Impact of microbial transglutaminase on gelling properties of Indian mackerel fish protein isolates

Impacts of microbial transglutaminase (MTGase) (0–0.6 units/g sample) on gel properties of Indian mackerel unwashed mince, surimi and protein isolates with and without prewashing were studied. Generally, lower myoglobin and lipid contents were found in protein isolate with and without prewashing, compared to those of unwashed mince and surimi (P < 0.05). Protein isolate had the decreased Ca²⁺-ATPase and protein solubility, indicating protein denaturation. When MTGase was incorporated, breaking force and deformation of all gels markedly increased, especially as MTGase levels increased (P < 0.05). At the same MTGase level, gel from protein isolate with prewashing exhibited the highest breaking force and deformation (P < 0.05). The addition of MTGase could lower the expressible moisture content of most gels. No change in whiteness of gel was observed with the addition of MTGase (P > 0.05), but gel from protein isolate gels had decreased whiteness as MTGase at high level was added. The microstructure of protein isolate gels without prewashing showed a similar network to unwashed mince gels, whilst a similar network was observed between surimi gel and gel from protein isolate with prewashing. Nevertheless, a larger void was noticeable in gels from protein isolates. All gels incorporated with MTGase (0.6 units/g) showed a slightly denser network than those without MTGase. Thus, gel with improved properties could be obtained from protein isolate from Indian mackerel with added MTGase.     

Effect of reducing agents on physicochemical properties and gel-forming ability of surimi produced from frozen fish

Effects of different reducing agents (cysteine, ascorbic acid and sodium bisulfite) at various levels on physicochemical properties of protein, transglutaminase activity and gel properties of surimi produced from frozen croaker, lizardfish, threadfin bream and bigeye snapper were studied. Addition of cysteine resulted in the highest increase in the breaking force and the deformation of surimi gels, compared with other reducing agents. The optimum levels of cysteine were 0.05, 0.1, 0.05 and 0.1% (w/w) for surimi from frozen croaker, lizardfish, threadfin bream and bigeye snapper, respectively. Surimi from frozen croaker with cysteine added showed a similar breaking force and deformation to that produced from fresh fish. With addition of cysteine, an increase in sulfhydryl content with a concomitant decrease in disulfide bond content was generally observed. Ca²⁺ ATPase activity also increased, indicating the renaturation of the myosin molecule. T_max of peak 1 (myosin peak) of all surimi sols in the presence of cysteine was shifted to higher temperature. The increased transglutaminase activity was observed with addition of cysteine. Therefore, reducing agents, especially cysteine, recovered the denatured muscle proteins and activated the transglutaminase in the muscle, leading to the increased gel-forming ability of surimi produced from frozen fish.     

Effect of porcine plasma protein and setting on gel properties of surimi produced from fish caught in Thailand

Effects of porcine plasma protein (PPP) and high temperature setting on gel properties of surimi from bigeye snapper, bigeye croaker, threadfin bream and barracuda were investigated. PPP was effective in increasing breaking force and deformation of kamaboko gels set at 40°C for 30 min and heated at 90°C for 20 min. The optimum levels of PPP were 0.5, 0.5, 1.5 and 1.5 g/100 g and the optimum setting times were 2, 1.5, 1.5 and 2 h for bigeye snapper, bigeye croaker, threadfin bream and barracuda surimi, respectively. However, the addition of PPP significantly decreased whiteness (P<0.05). An increase in gel-forming ability of surimi with PPP coincided with a decrease in solubility in mixture of SDS, urea and β-mercaptoethanol, indicating the formation of nondisulfide covalent bond induced by both endogenous and plasma transglutaminase. The results supported that PPP improve the gelation of surimi in combination with setting.     

