Effect of Temperature and Alkaline pH on the Physicochemical Properties of the Protein Isolates Extracted from the Whole Ungutted Lanternfish (Benthosema pterotum)

The aim of this study was to evaluate functional properties of the protein extracted from lanternfish (Benthosema pterotum). Extraction of the fish protein was performed in alkaline pHs (10 and 12) followed by precipitation at its isoelectric pH. The effects of different extraction temperatures (0, 4, 11, 25, and 30°C) were also studied. The results showed that the protein recovery yield was higher when extracted at pH 12 compared to pH 10. Furthermore, some functional properties including water holding capacity, oil holding capacity, emulsifying capacity, foaming capacity, and solubility of the protein isolated at pH 12 were higher than that isolated at pH 10 (p < 0.05). The color evaluation (L*, a*, and b*) of the samples showed protein isolated at pH 12 was lighter (higher L*) than protein isolated at pH 10, but redness (a* value) declined in both samples. Evaluation of different extraction temperatures showed that protein recovery yield and functional properties were improved with increasing temperature. Fish protein isolate can be used in the formulation of value-added products because of their distinctive functional properties.     

Stability of Fish Powder Made from Saithe (Pollachius virens) as Measured by Lipid Oxidation and Functional Properties

ABSTRACT

Lipid oxidation and functional properties were monitored in spray dried fish powder made from saithe (Pollachius virens) by-products. The fresh powder exhibited slight antioxidant activity in a model system of linoleic acid emulsion. The freshly made powder had low lipid extract-ability in polar solvents and over 30% free fatty acids (FFA). Further lipid oxidation took place during storage, independent of storage temperatures. Functional properties measured by color changes, water-binding capacity, apparent viscosity and protein solubilty changed more during storage at 30°C than 0°C.     

加工鱼产品种类的电泳鉴定

介绍了几种鱼的白肌在乳酸脱氢酶和蛋白电泳表型上种的特异特征。链,镛,草,青,尼罗罗非鱼白肌乳酸脱氢酶的谱带数不同,活性强度亦不同;蛋白质电泳图谱的迁移率也有差异。这类特征可为加工产品的种类鉴定提供可靠判据。鱼类电泳鉴定技术的标准化及其应用将为规范鱼品加工业,检验鱼产品提供理想的检测手段。     

Characteristic and Functional Properties of Gelatin from the Bones of Alaska Pollock (Theragra chalcogramma) and Yellowfin Sole (Limanda aspera) with Papain-Aided Process

Fish gelatin was extracted from the bone of Alaska pollock (Theragra chalcogramma) and yellowfin sole (Limanda aspera) using papain-aided process and the characteristic and functional properties were analyzed. The bones of Alaska pollock and yellowfin sole yielded 9.07% and 7.15% gelatin, respectively. Protein was the main component (84.67–91.76 g/100 g) in both gelatins. There was no significant difference in whiteness between the two gelatins. The absorption peak of Alaska pollock bone gelatin (ABG) and yellowfin sole bone gelatin (YBG) in ultraviolet-visible (UV-vis) spectra was 209 nm and 211 nm, respectively. Scanning electron microscope (SEM) and Fourier transform infrared (FTIR) investigations indicated the existence of helical arrangements and uniform network structures in the two gelatins. The gel strength of ABG (105.64 g) was significantly lower than that of YBG (187.39 g), possibly due to the presence of shorter chains as indicated by the degradation of α-, β-, and γ-chains. ABG also had lower emulsibility and foamability than YBG, which was associated with relatively lower hydrophobic amino acids. Therefore, yellowfin sole would be a better potential marine source of gelatin obtained from fish processing by-products.     

Use of avoidance response by rainbow trout to carbon dioxide for fish self-transfer between tanks

Convenient, economical, and reduced labor fish harvest and transfer systems are required to realize operating cost savings that can be achieved with the use of much larger and deeper circular culture tanks. To achieve these goals, we developed a new technology for transferring fish based on their avoidance behavior to elevated concentrations of dissolved carbon dioxide (CO₂). We observed this behavioral response during controlled, replicated experiments that showed dissolved CO₂ concentrations of 60–120 mg/L induced rainbow trout (Oncorhynchus mykiss) to swim out of their 11 m³ “growout” tank, through a transfer pipe carrying a flow with ≤23 mg/L dissolved CO₂, into a second 11 m³ “harvest” tank. The research was conducted using separate groups of rainbow trout held at commercially relevant densities (40–60 kg/m³). The average weight of fish ranged from 0.15 to 1.3 kg during the various trials. In all trials that used a constant flow of low CO₂ water (≤23 mg/L) entering the growout tank from the harvest tank, approximately 80–90% of the fish swam from the growout tank, through the transfer pipe, and into the harvest tank after the CO₂ concentration in the growout tank had exceeded 60 mg/L. The fish that remained in the growout tank stayed within the area of relatively low CO₂ water at the entrance of the transfer pipe. However, the rate of fish transfer from the growout tank to the harvest tank was more than doubled when the diameter of the transfer pipe was increased from 203 to 406 mm. To consistently achieve fish transfer efficiencies of 99%, water flow rate through the fish transfer pipe had to be reduced to 10–20% of the original flow just before the conclusion of each trial. Reducing the flow of relatively low CO₂ water near the end of each fish transfer event, restricted the zone of relatively low CO₂ water about the entrance of the fish transfer pipe, and provided the stimulus for all but a few remaining fish to swim out of the growout tank. Results indicate that the CO₂ avoidance technique can provide a convenient, efficient, more economical, and reduced labor approach for fish transfer, especially in applications using large and well mixed circular culture tanks.     

