Structural and biochemical properties of silver carp surimi as affected by comminution method

Effects of modified KGM on the gelling capability of fish protein: Novel insights into hooking effect

This study investigated the effects of modified Konjac-Gluco-Mannan (KGM) on the gelling capability of fish protein through experimental and dynamic simulation methods. The addition of deacetylated KGM (DKGM) and carboxymethylated KGM (CKGM) significantly increased the gel strength of myosin gel by 0.69 times and 0.36 times, respectively, compared to KGM. Notably, myosin with DKGM exhibited the highest storage modulus (G') and facilitated the conversion of α-helix structures during heating, leading to a denser gel network. Thermodynamic analysis revealed DKGM had the highest stoichiometric binding ratio with fish protein, indicating strong intermolecular interactions. Molecular docking identified binding sites between KGM tails and myosin heads, showing DKGM formed the most hydrogen bonds and hydrophobic interactions. The simulation of the DKGM-myosin complex demonstrated the highest interaction energy and lowest molecular radius of gyration, supporting the hypothesis that DKGM's tails enhance gelling capability through a hooking effect on adjacent proteins.

Changes in physicochemical properties of snakehead fish slices incorporated with nano fish bones during freeze-thaw cycles: Effects of marinating methods

This study investigates the influence of nano fish bone (NFB) incorporated with different marination methods (traditional static marination (Ck), vacuum-assisted marination (VM), and ultrasound-assisted marination (US)) on the quality of snakehead fish slices subjected to 9 freeze thaw (FT) cycles. The NFB particles exhibited near-spherical surface and an average diameter of 197.5 nm. As compared with the marinade treated by Ck and VM, US facilitated the formation of smaller size and more uniform Pickering emulsion stabilized by NFB. Consequently, this method delayed changes in surface hydrophobicity (up to 15 %), sulfhydryl content (up to 20 %), and maintained secondary structure, water distribution while reducing cellular damage during FT cycles. These changes contributed to the slice quality by improving texture and reducing thawing (up to 25 %) and cooking loss (up to 30 %). Our findings suggest that NFB combined with ultrasound can enhance quality of aquatic products, intended for long-distance distribution and storage.

Insight into the mechanism of gel properties, microstructure and flavor of surimi gels improved by wheat bran with different particle sizes

This study investigated the effect of wheat bran (WB) with different particle sizes (W1, 155.00 ± 2.08 μm; W2, 78.33 ± 0.52 μm; W3, 46.90 ± 0.60 μm; W4, 23.53 ± 0.49 μm; and W5, 12.97 ± 0.19 μm) on the gel strength, texture, microstructure, dynamic rheological, secondary structures and flavor of surimi gels. Results demonstrated that the gel strength and water-holding capacity (WHC) of the surimi gels gradually increased with the decrease in WB particle size. The added W5 (12.97 ± 0.19 μm) increased the bound water content in the surimi gels by 12.60 % whereas the free water decreased by 6.59 % (p < 0.05), indicating that the addition of superfine WB contributed to the conversion of free water into bound water in the surimi gels matrices. Microstructural observations indicated that WB with different particle sizes promoted the formation of a continuous gel matrix and a denser surimi gel network structure. The β-sheet dominated in the secondary structure of surimi gels. Electronic tongue results showed that the addition of WB reduced the bitterness of surimi gels. Gas chromatography-ion mobility spectrometry (GC-IMS) results revealed that more esters were present in the samples when W1, W2, and W3 were added. Overall, W5 had the best enhancement effect on the quality of surimi gels, and this study lays the reference value for WB as an agricultural by-product to improve the quality of surimi products.

