Quality of Crude Fish Oil Extracted from Herring Byproducts of Varying States of Freshness

ABSTRACT: Herring byproducts were stored at 2 and 15 °C for up to 72 h. Over time, significant increases of total volatile bases (TVB), histamine, putrescine, cadaverine, and tyramine were detected. However, only tyramine and TVB levels were temperature-dependent. The level of total polyunsaturated fatty acids (PUFAs) was constant. Longer byproducts storage gave rise to an oil with higher levels of free fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total PUFAs, while fluorescent compounds were lower. A higher storage temperature led to oil higher in α-tocopherol and EPA levels and lower in anisidine value. Surprisingly, the oil with the highest content of PUFAs was not produced from the freshest byproducts, and oil with low oxidation products can be extracted from stored byproducts.     

Influence of Production Process Parameters on Fish Oil Quality in a Pilot Plant

ABSTRACT: A pilot plant used for upgrading herring byproducts into fish oil was analyzed on its operational efficiency and product quality. The temperature of the heat exchanger and the speeds of the pump and the 3-phase decanter were varied according to a 2³ fractional factorial design. The initial amount of oxidation products present in the crude oil, its storage stability, and the yields from the different obtained products were determined. Multivariate data analysis of the advanced screening stage showed that T had neither influence on the quality nor on the yield in contrast to D and MP (P < 0.05). Process optimization results showed that the quality of the oil was influenced by an interaction effect between the speed of the MP and the D. Oils processed with the highest MP speed were the most stable during storage.     

共振散射光谱法研究槲皮素与DNA相互作用

在BR缓冲液中,槲皮素存在微弱的共振散射现象,分别在288 nm、466 nm、562 nm处出现共振散射峰,随着DNA的加入,散射信号逐渐增强,且以上3处的峰值明显增加,并且562 nm处的增加值与DNA在3.024×10-7 mol/L～9.072×10-5 mol/L范围内呈现出良好的线性关系.在20℃时,通过Scatchard方程计算出槲皮素与DNA结合常数K=9.91×106 mol-1.L.     

Effect of Cover Brine Type on the Quality of Meat from Herring Marinades

Effects of vinegar, oil, and sour cream brines on meat quality of 4 popular cold marinades from herring were investigated in the study. Cover brine type affected the composition and nutritive value of meat as well as the sensory and microbiological quality of marinated herring. Qualitative differences resulted from cover brine penetration into meat, and from diffusion of components from meat to vinegar brine. Compared to oil and sour cream, vinegar brine contributed to increased concentrations of salt and acetic acid, hardness, color brightness of marinades meat and to increased microbial contamination of meat. Furthermore, vinegar caused nitrogen losses to 15%, including valuable products of protein hydrolysis, enzymes, and total volatile bases. The rolling up of fillets reduced diffusion even by 50%. In turn, oil and sour cream were causing mainly a higher fat content and overall sensory evaluation of the marinades.     

Functional Properties of Fish Protein Hydrolysate from Herring (Clupea harengus)

Raw herring (Clupea harengus), a waste product from the roe industry, was hydrolyzed, using an endopeptidase preparation from Bacillus licheniformis. Aliquots were taken at 0, 5, 10, 20, 30, 45, and 60 min hydrolysis to measure the degree of hydrolysis. The functional properties tested were emulsifying activity index (EAI), foamability, and foam stability of the hydrolysate. At 36% hydrolysis, the herring hydrolysate presented good emulsifying stability (> 120 minutes) and an adequate foam expansion (142%), as compared to the soluble fraction from the unhydrolyzed control herring. The lipid content decreased considerably to 0.77% for the fish protein hydrolysate, while its protein content increased to 77%. The amino acid composition remained similar to that of the control.     

Solubility and viscosity of herring (Clupea harengus) proteins as affected by freezing and frozen storage

