Interactions of dietary fibre and omega-3-rich oil with protein in surimi gels developed with salt substitute

Comparison of the effect of vegetable oil and oleogels with different unsaturation on gel properties of Nemipterus virgatus surimi

The effect of oleogels prepared using γ-oryzanol, β-sitosterol and vegetable oils with different unsaturation on the gel properties of surimi was compared. The findings from SEM and optical microscopy demonstrated that direct addition of vegetable oils caused loose surimi gel three-dimensional network structure, which negatively impacted the water holding capacity (WHC) and texture properties. However, oleogels increased the hydrophobic interaction and disulfide bond content, facilitated the transition from α-helix to β-sheet, improving the WHC and gel strength of surimi. Among them, the surimi containing oleogels prepared by linseed oil with the highest polyunsaturated fatty acid (PUFA) content had the highest gel strength and WHC, which were 3936.067 g·mm and 66.77 %, respectively. The results of microstructure showed that linseed oil based oleogels were able to fill the gaps of gel network more uniformly with smaller holes. Therefore, oleogels enriched with PUFA were more effective in enhancing the gel properties of surimi.

Unveiling the protein-lipid interaction mechanism: How the sturgeon lipids diminish the surimi gel properties

Sturgeon, with 4 times higher lipid content than silver carp (ubiquitously applied for surimi production in China), affects surimi gelling properties. However, how the flesh lipids affect gelling properties remains unclear. This study investigated how flesh lipids impact surimi gelling properties and elucidated the interaction mechanism between lipids and proteins. Results revealed yellow meat contains 7 times higher lipids than white meat. Stronger ionic protein-protein interactions were replaced by weaker hydrophobic forces and hydrogen bonds in protein-lipid interaction. Protein-lipid interaction zones encapsulated lipid particles, changing protein structure from α-helix to β-sheet structure thereby gel structure becomes flexible and disordered, significantly diminishing surimi gel strength. Docking analysis validated fatty acid mainly binding at Ala577, Ile461, Arg231, Phe165, His665, and His663 of myosin. This study first reported the weakened surimi gelling properties from the perspective of free fatty acids and myosin interactions, offering a theoretical basis for sturgeon surimi production.

Effect of three unsaturated fatty acids on the protein oxidation and structure of myofibrillar proteins from rainbow trout (Oncorhynchus mykiss)

In this study, the impact of three unsaturated fatty acids (Oleic acid: OA, Eicosapentaenoic acid: EPA, Docosahexaenoic acid: DHA) on the oxidation and structure of rainbow trout myofibrillar protein (MP) was explored. The findings revealed a notable increase in carbonyl content (P < 0.05) and a significant decrease in total sulfhydryl content (P < 0.05) of MP with the concentration increase of the three unsaturated fatty acids. Endogenous fluorescence spectroscopy and surface hydrophobicity analyses showed that unsaturated fatty acids can cause unfolding and exposure of hydrophobic groups in MP. In addition, SDS-PAGE showed that disulfide bonds were associated with MP cross-linking and aggregate size induced by unsaturated fatty acids. Overall, three unsaturated fatty acid treatments facilitated the oxidation of myofibrillar proteins, and the extent of protein oxidation was closely associated with the concentration of unsaturated fatty acids.

Influence mechanisms of linoleic acid and oleic acid on the gel properties of egg yolk protein

BACKGROUND

Gel property is among the crucial functional properties of egg yolk (EY), which determines the texture and flavor of EY products. In the present study, the effects of two unsaturated fatty acids [monounsaturated fatty acid oleic acid (OA) and diunsaturated fatty acid linoleic acid (LA)] on the gel properties of EY protein were investigated.

RESULTS

Compared with the blank group, the addition of LA and OA (10-50 g kg-1) improved the gel hardness (from 270.54 g to 385.85 g and 414.38 g, respectively) and viscosity coefficient (from 0.015 Pa.sn to 11.892 Pa.sn and 1.812 Pa.sn, respectively). The surface hydrophobicity of EY protein increased to a maximum value of 40 g kg-1 with the addition of both fatty acids (39.06 μg and 41.58 μg, respectively). However, excess unsaturated fatty acids (≥ 50 g kg-1) disrupted the completeness of the gel matrix and weakened the structural properties of the EY gel.