Effects of chopping and salting on the properties of pre-rigor silver carp muscle: Metabolic process, protein functionality, and ultrastructure

Chopping and salting are two important processing steps in emulsified meat products. Effects of chopping and salting on metabolic process, protein functionality, and ultrastructure of pre-rigor silver carp muscle, and how these three aspects changed during rigor transformation were explored. Chopping caused an accelerated loss of adenosine triphosphate (ATP) from 1.16 μmol/g to 0.16 μmol/g, and salt addition inhibited accumulation of hypoxanthine nucleoside (HxR) and hypoxanthine (Hx). Similarly, chopping led to faster decrease of glycogen from 4.59 mg/g to 1.50 mg/g and increase in lactic acid from 0.52 mmol/g protein to 0.82 mmol/g protein, and salt exerted an inhibition effect. In agreement with ATP and glycogen breakdown, metabolic profiling revealed that chopping and salting altered the metabolism in fatty acids and amino acids during rigor transformation. After rigor transformation, chopping with salt led to significant reduction in radical scavenging ability, accompanied by greater loss of sulfhydryl groups. Salt also promoted protein denaturation, evidenced by increased surface hydrophobicity and decreased intrinsic fluorescence. The ultrastructure of fish muscle after chopping or chopping with salt was similar between pre- and post-rigor stages. The abovementioned findings can provide valuable insight into the production of fish products.

Synergistic cryoprotective effects of mannan oligosaccharides and curdlan on the grass carp surimi

The cryoprotective effects of mannan oligosaccharides (MOS) and curdlan (CU) on the quality of grass carp surimi after freeze-thaw cycles (FTCs) were assessed using the response surface methodology. The optimal contents of MOS (6.79 %, w/w) and CU (0.45 %, w/w) produced minimum thawing losses and the highest gel strength of surimi after five times FTCs. MOS, CU, and their mixture demonstrated cryoprotective effects on grass carp surimi. Compared to MOS or CU alone, MOS-CU displayed synergistic cryoprotective effects, as evidenced by the better prevention of thawing losses of surimi, the superior retardation of the aggregation and denaturation of MP, the amelioration of the gel strength and WHC of surimi gel. Moreover, the MOS-CU mixture demonstrated cryoprotective effects equivalent to those of commercial cryoprotectant on grass carp surimi from zero to five times FTCs and even outperformed CC after seven times FTCs.

Proteomic analysis revealed the deterioration of surimi gelling capability to fish stress during transportation

Live silver carp with various transportation durations (3 h, 6 h, 12 h and 24 h) was processed into surimi. Proteomics and other technical methods were applied to investigate the changes in protein composition and structure aiming to explore the mechanism through which transportation stress affects gelling capability of surimi. As the transportation time was prolonged from 3 to 24 h, the gel strength of surimi gel decreased by 28.97 %, and the whiteness value decreased significantly (p < 0.05). Moreover, malondialdehyde content in fish serum and surface hydrophobicity of surimi also increased significantly (p < 0.05), suggesting that oxidation induced protein unfolding. Proteomic analysis identified eleven significantly differential proteins in the samples after 24 h of transportation compared to those transported for 3 h. Notably, the expression levels of myosin heavy chain and glutathione peroxidase were significantly down-regulated. Additionally, the PI3K-Akt signaling pathway was activated. Prolonged transportation time resulted in a looser microstructure of surimi gels, increased free water content and uneven water distribution. These results indicated that the altered properties of surimi gel due to transportation stress are primarily related to oxidative stress which leads to oxidative denaturation of proteins and the degradation of myosin.

Cryoprotective effects and mechanisms of soybean oligosaccharides on the grass carp (Ctenopharyngodon idellus) surimi during frozen storage

BACKGROUND

Conventional cryoprotectant mixtures (sucrose and sorbitol) impart excessive sweetness and calories to surimi. Therefore, there is a need to explore alternative cryoprotectants with low sweetness and low-calorie content. The cryoprotective effects and possible mechanisms of soybean oligosaccharides (SBOS) on the frozen stability of grass carp (Ctenopharyngodon idellus) surimi were investigated during 120 days of frozen storage in a comparison with commercial cryoprotectants (4% sucrose and 4% sorbitol, w/w).

RESULTS

SBOS at 6-8% (w/w) and commercial cryoprotectants could restrain water mobility and reduce thawing loss of frozen surimi by increasing non-freezable water content. SBOS could maintain the structural stability of proteins by preventing sulfhydryl groups from being rapidly oxidized to disulfide bonds, retarding the reduction of the solubility, Ca2+-ATPase activity and α-helix content of myofibrillar proteins (MP), as well as hindering the increasing surface hydrophobicity of MP of surimi during 120 days of frozen storage. The introduction of SBOS increased the gel strength and water-holding capacity of frozen-stored surimi. Compared with commercial cryoprotectants, 8% SBOS was more effective in stabilizing protein structure, whereas it was slightly less effective with respect to ice-forming inhibition.

