Effects of radio frequency heating on water distribution and structural properties of grass carp myofibrillar protein gel

Factors influencing surimi gelling properties and natural additive-based gel fortification strategies: A review

Gelation and gel properties are crucial to surimi-based seafood products, and many factors significantly influence surimi gel quality. Although physical and chemical modifications can improve surimi gel performance, challenges such as high cost, difficulties in industrialization and environmental pollution pose significant barriers to their practicality. Natural additives offer a promising alternative by reinforcing and improving the characteristics of surimi gel through mechanisms such as protein conformational transformation, protein denaturation, and altered chemical forces. By incorporating different substances into surimi gel, it is possible to tune the interaction between the additives and the myofibrillar proteins, thus enhancing the gelation process and achieving the desired textural profiles. This review comprehensively explored the factors influencing the surimi gelation chemistry, with a focus on how the natural additives such as proteins, lipids, polysaccharides, salts, enzymes, and extracts impact the surimi gel properties. It elucidated the reinforcing mechanisms of these additives and proposed a general interaction model between natural substance and myofibrillar proteins. Furthermore, this review well established the interrelation between the performance and mechanism of enhancement effects of typical natural substances on surimi gels and provided new insights on tuning surimi gelation and gel properties by adding natural additives with specific physicochemical properties, thus facilitating the production of high-quality surimi products with satisfactory gel characteristics in food industry.

Effects of Carbon Dots/PVA Film Combined with Radio Frequency Treatment on Storage Quality of Fried Meatballs

The combination of carbon dots/polyvinyl alcohol (CDs/PVA) active film and radio frequency (RF) was performed to improve the storage quality of fried meatball samples. The microbicidal effect of RF, and the antioxidant and antibacterial activities of CDs/PVA film were investigated. The CDs/PVA film can effectively restrain the growth of B. subtilis, S. aureus, and E. coli, and eliminate DPPH and ABTS free radicals. RF exerts inhibitory effects on C. albicans, B. subtilis, and E. coli. For meatball samples, CDs/PVA+RF20 can extend the refrigerated shelf life from 2 w to 6 w. At the sixth week, the total bacterial count (TBC) in CDs/PVA+RF20 group (3.72 log CFU/g) was remarkably lower than those in polyethylene terephthalate (PET) group (7.78 log CFU/g) and CDs/PVA (6.41 log CFU/g) group. CDs/PVA+RF20 can also inhibit the increase in TBARS and POV values. The results manifest the feasibility of CDs/PVA+RF as a novel mild pasteurization or preservation technology.

Abelmoschus manihot gum improves the water retention capacity of low-salt myofibrillar protein gels: Perspective on aggregation behaviour and conformational changes during heating

This study aimed to investigate the effect of Abelmoschus manihot gum (AMG) on the water retention capacity of low-salt myofibrillar protein (MP) gel by analysing its aggregation behaviour and conformational changes during heating (30-80 °C). The results revealed that AMG significantly increased the water holding capacity and facilitated the formation of a more uniform gel network structure in low-salt MP gel (P < 0.05). During the heat-induced gelation process, the solubility of low-salt MP significantly decreased, whereas its turbidity evidently increased as the level of added AMG increased (P < 0.05). Furthermore, the dynamic rheological behaviours indicated that low-salt MP-AMG gels underwent early denaturation and unfolded at 58 °C, finally forming an irreversible three-dimensional network at 80 °C. Moreover, adding AMG promoted α-helix-to-β-sheet transition in low-salt MP and decreased its fluorescence intensity during the heating process. Hydrophobic interactions and disulfide bonds were the two dominant forces governing the formation and maintenance of low-salt MP gel. The present study provides theoretical guidance for the production of novel low-salt healthy meat products.

