钙离子添加量对未漂洗海鲈鱼糜凝胶特性的影响

为探明钙离子(Ca~(2+))能否提高未漂洗海鲈鱼糜的凝胶品质,为海鲈鱼糜生产提供新方法。以海鲈鱼为原料,比较氯化钙(CaCl_2)不同添加量(0.01～0.08 M)对采肉后未经漂洗工序直接制成海鲈鱼糜的凝胶强度、质构特性(TPA)、持水力、白度、微观结构等的影响,并与传统方法制备的海鲈鱼糜进行比较。结果表明Ca~(2+)对未漂洗的海鲈鱼糜品质有显著影响(P0.05);CaCl_2的添加可显著提高未漂洗海鲈鱼糜凝胶强度、TPA、持水力和白度,使鱼糜组织结构紧密均匀;当CaCl_2添加量在0.02 M时,未漂洗的海鲈鱼糜的凝胶特性(凝胶强度7 364.21 g·mm、持水力88.93%、硬度421.8 g、弹性10.03 mm、胶着性229.5 g、咀嚼性22.21 mJ、白度86.72)与传统鱼糜品质相近,其效果最好;而当CaCl_2添加量达到0.08 M时,Ca~(2+)与鱼肉蛋白过度交联,形成钙桥结构,造成凝胶强度和硬度增加、弹性下降。研究表明,适量添加Ca~(2+)可使海鲈鱼糜不需经过漂洗工序而达到传统漂洗生产鱼糜的品质,这为开发营养流失少、节水、节能的海鲈鱼糜加工提供理论和技术支撑。     

用鲢鱼加工模拟蟹腿肉的试验

本试验以国内大宗养殖产品鲢鱼为原料,取代部份进口原料生产模拟蟹腿肉。结果显示,添加30%的鲢鱼鱼糜不影响产品质量,与100%用狭鳕鱼糜生产的产品无明显质量差别。本文同时总结了鲢鱼鱼糜凝胶形成能的特性,以及提高凝胶强度的方法;讨论了在我国发展鲢鱼模拟制品生产的可行性和急待研究解决的课题。     

添加圆苞车前子壳粉的鲢鱼糜凝胶工艺优化及其凝胶特性

圆苞车前子壳粉(psyllium husk powder, PHP)是一种富含膳食纤维的食品亲水胶体。为了解其在鱼糜制品中的作用,本实验以冷冻鲢鱼糜为研究对象,以凝胶强度和持水性(water holding capacity, WHC)为考察指标,研究了PHP的添加量、凝胶化温度和凝胶化时间3个因素对鱼糜凝胶特性的影响。在单因素试验的基础上,进行了三因素三水平的正交试验和验证试验。正交试验结果得到最佳工艺条件:PHP添加量0.1%,凝胶化温度45°C,凝胶化时间2 h。单因素试验结果表明,添加适量PHP (0.1%～0.3%)能够增加鱼糜凝胶的硬度和WHC,但对破断距离有不利影响;根据验证试验中蒸煮损失率、SDS-聚丙烯酰胺凝胶电泳(SDS-polyacrylamide gel electrophoresis, SDS-PAGE)和扫描电镜(scanning electron microscopy, SEM)分析,PHP的添加降低了较高凝胶化温度时凝胶的蒸煮损失,PHP或许可以促进肌球蛋白重链(myosin heavy chain, MHC)分子间交联,减缓蛋白质降解,形成更加致密的凝胶结构。本研究对PHP作为一种新型食品原料应用于开发优质健康鱼糜制品进行了初步的探究,以期为丰富亲水胶在影响鱼糜凝胶特性中的应用研究提供一定的参考。     

不同添加物对微山湖四鼻鲤鱼糜凝胶性的影响

鱼糜制品的凝胶强度是评价鱼糜制品质量的重要指标,本研究以微山湖四鼻鲤(Cyprinus carpio L.)为原料,经过一定的处理后,探讨添加物玉米淀粉、蛋清蛋白、卡拉胶对鱼糜凝胶品质的影响。实验结果表明,通过单因素实验,确定了玉米淀粉、蛋清蛋白和卡拉胶对改良鱼糜凝胶性的最佳添加量为玉米淀粉25%、蛋清蛋白6%、卡拉胶2.0%。通过正交实验确定了玉米淀粉、蛋清蛋白和卡拉胶对鱼糜凝胶性最佳添加组合为玉米淀粉25%、蛋清蛋白6%、卡拉胶1.8%,此组合对鲤鱼糜凝胶品质的改善作用最强。本研究可为今后制备高品质的四鼻鲤鱼糜制品提供一定的参考。     

