Characterization of Acid-soluble Collagen from Pacific Whiting Surimi Processing Byproducts

ABSTRACT: Three different solid byproducts (skin, frame, and refiner discharge) from Pacific whiting surimi manufacturing are a good resource for collagen extraction according to their total protein concentrations and other biochemical properties. Denaturation temperature of acid-soluble collagens was 23.3°C for refiner discharge, 21.7 °C for skin, and 20.6°C for frame. Based on the functional properties, acid-soluble collagen from refiner discharge was the best and showed potential as an ingredient in processed food manufacturing.     

Surimi Production from Partially Processed and Frozen Pacific Whiting (Merluccius productus)

Pacific whiting surimi was made from stabilized mince (SM), unstabilized mince (UM), and headed and gutted (H&G) fish kept in frozen storage and compared to a surimi control made from fresh fillets. SM was made by mixing fresh mince with 12% w/w sucrose and 0.2% w/w polyphosphates. Surimi was produced from SM, UM, H&G at 1, 30, 90, and 180 days and evaluated by torsion, measuring shear stress, and true strain. After 6 months, there were no differences (p>0.05) between surimi samples prepared from SM stored at - 20° and -50° and the control surimi. UM and H&G fish produced surimi of inferior quality.     

Cathepsin Degradation of Pacific Whiting Surimi Proteins

Cathepsin B was the most active cysteine protease in Pacific whiting fish fillets; cathepsin L was predominant in surimi. Cathepsin L showed highest activity at 55°C in both fish fillets and surimi, indicating its function in myosin degradation during conventional heating of fillets and surimi, gels. Washing during surimi processing removed cathepsin B and H but not cathepsin L. Myosin heavy chain was the primary substrate during autolysis of surimi paste and actin and myosin light chain showed limited hydrolysis during 2 hr incubation. Purified Pacific whiting cathepsin L hydrolyzed myofibrils, myosin and native and heat-denatured collagen. The degradation pattern of myofibrils by the protease was the same as the autolytic pattern of surimi.     

Functional Properties and Shelf Life of Fresh Surimi from Pacific Whiting

Total aerobic plate count (APC), shear stress, shear strain, and color of fresh Pacific whiting surimi stored at 5°C were determined at day 0, 1, 3, 5, and 7. Frozen surimi was prepared with four levels of cryoprotectams (0, 3, 6, and 9%) and was compared with fresh surimi for gelforming ability. Fresh Pacific whiting surimi had a shelf life of 5 days. The gel functionality remained unchanged throughout the storage time. Strain values of fresh surimi were not different from those of frozen surimi with 9% cryoprotectants, but stress values of fresh surimi were almost three times higher than those of frozen surimi.     

Ohmic Heating Maximizes Gel Functionality of Pacific Whiting Surimi

Surimi without enzyme inhibitors containing 78% moisture and 2% NaCl was heated conventionally and ohmically to 90°C after holding at 55°C for 0, 1, 3 and 5 min. Gels heated slowly in a water bath exhibited poor gel quality, while the ohmically heated gels without holding at 55°C showed more than a twofold increase in shear stress and shear strain over conventionally heated gels. Degradation of myosin and actin was minimized by ohmic heating, resulting in a continuous network structure. Ohmic heating with a rapid heating rate was an effective method for maximizing gel functionality of Pacific whiting surimi without enzyme inhibitors.     

Potassium Bromate Effects on Gel-forming Ability of Pacific Whiting Surimi

Physical and chemical analyses defined the reinforced oxidation of sulfhydryl groups on the myofibrillar proteins to disulfide bonds by bromate. Electrophoretic studies demonstrated myosin degradation during heat-setting and its protection from proteinase attack by bromate. A bromate level of 0.075% inactivated 89.9% of the proteinase activity in surimi sols. Maximum gel hardness was 0.15%. Major increases in cohesiveness and elasticity were achieved at levels s 0.075%, brittle-ness occurred at levels a0.1%. Surimi gels with AA folding test grade was achieved with 0.15%. Potassium bromate probably improved surimi gelation through proteinase inactivation and reinforced disulfide formation during heat-setting.     

