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To provide an insight into the oxidation behavior of cysteines in myofibrillar proteins (MPs) during microwave heating (MW), a quantitative redox proteomic analysis based on the isobaric iodoacetyl tandem mass tag technology was applied in this study. MPs from silver carp muscles were subjected to MW and water bath heating (WB) with the same time-temperature profiles to eliminate the thermal differences caused by an uneven energy input. Altogether, 422 proteins were found to be differentially expressed after thermal treatments as compared to that with no heat treatment. However, MW triggered a larger number of proteins and cysteine sites for oxidation. Myosin heavy chain, myosin-binding protein C, nebulin, α-actinin-3-like, and titin were found to be highly susceptible to oxidation under microwave irradiation. Notably, MW caused such modifications at cysteine site 9 in the head of myosin, revealing the enhancement mechanism of MP gelation by excess cysteine cross-linking during microwave processing. Furthermore, Gene Ontology and functional enrichment analyses suggested that the two thermal treatments resulted in some differences in ion binding, muscle cell development, and protein-containing complex assembly. Overall, this study is the first to report the redox proteomic changes caused by MW and WB treatments, thus providing a further understanding of the microwave-induced oxidative modifications of MPs.

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.

The aim of this work was to investigate the role of microwave on myosin aggregation during different heating process and to explore the potential relationship between conformation changes and physicochemical properties of myosin. Microwave heating lead to the increasing of turbidity of myosin, but this result was largely influenced by the temperature. Surface hydrophobicity were the dominant binding forces in the formation of myosin aggregation. However, the disulfide bonds play a much more important role in the protein aggregation forming in heat treatment at 60 and 90 °C. Circular dichroism revealed that microwave heating considerably altered the secondary structure of myosin. The gradual disappearance of negative peaks at 202 and 222 nm indicated that a significant decrease in α-helix formation. Particle size distribution and atomic force microscopy analyses demonstrated a more rapid myosin aggregation in response to the microwave treatment at 60 and 90 °C. These results helps to better understand the gel formation mechanism of surimi under microwave field and to improve myosin-based food quality by using microwave treatment.

With the aging problems increasing, the discovery of anti-aging compounds has become a popular research direction. Accumulation of free radicals and the consequent oxidative stress are the chief culprit of aging. Given this, cultured crocodile meat peptides-Maillard reaction product (CMP-MRP) with remarkable antioxidant activity was obtained via Maillard reaction of cultured crocodile meat hydrolysates and xylose. The antioxidant activity in vitro and anti-aging activity in vivo of CMP-MRP were investigated. Results indicated that the lifespan and the athletic ability of Drosophila were significantly improved after the administration of CMP-MRP in natural aging, H2O2- and paraquat-induced models. Furthermore, the antioxidant enzyme activities of Drosophila treated with CMP-MRP were enhanced while the levels of malondialdehyde (MDA) and protein carbonyl (PCO) were reduced in three Drosophila models. With the supplement of 5 mg/mL CMP-MRP in natural aging Drosophila model, the maximum lifespan increased from 61 days to 73 days, athletic ability raised by 95.45%, MDA and PCO reduced by 52.72% and 47.43%, respectively. Taken together, CMP-MRP exhibited outstanding antioxidant and anti-aging capacities in Drosophila models, suggesting that CMP-MRP possesses great potential in the health food and biomedicine fields as a food-derived anti-aging agent.

This work was aimed to compare the effect of microwave (MW) heating on the cathepsin L (Cat L)-induced degradation of myofibrillar protein (MP) gels with that of water bath (WB) heating. First, Cat L from silver carp was purified and determined to be 45 kDa. The gel strength of the MW-heated MP gels were significantly higher than those of the WB-heated when Cat L was added (P 0.05). The gel electrophoresis pattern and scanning electron microscopy analysis indicated that MW heating inhibited the Cat l-induced hydrolysis of MP gels. In addition, the number of sulfhydryl groups and surface hydrophobicity of MW-heated gels were lower than those of WB-heated gels when Cat L was added. These results indicated that MW heating could effectively weaken the degradation of Cat L on MP gels by manipulating disulfide bonds and hydrophobic amino acids, resulting in good gel properties and a compact protein network.