超声时间对鲢鱼糜凝胶特性和蛋白结构的影响及相关性

为探究超声预处理对鱼糜凝胶特性的影响，并进一步阐明凝胶特性变化与蛋白二级结构之间的相关性规律，本实验对鲢鱼糜进行超声预处理，探究超声过程中(0～50 min)凝胶强度、色泽、水分分布、微观结构、蛋白分子量以及二级结构的变化。结果显示，超声波处理10 min，鱼糜凝胶强度显著提高，束缚水的能力增强，凝胶网络结构更为致密；但随超声时间的增加，凝胶劣化，不易流动水转变为自由水。凝胶电泳及红外光谱结果显示，随着超声时间增加，鱼糜中蛋白未发生降解或聚集；二级结构中α-螺旋相对含量降低，β-折叠、无规则卷曲和β-转角相对含量增加。通过皮尔逊相关性分析可知，超声预处理促进蛋白质结构展开，更利于鱼糜在加工过程中形成均匀的网络结构，提高凝胶强度以及保水能力。研究表明，适量超声预处理可以通过改变鱼糜蛋白结构，改善鱼糜凝胶特性。本研究可为超声波技术在鱼糜制品加工中的应用提供参考。     

木薯淀粉对金线鱼鱼糜3D打印效果的影响

以金线鱼鱼糜为研究对象,通过添加木薯淀粉能使鱼糜制品的凝胶特性得到改善,持水性和弹性得以提升,实验从表观黏度和流变特性(输送难易程度)、打印效果(外观形貌、定型性)、鱼糜制品凝胶特性3个方面研究了木薯淀粉对金线鱼鱼糜3D打印效果的影响。采用质构分析、低场核磁分析、流变分析、成型效果分析方法,对凝胶强度、质构特征、持水性、水分分布及组成、表观黏度、动态流变进行测定。结果显示,随着木薯淀粉添加量的增加,金线鱼鱼糜浆料的凝胶强度、硬度、弹性、持水性均呈先上升后下降的趋势,在木薯淀粉添加量为2%时达到最高值,较对照组相比分别提高了113.63%、249.00%、28.00%和9.14%。鱼糜中的不易流动水(T23)相对含量在木薯淀粉添加量为2%时达到最高,T23峰比例为0.98。随着木薯淀粉添加量的增加,鱼糜浆料的表观黏度和屈服应力上升,浆料的弹性模量(G?)和损失模量(G??)随着木薯淀粉添加量的增加呈先上升再下降的趋势,在木薯淀粉浓度为3%时达到最高,损失正切(tanδ)在淀粉浓度为2%时达到最高。研究表明,在木薯淀粉添加量为2%时,鱼糜3D打印的效果最佳。本研究对鱼糜3D打印有积极指导意义,为实现食品领域3D打印的实用化、广泛化、多样化提供了参考。     

不同处理条件下鲢鱼糜凝胶水分状态和微观结构的特征

为探讨超高压改善低盐鲢(Hypophthalmichthys molitrix)鱼糜凝胶品质的机制,利用低场核磁共振(low field nuclear magnetic resonance,LF-NMR)、差示扫描量热法(differential scanning calorimeter,DSC)、傅里叶红外光谱(fourier transform infrared spectroscopy,FT-IR)以及扫描电镜分析比较了超高压低盐鱼糜凝胶[300 MPa,1.5%氯化钠(NaCl)]与常压低盐鱼糜凝胶(0.1 MPa,1.5%NaCl)以及常压普通鱼糜凝胶(0.1 MPa,2.5%NaCl)在水分状态和微观结构上的差异。DSC结果表明超高压低盐鱼糜凝胶可冻结水的冰点降低,结合水含量(17.58%)较低盐对照组(10.89%)显著提高;LF-NMR表明超高压低盐鱼糜凝胶弛豫时间T21、T23和T24左移,不易流动水的含量(76.65%)较低盐对照组(67.29%)提高了9.39%;超高压处理能使低盐鱼糜凝胶形成光滑、连续、均匀的三维网络结构。因此,超高压处理(300 MPa,10 min)能够提高低盐鲢鱼糜凝胶结合水含量、改善微观结构。     

