Quantification of Alaska pollock surimi in prepared crabstick by competitive ELISA using a myosin light chain 1 specific peptide

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for quantification of Alaska pollock (AP) surimi in crabsticks. Identification of fish species is complicated by processing, cooking, and additional ingredients. ELISA is a powerful tool for identification and quantification of fish species. Polyclonal antibodies were raised in rabbits against a 15-amino-acid peptide (Ala–Pro–Lys–Lys–Asp–Val–Lys–Ala–Pro–Ala–Ala–Ala–Ala–Lys–Lys) determined from the myosin light chain 1 (MLC 1) of AP. Immunoblotting showed the anti-pep-AP antibody had no significant cross-reactivity with protein additives. However, cross-reactivity of the MLC 1 from Pacific whiting, and threadfin bream surimi was observed. MLC 1 was purified from AP surimi and used as the coating protein in the competitive ELISA. MLC 1 was serially diluted and had a R² of 0.9845 following a logarithmic curve. All estimations of AP surimi were within 9% of the actual value. Inter-assay coefficients of variance ranged from 4.2% to 4.9%.     

At line prediction of PUFA and biohydrogenation intermediates in perirenal and subcutaneous fat from cattle fed sunflower or flaxseed by near infrared spectroscopy

NIRS potential to estimate the proportion of PUFA and their biohydrogenation products in adipose tissues from cattle fed sunflower or flaxseed was tested. Immediately after skinning, perirenal and subcutaneous fat samples from 63 steers were collected, scanned intact at 37 °C and 33 °C, respectively, over a NIR spectral range from 400 to 2498 nm using benchtop equipment and then analyzed for fatty acid composition. NIRS calibrations in perirenal fat showed high predictability for total and major omega − 6 and omega − 3, conjugated linolenic acids, t,t-conjugated linoleic acids (CLA), non-CLA dienes and trans-monounsaturated fatty acids, with R² (RMSECV, %) of 0.88–0.89 (0.16–0.20), 0.89–0.91 (0.07–0.08), 0.86–0.89 (0.01–0.09), 0.82 (0.07), 0.89 (0.46) and 0.86–0.88 (0.87–1.29), respectively. NIRS predictions in subcutaneous fat were less reliable, probably due to lower fatty acid variability. The results show NIRS to be a useful technique for the early, fast and relatively inexpensive estimation of proportions of fatty acids with potential human health effects in cattle perirenal fat.     

RECOVERY AND UTILIZATION OF PROTEIN DERIVED FROM SURIMI WASH‐WATER

ABSTRACT

Surimi processors are committed to improve utilization of seafood resources, increase productivity and reduce organic matter discharged into the environment. The object of this study was to recover protein from pollock surimi processing wash‐water using membrane filtration and characterize properties of the recovered material. A pilot unit equipped with membrane elements concentrated protein from the surimi wash‐water. Membrane concentrate and control surimi samples were analyzed for proximate composition, lipid oxidation, color, sodium dodecyl sulfate gel electrophoresis, amino acids and minerals. Membrane concentrate, membrane concentrate plus surimi and control surimi were monitored for 180 days of storage at ?20C. The membrane concentrate had significantly higher moisture and lipid, but lower protein content than surimi. As determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, membrane concentrate proteins displayed a greater amount of lower molar mass molecules compared with surimi. The amino acid profile was comparable to control surimi and the recovered membrane concentrate proteins had similar nutritional values to that of surimi. The results indicate that the addition of 5% membrane concentrate to surimi will not adversely affect the storage at ?20C and that the recovered wash‐water protein could be used to obtain a fish protein ingredient or added back at a low percentage to surimi products.

PRACTICAL APPLICATIONS

In order to increase productivity and improve utilization of seafood resources, surimi processors are looking into alternative technologies to recover proteins and other material from the wastewater. Membrane filtration is a promising option for the concentration of wastewater. This study was conducted to determine the recovery and characterize the material recovered from surimi wash‐water using a commercial membrane filtration unit. It was demonstrated that the recoverable material is nutritionally similar to the final surimi product and that the overall yield can be increased using membrane technology. In addition to the benefit of recovering protein, the membrane filtration can reduce the amount of material in the waste stream.