CONCLUSION

Both fatty acids improved the gel properties of EY protein. At the same addition level, OA was superior to LA in improving gel properties. The present study provides a theoretical underpinning for the sensible application of unsaturated fatty acids in improving EY gel properties. © 2024 Society of Chemical Industry.

Investigation on 3D Printing of Shrimp Surimi Adding Three Edible Oils

Three-dimensional (3D) printing provides a new method for innovative processing of shrimp surimi. However, there still exists a problem of uneven discharge during the 3D printing of surimi. The effects of different amounts of lard oil (LO), soybean oil (SO), and olive oil (OO) (0%, 2%, 4%, and 6%, respectively) added to shrimp surimi on the 3D printability of surimi were evaluated. The findings showed that with the increase in the added oil, the rheological properties, texture properties, water-holding capacity (WHC), and water distribution of surimi with the same kind of oil were significantly improved; the printing accuracy first increased and then decreased; and the printing stability showed an increasing trend (p < 0.05). The surimi with 4% oil had the highest printing adaptability (accuracy and stability). Different kinds of oil have different degrees of impact on the physical properties of surimi, thereby improving 3D-printing adaptability. Among all kinds of oil, LO had the best printing adaptability. In addition, according to various indicators and principal component analysis, adding 4% LO to shrimp surimi gave the best 3D-printing adaptability. But from the aspects of 3D printing properties and nutrition, adding 4% SO was more in line with the nutritional needs of contemporary people.

Interaction between liposome and myofibrillar protein in surimi: Effect on gel structure and digestive characteristics

This study investigated the effects of the interaction between liposomes and myofibrillar protein (MP) on tilapia surimi. The strong interaction between liposomes and MP was primarily mediated through hydrogen bonding and hydrophobic interaction. Liposomes caused the unfolding of MP structure, resulting in the decrease of α-helix content and transformation of spatial structure. Notably, the appropriate ratio of liposomes improved the gel properties of tilapia surimi. The water distribution, microstructure, and texture characteristics further confirmed that liposomes strengthened the structure of surimi gel through non-covalent bonds. However, excessive liposomes (1.0 %) weakened gel characteristics and texture. Moreover, the proper ratio of liposomes enhanced the stability of surimi gels during digestion, reducing protein digestibility from 66.0 % to 54.8 %. Curcumin-loaded liposomes in gel matrix notably delayed digestion and improved bioavailability. This delay in digestion was attributed to the ability of liposomes to decrease the interaction between MP and digestive enzymes. This study provides new insight into the application of liposomes in protein-rich food matrixes.

Nutrification and fat reduction of deep-fried protein isolates

Deep-fried (DF) foods are considered nutritionally-inferior due to increased fat content, although they are popular with consumers due to desirable sensory characteristics. This study attempted to reduce fat of DF surimi, DF fish-protein-isolate (FPI), and DF chicken-protein-isolate (CPI) by pre-baking or pre-roasting. Surimi, FPI, and CPI were also nutrified with ω-3-rich oil, fiber, and KCl-based salt substitute. Pre-baking decreased (p < 0.05) fat content, while pre-roasting increased (p < 0.05) it. Pre-baking resulted in less (p < 0.05) changes to cook loss, moisture loss, expressible moisture, water-holding-capacity, whiteness, and texture when compared to pre-roasting. Pre-baking also better maintained ω-3 PUFAs concentration than pre-roasting, resulting in higher (p < 0.05) concentration of α-linolenic (ALA, 18:3ω3), eicosapentaenoic (EPA, 20:5ω3), and docosahexaenoic (DHA, 22:6ω3) FAs as well as unsaturated FAs and total ω-3 FAs in DF surimi, DF FPI, and DF CPI. Pre-baking in combination with nutrification using ω-3 PUFAs improved nutritional value of DF foods, while causing minimal quality changes.