鲢鱼糜凝胶形成过程中化学作用力及蛋白质构象的变化

采用化学法、激光拉曼光谱、圆二色谱等先进的现代检测分析手段，研究鲢（Hypophthalmichthys molitrix）鱼糜凝胶形成过程中离子键、氢键、疏水相互作用、二硫键、非二硫共价键等化学作用力对鱼糜凝胶形成的作用，并对蛋白质构象进行了表征，探索化学作用力及蛋白质构象对鲢鱼糜凝胶网络结构形成的作用。结果表明，在鱼糜凝胶形成过程中，离子键、氢键显著减少，而疏水相互作用、二硫键、非二硫共价键显著增加。疏水相互作用、二硫键、非二硫共价键是维持鲢鱼糜凝胶稳定结构的主要化学作用力。40℃和90℃两段加热过程中，鲢肌球蛋白的α-螺旋结构部分转变成转角和无规卷曲结构，以无规卷曲结构为主。鲢鱼糜凝胶中肌球蛋白的二级结构单元α-螺旋、转角、无规卷曲结构的百分含量分别为33．70％、12．40％、53．90％，其中α-螺旋和无规卷曲结构是维持鲢鱼糜凝胶网络结构的主要蛋白质构象。维持鲢鱼糜凝胶稳定结构的主要化学作用力为疏水相互作用、二硫键、非二硫共价键，主要蛋白质构象为α-螺旋和无规卷曲结构。[中国水产科学，2008，15（3）：469-475]     

淡水鱼鱼糜性质研究

采用清水漂洗、盐水漂洗和碱水漂洗、钙离子、热处理方法对草鱼、白鲢鱼糜进行试验,阐明诸因素对草鱼、白鲢鱼糜凝胶性能的影响,为生产鱼糜制品提供合理的工艺参数、研究表明,草鱼2次清水与1次盐水漂洗凝胶性能较好,鲢鱼鱼糜的最佳钙离子质量分数为0 5%。     

几种添加剂对宽体舌鳎盐溶蛋白凝胶特性的影响

鱼肉盐溶蛋白的凝胶特性与鱼糜制品的质地密切相关,而盐溶蛋白的凝胶特性又受到许多因素影响。为研究添加转谷氨酰胺酶(TGase)、海藻酸钠、卡拉胶、魔芋胶对宽体舌鳎盐溶蛋白凝胶特性的影响,本实验通过四元二次通用旋转试验设计,采用响应面法建立了宽体舌鳎盐溶蛋白凝胶保水性(Y)和凝胶强度(y)与各添加剂用量的二次多项回归方程,确定了TGase、海藻酸钠、卡拉胶、魔芋胶的适宜添加量分别为0.36%,1.00%,1.00%,0.71%,添加后舌宽体鳎盐溶蛋白凝胶网状结构致密均匀,保水性和凝胶强度分别为60.36%和55.20 g,比对照组分别增加了36.41%和351.80%。结果说明,合适的添加剂组合可以显著的增加宽体舌鳎盐溶蛋白凝胶的保水性和凝胶强度。     

In vitro and in vivo antibacterial activity of shrimp chitosan against some intestinal bacteria

ABSTRACT:   The effects of shrimp chitosan with deacetylation degrees (DD) of 50%, 70% and 95% (DD50, DD70, DD95) on the growth of the intestinal bacteria were investigated in vitro in the laboratory media, and in vivo by an oral feeding test using hamsters as the animal model. The antibacterial activities of these chitosan products against one strain of pathogenic Clostridium perfringens and 13 strains of probiotics, including seven strains of Lactobacillus , and six strains of Bifidobacterium were evaluated. In vitro , the antibacterial activities of DD95 and DD70 were much higher than that of DD50. The strains of probiotics were more resistant to chitosan than the pathogen of C .  perfringens . The minimal lethal concentration for DD95 against C. perfringens was 250 p.p.m., whereas the survival percentages for most probiotics tested were above 90% for DD95 at 500 p.p.m. The animals were fed on either a control diet, or diets containing powdered chitosan instead of 5% cellulose in the control diet for 4 weeks. The cecal bacterial counts of total aerobes, total anaerobes, lactobacilli, bifidobacteria and clostridia were similar for the control and experimental groups. The reasons for the differences in the antibacterial activity in vitro and in vivo are discussed.     