     

3D printing and controlled release of functional ripening surimi improved by nano starch-xylo-oligosaccharides: Chemical bonds and microstructure influences

To solve the problem of fast release, unsustainability of functional compounds in 3D printed surimi, nano scale of rice starch-xylo-oligosaccharides (XOS) was prepared. Meanwhile, its characteristics and printing effects on surimi were determined. Results shown that the nano rice starch and XOS with ratio of 1:2.5 had good characteristics (particle size 444 nm, embedding rate 86%, stable particle size with Na⁺ and heating process). Moreover, it endowed surimi with antioxidant ability and prolonged the release of XOS in surimi during in vitro digestion, which might keep it for continuous release. Additionally, nano starch-XOS increased ionic bonds and hydrogen bonds by 78% and 58% respectively to enhance gel strength, texture of surimi. As well as it also could fill up gel network gaps to form denser structure, which increased self-supporting ability to improve printing effects. While excessive XOS (>1%) could wrap protein to inhibit gel formation to produce burs and pores of printed surimi-XOS, leading to the pores enlargement and collapse due to the enhancement of hydrophobic force and disulfide bonds after ripening. However, nano starch could aggregate XOS to delay the occurrence of collapse (>2% XOS content). Thus, nano starch-XOS could promote the application of functional surimi in 3D printing.     

鱼糜凝胶形成过程中物理化学变化

采用化学法测定鱼糜凝胶形成过程中离子键、氢键、疏水相互作用和二硫键的变化,借助拉曼光谱仪分析草鱼鱼糜凝胶形成过程中鱼糜蛋白质构象的变化,进而研究化学作用力和蛋白质构象对鱼糜凝胶形成的影响。结果表明：在草鱼鱼糜凝胶的形成过程中,离子键、氢键显著减少,疏水相互作用、二硫键和非二硫共价键增加;α- 螺旋结构部分转化为无规卷曲结构。疏水相互作用、二硫键及非二硫共价键是影响凝胶形成的主要作用力,α- 螺旋和无规卷曲是草鱼鱼糜凝胶形成过程中维持鱼糜凝胶稳定结构的主要蛋白质构象。     

Effects of adding fish gelatin on Alaska pollock surimi gels

Fish gelatin is a food additive obtained after hydrolysis of collagen from fish skin. The importance of fish gelatin as a food additive is increasing due to its increased commercial availability. Surimi is washed minced fish meat used as the raw material for seafood analogs like crabmeat substitutes. The most important attributes of surimi are gelling and whiteness. The objective of this work was to determine the effect of using fish gelatin as an additive in surimi to improve the mechanical and functional properties of gels. Surimi gels were prepared by mixing grade A or FA surimi (Alaska pollock) with salt (20 g/kg w/w) and commercial fish gelatin at 0 (control), 5, 7.5, 10, or 15 g/kg (w/w) previously dissolved in water (200 mL/kg surimi). The solubilized paste was incubated at 40 °C for 30 min followed by cooking at 90 °C for 15 min. Changes in mechanical properties (torsion test), a functional property (expressible water content) and color attributes of surimi gels were measured. Grade FA surimi gels containing 7.5–15 g/kg of fish gelatin showed an improved expressible moisture. However, gelatin added at 15 g/kg showed a disruptive effect detrimental to the mechanical properties. Color parameters were modified slightly. Whiteness attribute as affected by increasing the fish gelatin was instrumentally detected but not observed by sensory panelists. Gelatin did not change the overall color attributes and all gels remained in the grayish region. These results indicated that fish gelatin did not have an advantage for using as a functional additive in Alaska pollock surimi grades A or FA. However, it can be used at up to 10 g/kg without a negative effect on the mechanical properties.     