Effects of Citrus Fiber on the Gel Properties of Mutton Myofibrillar Protein

This work investigated the effects of different additions of water-soluble citrus fiber (SCF) and water-insoluble citrus fiber (ICF) on the gel properties of the mutton myofibrillar protein (MP). The key parameters of water-holding capacity (WHC), rheological properties, and microstructure were evaluated. The addition of 2.5-10% of SCF and ICF significantly improved (p < 0.05) the WHC and gel strength of mutton MP gel. The rheological results showed that the viscoelasticity of MP with 5% SCF was the best, and the T₂ relaxation time of the gel was significantly shortened. SEM results showed SCF reduced the number of pores in the MP gel, forming a more compact network structure. ICF stabilized the MP gel network structure as a filler after water absorption and expansion. However, the gel lost moisture under the action of strong external force (freeze-drying), which left large pores. These data confirmed that SCF and ICF could effectively improve the gel properties of meat products.

Identification of candidate genomic regions for thermogelled egg yolk traits based on a genome-wide association study

Egg yolk texture is an important indicator for evaluating egg yolk quality. Genetic markers associated with economic traits predict genomes and facilitate mining for potential genes. Numerous genome-wide association studies have been conducted on egg traits. However, studies on the genetic basis of thermogelled yolk texture are still lacking. The aim of the present study was to find significant single nucleotide polymorphism (SNP) sites and candidate genes related to thermogelled yolk texture in Hetian Dahei chicken (HTHD) flocks that can be used as genetic markers. Five traits, including hardness, cohesiveness, gumminess, chewiness, and resilience, had low heritability (0.044-0.078). Ten genes, including U6, FSHR, PKDCC, SLC7A11, TIMM9, ARID4A, PSMA3, ACTR10, EML4, and SLC35F4 may control the hardness of the thermogelled egg yolks. In addition, 12 SNPs associated with cohesiveness were identified. RELCH located on GGA2 participates in cholesterol transport. The candidate gene LRRK2, which is associated with gumminess, influences the concentrations of very low-density lipoprotein in blood. Eight SNPs associated with resilience were identified, mainly on GGA3 and GCA28. In total, 208 SNPs associated with chewiness were identified, and 159 candidate genes, which were mainly involved in proteasome-mediated ubiquitin-dependent protein catabolic process, negative regulation of transport, lipid droplet organization, and vehicle docking involved in exocytosis, were found near these regions. Thermogel egg yolk texture is a complex phenotype controlled by multiple genes. Based on heritability assays and GWAS results, there is a genetic basis for the texture of thermogelled egg yolks. We identified a series of SNPs associated with yolk texture and candidate genes. Our result provides a theoretical basis for breeding high-quality egg yolk using molecular marker-assisted selection and could facilitate the development of novel traits.

Effects of exogenous lipids on gelling properties of silver carp surimi gel subjected to microwave heating

Lipids are important components of surimi products because they enhance the whiteness and flavor of food. The effects of three common types of exogenous lipids on the gel properties of surimi subjected to two different heating methods were investigated in this work, using frozen silver carp (Hypophthalmichthys molitrix) surimi as the raw material. The surimi gels were prepared by two-stage water bath heating or single-stage water bath heating followed by microwave heating. We found that the quality of surimi gels was in the order of lard > chicken fat/soybean oil, which may be associated with polyunsaturated fatty acid content. The surimi gel strength was reduced with an increase in the amount of lipid added. Microwave heating significantly increased the gel strength of surimi containing exogenous lipids when compared to conventional heating. Surimi gels prepared by microwave heating showed more denser protein network microstructures by scanning electron microscopy (SEM), suggesting aggregation of protein molecules. The findings of this study provide a theoretical basis for using microwave heating to generate surimi gels with exogenous lipids.