Cellulase degradation of shrimp chitosan for the preparation of a water-soluble hydrolysate with immunoactivity

ABSTRACT:   Samples of colloidal chitin and chitosans with deacetylation degrees (DD) of 50, 65, 75 and 95% (DD50, DD65, DD75 and DD95, respectively) were prepared from shrimp chitin. The hydrolytic activity of cellulase on these samples increased with the increasing DD of chitosan, with DD95 being the most easily hydrolyzed. Colloidal chitin was hardly hydrolyzed. The optimal reaction temperature and pH for cellulase digestion of chitosan were 55°C and pH 5.2, respectively. During cellulase digestion of chitosan, the 9-h hydrolysate had the highest enhancing effect on the proliferation of a human hybridoma cell, HB4C5. This hydrolysate is composed of low-molecular-weight chitosan (LMWC), with a molecular mass of 20.0 kDa, and chitooligosaccharides, which are composed of sugars with a degree of polymerization of 1–6. In vitro , the 9-h hydrolysate increased both cell proliferation and immunoglobulin (Ig)M secretion of HB4C5 because of the presence of chitooligosaccharides for the former activity and LMWC for the latter activity. In vivo , samples of the chitosan hydrolysate, chitooligosaccharide mixture and LMWC significantly increased the levels of serum IgG and IgM, and enhanced concanavalin A- and lipopolysaccharide-induced proliferation of mouse lymphocytes.     

热塑挤压蒸煮处理对鱼肉蛋白分子影响的研究

用热塑挤压蒸煮加工技术与传统食品加工技术比较了不同加工技术对鱼肉蛋白分子的影响.通过采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳对原料鱼肉,3种传统加工方法即常规蒸煮、热力杀菌和鱼糜加工处理的鱼肉制品及热塑挤压蒸煮的鱼肉制品进行蛋白质分子量的测定,分析比较各种鱼肉制品的蛋白质分子量的测定结果,初步探索了热塑挤压蒸煮对鱼肉蛋白质分子量的影响.研究结果表明,热塑挤压蒸煮对鱼肉蛋白质的分子量有一定的影响.     

Antioxidant Properties of Chitosan Coatings on Frozen Atlantic Salmon Fillet Portions

Atlantic salmon contain omega-3 fatty acids, which play important roles in promoting human health but are highly susceptible to oxidation. Chitosan has been shown to have antioxidant properties which could be beneficial in extending the shelf life of Atlantic salmon; however, the effects of chitosan molecular size on oxidation of salmon fillets have not been reported. The primary objective of this study was to evaluate the effects of chitosan coatings on lipid oxidation of Atlantic salmon fillet portions during 5 months frozen storage. The effects of chitosan molecular weight (high molecular weight, low molecular weight, and enzymatically degraded chitosan), concentration (0.5 and 1.0%), and the addition of 1% ascorbic acid to the chitosan coating were evaluated. Chitosan molecular weight significantly affected oxidation as evaluated by propanal levels and changes in L* values of the fillet portions. The chitosan treatment with added ascorbic acid resulted in the lowest propanal levels during 5 months of frozen storage. Manipulation of chitosan molecular weight and incorporation of natural antioxidants into chitosan coatings can provide an effective method of reducing lipid oxidation during extended frozen storage of seafood products.     

Rapid enumeration of bacteria grown on surimi-based products by flow cytometry

ABSTRACT: A rapid method to enumerate bacteria adhered on a surimi-based product (kamaboko) by flow cytometry (FCM) is described. To remove Escherichia coli cells from the surface of kamaboko, ultrasonic energy was used. Almost all cells can be removed from kamaboko in 3 min with ultrasonic treatment. Because the sample might contain various non-bacterial particles such as food additives and debris of products, propidium iodide was used to discriminate bacterial cells from non-bacterial particles. Fluorescence scattergrams could distinguish bacteria from the particles, and the FCM method could be used to enumerate bacteria adhered on the surface of kamaboko during storage. Cell numbers determined by FCM paralleled well with those measured using a traditional colony counting method in the range of 10⁴–10⁸ cells/g. The FCM assay could enumerate cells within 1 min and the total assay time, including sample preparation, was less than 30 min.     