Freezing technology is important for storage of animal products such as surimi. However, mechanical damage caused by ice crystals would lead to quality deterioration. This study aims to investigate the protective effect of antifreeze peptides (AFPs) on the quality of surimi during freezing storage and its possible mechanism. We found that AFPs exhibited a strong inhibition of ice crystal recrystallization, and the molecular weight ranged from 180 to 3000 Da. AFPs can prevent the degeneration of myofibrillar protein by reducing the loss of Ca2+-ATPase activity, slowing oxidation of sulfhydryl groups to disulfide bonds, and maintaining surface hydrophobicity and solubility of myofibrillar protein. Moreover, AFPs can reduce the influence of freezing stress on water mobility, thereby protecting the surimi from losing immobilized water and bound water during frozen storage. These findings indicate that AFPs could potentially serve as a food ingredient with antifreeze functional for the storage of surimi products.

Lactic acid bacteria as starter cultures can lead to rapid acidification for gel formation in fermented fish sausages. However, there is lack of study on the volatile flavor characteristics after starter culture addition and how they affect the microbial community on the flavor formation in fish sausages. In this work, the changes of volatile compounds and microbial community in the tilapia sausage during fermentation with Pediococcus pentosaceus were respectively studied by the headspace solid-phase microextraction gas chromatography-mass spectrometry and 16S rRNA gene high-throughput sequencing. A total of 83 volatile compounds were identified, among which 32 compounds were selected as the core volatile flavor compounds. The microbial diversity in the sausage significantly decreased as the fermentation time increased. There were 12 main microbial genera in whole fermentation stages. The anaerobes such as Pediococcus, Lactococcus, Enterobacter, and Citrobacter increased obviously after fermentation, especially for Pediococcus and Lactococcus, whose total abundance reached over 95% at the end of fermentation. The correlation network model showed that Pediococcus and Lactococcus contributed most to the volatile flavor formation, followed by Enterobacter, Citrobacter, and Photobacterium. This research provides an effective method to accelerate the volatile flavor formation and inhibit the spoilage microorganisms in the fermented tilapia sausage.

The aim of this study was to compare the physicochemical properties of chitosan prepared by microwave and water bath heating with an equivalent quantity of heat intake. The structure and physicochemical properties of the chitosan obtained by these two methods were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffractometry (XRD), gel permeation chromatography (GPC), and scanning electron microscopy (SEM). The FTIR and XRD patterns show that there was no significant difference in the structure of chitosan produced by the two heat sources. The results showed that chitosan with 73.86% deacetylation was successfully prepared by microwave heating within 60 min, while a longer time of 180 min was required for the preparation of chitosan with the same deacetylation degree (74.47%) using the conventional heating method under the same heating rate. Even under the same temperature conditions, microwave technology can greatly reduce the reaction time by approximately 1/3, while the chitosan produced by microwaves can obtain relatively low molecular weight and viscosity. These results showed that microwaves may efficiently promote complete chemical reactions by the friction heating mechanism generated by molecular vibration beyond a rapid heating source, turning into a more efficient, energy‐saving, and environmentally friendly method for the further use of rigid shrimp shells and highly crystalline crustacean materials., The physicochemical properties of chitosan prepared by microwave and water bath heating were compared with an equivalent quantity of heat intake. There was no significant difference in the structure of chitosan produced by the two heat sources. Microwave technology can greatly reduce the reaction time by approximately 1/3, while the chitosan produced by microwaves can obtain relatively low molecular weight and viscosity.

To improve the gelation performance of konjac glucomannan (KGM) thermo-irreversible gel in the condition of alkaline, this study investigated the interactions between KGM and curdlan (CUD) in terms of the sol state and gelation process. The apparent viscosity, rheological properties during heating and cooling, thermodynamic properties, gelation properties and water holding capacity of KGM/CUD blend systems in an alkaline environment were studied using physical property testing instruments and methods. The results showed that the viscosity of the KGM/CUD blended solution was greater than the value calculated from the ideal mixing rules in the condition of alkaline (pH = 10.58). As the proportion of CUD in the system increased, the intersection of storage modulus (G&rsquo, ) and loss modulus (G&rdquo, ) shifted to low frequencies, the relaxation time gradually increased, and the degree of entanglement of molecular chains between these two components gradually increased. The addition of CUD helped decrease the gelation temperature of KGM, increased the gelation rate and inhibited the thinning phenomenon of KGM gels at low temperatures (2&ndash, 20 &deg, C). The addition of CUD increased the hardness and gel strength of KGM but did not significantly improve the water holding capacity of the KGM/CUD blend gel. The process of mixing KGM and CUD improved the thermal stability of the gel. In summary, KGM/CUD exhibited excellent compatibility under alkaline conditions, and the blend systems produced a &ldquo, viscosifying effect&rdquo, KC8 and KC5 show better thermal stability, low temperature resistance and gel strength compared to KGM. This blended gel can be used as a structural support material to provide reference for the development of konjac bionic vegetarian products.