Gel-type emulsified muscle products: Mechanisms, affecting factors, and applications

The gel-type emulsified muscle products improve fatty acid composition, maintain the oxidative stability, and achieve a better sensory acceptability. This review emphasizes the stabilization mechanisms of these emulsified muscle products. In particular, factors associated with the stability of the emulsified muscle systems are outlined, including the processing conditions (pH and heating), lipids, and emulsifiers. Besides, some novel systems are further introduced, including the Pickering emulsions and organogels, due to their great potential in stabilizing emulsified gels. Moreover, the promising prospects of emulsion muscle products such as improved gel properties, oxidative stability, freeze-thaw stability, fat replacement, and nutraceutical encapsulation were elaborated. This review comprehensively illustrates the considerations on developing gel-type emulsified products and provides inspiration for the rational design of emulsified muscle formulations with both oxidatively stable and organoleptically acceptable performance.

Role of low molecular additives in the myofibrillar protein gelation: underlying mechanisms and recent applications

Understanding mechanisms of myofibrillar protein gelation is important for development of gel-type muscle foods. The protein-protein interactions are largely responsible for the heat-induced gelation. Exogenous additives have been extensively applied to improve gelling properties of myofibrillar proteins. Research has been carried out to investigate effects of different additives on protein gelation, among which low molecular substances as one of the most abundant additives have been recently implicated in the modifications of intermolecular interactions. In this review, the processes of myosin dissociation under salt and the subsequent interaction via intermolecular forces are elaborated. The underlying mechanisms focusing on the role of low molecular additives in myofibrillar protein interactions during gelation particularly in relation to modifications of the intermolecular forces are comprehensively discussed, and six different additives i.e. metal ions, phosphates, amino acids, hydrolysates, phenols and edible oils are involved. The promoting effect of low molecular additives on protein interactions is highly attributed to the strengthened hydrophobic interactions providing explanations for improved gelation. Other intermolecular forces i.e. covalent bonds, ionic and hydrogen bonds could also be influenced depending on varieties of additives. This review can hopefully be used as a reference for the development of gel-type muscle foods in the future.

Improvement of gelation properties of silver carp surimi through ultrasound-assisted water bath heating

The present work investigated the effects of water bath heating coupled with different ultrasound treatments on the gel properties, protein conformation, microstructures and chemical interactions of silver carp surimi at low/high salt levels. Results showed that the gel strength, hardness, springiness and water holding capacity (WHC) of surimi gels at low salt concentration were inferior to those at high salt content, regardless of the treatments. Compared with the traditional water bath heating, ultrasonic-assisted treatments significantly improved the gelation properties of surimi at the same salt level. In fact, ultrasound treatment also facilitated the unfolding of α-helix structure of the protein, with the resulting exposure of internal groups further enhancing hydrophobic interactions and hydrogen bonds between protein molecules, thereby leading to the formation of denser microstructures with smaller holes. Furthermore, the most noteworthy ultrasonic treatment group was ultrasound-assisted preheating (U + W) group, whose gelation performance under low salt condition, was comparable with that of the traditional two-stage heating (W + W) group with high salt content. Overall, ultrasound-assisted water bath preheating proved to be a feasible approach to improve the gel properties and microstructures of low-salt surimi gels.

Diacylglycerol pre-emulsion prepared through ultrasound improves the gel properties of golden thread surimi

This study determined the influence of diacylglycerol (DAG) pre-emulsion on the gel properties and microstructure of golden thread surimi gels. DAG emulsion stabilized using sodium caseinate was pre-emulsified through ultrasound. The average particle size of DAG pre-emulsion decreased from 1324.15 nm to 41.19 nm, with notable improvements in apparent viscosity and storage stability. The surimi gels with different amounts (0%, 1%, 3%, 5%, and 7% w/w) of DAG pre-emulsion were prepared under heat induction. The whiteness of the composite gels markedly increased with the incorporation of DAG pre-emulsion. The peak T₂₂ value of immobilized water, the gel strength, and water-holding capacity increased gradually, but it slightly decreased with the addition of 7% pre-emulsion. The curve of G' and G″ kept climbing as the concentration of pre-emulsion, and the microstructure of the gel network tended to become denser and more orderly. Principal component analysis (PCA) of electronic nose results showed that the surimi gels containing pre-emulsion could be clearly distinguished from the control group. In conclusion, the addition of 5% DAG pre-emulsion to surimi not only improved gel properties to the highest extent but also be compensated for lipid loss during the rinsing of surimi.

