society of Chemical Industry     

Effect of ginger extract and vinegar on ATP metabolites,IMP‐related enzyme activity,reducing sugars and phosphorylated sugars in silver carp during postslaughter storage

This study aimed to investigate the utilisation of ginger extract and vinegar for retarding decomposition of inosine monophosphate (IMP), and IMP‐related enzyme activity (the activity of acid phosphatase (ACP) and alkaline phosphatase (ALP)) in salted silver carp (Hypophthalmichthys molitrix) during early postslaughter and chilled storage. We also quantified the decomposition pathway of ATP‐related compounds, the reducing and phosphorylated sugar, and free amino acids (FAAs) in samples. Rapid glycolysis in control occurred during postmortem storage. Vinegar and ginger extract inhibited the activity of ACP and ALP, thereby inhibiting the decomposition of IMP and the increase in hypoxanthine (Hx). IMP concentrations in treated sample were significantly higher than those of the control. Moreover, vinegar and ginger extract promoted the increase in FAAs. Therefore, vinegar and ginger extract could inhibit ACP and ALP activities and contributed to the accumulation of IMP and FAAs in silver carp during chilled storage.     

微胶囊化姜黄油对冷藏鲢鱼鱼丸的保鲜效果

以鲢鱼鱼丸为研究对象,将姜黄油及微胶囊化姜黄油添加到鱼丸中,测定分析其在冷藏过程中微生物、理化和感官等品质指标的变化,评价微胶囊化姜黄油对鲢鱼鱼丸的保鲜效果。结果表明:4℃下空白组鱼丸在贮藏5 d后菌落总数(TVC)达到6.2×104 cfu/g,超过国家规定的卫生标准;而添加0.1%微胶囊化姜黄油的鱼丸样品细菌生长受到明显抑制,可使鱼丸货架期延长8 d(TVC值为5.9×104 cfu/g)。微胶囊化姜黄油还可以有效地减缓脂肪氧化,提高了鱼丸的白度,而对弹性影响不大。该生物保鲜剂在鱼糜制品保鲜中具有明显效果,使产品在较长时间内保持良好的食用品质。      

鲢鱼头及骨中蛋白质的酶解条件优化

采用木瓜蛋白酶对鲢鱼头及骨中蛋白质进行水解,研究了酶用量、料液比(底物浓度)、酶解温度及时间对水解度的影响,采用正交试验对酶解条件进行了优化。结果显示,水解度随酶用量、酶解温度和时间的增加而增大,底物浓度过低或过高均不利于原料中蛋白质的提取。鲢鱼头及骨中蛋白质提取的最佳条件为木瓜蛋白酶用量2%(w/w,以蛋白质质量计)、料液比1∶1.4(w/v)、酶解温度55℃、酶解时间7h。该条件下蛋白质的水解度为12.07%,所得水解物色泽较浅,且无苦味。