Physicochemical properties, gel-forming ability and myoglobin content of sardine (Sardinella gibbosa) and mackerel (Rastrelliger kanagurta) surimi produced by conventional method and alkaline solubilisation process

Characteristics and gel properties of sardine and mackerel surimi produced by conventional washing process and alkaline solubilising process were investigated. The decrease in Ca²⁺-ATPase activity with the changes in the surface hydrophobicity was found in surimi produced by alkaline solubilising process (p<0.05), suggesting the denaturation of protein induced by this process. The alkal-ine solubilising process with prewashing could remove myoglobin most effectively from sardine muscle, whereas the process without prewashing resulted in the greatest myoglobin removal in mackerel muscle (p<0.05). Surimi conventionally prepared by water or NaCl washing showed the gel with greater breaking force and deformation than that from alkaline solubilising process (p<0.05). The hig-her expressible moisture was found in the gels of surimi pre-pared by alkaline process, indicating the poor water holding capacity of the gel matrix. The highest whiteness was found in the gel of sardine surimi produced by alkaline process with prewashing but the highest whiteness was obtained in the gel of mackerel surimi washed with distilled water.     

4种鱼糜加工漂洗液回收蛋白对罗非鱼鱼糜凝胶特性与质构的影响

目的 探究4种回收水溶性蛋白对罗非鱼鱼糜凝胶特性及质构的影响。方法 分别将等电点沉降法回收蛋白、海藻酸钠单一絮凝剂回收蛋白、壳聚糖单一絮凝剂回收蛋白和海藻酸钠-壳聚糖复合絮凝剂沉降回收蛋白以0%、5%、10%、15%、20%掺入罗非鱼鱼糜制备鱼肠,比较各样品在凝胶强度与全质构分析(texture profile analysis, TPA)参数上的差异,包括硬度、胶着性、咀嚼性、内聚性与弹性。结果 4种回收蛋白替代会对凝胶强度产生不利影响,通过等电点沉降法回收的蛋白对凝胶强度的影响最大,凝胶强度持续下降,最低达1708g·mm;以复合絮凝剂回收蛋白的掺入对原凝胶强度的影响最小,通过替代5%鱼糜,凝胶强度降为3833 g·mm。当用壳聚糖单一絮凝剂回收蛋白掺入5%时,与原鱼糜制品的TPA参数最接近,表现为硬度2505 g,胶着性1788 g,咀嚼性192.3 mJ,且内聚性和弹性也没有表现出明显差异。结论 这4种回收蛋白均以5%的添加量替代罗非鱼鱼糜时,制品凝胶强度在企业的可接受线性范围内,综合凝胶强度与TPA参数,以壳聚糖单一絮凝剂回收的蛋白替代产生的影响最小,可为回收鱼糜蛋白这一资源...     

Effect of oxidised tannic acid on the gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing processes

Effect of oxidised tannic acid (OTA) at different levels (0, 0.25, 0.50 and 0.75% of protein content) on the gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing processes was investigated. Breaking force and deformation of gels varied with washing processes and concentrations of OTA. The gel of alkaline-saline washing process surimi (ASWPS) added with 0.25% OTA had the increases in breaking force and deformation by 166.2 and 45.9%, respectively, compared with that of conventional washing process surimi (CWPS) without OTA addition. Those increases were associated with the lowered expressible moisture content. Electrophoretic studies revealed that the greater polymerisation was found in ASWPS added with 0.25% OTA. Slight retention of myosin heavy chain (MHC) with lowered trichloroacetic acid (TCA) soluble peptide contents was observed in ASWPS gel added with 0.25% OTA, suggesting the decreased degradation induced by indigenous proteases. The microstructure of ASWPS gels became more ordered, compact and denser with the addition of 0.25% OTA. The use of OTA in conjunction with alkaline-saline washing process could improve the properties of gel from mackerel surimi without adverse effect on sensory properties.     