CONCLUSION

The results obtained in the present study suggest that 8% SBOS could be potentially developed as a new cryoprotectant for surimi as a result of its ice-forming inhibition abilities and protein structure stability. © 2024 Society of Chemical Industry.

Various factors affecting the gel properties of surimi: A review

As an important aquatic prepared food, surimi products are favored by consumers due to their unique viscoelastic properties and high nutritional value. Gel properties are the main indicators to measure the quality of surimi products. The gelation of surimi mainly involves intramolecular (conformational change) and intermolecular (chemical force) changes. Factors such as processing treatments, raw fish species and exogenous additives affect surimi protein structure, chemical forces and endogenous enzyme activities, which further affect the gel properties of surimi products. This review focuses on the mechanism of surimi heat-induced gel, mainly including protein chain expansion and aggregation through various chemical forces to form a three-dimensional network structure. In addition, the mechanism and application of different factors on the gel properties of surimi were also discussed, providing a reference for the selection of fish species, the control of heating conditions in the gel process of surimi products, the selection of additives and other measures to improve the gel performance.

Study on the effect and mechanism of chicken breast on the gel properties of silver carp (Hypophthalmichtys molitrix) surimi

BACKGROUND

Adding appropriate exogenous substances is an effective means to improve the quality of freshwater fish surimi. The present study investigated the effects of chicken breast on the gel properties of mixed minced meat products.

RESULTS

With the increase in the proportion of chicken breast, the breaking force of mixed gels gradually increased. When the addition ratio was 30:70, the gel strength of mixed gels had the highest strength of 759.00 g cm-1 and also the highest water holding capacity of 87.36%. Compared with surimi gels (0:100), the hardness, adhesiveness and chewiness of mixed gels were significantly improved. The increase in the proportion of chicken breast increased the thermal stability of the mixed sol and improved the rheological properties of the mixed sol. When the proportion was 40:60, the area of immobile water (A22 ) in the mixed gel increased significantly, and the highest A22 was 3463.24. The hydrophobic interactions and disulfide bonds in the mixed gel were significantly increased as a result of the addition of chicken breast. The results of microstructure, electrophoresis and Raman spectroscopy indicated that the addition of chicken breast promoted the cross-linking of the proteins in mixed gels, which facilitated the transformation of the protein secondary structure from α-helical to β-folded structure, thus forming a more uniform and orderly network structure.

CONCLUSION

These results suggest that improving the gel properties of silver carp surimi by use of chicken breast has practical implications for the development of new blended products for surimi processing. © 2023 Society of Chemical Industry.

Physicochemical and structural changes of myofibrillar proteins in muscle foods during thawing: Occurrence, consequences, evidence, and implications

Myofibrillar protein (MP) endows muscle foods with texture and important functional properties, such as water-holding capacity (WHC) and emulsifying and gel-forming abilities. However, thawing deteriorates the physicochemical and structural properties of MPs, significantly affecting the WHC, texture, flavor, and nutritional value of muscle foods. Thawing-induced physicochemical and structural changes in MPs need further investigation and consideration in the scientific development of muscle foods. In this study, we reviewed the literature for the thawing effects on the physicochemical and structural characters of MPs to identify potential associations between MPs and the quality of muscle-based foods. Physicochemical and structural changes of MPs in muscle foods occur because of physical changes during thawing and microenvironmental changes, including heat transfer and phase transformation, moisture activation and migration, microbial activation, and alterations in pH and ionic strength. These changes are not only essential inducements for changes in spatial conformation, surface hydrophobicity, solubility, Ca2+ -ATPase activity, intermolecular interaction, gel properties, and emulsifying properties of MPs but also factors causing MP oxidation, characterized by thiols, carbonyl compounds, free amino groups, dityrosine content, cross-linking, and MP aggregates. Additionally, the WHC, texture, flavor, and nutritional value of muscle foods are closely related to MPs. This review encourages additional work to explore the potential of tempering techniques, as well as the synergistic effects of traditional and innovative thawing technologies, in reducing the oxidation and denaturation of MPs and maintaining the quality of muscle foods.