Effect of formaldehyde on protein cross-linking and gel forming ability of surimi from lizardfish induced by microbial transglutaminase

Impact of formaldehyde (FA) at various levels (0–9 μmol/g surimi) on gel properties of surimi from lizardfish added with microbial transglutaminase (MTGase) was studied. During iced storage of 10 days, total and free FA in lizardfish flesh increased continuously (P < 0.05). In the presence of FA, breaking force of gels slightly increased, whilst the deformation decreased (P < 0.05). The addition of MTGase (0.4 units/g surimi) was able to increase gel strength and water holding capacity of resulting gel. Nevertheless, gel strengthening effect of MTGase was lowered when FA at higher level was present. Myosin heavy chain (MHC) dominantly underwent polymerisation to a higher extent when either MTGase or FA was added. The higher reduction in ε-amino group content was observed in natural actomyosin (NAM) when FA at higher levels (0–30 μmol/g protein) was incorporated. Acyl transfer reaction mediated by MTGase was impeded in NAM containing FA, especially at higher levels. Generally, FA had an adverse effect on cross-linking ability towards surimi proteins induced by MTGase. Therefore, cross-linking and gel-forming ability of lizardfish surimi could be maximised by MTGase when surimi contained no FA.     

油茶籽油对鱼糜凝胶特性及凝胶结构的影响

为探讨脂质对鱼糜蛋白凝胶功能特性的影响及其机理,研究不同油茶籽油添加量对鱼糜凝胶特性、水分分布、脂质及蛋白质结构等的影响。结果表明:随着油茶籽油添加量的增加,鱼糜凝胶强度、乳化稳定性和持水性显著增加(P0.05),当油茶籽油添加量增加到8%时各指标基本稳定,此时鱼糜凝胶强度为225.1 g·cm,游离出来的液体质量分数为2.60%。拉曼光谱分析发现,油茶籽油的添加改变了鱼糜凝胶体系中脂质和蛋白质的化学结构,主要表现为C—H谱带峰宽的增加、O—H谱带相对强度的下降,以及鱼糜蛋白中β-折叠、β-转角和无规卷曲结构相对含量的增加和α-螺旋结构相对含量的降低。同时,随着油脂质量分数的增加,水分以更加细小的状态分布在鱼糜凝胶体系之中。以上结果进一步揭示了油茶籽油的添加可增加鱼糜凝胶强度、乳化稳定性和持水性的内在原因。     

表没食子儿茶素没食子酸酯对冷冻罗非鱼鱼糜抗冻作用机制

通过肌原纤维蛋白理化指标、鱼糜凝胶特性的测定及十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）,研究表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）对冷冻罗非鱼鱼糜的抗冻效果并探讨其作用机制。结果表明,罗非鱼鱼糜中添加EGCG具有一定的抗冻效果,对比空白组具有显著差异性。冻藏期间空白组鱼糜中盐溶性蛋白含量、总巯基含量分别下降了68.2%和62.9%,而添加0.01% EGCG后二者的降幅分别为54.5%和49.2%,且EGCG还明显延缓了肌原纤维蛋白的氧化羰基化作用。此外,冻藏过程中,EGCG组和空白组鱼糜凝胶强度和持水性随冻藏时间延长逐渐降低,且EGCG添加量较大时,反而加快凝胶劣化。SDS-PAGE显示,EGCG能够有效抑制肌原纤维蛋白降解,其中质量分数为0.01%的EGCG效果最佳。EGCG能延缓肌原纤维蛋白变性和降解程度,延缓鱼糜氧化变质程度,有望成为一种新型的鱼糜抗冻剂。     

Optimal blending of differently refined fish proteins based on their functional properties

Two different mixtures (Alaska pollock surimi with grass carp fish protein isolate (FPI) and grass carp surimi with grass carp FPI) were investigated for their compatibility and functionalities. As the proportion of FPI increased, it was observed surface hydrophobicity and surface reactive sulfhydryl (SRSH) content increased significantly, indicating the degree of fish protein unfolding prior to gelation was much higher than surimi alone. Comparable results were shown as measured by storage modulus (G′) in oscillatory dynamic rheology, demonstrating the gelling temperature was reduced when the proportion of FPI increased. Effects of mixing surimi and FPI on gel functionality (hardness, cohesiveness, and whiteness) exhibited a linear pattern when the proportion of surimi was larger than or equal to that of FPI. However, there were no linear relationships when the proportion of FPI exceeded that of surimi.