Gelation of protein isolates extracted from tilapia light muscle by pH shift processing

The gelation properties of protein isolates extracted from tilapia muscle with acid and alkali-aided processing were compared to washed tilapia muscle. Gels were prepared with and without the addition of 2% NaCl (w/w) slightly above neutral pH and gelation properties and gel quality were determined using various procedures. Hardness and elasticity of gels as assessed by torsion testing was improved using 2% NaCl (w/w) compared to treatments without salt. Small strain oscillatory testing showed that storage modulus (G′) of gel pastes prior to thermal gelation was significantly higher in the absence of salt, while smaller differences were seen after thermal gelation. Small strain oscillatory tests demonstrated a different gel forming mechanism for acid and alkali treated proteins compared to washed muscle. Fold tests demonstrated that acid treated proteins and washed muscle had significantly lower gel quality compared to alkali treated proteins. Addition of salt in gels improved gel water-holding capacity for acid and alkali treated proteins. Overall, the acid treated proteins exhibited poorer gelling ability compared to alkali treated proteins. Total content of SH-groups was measured before and after gelation and S–S bonding did not explain the difference in gel forming ability of different treatments. The results indicate that the alkali-aided process can be used to produce high quality protein gels from tilapia muscle suitable for manufacturing of imitation seafood products.     

Enhancement of gel strength of bigeye snapper (Priacanthus tayenus) surimi using oxidised phenolic compounds

Effects of different oxidised phenolic compounds (ferulic acid, OFA; tannic acid, OTA; catechin, OCT and caffeic acid, OCF) at different levels (0–0.25% of protein content) on the properties of gels from bigeye snapper (Priacanthus tayenus) surimi were investigated. Breaking force and deformation of surimi gel varied with types and amounts of oxidised phenolic compounds. Gels added with 0.20% OFA, 0.05% OTA, 0.15% OCF and 0.05% OCT exhibited the marked increases in both breaking force and deformation, compared with the control (P < 0.05). Those increases were associated with lower expressible moisture content. No increases in both breaking force and deformation were observed when ferulic acid without oxygenation at alkaline pH was added, regardless of amount added (P > 0.05). No changes in the whiteness of gel were found with addition of OFA (P > 0.05), but the decreases in whiteness were noticeable as other oxidised phenolics were incorporated (P < 0.05). Different microstructures were obtained among gels with different oxidised phenolics. The physicochemical properties of natural actomyosin suggest that oxidised phenolics could induce conformational changes and the cross-linking through amino groups or the induction of disulphide bond formation. Therefore, the addition of oxidised phenolic compounds at the optimum level could increase the gel strength of surimi gel.     

Gelation properties of goose liver protein recovered by isoelectric solubilisation/precipitation process

Isoelectric solubilisation/precipitation (ISP) process was applied to goose liver (GL) for protein extraction. The gelation properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were estimated, where the unextracted ground GL was set as the control. Nearly 58.39~79.00% of GL proteins were recovered by ISP treatments. High molecular weight (100~250 kDa) proteins were found to be partially hydrolysed by ACP, while few changes in proteins occurred during ALP. As evidenced by rheological and textural measurements, ALP proteins formed gels with high elasticity and superior texture, whereas ACP proteins had inferior gelation properties. Moreover, ALP proteins were able to form a highly interconnected and homogeneous three‐dimensional microstructure. Predominantly, gels produced by 11.0 had optimal texture and the lowest cooking loss (P < 0.05). These results suggested that the ISP process (ALP) is a potential method to improve the economic value of GL.     