Collagens for surimi gel fortification: Type-dependent effects and the difference between type I and type II

Surimi products have unsatisfactory gel properties. Hence, this study evaluates the effect of collagen-adding on surimi gel properties and provides the first observation results regarding collagen type influence. With higher water solubility and more charged amino acids than type II, collagen type I intertwines with surimi myofibrillar proteins better to induce higher exposure of protein functional domains, more sufficient conformational changes of myosin and greater formation of chemical forces among proteins. These enhancements accelerate the gelation rate, leading to a well-stabilized surimi gel. The collagen I-containing surimi gels show more compact structures with uniformly distributed smaller pores than those containing collagen II, thereby providing the final products with higher water holding capacity and better textural profiles. As such, the surimi gel fortification performance of collagen I and the well-elucidated collagen-myofibrillar protein interaction mechanism will guide the further exploitation of collagen as an effective additive in the food industry.

Properties of whey protein isolation/konjac glucomannan composite gels: Effects of deacetylation degrees

The effects of konjac glucomannan (KGM) with different deacetylation degrees (DDs) on the gel properties of whey protein isolate (WPI) were investigated. The appropriately deacetylated KGM (DDs in the range of 0-53.85 %) incorporated within WPI and formed relatively uniform compound gels, while excessive deacetylated KGM (DDs = 63.46 or 71.63 %) caused macroscopic precipitation and aggregation in WPI-KGM system. The water holding capacity of WPI-KGM gels decreased with the gradual increase of DDs, and the removal of acetyl groups reduced the whiteness of the composite gels. The hardness and chewiness of the composite gel tended to increase and subsequently decrease with the enhancement of DDs, and reached the maximum (244.15 and 148.88 g, respectively) at the DDs of 53.85 %. The rheological analysis indicated that rigid structured WPI-KGM gels could be formed when incorporated with moderately deacetylated KGM. The deacetylated KGM (DDs = 53.85 %) enhanced the hydrogen bond and disulfide bond within the mixed system, resulting in a more compact network structure of the composite gels. Moreover, deacetylated KGM particles might also reinforce the gel strength by the "filling effects". Overall, the gelation characteristics of the WPI-KGM system can be regulated by controlling the DDs of KGM.

Ultrasound combined with slightly acidic electrolyzed water thawing of mutton: Effects on physicochemical properties, oxidation and structure of myofibrillar protein

The effects of air thawing (AT), water immersion thawing (WT), microwave thawing (MT) and ultrasound combined with slightly acidic electrolyzed water thawing (UST) on the myofibrillar protein (MP) properties (surface hydrophobicity, solubility, turbidity, particle size and zeta potential), protein oxidation (carbonyl content and sulfhydryl content) and structure (primary, secondary and tertiary) of frozen mutton were investigated in comparison with fresh mutton (FM). The solubility and turbidity results showed that the MP properties were significantly improved in the UST treatment. UST treatment could effectively reduce the MP aggregation and enhance the stability, which was similar to the FM. In addition, UST treatment could effectively inhibit protein oxidation during thawing as well. The primary structure of MP was not damaged by the thawing methods. UST treatment could reduce the damage to MP secondary and tertiary structure during the thawing process compared to other thawing methods. Overall, the UST treatment had a positive influence in maintaining the MP properties by inhibiting protein oxidation and protecting protein structure.

Gel performance of surimi induced by various thermal technologies: A review

Heating is a vital step in the gelation of surimi. Conventional water bath heating (WB) has the advantages of easy operation and low equipment requirements. However, the slow heat penetration during WB may lead to poor gel formation or gels prone to deterioration, especially with one-step heating. The two-step WB is time-consuming, and a large amount of water used tends to cause environmental problems. This review focuses on key factors affecting the quality of surimi gels in various heating technologies, such as surimi protein structure, chemical forces, or the activity of endogenous enzymes. In addition, the relationships between these factors and the gel performance of surimi under various heating modes are discussed by analyzing the heating temperature and heating rate. Compared with WB, the gel performance can be improved by controlling the heating conditions of microwave heating and ohmic heating, which are mainly achieved by changing the molecular structure of myofibrillar proteins or the activity of endogenous enzymes in surimi. Nevertheless, the novel thermal technologies still face several limitations and further research is needed to realize large-scale industrial production. This review provides ideas and directions for developing heat-induced surimi products with excellent gel properties.