Effects of emerging food pretreatment and drying techniques on protein structures, functional and nutritional properties: An updated review

Protein is one of the most important components of food which significantly contributes to the structure, functionality, and sensory properties which may affect consumer acceptability of processed products. Conventional thermal processing affects protein structure and induce undesirable degradation of food quality. This review provides an overview of emerging pretreatment and drying technologies (plasma treatment, ultrasound treatment, electrohydrodynamic, radio frequency, microwave, and superheated steam drying) in food processing by assessing protein structural changes to enhance functional and nutritional properties. In addition, mechanisms and principles of these modern technologies are described while challenges and opportunities for the development of these techniques in the drying process are also critically analyzed. Plasma discharges can lead to oxidative reactions and cross-linking of proteins that can change the structure of proteins. Microwave heating contributes to the occurrence of isopeptide or disulfide bonds which promotes α-helix and β-turn formation. These emerging technologies can be adopted to improve protein surface by exposing more hydrophobic groups which restrict water interaction. It is expected that these innovative processing technologies should become a preferred choice in the food industry for better food quality. Moreover, there are some limitations for industrial scale application of these emerging technologies that need to be addressed.

Properties of co-gel between Tenebrio Molitor larvae protein and myofibrillar protein induced by transglutaminase

This study explored the effect of adding transglutaminase (TGase) to a co-gel of Tenebrio Molitor larvae protein (TMLP) and myofibrillar protein (MP). Different concentrations of TGase (0-90 U/g) were added to the co-gel. The results showed that 60 U/g TGase treatment significantly improved the gel strength and water holding capacity (WHC) by 26.51 g and 9.2 %, respectively. TGase promoted the rheological properties and accelerated the three-dimensional network structure of the co-gel. Moreover, TGase significantly increased (P < 0.05) the tyrosine residues, tryptophan residues content and hydrophobic interactions of the aliphatic groups. The chemical forces between the protein molecules changed. TGase promoted the transition of α-helix to β-sheet and free water to immobilized water, thereby improving the WHC of co-gel. The principal component analysis reflected the links among indicators. This study illustrated that TGase might be an effective strategy to improve the co-gel of TMLP and MP and emulsified meat products with insects.

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.

Evaluating the effect of thermo-reversible and thermo-irreversible curdlan gels on the gelling properties and in vitro digestibility of myofibrillar protein gels under low-salt condition

The purpose of the present study was to investigate the gelling properties and in vitro digestibility of myofibrillar protein (MP) gels under low-salt condition as mediated by different concentrations of thermo-reversible curdlan gels (TRC) or thermo-irreversible curdlan gels (TIRC). The results showed that the incorporation of TRC or TIRC obviously improved the gel strength and water holding capacity of MP gels (P < 0.05). Those properties were most improved by adding 0.3 % TRC or TIRC with gel strength of 0.18 N or 0.17 N and WHC of 54.85 % or 49.05 %. Meanwhile, both TRC and TIRC promoted the transformation of α-helix into β-sheet, as well as hydrophobic interactions and disulfide bonds, which are the main forces for the maintenance of the MP gels. The microstructure revealed that the formation of dense and uniform protein network structures can be promoted by the addition of TRC or TIRC. The different modes of interaction between TRC or TIRC and MP resulted in different microstructures of the MP gels. Furthermore, incorporation of TRC or TIRC significantly reduced in vitro protein digestibility, especially for the 0.3 % (w/w) form (P < 0.05). Meanwhile, MP gels had the lowest in vitro protein digestibility after the addition of TRC (66.67 %) compared to the form of TIRC (70.93 %). Therefore, our present study indicated that incorporation form of TRC or TIRC have distinct implications on regulating the gelling properties and in vitro digestibility of MP gels under low-salt condition.

From amino acid analysis to improved gel properties: The role of dl-valine in Landaise goose myofibrillar protein

The impact of exogenous limiting amino acids on protein gel formation was investigated to enhance the gelation properties of Landaise goose myofibrillar protein (MP). Amino acid composition and gel properties were analyzed, and homologous protein modeling and molecular docking techniques were used to simulate binding sites. Valine was identified as the first limiting amino acid. The addition of 0.075 % dl-valine proved optimal to enhance the gel strength (59.5 g) and water retention (76.76 %) of MP gels. Hydrophobic interactions and disulfide bonds were found to be the main forces maintaining conformational stability of the MP-dl-valine gels. The propyl group of dl-valine can form hydrophobic interactions with protein, contributing to stable complexes. DL valine could also strengthen chemical bonds and secondary structure, convert free water to immobile water, and improve the microstructure of the gel. Therefore, valine can be utilized as a nutritional and gel enhancer in Landaise goose meat products.