Physicochemical characteristics,protein hydrolysis,and textual properties of surimi during fermentation with Actinomucor elegans

Solid-fermentation is a promising way of producing novel surimi-based food. In the present study, changes in physicochemical characteristics, protein hydrolysis, and textual properties of surimi during the fermentation, including pehtze preparation, salting, and ripening stages, were studied. The protease produced by Actinomucor elegans led to continuous hydrolysis of surimi protein, reflected from the high value of protease activity which reached 69.34 U/g after pehtze preparation stage, the decrease of protein bands intensity in sodium dodecyl sulfate polyacrylamide gel electrophoresis image especially for bands of 200, 43, and 36 KDa, and the increasing contents of free amino acids and trichloroacetic acid-soluble nitrogen. Hardness, springiness, and cohesiveness of the surimi all decreased during pehtze preparation stage, increased after salting, and decreased again after ripening, while adhesiveness kept increasing until the ripening stage started. Scanning electron microscopy images showed a dense and soft microstructure of surimi after ripening. The final surimi product showed high overall acceptability and no Enterobacteriaceae was detected.     

Nondestructive determination of water and protein in surimi by near-infrared spectroscopy

Nondestructive near-infrared spectroscopy (NIRS) between 400 and 1100 nm regions was employed directly on surimi using a surface interactance fibre optic accessory, to investigate the potential of NIRS as a fast method to determine water and protein contents. The reason why NIRS is well suited when assessing the presence of water or protein is due to the specificity of O–H and N–H bindings. At 980 nm only one broad peak in the original spectra can be seen due to the absorption of water since it contained nearly 80% of surimi. Predictive equations were developed using partial least squares (PLS) regression where excellent predictions for protein and water are noticed. Regression coefficients are higher than 0.98, errors are small and RPD value for protein is well over 8 and that for water is very close to it which can be used for any analytical purpose.     

Whey protein concentrate: Autolysis inhibition and effects on the gel properties of surimi prepared from tropical fish

Effects of whey protein concentrate (WPC) on autolysis inhibition and gel properties of surimi produced from bigeye snapper (Priacanthus tayenus), goatfish (Mulloidichthys vanicolensis), threadfin bream (Nemipterus bleekeri) and lizardfish (Saurida tumbil) were investigated. WPC (0–3%) showed inhibitory activity against autolysis in all surimi at both 60 and 65 °C in a concentration-dependent manner. Myosin heavy chain (MHC) of surimi was more retained in the presence of WPC. Breaking force and deformation of kamaboko gels of all surimi increased as added levels of WPC increased (P < 0.05). This was associated with lower levels of protein degradation, as evidenced by the decrease in trichloroacetic acid-soluble peptide content (P < 0.05). WPC at 3% (w/w) significantly decreased the whiteness of gels. However, water-holding capacity of kamaboko gels was improved with increasing concentration of WPC. The microstructure of surimi gels generally became denser with the addition of WPC.     

Effect of zinc sulphate on gelling properties of phosphorylated protein isolate from yellow stripe trevally

Impacts of zinc sulphate (ZnSO₄) (0–140 μmol/kg) on gel properties of yellow stripe trevally surimi added with sodium tripolyphosphate (STPP) (0.25% and 0.5%, w/w) and protein isolate phosphorylated with STPP at 0.25% and 0.5% (w/w) were studied. Gels from surimi added with 60 μmol ZnSO₄/kg in the absence and presence of 0.5% STPP had the increases in breaking force and deformation by 20.9% and 33.3%, and 11.6% and 18.6%, respectively, compared with the control surimi gel (without additives). Gel of protein isolate phosphorylated with 0.5% STPP containing 100 μmol ZnSO₄/kg had the increases in breaking force and deformation by 14.87% and 5.6%, respectively, compared with the gel from non-phosphorylated protein isolate at the same ZnSO₄ level, suggesting that the phosphorylated protein isolate was more crosslinked by Zn²⁺. The addition of ZnSO₄ at the suitable level lowered the expressible moisture content, but increased whiteness of surimi or protein isolate gels (P < 0.05). Non-covalent bonds, more likely salt bridge and ionic interactions, played a major role in cross-linking of proteins in both surimi and protein isolate added with ZnSO₄, regardless of phosphates incorporated. Microstructure study revealed that a gel having highly interconnected and denser network with smaller voids was formed when protein isolate phosphorylated with 0.5% STPP was added with ZnSO₄ at a level of 100 μmol/kg. Thus, gel with improved properties could be obtained from protein isolate from yellow stripe trevally phosphorylated with STPP in conjunction with addition of ZnSO₄ at an appropriate level.     