Bioactivity of Cooked Standard and Enriched Whole Eggs from White Leghorn and Rhode Island Red in Exhibiting In-Vitro Antioxidant and ACE-Inhibitory Effects

Hen breed, diet enrichment, cooking methods, and gastrointestinal (GI) digestion modulates the bioaccessibility of the bioactive compounds in eggs, but their synergistic role in modulating bioactivity is still unclear. The present study evaluates the effect of hen breed, diet enrichment, and GI digestion on the cooked whole egg-derived peptides in-vitro antioxidant and antihypertensive activities. Standard and enriched whole eggs from White Leghorn (WLH) and Rhode Island Red (RIR) hens were boiled or fried and subjected to GI digestion. Antioxidant activity was measured through oxygen radical absorbance capacity (ORAC) and gastrointestinal epithelial cell-based assays, and the antihypertensive capacity by in-vitro Angiotensin-I Converting Enzyme (ACE) inhibition assay. WLH fried standard egg hydrolysate showed a high ORAC antioxidant activity but failed to show any significant antioxidant effect in the cell-based assay. No significant differences were observed in the antihypertensive activity, although enriched samples tended to have a higher ACE-inhibitory capacity. The peptide profile explained the antioxidant capacities based on antioxidant structural requirements from different peptide fractions, while previously reported antihypertensive peptides were found in all samples. The study validates the importance of physiologically relevant models and requires future studies to confirm mechanisms that yield bioactive compounds in whole egg hydrolysates.

Effect of lipase incorporation on gelling properties of catfish (Clarias lazera) surimi and its mechanism

BACKGROUND

Recently, fatty fish have been utilized as a potential approach for the fabrication of surimi products, with the yield of fatty fish surimi being > 10 000 tons in 2019. However, the gelling properties of catfish surimi can be influenced by intermuscular lipid. Lipase could effectively enhance the gel quality of catfish surimi gels, although the chemical forces involved in gel formation and alteration in lipid and protein oxidation status are not well understood. The present study investigated the gelation-enhancing effects of lipase on catfish surimi based on changes in chemical oxidation interactions.

RESULTS

The addition of 7.5 g kg^-1 lipase significantly increased the hydrophobic interactions and disulfide bond contents, both of which facilitated gel formation, in surimi gels. The 2-thiobarbituric acid reactive substance and carbonyl concentrations demonstrated that lipase promoted lipid and protein oxidations. Furthermore, an appropriate dose of malondialdehyde accelerated protein oxidation, thereby resulting in the covalent cross-linking of proteins. Consequently, the gel strength increased from 55.72 to 127.71 g × cm with lipase contents of up to 7.5 g kg^-1 , and strong chemical cross-linking and a compact network were observed via sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. However, excessive oxidation led to the degeneration of the gel matrix. A schematic mechanism, mainly based on the chemical changes, is proposed.

CONCLUSION

The present study revealed the gelation mechanism of catfish surimi gels with lipase, and suggested that lipase treatments may be an effective approach for improving the textural properties of fatty fish surimi gels. © 2021 Society of Chemical Industry.

Recent developments in maintaining gel properties of surimi products under reduced salt conditions and use of additives

Salt is a necessary condition to produce a surimi product that is based on the gelation of salt-soluble myofibrillar proteins. Recently, there has been a growing concern among consumers to consume healthy foods due to the threat of several chronic diseases caused by an unhealthy diet. Methods of reducing salt content out of concern for health issues caused by excessive sodium intake may affect the gel properties of surimi, as can many health-oriented food additives. Several studies have investigated different strategies to improve the health characteristics of surimi products without decreasing gel properties. This review reports recent developments in this area and how the gel properties were successfully maintained under reduced-salt conditions and the use of additives. This review of recent studies presents a great deal of progress made in the health benefits of surimi and can be used as a reference for further development in the surimi product processing industry.