ABSTRACT:  The aim of this work was to evaluate the effects of freezing and frozen storage at –24 °C on the quality of Icelandic herring fillets, focusing on protein solubility and viscosity at pH 2.7 and 11 used for pH-aided protein isolation. The evaluation of quality was based on chemical analyses, protein degradation measurements, and changes in protein solubility and viscosity at pH 2.7 and 11 after up to 6-mo frozen storage of the herring fillets. Lipid oxidation measured as TBARS values increased significantly during the frozen storage ( P < 0.05). Protein solubility at pH 2.7 decreased during frozen storage for 6 mo, where the solubility was about 10% lower after 6-mo frozen storage compared to the beginning ( P < 0.05). At pH 11, the solubility became approximately 15% lower after 6-mo frozen storage compared to initial solubility ( P < 0.05). Viscosity, measured at pH 2.7, increased after 3 mo of frozen storage ( P < 0.05). At pH 11, the viscosity increased significantly after 1-wk frozen storage, compared to fresh herring fillets, but did not increase significantly with further storage ( P < 0.05). Changes found in solubility and viscosity indicated protein degradation due to freezing and frozen storage. SDS-PAGE analysis did not reveal any protein cross-linking or aggregation formation, either with frozen storage or due to exposure to low pH.     

In situ activity of chymotrypsin in sugar‐salted herring during cold storage

In situ activity of intestinal chymotrypsin in sugar‐salted whole herring during cold storage was evaluated by analysing changes in the low‐molecular‐weight nitrogen fraction when a specific inhibitor was added. Addition of chymostatin (0.01 mM ) to sugar‐salted herring gave 100% inhibition of chymotrypsin activity compared to sugar‐salted herring without chymostatin. Inhibition of chymotrypsin did not affect the profile of low‐molecular‐weight peptides analysed by capillary zone electrophoresis, but resulted in 22% lower content after 26 weeks of storage. Inhibition of chymotrypsin resulted in 17% lower content of free amino acids. The relative amount of single free amino acids was unaffected by the presence of inhibitor, except for valine, leucine, isoleucine, methionine, phenylalanine and tyrosine, which were formed in lower relative amount. Removal of intestines (gutted herring) and thereby all intestinal proteolytic activity did not change the free amino acid profile, except for the concentration of histidine which decreased more when intestines were present. © 2000 Society of Chemical Industry     

Cross-Linking of Myosin Heavy Chains from Cod, Herring and Silver Hake During Thermal Setting

Cross-linking of myofibrillar proteins extracted from cod (Gadus morhua), herring (Clupea harengus) and silver hake (Merluccius bilinearis) was studied in 0.6M NaCl, pH 6.5 at 40°C and evaluated turbidimetrically and by SDS polyacrylamide gel electrophoresis coupled with l-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a zero-length crosslinker. Turbidities of heat-treated cod and silver hake myofibril/myosin solutions were significantly higher than those of herring. Electrophoretic results showed that the myosin heavy chain (MHC) was the principal myofibrillar protein cross-linked to form a polymerized complex during the heat treatment. Cross-linking ability of MHC from the three fish species was different; herring MHC formed only small polymers (n≦3) but cod and silver hake MHC formed both small and large polymers (n≦6).     

基于电子舌的鳓鱼固态发酵过程理化指标预测模型

为实现对鳓鱼固态发酵过程的监测,用常规分析方法和电子舌技术分别测定了鳓鱼发酵过程中水分、p H、总酸、氨基态氮(ANN)、挥发性盐基氮(TVB-N)和味觉指纹的变化;基于电子舌数据,采用主成分分析(PCA)和判别分析(DA)对不同发酵时间的鳓鱼样品进行识别;采用偏最小二乘回归分析(PLSR)建立电子舌数据与相关理化指标之间的预测模型,并对模型进行评价。结果表明:发酵过程中鳓鱼理化指标和滋味特征均有显著变化;主成分分析提取的3个主成分的累积贡献率可达94.49%,判别分析的判别符合率为100%,不同发酵时间的鳓鱼能被有效识别;基于电子舌响应信号建立的5种理化指标预测模型中,水分和ANN模型的相对分析误差(RPD)均为1.80,可用于定性分析。TVB-N模型的RPD为2.47,具有一定定量检测分析能力。p H和总酸的PLSR预测模型的RPD大于5,定量效果良好,稳定性优良,预测精度高。因此,利用电子舌结合相关化学计量方法对鳓鱼固态发酵过程进行识别和监控可行。     

醋渍小鲥鱼生鱼片制作工艺研究

研究利用醋渍的方法将小鲥鱼制成生食制品。醋渍不但能起到杀灭微生物的作用,还能使蛋白质发生变性,使鱼片口感柔韧适中,适合生食。通过正交试验确定了小鲥鱼的最佳醋渍条件:醋与鱼的质量比为1:2,醋渍时间9h,温度5℃。醋渍产品色白而亮,口感佳,且细菌总数低于3000个/g(鱼肉)。