Practical applications

Commercial surimi has been successfully used in the Western world over 30 years. Unlike surimi which is a refined fish myofibrillar protein composite, fish protein isolate (FPI) is a refined composite of myofibrillar protein and sarcoplasmic protein. The former is made by avoiding any chemical/physical denaturation, while the latter can be made by inducing chemical denaturation and renaturation with pH shift. Even though FPI is not currently available in a commercial scale, it has a great potential to replace all or a part of surimi for the manufacture of fish protein gel products. This study reveals how to optimally mixed these two differently refined fish proteins based on their functional properties. The results suggested that blending surimi and FPI may be feasible only when the proportion of FPI does not exceed 50%.     

Protein Structural Changes During Preparation and Storage of Surimi

The changes in protein structure associated with the preparation and frozen storage of surimi were investigated. Raw surimi was prepared by repeatedly washing Alaska pollock flesh with chilled water. The product was either slowly frozen or underwent rapid freezing using liquid air; in either case it was then subjected to frozen storage at ‐20 °C for 24 mo. Fourier transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy showed that during preparation of surimi, the a‐helix content increased with increased number of washing cycles. Differential scanning calorimetry (DSC) revealed a shift in the thermal transition of actin to a higher temperature during surimi preparation. Electrophoresis, FTIR/ATR spectroscopy, and DSC results revealed a loss of myofibrillar proteins from surimi after 3 washing cycles, suggesting that 3 washing cycles were adequate to prepare surimi. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) showed relatively minor changes in protein subunit structure with some loss of the myosin light chains (MLC); myosin heavy chain (MHC), actin, and tropomyosin were found to be relatively stable. Native‐PAGE showed no major changes in surimi after 24 mo storage at ‐20 °C. FTIR/ ATR spectroscopy indicated a significant decrease in a‐helix relative to p‐sheet structure in surimi after 2 y of storage at ‐20 °C. The loss of α‐helical content was more significant in slowly frozen surimi compared with rapid‐frozen surimi samples. DSC results revealed a shift in the thermal transition of actin to lower temperatures during frozen storage of surimi.     

Protein and water structural changes in fish surimi during gelation as revealed by isotopic H/D exchange and Raman spectroscopy

Structural changes of proteins and water during gelation of fish surimi, have been studied by isotopic H/D exchange of water and Raman spectroscopy assisted by monitoring of rheological characteristics, in order to get insights into the structural and functional properties of surimi gels. The results indicate the following: (i) Protein hydrogen bond rearrangements occur involving mainly α-helix to β-sheet transition, (ii) the relative intensity of the symmetric H₂O stretching band near 3220 cm⁻¹ tends to decrease upon gelation, (iii) H/D exchange reveal a slower deuteration kinetics in the gels as compared to the surimi, (iv) the low temperature scanning electron microscopy shows a smaller pore size of the gel network as compared to the surimi, and suggests that water domains in gel are more inaccessible to D₂O, which is consistent with higher water holding capacity in the gel.     

鳕鱼皮的添加对鱼糜凝胶特性及其蛋白质结构的影响

目的 研究添加黑线鳕鱼(Melanogrammusaeglefinus)皮对鱼糜凝胶特性和蛋白质结构的影响。方法以傅里叶变换红外光谱法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳技术的分析方法,探究黑线鳕鱼皮不同添加比率对鱼糜凝胶的凝胶强度、质构、持水性、p H和蛋白质分子组成及其二级结构的影响规律。结果 当鱼皮添加比率为5%时,混合凝胶的凝胶强度、弹性和持水性虽下降但无显著变化(P>0.05),分别为2654.4 g·mm、2.83 mm和85.7%,而硬度显著下降至22.83 N (P<0.05);随着鱼皮添加比率的增加,鱼糜凝胶的凝胶强度、质构、持水性均下降;鱼皮的添加阻碍了肌球蛋白重链发生交联,同时,鱼糜凝胶蛋白质结构无显著变化(P>0.05)。结论为提高鱼皮的利用率,可适量将鱼皮与鱼糜混合制备鱼糜凝胶,鱼皮添加比率不宜超过5%。     