Effects of wheat fiber addition on emulsion and lipid/protein stabilities of an omega-3 fatty acid-fortified chicken surimi product

Meat, except marine sources, is a highly nutritious food but generally lacks some healthy ingredients, such as omega-3 fatty acids (ω-3 FA) and dietary fiber. However, ω-3 FA and dietary fiber could be incorporated during the manufacture of surimi-like products. In our previous study, chicken surimi was successfully developed from spent-hen breast. Although there was no (P > 0.05) difference in water-holding capacity between wheat fiber and carrageenan, an increased (P < 0.05) flaxseed oil–holding capacity was observed in wheat fiber samples. Furthermore, an addition of 5% wheat fiber resulted in optimal emulsification capacity and less cooking loss at 4°C for 14 d and at −20°C for 60 d (P < 0.05). Because of the lower (P < 0.05) purge and centrifugation losses, thiol group content, and thiobarbituric acid reactive substance value than those formulated with more flaxseed oil, 12% flaxseed oil was an optimal level in chicken surimi with 5% wheat fiber. Scanning electron microscopy results also showed better emulsification of surimi batters with wheat fiber compared with those without wheat fiber, and meanwhile, the formulation with 5% wheat fiber could hold up to 12% flaxseed oil as well. To enhance flaxseed-oil addition, semi-manufactured chicken surimi batter was successfully fortified with a combination of 12% flaxseed oil and 5% wheat fiber. This surimi-like product with dietary fiber and ω-3 FA would fit the need in the current market regarding consumers' demands for high nutritional value and improved processing characteristics.

Effect of lipid on surimi gelation properties of the three major Chinese carp

BACKGROUND

Gel properties are important in determining the quality of surimi. In addition to myofibrillar proteins, lipids play an important role in the formation of surimi gel. Phospholipids (PL) are amphoteric lipids that cannot be removed through rinsing. Paradoxically, the addition of PL increases or decreases gel strength. This research aimed to investigate the effects of specific lipids on the gelation properties of surimi from three different carp.

RESULTS

The hardness, chewiness, and gel strength of bighead carp (Aristichthys nobilis: BC) surimi were higher, and the total lipid content was lower when compared with grass carp (Ctenopharyngodon idellus: GC) and silver carp (Hypophthalmichthys molitrix: SC) surimi. Bighead carp surimi had lower levels of phosphatidylethanolamine (PE), phosphatidylinositols (PI), and phosphatidylcholine (PC), and higher phosphatidylserine (PS) and sphingomyelin (SM) content. The gelation properties of surimi increased with increasing concentrations of SM and PS. Furthermore, increased levels of saturated fatty acids (SFAs) and decreased levels of polyunsaturated fatty acids (PUFAs) increased gelation properties. Finally, higher hydrophobic interactions and more disulfide bonds were shown to increase gel network structure stability, resulting in improving gel strength in BC surimi.

CONCLUSION

The textural characteristics and gel strength of surimi were dependent on the PL content, including total lipid levels and the types of fatty acids. This may account for previous conflicting reports on PL effects on gel strength. This study provides insight into how the texture of surimi can be improved and provides a starting point for further research. © 2020 Society of Chemical Industry.

Insight into the mechanism of myofibrillar protein gel influenced by konjac glucomannan: Moisture stability and phase separation behavior

The effect and mechanism of myofibrillar protein (MP) gelation influenced by konjac glucomannan (KG) addition were studied. The KG addition significantly improved gel strength and water holding capability (WHC) of MP-KG composite gel, but it had additive limitation at 1.0%. The SEM showed that KG (<1.0%) reduced the appearance of moisture channels and promoted the formation of an integral MP gel network. Raman spectroscopy showed that KG addition (<1.0%) promoted the protein unfolding and the interaction of hydrophobic groups during thermal processing. However, the KG (>1.0%) would form continuous viscous hydrogel and interpenetrate with the MP solution, which hindered the interaction of hydrophobic groups during thermal process, and the MP formed a loose and degraded final structure. Hence, MP gels produced with the addition of KG underwent a transformation from a loose structure to a compact structure to an unaggregated structure, which was influenced by moisture stability and phase separation behavior.