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.

Effects of eugenol on the structure and gelling properties of myofibrillar proteins under hydroxyl radical-induced oxidative stress

The effects of eugenol (EG; 0, 5, 20, and 50 mg/g protein) on the structure and gel properties of pork myofibrillar protein (MPs) under a hydroxyl radical-generating system were explored in this study. The results revealed that the addition of a high concentration of EG (50 mg/g protein) markedly reduced the carbonyl content and enhanced the fluorescence intensity, surface hydrophobicity, and protected the secondary structure of MPs, compared to oxidized MPs. In addition, the high concentration group noticeably increased the storage modulus (G'), gel strength, and water-holding capacity (WHC), and significantly hindered the oxidation-induced transformation of immobilized water of the MPs gel to free water and basically favored the formation of a finer and more homogeneous three-dimensional network structure, This work verified that the adding of EG could effectively improve the gel quality of oxidized MPs and more successfully delay oxidation-induced damage to muscle protein structure.

Insoluble dietary fibers from Lentinus edodes stipes improve the gel properties of pork myofibrillar protein: A water distribution, microstructure and intermolecular interactions study

This paper investigated the effects of Lentinus edodes stipes insoluble dietary fiber (LESIDF, 0%-3.0%) on the quality and microscopic properties of pork myofibrillar protein (MP) gels. The results showed that the water holding capacity and gel strength of composite gels enhanced with increasing LESIDF (1.0%-2.5%), and reached the maximum at the level of 2.5%-3.0%. Disulfide and non-disulfide covalent bonds were major chemical forces maintaining the 3D network of LESIDF-MP composite gels. LESIDF also promoted the formation of ionic and hydrogen bonds, confirmed by the self-assembly of β-sheets to α-helices, leading to a compact gel network structure. The observation of paraffin section revealed that LESIDF could capture more water molecules in gels, which was consistent with the transformation of free water to immobilized water. Overall, the optimal addition of LESIDF was 2.5%-3.0%, which provided a good strategy for LESIDF as an agricultural by-product to improve the quality of gel meat products.

Ultrasound-assisted processing: Changes in gel properties, water-holding capacity, and protein aggregation of low-salt Hypophthalmichthys molitrix surimi by soy protein isolate

The effects of ultrasound combined (25 kHz, 400 ± 20 W/L, ultrasonic time of 5, 10 and 15 min) with soy protein isolate processing on gelling properties of low-salt silver carp surimi, aggregation and conformation of myofibrillar protein were investigated. The results revealed that, compared with only adding soy protein isolate components, ultrasound-assisted soy protein isolate had a more obvious effect on the protein structure in low-salt surimi, leading to the decrease in α-helix and total sulfhydryl contents, and the increase in β-sheet content and protein solubility. As a result, more proteins participated in the formation of the gel network, and significant improvements in hardness, gel strength and water-holding capacity of the low-salt surimi gel were observed, while the myosin heavy chain in SDS-PAGE was weakened. The low-field NMR results showed that the initial relaxation time of T₂ was apparently shorter, the free water content decreased and the bound water content increased under the action of ultrasound. Scanning electron microscope observation found that the surimi gel treated by ultrasound exhibited smaller holes, and had a more stable and denser network structure. In conclusion, the results of our work demonstrated that ultrasound combined with soy protein isolate can significantly improve the gel quality properties of low-salt silver carp.

Interaction between Kidney-Bean Polysaccharides and Duck Myofibrillar Protein as Affected by Ultrasonication: Effects on Gel Properties and Structure

The interaction of polysaccharides-protein with varied origins and structures provides opportunities for tailoring the physicochemical qualities of food protein-based materials. This work examined the feasibility of ultrasound-modified interaction between kidney bean dietary fiber (KSDF) and duck myofibrillar proteins (MP) to improve the physicochemical properties of the gel matrices. Accordingly, gel strength, water holding capacity, solubility, chemical interaction, secondary structure, and network structure of MP were determined. The addition of KSDF combined with the ultrasound treatment contributed to the improved water retention capability, G' values, and the reduced particle size of protein molecules, corresponding with the formation of dense pore-like structures. The results demonstrated that 1% KSDF and ultrasonication at 400 W significantly enhanced gel strength by up to 109.58% and the solubility increased by 213.42%. The proportion of α-helices of MP gels treated with 1% KSDF and ultrasonication at 400 W was significantly increased. The sonication-mediated KSDF-MP interaction significantly improved hydrophobic interactions of the proteins, thus explaining the denser network structure of the MP gels incorporated KSDF with ultrasound treatments. These results demonstrated the role of ultrasonication treatments in modifying KSDF-protein interaction to improve the gel and structural properties of the MP gels.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

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.