带鱼鱼糜漂洗水中回收蛋白的性质及其在鱼糜中的再利用

为提高鱼糜加工品附加值,探究回收的鱼糜漂洗水可溶蛋白添加至鱼糜中的可行性,本文对絮凝法沉淀的漂洗水可溶蛋白进行氨基酸组成、重金属含量和挥发性风味成分分析,评价其营养价值、安全性及风味特点,并进一步将回收蛋白添加至鱼糜,以鱼糜白度、凝胶强度等为指标,确定其最适添加量。结果表明,从鱼糜漂洗水中回收的蛋白质,其氨基酸含量达73.11%,其中必需氨基酸占氨基酸总量的43.95%,必需氨基酸指数(EAAI)为70.04%,具较高的营养价值;回收蛋白的重金属(铅、镉、汞、铬、砷)含量均在国家标准限定值之内,具较好的安全性;气质联用仪(GC-MS)结合感官分析,鱼糜漂洗水中的回收蛋白鱼香味明显,无令人不愉快的气味,添加至带鱼鱼糜后能改善鱼糜凝胶特性,合适的添加量为3%。表明鱼糜漂洗水中的可溶蛋白营养价值高、安全,重新添加到鱼糜中能提高鱼糜白度,一定程度上改善鱼糜的凝胶特性。     

Roles of Starch in Surimi Seafood: A Review

Surimi seafood is a cooked gel product that utilizes fish protein from surimi to produce seafood analog products. Starch is the second most important ingredient used in the manufacture of surimi seafood due to its water holding ability and capacity to partially replace fish proteins while maintaining desired gel characteristics at a reduced cost. Typically, starch is added to surimi seafood formulations at 4–12%. Functional properties of surimi seafood to control wetness, stickiness, and/or thermal stability upon different storage and serving temperatures have been extensively studied using modified starches. There is a great need to review the role of starches in various applications of surimi seafood.     

Combined effect of aminoacids and microbial transglutaminase on gelation of low salt surimi content under high pressure processing

The paper examines the effect of High Pressure Processing (HPP) (300 MPa), the incorporation of microbial transglutaminase (MTGase) and the addition of different additives such as lysine and cystine, as potential enhancers of low-salt (0.3%) surimi gel. Effects on myosin as the molecule responsible for gelation was monitored by Fourier transform infrared spectroscopy, Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and dynamic rheometry measurements. The effects on physicochemical properties of surimi gels were determined by Folding and Puncture tests and water holding capacity.Results indicated an increase in β-sheet when HPP was applied or additives added (cystine and lysine), especially when samples are treated with MTGase. Protein aggregation due to HPP and the additives resulted in lower myosin heavy chain (MHC) band density in the SDS–PAGE. Rheometry measurements indicated that MTGase activity was prompted by the incorporation of cystine and lysine in the absence of HPP. Also, HPP assisted gelation, resulting in improved mechanical properties of the gels. Samples containing additives, with or without HPP, exhibited the highest Folding test scores, indicating greater network flexibility. Lastly, water binding capacity was also enhanced by both additives and HPP.Industrial relevanceThe industrial relevance of the present work is focused on the appropriated gelation of myofibrillar proteins which is an essential step in the elaboration of surimi-based products. Sodium chloride has an important role in that fact inducing protein unfolding and solubilization. The reduction in NaCl content, following the NAOS strategy, required the application of different technologies to facilitate surimi adequate gelation. High-pressure processing has been commonly used as an innovative technology to prolong shelf life but it can be successfully used to induce proteins gelation. Due to that ability, the use of high pressure on surimi-based products result an interesting tool to facilitate surimi gelation. The use of Microbial transglutaminase (MTGase) alone or in combination with some aminoacids such as lysine and cystine can significantly improve surimi gelation added in a very small proportion.     