Addition of seaweed powder and sulphated polysaccharide on shelf_life extension of functional fish surimi restructured product

This study aimed to investigate the performance of equal amounts of edible green seaweed, Ulva intestinalis powder (2.77 g kg^-1), and its sulphated polysaccharide ([USP], 0.5 g kg^-1, based on the extraction yield from U. intestinalis powder) on the proximate compositions, lipid oxidation, pH, colour, textural properties, cooking yield and sensory attributes of fish-surimi restructured products during storage at - 18 °C as compared with the control. Results showed incorporation of two functional components resulted in lower TBARS values compared with the control over 6 months (P ≤ 0.05). The USP incorporated fingers showed the least moisture loss over 6 months (P < 0.05). Textural properties for two functional fingers remained relatively stable from month 0 to month 6, while the hardness increased significantly (P < 0.05) in the control fingers (67 to 80 N). Additionally, the sensory attributes of all formulated fingers were judged acceptable; however, the USP containing fingers were preferred by the sensory panelists, due to their juicy texture as a result of less cooking loss comparing with others. In conclusion, this study suggests the potential use of such natural marine ingredients to maintain the quality and to extend the shelf life of surimi-based products with beneficial health effects.

Effect of pH and heating conditions on the properties of Alaska pollock (Theragra chalcogramma) surimi gel fortified with fish oil

To improve the quality and functionality of emulsified surimi gels, the effect of pH and heating conditions on the properties of surimi gel fortified with fish oil was investigated. Results showed that pH conditions influenced the solubility and emulsifying properties of surimi proteins and that the gel properties were associated with the protein properties. Under direct heating, the highest gel strength was achieved at pH 8.0, in which condition the solubility was significantly higher than others. Higher emulsifying stability resulted in enhanced gel strength relative to that of the control group. However, the changes in the gel strength were not consistent under two-step heating. In addition, the expressible moisture and oil content were found to vary depending on the pH values under both heating conditions. The corresponding changes in expressible moisture and oil content could be attributed to the high protein solubility and emulsifying properties of surimi proteins. Analysis of the dynamic rheological properties of the resulting surimi paste revealed that the gelation properties varied depending on the pH conditions during the heating process. In addition, the temperatures of myosin cross-linking changed according to the structure of surimi proteins, which in turn varied depending on the pH conditions. PRACTICAL APPLICATIONS: To improve the functionality of surimi-based product, the fish oil was added to prepare surimi gel. pH and heating conditions play important roles in the gelation of fish proteins. Therefore, this study investigated the effect of combined pH and heating condition on the property of surimi gel fortified with fish oil. The emulsified surimi gel with fine texture was obtained at pH of 8-8.5; moreover, heating conditions (direct heating and two-step heating) also influenced texture of emulsified surimi gel. These results provide the evidence to produce the emulsified surimi-based product with the high gel strength, water- and oil-holding capacity.

Effect of emulsifying stability of myofibrillar protein on the gel properties of emulsified surimi gel

Several kinds of emulsified surimi gels were prepared from different quality levels of Alaska Pollack surimi, and the relationship between the emulsifying stability (ES) of myofibrillar protein and the properties of the emulsified surimi gels was investigated. Fish oil emulsified into surimi gels enhanced the breaking strength, but this was decreased by denaturation of the surimi protein, and the rate of enhanced gel-forming ability with emulsification decreased with decreasing ES. Expressible drip also decreased with emulsification; however, increasing amounts of lipid in the expressible drip were separated out from the gel upon protein denaturation of the source surimi. Scanning electron microscopy revealed that the shape of fish oil particles became irregular and some voids caused by oil leakage were observed with increasing storage period of source surimi. The results suggested that improvement in gel properties of the emulsified surimi gels was correlated with ES as well as the level of protein denaturation.

Effects of microwave heating on the gelation properties of heat-induced Alaska Pollock (Theragra chalcogramma) surimi

In the present study, we examined the properties of Alaska Pollock ( Theragra chalcogramma) surimi gels in response microwave heating at different powers (300, 400, or 500 W) and time (10, 20, or 30 min). The surimi gels heated by a microwave at 300 W for 10 min showed the highest gel strength and water-holding capacity. Increasing the power and time resulted in decreases in both the gel strength and water-holding capacity. The gel formation rate of microwave-heated gels was significantly higher than that produced by water bath heating. In addition, differential scanning calorimetry indicated that microwave heating caused less damage to the native structures of myosin and actin than water bath heating. Microstructure studies revealed that microwave heating contributed to the formation of a denser and stronger frame of the surimi gels. Raman spectroscopy indicated that the degree of the secondary structure denaturation caused by microwave heating was less than that induced by water bath heating. Thus, the results demonstrated that microwave heating is a promising method to enhance the gelation properties of surimi.