Effects of repeated deboning on structure, composition, and gelling properties of silver carp surimi

BACKGROUND

Surimi is produced from the various sequences of filleting, deboning, washing, dehydrating, blending with cryprotectant, and freezing. Deboning, after which fish flesh is minced and separated from bone, skin, etc., is a vital step in the surimi production. In this study, effects of repeated deboning on yield, structure, composition, and gelling properties of silver carp surimi were investigated.

RESULTS

Surimi yield increased rapidly from 10% to 23% as the cycle of repeated deboning was increased from one to three, and then slowly increased up to 26%. As the cycle increased, cellular structure and ultrastructure of muscle fibers progressively fractured. Contents of fat, cathepsins, heme proteins, and transglutaminase of surimi obviously increased and then decreased. Three-dimensional network of surimi gel without setting (NS gel) became more porous with the increase of cycles. It became more compact, and then turned to aggregated forms with lower homogeneity, for the surimi gel with setting (WS gel). Correspondently, the NS gel textural values gradually decreased with the cycles, while the WS gel textural values increased up to three cycles and then decreased. Regardless of setting, whiteness of surimi gels decreased and then increased with the cycles.

CONCLUSION

Our results suggested that structure and compositions of surimi changed with the cycle of repeated deboning, which affected gelling properties of surimi. It is recommended to debone three or four cycles in silver carp surimi production. © 2022 Society of Chemical Industry.

Study on the quality and myofibrillar protein structure of chicken breasts during thawing of ultrasound-assisted slightly acidic electrolyzed water (SAEW)

The effects of air thawing (AT), water thawing (WT), slightly acidic electrolyzed water (ET), ultrasound-assisted water thawing (WUT) and ultrasound-assisted slightly acidic electrolyzed water (EUT) on the quality and myofibrillar protein (MP) structure of chicken breasts were investigated. The results showed that WUT and EUT could significantly improve the thawing rate compared with AT, WT, and ET groups. The EUT group not only had lower thawing loss, but also their immobilized and free water contents were similar to fresh sample according to the low-field nuclear magnetic resonance (LF NMR) results. The EUT treatment had no adverse effect on the primary structure of the protein. The secondary and tertiary structures of MP were more stable in the EUT group according to Raman and fluorescence spectra. The muscle fibers microstructure from EUT group was neater and more compact compared with other thawing methods. Therefore, EUT treatment could be considered as a novel potential thawing method in the food industry.

Thermal aggregation behavior of egg white protein and blue round scad (Decapterus maruadsi) myofibrillar protein

In the present study, egg white protein (EWP) and myofibrillar protein (MP) were mixed in different ratios (0/100, 10/90, 20/80, 30/70, 40/60, 50/50, 100/0 for EWP/MP) and subjected to unheated, preheated (40°C/30 min), two-step heated (40°C/30 min, 90°C/20 min), and one-step heated (90°C/20 min) treatments to study the thermal aggregation of the two proteins. Their aggregation behavior was characterized by turbidity, active sulfhydryl, degree of protein cross-linking, protein characteristic spectra, and microscopic morphology. The results indicated that for the mixed protein system composed of EWP and MP, the mixed protein aggregation volume was larger and regular at an EWP/MP of 30/70, when the degree of cross-linking was best. When the ratio of EWP/MP was 50/50, the aggregate-protein interaction was dominant, and the excess EWP acted as a barrier to cross-linking and wrapped around the surface of the aggregates to form larger aggregates. Comparing the two-step heated and one-step heated conditions, the former is superior. PRACTICAL APPLICATION: The combination of egg white protein and myofibrillar protein can provide a theoretical reference for the protein content in surimi products, and moderate addition has an enhancing effect on surimi protein cross-linking and promotes gel formation. Excessive addition will form aggregates outside the egg white protein wrapping phenomenon, and the quality of surimi gel products will be affected.