Electrical Conductivity of Pacific Whiting Surimi Paste during Ohmic Heating

Electrical conductivities of Pacific whiting surimi paste with various moisture contents (75, 78, 81, and 84%) and added salt (1, 2, 3, and 4%) were measured using ohmic heating at alternating current of 3.3, 6.7, and 13.3 V/cm. Electrical conductivity of surimi increased with temperature and salt content and slightly increased with moisture content. Electrical conductivity correlated linearly with temperature (r²= 0.99). Generally, voltage gradient did not affect conductivity. However, variations of conductivity with voltage gradient observed in surimi containing 3–4% salt, were probably caused by electrochemical reactions at electrode surfaces. The empirical model of electrical conductivity predicted values ± 16% of independent experimental results.     

Protease Inhibitor Effects on Torsion Measurements and Autolysis of Pacific Whiting Surimi

Beef plasma protein (BPP), egg white and potato extract were tested for their ability to inhibit proteolysis in fish mince and surimi made from Pacific whiting (Merluccius productus). Strong inhibition resulted from all three compounds in fish mince when measured by autolysis. However, when tested in surimi significant differences occurred among the compounds. BPP showed strongest inhibition of proteolytic effect followed by egg white and potato extract when measured by autolysis, gel electrophoresis and torsion. BPP was an effective inhibitor in surimi at a concentration as low as 1%.     

Linear Heating Rate Affects Gelation of Alaska Pollock and Pacific Whiting Surimi

Shear stress of Alaska pollock surimi gels with and without beef plasma protein (BPP) increased as heating rate decreased, but shear strain was unaffected. An increase in shear stress was accompanied by an increase of cross-linked myosin heavy chain. Slow heating rates increased proteolysis in Pacific whiting surimi as shown by degradation of myosin heavy chain and low shear stress and shear strain. Proteolysis of whiting surimi was lessened by BPP to a greater extent at rapid heating rates (20 and 30°C/min) than at slow heating rates (1 and 5°C/min).     

Calcium Compounds to Improve Gel Functionality of Pacific Whiting and Alaska Pollock Surimi

The effect of calcium compounds during three thermal treatments with or without setting was studied. Formation of cross-linking was investigated using SDS-PAGE. Solubility varied. Calcium acetate, chloride, and caseinate were extremely soluble. Calcium lactate had good solubility at 0.2% or higher, then in descending order were phosphate, citrate, sulfate, and carbonate. Effects of temperature on solubility were not measurable except for caseinate. When 25°C setting was applied to surimi, calcium was most effective. Effect of calcium on shear stress was dependent on species, setting temperature, and specific compound. SDS-PAGE indicated that improved gel functionality was likely due to Ca⁺⁺-dependent trans-glutaminase. Shear strain values were not affected by adding calcium compounds regardless of species or thermal treatments.     

Characteristics of Fish Sauce Made from Pacific Whiting and Surimi By-products During Fermentation Stage

ABSTRACT: The fermentation condition for producing Pacific whiting fish sauce was static atmospheric fermentation with 25% salt at 50 °C. The effective enzymes in fermentation were heat stable and salt tolerant. Fermentation at 50 °C gave higher yields than at 35 °C. Total nitrogen content of whole fish fermented at 50 °C reached the equivalent level of commercial fish sauce before 15 d, supporting the strong degradation effects of Pacific whiting enzymes at earlier stages. Soluble solid and relative gravity also reached commercial level at 60 d. However, color value of unripened fish sauce was far from commercial fish sauce, indicating that ripening may be necessary to develop proper color. Staphylococcus, Bacillus , and Micrococcus were found as predominant microorganisms during fermentation.     