Effect of 6-gingerol on physicochemical properties of grass carp (Ctenopharyngodon idellus) surimi fortified with perilla oil during refrigerated storage

BACKGROUND

Surimi is produced from deboned fish muscle through washing to remove blood, lipids, sarcoplasmic proteins and other impurities. There is an increasing interest in the fortification of surimi with ω-3 polyunsaturated fatty acids because of their health benefits. However, lipid oxidation should be considered as an important factor during storage. Hence, in this study, the quality properties and oxidative stability of surimi fortified with 30 g kg^-1 perilla oil (PO), or 5 g kg^-1 6-gingerol (GI) or their combination (PO+GI) was investigated.

RESULTS

Perilla oil significantly improved whiteness of surimi gel, but negatively influenced its gel strength, water holding capacity (WHC) and texture. However, there was no significant difference in texture properties among GI, PO+GI and control groups. During the whole storage period, GI and PO+GI groups had higher gel strength and WHC than control and PO groups. Moreover, lower thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), carbonyl content and total plate count (TPC) were observed in GI group compared with other groups.

CONCLUSION

Perilla oil and 6-gingerol could be applied together to effectively fortify surimi qualities. Additionally, 6-gingerol could prevent lipid and protein oxidation and microbial growth of surimi during refrigerated storage. © 2017 Society of Chemical Industry.

Natural Food Additives and Preservatives for Fish-Paste Products: A Review of the Past, Present, and Future States of Research

Fish-paste products, also known as fish cakes or surimi-based products, are worldwide favorites. Surimi, a wet protein concentrate of fish muscle, is used as an intermediate raw material to produce surimi seafood. The flavor, texture, taste, shelf-life, and market value of surimi-based products depend on the source of the fish meat, type of applied heat treatment, and additives used to prepare the surimi. While preparing surimi with chemical additives, several problems have been observed, such as a lack of unique characteristics, inferior acceptability, and poor functionality. Various types of fish-paste products have been developed by using different ingredients (e.g., vegetables, seafood, herbs and oriental medicines, grains and roots including carrots, and functional food materials). However, a systematic review of fish-paste products prepared using natural food additives has not yet been performed. Therefore, the quality characteristics of fish-paste products and their functionalities were elucidated in this study. With the increasing demand for surimi seafood products, the functional properties, physiochemical properties, and shelf-life of surimi-based products need to be improved. This review will aid the preparation of new value-added products in the surimi industry.

Rheological and microstructural properties of beef sausage batter formulated with fish fillet mince

Rheological properties and microstructure of beef meat sausage batter, incorporated with different percentages of fish fillet mince (5 %, 20 %, 35 % and 50 %), were investigated and compared to the control (0 % fish). By increasing the proportion of fish fillet mince to the sausage formula up to 35 % and 50 %, hardness was increased by 40 % and 16 %, respectively, (P < 0.05), whereas, cohesiveness and springiness showed no significant differences (P > 0.05). In terms of temperature sweep test, storage modulus (G') of control sample faced a substantial slop from 10 °C to 58 °C, corresponding to the lowest magnitude of G' at its gelling point (~58°), but completed at around 70 °C, as same as the other treatments. Whereas the gelling point of batter sample with 50 % fish mince remained at nearly 42 °C, which was remarkably lowest among all treatments, indicating the better gel formation process. SEM micrographs revealed a previous orderly set gel before heating in all treatments whereas after heating up to 90 °C gel matrices became denser with more obvious granular pattern and aggregated structure, specifically in sample with 50 % fish mince. In conclusion, addition of fish mince up to 50 % into beef sausage formula, positively interacted in gel formation process, without diminishing its rheological properties.