Comparison of Atlantic menhaden gels from surimi processed by acid or alkaline solubilization

Heat-induced gelling abilities of surimis prepared by pH shifting (isoelectric precipitation following acid (AC) or alkaline (AL) solubilization) were compared to that of conventionally washed (CW) surimi. Greater endogenous transglutaminase activity (evidenced as enhanced strength of cooked gels subjected to 30–40 °C preincubation) was measured for CW and AL surimi than for AC surimi (all at pH 7). Upon addition of microbial transglutaminase (MTGase), increased crosslinking of myosin heavy chain and gel strengthening during 30–40 °C preincubation were apparent for all three types of surimi, most markedly in CW and AL surimi. Salt addition improved CW gels most, but seemed to adversely affect MTGase activity in AC and AL surimi. AC and AL surimi gels were of lower whiteness than were CW surimi gels.     

Estimating the quantity of egg white and whey protein concentrate in prepared crabstick using ELISA

Indirect enzyme-linked immunosorbent assays (ELISA) technique was used to identify and quantify the use of dried egg white (DEW) and whey protein concentrate (WPC) in crabsticks. The use of SDS–PAGE for the quantification of protein additives has had limited success due to the high shear and high temperature processes of surimi crabstick. Monoclonal (anti-heat-denatured ovalbumin) and polyclonal (anti-β-lactoglobulin) antibodies were used. Antibodies showed no significant cross-reactivity with non-target crabstick proteins. An optimised extraction solution of 10% SDS and 2.5% 2-ME yielded high extractability with improved consistency. Quantification of DEW and WPC was achieved using the optimised extraction solution and indirect ELISA. Estimated DEW values were within 7% of actual values, WPC samples were within 17%. Inter-assay coefficients of variance for DEW ranged from 0.9% to 3.1% and those of the WPC were 1.0–8.0%.     

Surimi from Fillet Frames of Channel Catfish

Surimi was prepared with channel catfish mince recovered from fillet frames. The deboned meat was washed once, twice, or three times with water for surimi processing. Unwashed mince was also blended with cryoprotectants for surimi processing. Heat-induced gels were prepared using washed or unwashed catfish surimi with or without starch. Results indicated no differences (P>0.05) in textural properties and Hunter color values due to number of washes in those gels prepared with washed surimi. Differences (P<0.05) in proximate composition, textural properties and Hunter color values were found between gels prepared with washed and unwashed surimi.     

Effect of laver powder on textual,rheological properties and water distribution of squid (Dosidicus gigas) surimi gel

In order to ameliorate the gel quality of Dosidicus gigas surimi, the effects of laver powder on gel properties, rheological properties, and water-holding capacity (WHC) were investigated. Results indicated that the addition of laver powder could significantly increase the hardness, chewiness, and breaking force of surimi gels. However, the texture indexes and gel strength began to decline when additional amount exceeded 0.6%. Rheological results demonstrated that the addition of laver powder increased the storage modulus (G′) and viscosity of surimi, prolonged protein denaturation temperature in surimi gels. Moreover, the WHC of surimi gel was improved with the increase of laver powder. Further analyses in low-field nuclear magnetic resonance revealed that laver powder could shorten the transverse relaxation time, enhanced the combination with water, and altered the distribution of different water categories. The proportion of bound water and immobilized water reached its maximum and minimum at 0.6% of laver powder, respectively. Correlation analyses showed that WHC of surimi gel was negatively correlated well with the proportion of loose-bound water, but positively correlated with the strong-bound water and free water. In conclusion, the results supported that 0.6% was the optimal additional amount of laver powder for the squid-based surimi production based on the current ingredients of surimi products.