Characterization of Thermorheological Behavior of Alaska Pollock and Pacific Whiting Surimi

ABSTRACT: Thermorheological behavior of Alaska pollock (AP) and Pacific whiting (PW) surimi was evaluated during gelation at different moisture contents (80% to 95%). The temperature sweep data (storage modulus, G', compared with temperature) for both surimi clearly indicated G' minima. Unlike for the PW surimi, the minimum values of the AP surimi was moisture-content dependent and there was a linear relationship between logarithm of concentration and reciprocal absolute temperature at gelation. The activation energy ( Ea ) for aggregation after gelation temperature at each moisture content was calculated by a nonisothermal kinetic model for both AP and PW Surimi. The Ea values increased with moisture content of the system and ranged from 172.8 to 232.9 kJ/mol. Based on the assumption that melting temperature for a thermo-reversible gel may be considered equivalent to gelation temperature for thermo-irreversible gels, an Arrhenius-type model was used to estimate the enthalpy of cross-links formation for AP surimi to be 300.3 kJ/mol.     

Rheological Behavior and Potential Cross-Linking of Pacific Whiting (Merluccius productus) Surimi Gel

Gelation behavior and potential cross-linking of Pacific whiting (Merluccius productus) surimi were affected by setting temperatures and an enzyme inhibitor. Gels of Pacific whiting surimi with salt and beef plasma protein were compared with those containing guanidine hydrochloride, sodium dodecyl sulfate, and β-mercaptoethanol. The strongest gels were formed at 25°C setting followed by 90°C heating. Hydrogen and hydrophobic bonds appeared to strongly influence gel formation, while the influence of disulfide bonds was moderate. Viscosity scanning during setting at different temperatures was also useful to estimate effects of enzymes and inhibitors.     

Physicochemical Properties of Pacific Whiting Surimi as Affected by Various Freezing and Storage Conditions

ABSTRACT: Effects of various freezing methods of surimi on the biochemical and physical properties, were examined. Stress values increased up to 3 mo and then decreased. Strain values significantly decreased over time, except freeze-dried surimi stored at -18 °C. Yellowness (b*) of the freeze-dried surimi stored at 22 °C increased significantly during storage. In addition, salt-extractable proteins (SEP) decreased while dimethylamine (DMA) increased. Freeze-dried surimi showed the highest SEP and the lowest DMA values after 9 mo storage. Electrophoretic patterns did not show any apparent damages to the MHC until 6 mo. At 6 and 9 mo, development of proteins with smaller molecular weights was observed, indicating proteolytic degradation during frozen storage.     

Gel Properties of Surimi from Pacific Herring

Surimi produced from male Pacific herring (Clupea harengus pallusi), a by-product of the roe fishery, formed gels comparable to those formed by lower-grade pollock surimi but were darker in color. Linear relationships were found between moisture content of surimi and punch force, torsion stress, torsion strain, and compression force at failure. Addition of dried beef plasma, egg white, whey protein, wheat gluten or potato inhibitor resulted in stronger gels, although no proteolysis was detected in a control sample. Low-temperature setting, or heating at 40°C prior to cooking at 90°C resulted in stronger gels, as measured by punch test.     

Assessment of Added Protein/Starch on the Functional Properties of Surimi Gels Manufactured from Atlantic Whiting

ABSTRACT: The functional properties (hardness, cohesiveness, color, and whiteness) of 5 food ingredients (2 whey protein concentrates [WPC 45 and WPC 76], whey protein isolate [WPI], egg white [EW], and potato starch [PS]) added to surimi gels were evaluated using 2 different thermal regimes. Hardness and cohesiveness of whiting surimi gels prepared using a rapid cook treatment (90°C for 15 min) did not significantly change on the addition of test ingredients. Hardness and cohesiveness of whiting surimi with added ingredients prepared using a suwari set treatment (0° to 4 °C for 12 h followed by 90°C for 15 min) were increased ( P < 0.05) on addition of additives with the exception of WPC 76, which decreased ( P < 0.05) surimi hardness and cohesiveness. Results showed that starch was more effective in improving the functional properties of surimi when compared with all other protein additives assessed.     