GC-IMS结合化学计量法分析不同炒制时间对郫县豆瓣酱挥发性化合物的影响

为阐明采肉次数对鱼糜风味特征的影响,本研究采用GC-IMS测定不同采肉次数下（1、2、3、4和5）制备的白鲢鱼糜的挥发性物质,同时测定TBARS值,并对它们进行相关性分析。结果显示：5组鱼糜中检测出的挥发性物质均为58种,其中壬醛、乙酸乙酯、2-丙酮、乙醇、2-甲基丁醛的含量相对较高;醛（39.13%~40.91%）、酮（15.52%~21.74%）、醇（19.28%~26.59%）是主要的挥发性物质种类。随着采肉次数的增加,醛类占比先下降后升高,酮类占比逐渐上升,醇类占比波动变化。挥发性物质的PCA和欧式距离结果表明,采肉次数为1制备的鱼糜样品和其它样品的风味特征差异明显。增加采肉次数,鱼糜的TBARS值先显著（P<0.05）增加后显著（P<0.05）降低。鱼糜中己醛、戊醛、E-2-戊烯醛、E-2-辛烯醛、3-辛醇,2,3-戊二酮等与TBARS值正相关（0.8>r>0.5）,苯酚、苯乙醛负相关（−0.8<r<−0.5）。采肉次数影响鱼糜风味特征,其主要原因可能是与脂肪氧化有关。

     

Physicochemical properties and gel-forming ability of surimi from three species of mackerel caught in Southern Thailand

Physicochemical and gelation properties of surimi prepared from three species of mackerel were investigated. The highest whiteness with the lowest redness index corresponding to the lowest myoglobin content especially its oxidised form, metmyoglobin, was found in short-bodied mackerel (Rastrelliger brachysoma) surimi (p < 0.05). Frigate mackerel (Auxis thazard) surimi contained the highest lipid content (p < 0.05). The pH of all surimi was in the range of 6.58–6.80. The highest sulfhydryl group and Ca²⁺-ATPase activity was found in natural actomyosin extracted from short-bodied mackerel surimi (p < 0.05). The highest TCA-soluble peptide content was found in frigate mackerel surimi gels (p < 0.05). Kamaboko gel of short-bodied mackerel surimi exhibited the highest breaking force with the lowest expressible drip (p < 0.05). Heating regime had no effect on deformability of gels from Indian mackerel (Rastrelliger kanagurta) and short-bodied mackerel but not for frigate mackerel. The highest metmyoglobin content with the lowest whiteness was found in frigate mackerel surimi gel (p < 0.05). Therefore, short-bodied mackerel was the best suited for the production of surimi with superior functional attributes including whiteness and gel-forming ability.     

Cryoprotective effects of trehalose and sodium lactate on tilapia (Sarotherodon nilotica) surimi during frozen storage

The cryoprotective effects of trehalose and sodium lactate at level of 8% (w/w) in tilapia surimi were studied in comparison with a conventional cryoprotectant (sucrose/sorbitol, 1:1) during extended storage at −18 °C for up to 24 weeks. All present cryoprotectants retarded the protein changes as evidenced by the lowered decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, total sulfhydryl content as well as the impeded increase in disulfide bond content and surface hydrophobicity. The gel-forming ability of frozen surimi was more retained with addition of cryoprotectants. Among all cryoprotectants used, trehalose exhibited the greatest protective effect on protein denaturation as shown by the effectiveness in maintaining Ca²⁺-ATPase activity and protein solubility. Additionally, the greatest breaking force and deformation were obtained in surimi added with 8% trehalose throughout the frozen storage up to 24 weeks. Sodium lactate showed a similar cryoprotective effect to sucrose/sorbitol blend. Therefore, trehalose and sodium lactate appeared to be promising alternative cryoprotectants for surimi owing to their low sweetness and caloric value.     