Analysis of Water Distribution and Muscle Quality of Silver Carp (Hypophthalmichthys molitrix) Chunks Based on Electron-Beam Irradiation

Electron-beam irradiation (EBI) is an efficient, safe, and nonthermal sterilization technique that is extensively used in food preservation research. Here we report the effects of different EBI doses (0, 4, 8 kGy) and preservation temperatures (room temperature [RT], 4 °C) on the muscle water distribution and muscle quality indices of silver carp chunks (SCCs). The highest entrapped water content was found in the 4-kGy-irradiated/4-°C-stored samples. The expressible moisture content (EMC) of the SCCs increased with increasing irradiation dose and was significantly lower in the RT group than in the 4 °C group. The irradiation dose and preservation temperature had no significant effect on the moisture content, whiteness value and protein content of SCCs (p > 0.05). When the irradiation dose reached 8 kGy, AV value, POV value and TVB value were significantly increased (p < 0.05). The myofibrillar protein content and actomyosin content of the SCCs in the 4 °C group was higher than that of the specimens in the RT group by 0.29−0.98 mg/mL (p < 0.05) and 36.21−296.58 μg/mL (p < 0.05), respectively. Overall, EBI treatment (4 kGy) and low-temperature preservation (4 °C) helped retain the muscle water content of the SCCs and preserve their quality, thereby endorsing the EBI treatment of silver carp products.

Asian Carp, an Alternative Material for Surimi Production: Progress and Future

Asian carp is a general designation for grass carp, silver carp, bighead carp, and black carp. These fish species belong to the family Cyprinidae. In 2018, more than 18.5 million tons of Asian carp were produced globally. Asian carp can be used for producing surimi, a stabilized myofibrillar protein concentrate that can be made into a wide variety of products such as imitation crab sticks, fish balls, fish cakes, fish tofu, and fish sausage. Surimi is usually made from marine fish, but Asian carp have been widely used for surimi production in China. The quality of surimi is affected by various factors, including the processing methods and food additives, such as polysaccharides, protein, salt, and cryoprotectant. With an impending shortage of marine fish due to overfishing and depletion of fish stocks, Asian carp have a potential to serve as an alternative raw material for surimi products thanks to their high abundancy, less emissions of greenhouse gases from farming, desirable flesh color, and sufficient gel forming ability. The utilization of Asian carp in surimi production could also contribute to relieving the overflow of Asian carp in the United States.

Relationship between Molecular Structure and Heat-Induced Gel Properties of Duck Myofibrillar Proteins Affected by the Addition of Pea Protein Isolate

This paper investigates the relationship between the molecular structure and thermally induced gel properties of duck myofibrillar protein isolate (DMPI) as influenced by the addition of pea protein isolate (PPI). The results showed that b* value of the gels increased; however, a* value decreased with the increase of PPI content (p < 0.05). The whiteness of the gels decreased significantly with the addition of pea protein compared with 0% vs. 0.5% addition. Nuclear magnetic resonance tests showed the area of immobilized water also increased with increasing PPI addition (0−2%), thus consistent with the increased water-holding capacity (p < 0.05). The penetration force of the gels increased with increasing PPI addition (p < 0.05), while the storage modulus and loss modulus of the gels were also found to increase, accompanied by the transformation of the α-helix structure into β-sheet, resulting in better dynamics of gel formation. These results indicated the gel-forming ability of DMPI, including water retention and textural properties, improves with increasing PPI addition. Principal component analysis verified these interrelationships. Thus, pea protein could improve the properties of duck myofibrillar protein gels to some extent and improve their microstructure, potentially facilitating the transition from a weak to a non-aggregated, rigid structure.