Purified NADPH-Sulfite Reductase from Saccharomyces cerevisiae Effects on Quality of Ozonated Mackerel Surimi

The NADPH-sulfite reductase from Saccharomyces cerevisiae was purified to electrophoretic homogeneity by ammonium sulfate fractionation, DEAE Sephacel, Sephacryl S-300 and DEAE Sephadex A-50 chromatography. Optimal pH was 7.3 and temperature 25°C. It was inhibited by IAA, PCMPS, PMSF, NEM, PCMB, cyanide and most divalent metal ions. For the ozonated mackerel surimi ground with purified reductase, the reactive SH increased from 2.29∞10⁵ to 4.46∞10⁵mole/g and gel strength from 256.7 to 360.5g·cm. According to SDS-PAGE, the recovery of myosin heavy chain was observed on the ozonated mackerel surimi with addition of NADPH-sulfite reductase.     

利用猪副产物酶法制备胶原多肽

近年科学研究发现,人体摄取蛋白质经酶消化后,并非主要以氨基酸形式吸收,而以肽的形式吸收;一些肽不仅能提供人体生长发育所需营养物质,同时还具有多种生理功能。猪副产物中含有丰富的胶原蛋白,利用蛋白酶水解胶原蛋白生产胶原多肽,对促进猪副产物的精深加工发展具有积极作用。本文介绍目前酶法制备胶原多肽研究进展,讨论影响酶解效果的因素,阐述了胶原多肽生理功能及发展前景。     

鱼糜副产物酶解物对冻融鲢鱼鱼糜品质的影响

为了解鱼糜加工副产物（鱼头、鱼骨、鱼鳞、鱼鳍等）酶解物的添加对冻融鲢鱼鱼糜品质及凝胶特性的影响,对酶解物的体外抗氧化性及反复冻融鱼糜的盐溶性蛋白含量、巯基含量、Ca2＋-ATP酶活性、表面疏水性、凝胶特性、凝胶持水性及色泽进行研究。结果表明：与其他酶相比,经胰蛋白酶及碱性蛋白酶酶解后,鱼糜加工副产物酶解物的体外抗氧化活性最强;与对照组及蔗糖添加组鱼糜相比,鱼糜加工副产物酶解物的添加能够有效减缓反复冻融后鱼糜肌原纤维蛋白的冷冻变性及氧化速率,鱼糜的盐溶性蛋白含量、巯基含量、Ca2＋-ATP酶活性较高,表面疏水性较低;同时,鱼糜加工副产物酶解物的加入增强了鱼糜凝胶的初始凝胶特性及持水性,并能够有效延缓鱼糜凝胶破断力、凹陷度及凝胶强度的劣变,改善鱼糜凝胶的持水性。     

等电点法纯化太平洋鳕鱼皮胶原蛋白及其结构特性研究

为研究等电点法纯化鳕鱼皮胶原的可行性,通过测定溶解度和Zeta电位来确定鳕鱼皮胶原的等电点。将粗提胶原溶液的pH调至等电点,后经离心、复溶、透析、冻干等步骤得到了等电点纯化后的胶原干品。采用SDS-PAGE法检验产品的胶原纯度;采用红外光谱、X-射线衍射、紫外光谱法对胶原的结构性质进行了研究。最后对等电点沉淀的工艺进行了单因素实验。结果显示鳕鱼皮胶原的等电点为6.83,且在该等电点下纯化得到的产品纯度较高。光谱学结果显示胶原的三螺旋结构仍保持完整。单因素实验结果显示最优条件为:pH6.8、沉淀6 h、6 mg/mL的胶原浓度,此时回收率可达85%,纯度可达90%以上。至此,确定了等电点沉淀是一种纯化胶原蛋白的有效方法。