Ultrasound treatment can increase digestibility of myofibrillar protein of pork with modified atmosphere packaging

We explored whether ultrasound treatment affected digestibility of myofibrillar protein (MP) isolated from modified atmosphere packed (MAP, 70% N₂ and 30% CO₂) pork. MP digestibility under pepsin and pancreatin treatments decreased significantly with storage time. Ultrasound treatment increased the digestibility and produced a greater number of smaller peptides. However, the total peptide count and unique peptide counts were significantly reduced. Moreover, active sulfhydryl, total sulfhydryl, particle size, turbidity and surface hydrophobicity of MP increased with time, while protein solubility and ATPase activity decreased. Compared with the untreated samples, ultrasound treatment increased protein solubility, surface hydrophobicity, and active sulfhydryl content, but decreased total sulfhydryl content (except 10 d), particle sizes, turbidity and ATPase activity. Ultrasound treatment resulted in a decline in β-turn and α-helix contents. Therefore, ultrasound is conducive to the digestion. Additionally, structural and functional properties of protein in MAP were less stable than those in vacuum-packed pork reported before.

Cryoprotective Roles of Carboxymethyl Chitosan during the Frozen Storage of Surimi: Protein Structures, Gel Behaviors and Edible Qualities

Carboxymethyl chitosan (CMCh) is an ampholytic chitosan derivative that manifests versatile applications in food industry, such as antibacterial ingredients and nutritional additives. However, its use as a cryoprotectant remains under-researched. In this study, the cryoprotective effect of CMCh oligosaccharide (CMCO) on frozen surimi (silver carp) was systematically investigated in terms of protein structures, gelling behaviors, and sensory qualities. CMCO (0.6%) was incorporated in the surimi before frozen storage (-18 °C for 60 days) while the commercial cryoprotectant (4% sucrose, 4% sorbitol) was used as a positive control. Results indicated that CMCO could inhibit the freezing-induced denaturation of myofibrillar protein, whose values of solubility, Ca2+-ATPase and sulfhydryl content were 24.8%, 64.7%, and 17.1% higher than the nonprotected sample, respectively, while the surface hydrophobicity was 21.6% lower. Accordingly, CMCO stabilized microstructure of the surimi gels associated with improved gel strength, viscoelasticity, water-holding capacities, and whiteness. Moreover, the cryoprotective effect of CMCO with higher degree of carboxymethyl substitution (DS: 1.2) was more pronounced than that of low-DS-CMCO (DS: 0.8). Frozen surimi treated with high-DS-CMCO achieved competitive gelling properties and sensory acceptability to those with the commercial counterpart. This study provided scientific insights into the development of ampholytic oligosaccharides as food cryoprotectants.

Influence of the Mixture of Carrageenan Oligosaccharides and Egg White Protein on the Gelation Properties of Culter alburnus Myofibrillar Protein under Repeated Freezing-Thawing Cycles

This study aims to investigate the influence of the mixture (CGO/EWP) of carrageenan oligosaccharide (CGO) and egg white protein (EWP) (CGO/EWP, CGO: EWP = 1:1, m/m) on the functional, structural, and gelling properties of Culter alburnus myofibrillar protein (MP) during repeated freezing-thawing cycles by treating MP samples separately with EWP, CGO, or CGO/EWP based on the wet weight (1%, m/m), using samples without any cryoprotectant as the blank group. After the second repeated freezing-thawing cycle, the sulfhydryl group content was found to be significantly (p < 0.05) higher in the CGO/EWP (30.57 nmol/mg) and CGO (36.14 nmol/mg) groups than in the EWP group (23.80 nmol/mg), indicating that CGO/EWP and CGO can more effectively delay the oxidative deterioration of functional groups. Additionally, the surface hydrophobicity was shown to be significantly lower in the CGO (25.74) and CGO/EWP (27.46) groups than in the EWP (34.66) and blank (39.32) groups. Moreover, the α-helix content was higher in the CGO (35.2%) and CGO/EWP (32.3%) groups than in the EWP (29.2%) and blank (25.0%) groups. These data indicated that CGO and CGO/EWP could more effectively increase the structural stability, thereby inhibiting the exposure of hydrophobic groups and curbing the decline of α-helix content. During the heat-induced gel-forming process, EWP and CGO/EWP could enhance the gel viscoelasticity and strength. After the second freezing-thawing cycle, when compared with the blank group, the CGO/EWP group showed significantly (p < 0.05) higher water-holding capacity (66.30% versus 53.93%) and shorter T22 relaxation time (413.56 versus 474.99 ms). The integrated results indicated that CGO/EWP could more effectively delay the decrease of protein-water molecular interaction forces in the MP gel. This study shed light on the mechanism of CGO/EWP as a cryoprotective mixture in improving the deterioration of MP gelation properties during repeated freezing-thawing cycles.