Effect of microbial transglutaminase and setting condition on gel properties of blend fish protein isolate recovered by alkaline solubilisation/isoelectric precipitation

The effect of microbial transglutaminase (M-TGase) (0–0.6 units g⁻¹ sample) and setting condition (25 °C/180 min, 30 °C/120 min, 35 °C/60 min and 40 °C/30 min) on gel properties of blend protein isolate of gutted kilka and silver carp was studied. The protein isolate provided a good substrate for M-TGase activity so that a low amount of M-TGase (0.2 unit g⁻¹ sample) substantially improved textural properties and water holding capacity (WHC) of the gels. Breaking force of the gels was positively affected by M-TGase up to 0.6 unit g⁻¹ sample, but it negatively affected their WHC. Prior setting at 25–35 °C increased the breaking force of proteins compared to directly heated gel, resulting in maximum breaking force at 35 °C/60 min. However, the setting at 40 °C/30 min caused proteolysis, which was reflected in higher amounts of TCA-soluble peptides and gel weakening. Denser microstructure and higher myosin heavy chain polymerisation observed in the gels which experienced the setting was well correlated with improvement in textural properties.     

6-姜酚对草鱼鱼糜凝胶特性及贮藏稳定性的影响

以微波超声波辅助制备的低盐罗非鱼糜凝胶为研究对象,分析谷氨酰胺转氨酶（TGase）、羟丙基二淀粉磷酸酯（HDP）、结冷胶和三者的复配物（THG）对其水分分布及蛋白质构象的影响;并通过体外模拟消化实验,探究不同外源物质对微波超声波辅助制备的低盐罗非鱼鱼糕体外消化特性的影响。结果表明：添加THG后,鱼糜结合水和不易流动水较空白组分别增加98.71%和14.75%,自由水含量显著减少（P<0.05）;THG促进了α-螺旋向β-折叠、β-转角和无规则卷曲结构转化。与空白组相比,添加0.4%TGase和THG对低盐罗非鱼糕的胃排空速度、蛋白体外消化率及蛋白水解度均有正面作用;其中THG可显著促进蛋白质分解成粒径较小的聚集体（P<0.05）,经胃-十二指肠消化结束后的消化产物颜色更加透明清晰,从激光共聚焦显微镜可观察到THG组的红色荧光亮点显著减少,反映其蛋白被消化得较为完全。由此可见,在THG的作用下,鱼糜中水分子与蛋白质结合更紧密,相对于单一的外源物质,THG更加明显地改变了蛋白质的构象,且更有利于疏水蛋白基团的暴露和蛋白间的相互作用,且对鱼糕的消化有促进作用。本研究的结果为罗非鱼糜凝胶特性研究及罗非鱼糕类食品的开发与应用提供理论参考。

     

Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella)

The cryoprotective effect of konjac glucomannan (KGM) on myofibrillar protein from grass carp (Ctenopharyngodon idella) during frozen storage at −18 °C and the influence of five levels of KGM (0%, 0.5%, 1%, 1.5%, and 2%) on texture properties, water-holding capacity, and whiteness of grass carp surimi gels were investigated. KGM as a novel cryoprotectant could significantly mitigate the decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, and total sulphydryl and active sulphydryl contents of myofibrillar protein during frozen storage. KGM at the level of 1% showed the same good cryoprotective effect as a conventional cryoprotectant (10% sucrose–sorbitol, 1:1, w/w). As the levels of KGM increased, breaking force and deformation of grass carp surimi gels increased significantly. Water-holding properties of the surimi gels are improved with the increasing addition of KGM, but the whiteness decreased and the colour became darker. The optimum addition level of KGM was suggested to be 1%.