防腐冰对鱼类保鲜效果研究↑（*）

防腐冰是水中添加防腐剂制成的,它能够增强对鱼在冰鲜期间的保藏效果。本文采用感官检定和ＴＶＢ－Ｎ等鲜度指标,研究了几种Ｎａ＿２－ＥＤＴＡ冰和苯甲酸钠冰对鲅鱼和带鱼的保鲜效果。结果表明：（１）１‰Ｎａ＿２－ＥＤＴＡ冰具有较稳定、持久的抑菌效果,能有效地延缓鱼品感官质量下降和ＴＶＢ－Ｎ上升,冰藏８天的带鱼细菌数,普通冰组为３．７×１０￣５个／ｇ,而１‰。Ｎａ＿２－ＥＤＴＡ,冰组仅为２．１×１０￣４个／ｇ。（２）以感官检定８０分为基准,与使用普通冰相比,使用１‰Ｎａ＿２－ＥＤＴＡ冰保鲜鲅鱼,保藏期由１１６ｈｒ提高到１４０ｈｒ,保鲜带鱼,保藏期由１０４ｈｒ提高到１６４ｈｒ。     

Influence of pH and temperature on force development and shortening velocity in skinned muscle fibres from fish

Three species of fish were studied: Atlantic cod (Gadus morhua), sculpin (Myoxocephalus scorpius) (from the North Sea, temperature 2 to 12°C) andNotothenia neglecta (from Antarctica, temperature –2 to +2°C). Single fast muscle fibres were isolated from anterior myotomes and skinned with detergent in order to directly determine the effects of pH and temperature on force production and shortening velocity.In all species maximum force production (Po) was independent of pH over the range 7.3–8.0. Decreasing the pH from 7.3 to 6.6 reduced maximum force by 28% in fibres fromG. morhua andN. neglecta but had no effect on fibres fromM. scorpius. The depression in maximum force with acidosis was accompanied by a proportional decrease in stiffness and an increase in the rate of force recovery after stretch.Unloaded contraction velocity of cod fibres (Vmax) showed a pH optimum at around pH 7.6 decreasing by 31% at pH 6.6. Vmax of fibres from the other species was independent of pH over the range 6.6–8.0.The effects of pH on Po and Vmax were similar at 0 and 10°C. Thus for maximally activated fibres both force and contraction velocity are independent of temperature induced changes in pH. In some species acidosis depresses contractility and is likely to be a contributory factor to muscle fatigue.     

鲤鱼单极虫病组织病理研究

本文报道了1989年以来,造成王快水库等网箱养鲤大批死亡的单极虫病,病鱼出现烂鳃、肛门红肿、腹部膨大,腹腔内有大量粘液等症状;显微观察的结果为:各组织器官发生病变,肠上皮细胞严重坏死,平滑肌纤维发生玻璃样变及解体,鳃丝充血,鳃小片融合,肝细胞核溶解、坏死。     

鱿鱼皮胶原蛋白的功能特性

测试了鱿鱼皮胶原蛋白的特征吸收光谱和分子量分布,比较了胶原蛋白的溶解性、保水性、湿润性、吸油性、乳化性及乳化稳定性、起泡性及泡沫稳定性等应用功能特性。结果表明：（1）三种方法(热水法、酸法和酶法)提取的鱿鱼皮胶原蛋白均在220nm处有最大吸收,胶原蛋白的分子量为220 kDa左右;（2）热水法和酶法提取的胶原蛋白的溶解性能要好于酸法胶原蛋白;（3）提取的三种胶原蛋白均具有一定的保水性,分别为0.54％、0.52％和0.55％;（4）热水法和酶法提取的胶原蛋白的润湿性较好;（5）三种胶原蛋白均具有良好的吸油性,分别为2.7mL/g、3.0mL/g和3.3mL/g;（6）三种胶原蛋白拥有较好的乳化性和乳化稳定性,其中酸法提取的胶原蛋白的即时乳化性最好,但酶法提取的胶原蛋白的乳化稳定性最好;（7）三种胶原蛋白具有良好的起泡性和泡沫稳定性,其中酸法提取的胶原蛋白的起泡性和泡沫稳定性最好,分别为83％和67％。     

Physicochemical and Gel Properties of Myofibrillar Protein from Sin Croaker (Johnius dussumieri) Fish During Ice Storage

The physicochemical and gel properties of myofibrillar protein (MFP) from sin croaker fish were studied during ice storage for 18 days. Significant changes in the trends of solubility, Ca²⁺ ATPase enzyme activity, surface hydrophobicity, and water holding capacity of extracted MFP were observed by the 6th day of storage. The Ca²⁺ ATPase enzyme activity reduced significantly (p < 0.05) by the 6th day of storage. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) did not show a remarkable change in the concentration of myosin heavy chain. Surface hydrophobicity increased almost four times from its original value of 18.98 µg; whereas, water holding capacity showed a fluctuating trend during storage. The emulsion capacity of the MFP was in the range of 0.89- to 1.92-mL oil/mg protein during storage. The gel strength value (313.45 g.cm) of heat-induced gel prepared from fresh minced meat decreased significantly (p < 0.05) by the 6th day of ice storage. Texture profile analysis revealed that changes in hardness and gumminess were concurrent to steeply reducing breaking force up to the 6th day. The histological observation showed gradually increasing gaps between muscle fibers. The histological observations and physicochemical quality indicated that the sin croaker fish can be used for producing good quality surimi when stored for up to 6 days in ice.