Gelling properties of silver carp surimi incorporated with konjac glucomannan: Effects of deacetylation degree

Effects of konjac glucomannan (KGM) with different deacetylation degrees on silver carp surimi gel properties were studied. As deacetylation degree increased, viscosity, solubility, and water absorption capability of KGM decreased gradually while particle size increased. The gel strength of surimi gel increased with the KGM deacetylation degree up to 50.72% and then significantly decreased. The maximum gel strength was 3.26 times higher than that of surimi gel with native KGM. The relaxation time of immobilized water decreased from 108.22 to 104.70 ms and then increased up to 110.92 ms with the deacetylation degree, while the proportion of the immobilized water increased from 92.74 to 98.59% and then decreased to 97.46%. Water distribution became less uniform as the deacetylation degree exceeded 50.72%. Surimi gel with KGM of a higher deacetylation degree formed a denser microstructure along with a higher dimensional fraction value. However, the microstructure was disrupted and the dimensional fraction value decreased as the deacetylation degree exceeded 50.72%. Chemical interactions including hydrogen bonds, hydrophobic interactions, and cross-linking extent increased with the KGM deacetylation degree up to 50.72% and then gradually decreased. The results suggest that KGM with a deacetylation degree of 50.72% is the most suitable for surimi products.

Ultrasonic treatment increased functional properties and in vitro digestion of actomyosin complex during meat storage

We investigated the effects of ultrasonic treatment (400 W, 20 kHz, 45.52 W/L) and storage time (0 d, 3 d, 7 d and 10 d) on functional properties, structural changes and in vitro digestion of actomyosin complex isolated from vacuum-packed pork. As storage time increased, turbidity, surface hydrophobicity, active sulfhydryl and total sulfhydryl of actomyosin complex increased, while protein solubility decreased. Ultrasonic treatment increased surface hydrophobicity, protein solubility and active sulfhydryl content but decreased turbidity and total sulfhydryl content compared with the control. Ultrasonic treatment caused a reduction in α-helix content on 0 day and the fluorescence intensity of tryptophan and tyrosine residues. It increased pancreatin digestibility of actomyosin complex and the number of peptides of smaller than 1 kDa. However, it decreased the number of peptides. The findings provide a new insight into the application of appropriate ultrasonic treatment to promote meat digestibility.

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.

Effects of Vacuum Freeze-Drying and Vacuum Spray-Drying on Biochemical Properties and Functionalities of Myofibrillar Proteins from Silver Carp

Fish protein powders were produced from silver carp myofibrillar proteins using vacuum freeze-drying and vacuum spray-drying. Biochemical properties and functionalities of freeze-dried and spray-dried powders were determined. The myofibrillar proteins were partially denatured under both the drying methods which were evidenced by the increase of free sulfhydryl content, surface hydrophobicity, and intrinsic fluorescence while the decrease of the Ca2+-ATPase activity and percentage of theα-helical structure. With respect to vacuum freeze-drying, the proteins were denatured to a higher degree by vacuum spray-drying. The spray-dried fish protein powder showed a higher water retention capacity and emulsifying stability index, but the same solubility and emulsifying activity index. The micrographs indicate that vacuum freeze-dried powder formed a spongy structure, while the powder under vacuum spray-drying mostly appeared spherical in shape with hollow inside. Thus, the two drying methods can be used to manufacture fish protein powders with varied molecular structures and functionalities.