Oxidative Stability of Spray-Dried Microencapsulated Fish Oils with Different Wall Materials

Multilayer microencapsulation of fish oil was evaluated by using fish gelatin (treated with or without microbial transglutaminase [MTGase]), chitosan, and maltodextrin for its ability to control lipid oxidation. This study showed that a mixture containing gelatin and maltodextrin obtained the highest percentage of core release. The oxidative stability of the formulated mixtures and the bulk oils was investigated during a period of 60 days. The peroxide value (PV) was assessed as a parameter for primary oxidation products, and p-anisidine (p-AV) and thiobarbituric acid reactive sub-stances (TBARS) was used to analyze secondary oxidation compounds. Observation of oxidation products showed that combinations of gelatin and maltodextrin made by adding MTGase and a mixture of gelatin and chitosan were able to increase the oxidative stability, and increases in PV and p-AV and TBARS were found for all oils.     

Quality improvement of the thermal gel of horse mackerel by sodium citrate and its inhibition of the insoluble metalloproteinase

Modori-inducing proteinases (MIPs) in horse mackerel and the effect of sodium citrate on the modori phenomenon were investigated. Cysteine protease caused the modori phenomenon only at 60 ℃, while metalloproteinase caused it at both 60 ℃ and 70 ℃. Moreover, the autolysis of myofibrillar proteins was mainly inhibited by ethylene diamine tetra-acetic acid (EDTA), verifying the existence of insoluble metalloproteinase. From the results comparing thermal gel properties and protease activities, we confirmed that increased activity of insoluble metalloproteinase corresponded to the weakening of the thermal gel. Thus, insoluble metalloproteinase was the major MIP in horse mackerel. Moreover, sodium citrate could markedly inhibit insoluble metalloproteinase activity at 60 ℃. The addition of sodium citrate significantly improved the breaking force of the thermal gel at 60 ℃ and 70 ℃, suggesting that sodium citrate could suppress the modori phenomenon by inhibiting insoluble metalloproteinase. Therefore, it is desirable to use sodium citrate in horse mackerel surimi-based products to prevent the modori phenomenon.

     

Effect of partial or total replacement of forage fish by a dry diet on the quality of reproduction in pikeperch, Sander lucioperca

The aim of this preliminary study was to evaluate the influence of different feeding regimes on the quality of reproduction in pikeperch. Three diets were tested: forage fish (FF), a commercial dry feed (DD) and a mix of both (FD).  The diets were given to fish throughout a complete reproductive cycle. During the spawning season, couples were injected with human chorionic gonadotropin (hCG) and let to spawn on nests. Proportion of running males, spawning and hatching success and larval quality (weight, length, body protein, total lipid, fatty acid and lipid class compositions and resistances to osmotic shock and starvation stress tests at hatching) were evaluated. The proportion of running male was lower in the DD group than in the FF and FD groups (54% for DD against 76–89% for FF and FD). In addition, 25%, 62.5% and 75% of injected couples gave spawning that hatched in DD, FF and FD groups respectively. Larval quality parameters were not significantly different between treatments. The results indicate that overall quality of reproduction was higher in FF and FD treatments than in DD. It suggests that the dry feed used was not totally adequate for pikeperch reproduction. Relations between breeder reproductive performances and the feed compositions are discussed.     

cDNA cloning and complete primary structures of myosin heavy chains from brushtooth lizardfish Saurida undosquamis and wanieso lizardfish S. wanieso fast skeletal muscles

ABSTRACT:   The complete cDNA sequences encoding predominant types of myosin heavy chain (MYH) in the fast skeletal muscle were determined for brushtooth lizardfish Saurida undosquamis and wanieso lizardfish S. wanieso , which are used as materials for preparing high-quality surimi-based products. The cDNA consisted of 5973 and 5987 bp, respectively, and both encompassed an open reading frame encoding a polypeptide of 1936 amino acid residues. Brushtooth and wanieso lizardfish MYH showed the amino acid sequence identity of 92–93% to white croaker MYH, which was higher than that of 90% to walleye pollack MYH. The putative binding sites for ATP, actin, and regulatory and essential light chains in the subfragment-1 region of brushtooth lizardfish MYH exhibited a high identity with white croaker counterparts as well as the sequences of subfragment-2 and light meromyosin. In contrast, phylogenetic tree, constructed by the neighbor-joining method based on mitochondrial 16S rRNA gene, revealed that the two lizardfish species formed a cluster with walleye pollack, which was paraphyletic with white croaker. Therefore, a good reputation for lizardfish and white croaker to have a high thermal-gel forming ability seemed to be reflected by MYH rather than biological similarity as revealed by the mitochondrial 16S rRNA gene.