Moisture content plays an important role in aspects of the food processing such as energy transfer, food yield, and quality. This study investigated the effects of the moisture content of surimi on its electromagnetic characteristics. At moisture contents between 78% and 80%, both the dielectric constant and the dielectric loss increased, but gradually decreased with the increase of frequency. The strongest microwave absorption appeared at a thickness of 8 mm at 2.45 GHz. A moisture content of 0.45% was supplied to surimi using steam as an auxiliary heating method. The gel strength was obviously improved by a combination of microwave treatment (35 kW) and steam heating, and scanning electron microscopy showed that the network structure was also denser. In addition, the new heating mode with medium microwave power received the highest score on the comprehensive sensory evaluation after frying. The combination of microwave and steam preparation can save 11.68% ± 1.8% of the energy used in the conventional heating method, even when taking into account the combustion of methane produced during the wastewater treatment process.

This study investigated the effects of fish mince size on the gelling properties of silver carp surimi gel produced by microwave heating combined with the water bath method. As the mince size increased, the mince protein and fat contents increased, but the moisture content decreased. Although the strength and water holding capacity of the surimi gel obtained from the larger mince were lower, the detrimental effect resulting from this larger size was considerably reduced by microwave heating; this afforded the fast and selective heating of the heterogeneous surimi. A soft textured compact gel structure was obtained from the 4 mm fish mince based on the results of the texture profile analysis and scanning electron microscopy. These results are anticipated to aid in the formulation of a method for reducing the loss in the processing of muscle fibers to realize the accurate and moderate processing of low-value fish.

Dried minced pork slices (DMPS) have been widely accepted owing to their unique flavor and taste, but traditional roasting (TR) process for making DMPS are time-consuming and complicated. This study presents a microwave heating (MH) method for rapid preparation of DMPS with different fat pork levels. The results indicated that DMPS size significantly affected the MH patterns. As the fat pork content increased, the complex permittivity showed a downward tendency, and the 30% fat pork content improved both the heating rate and uniformity. Fat components significantly altered the texture and color characteristics, but DMPS made by MH possessed a higher hardness and toughness values than TR. Low-field nuclear magnetic resonance analysis demonstrated that the proportion of T21 gradually decreased in MH group, while no distinct changes were observed in the TR group with the increase of fat pork content. In addition, the results of comprehensive sensory evaluation in the MH and TR groups revealed that such a convenient MH technology is alternative for the fabrication of DMPS with acceptable product quality.

The effects of ultrasound parameters, and of the container materials used for surimi, on acoustic intensity were investigated. The frequency of ultrasound significantly affected the acoustic intensity. However, the relationship between the acoustic intensity and the frequency of the ultrasound device was not linear. The acoustic intensity increased as the height of the media increased. In addition, the acoustic intensity increased initially, but then decreased, as the volume of the media increased. Two container materials were tested: polyvinyl chloride (PVC) film and an aluminum box. The acoustic intensity was decreased significantly by the use of either material. The barrier effect of the aluminum box was weaker than that of the PVC film at lower frequencies, whereas the barrier effect of the PVC film was weaker than that of the aluminum box at higher frequencies. The gel strength of surimi increased with as the acoustic intensity increased when the latter was above a certain level. Changes in the secondary structure of myofibrillar protein were found to cause the increase in the gel strength.

Glucose and lysine are important substrates involved in the Maillard reaction. The lack of studies on their electromagnetic properties has made it impossible to understand the influence of electromagnetic properties on the microwave heating process, and has hindered the application of the Maillard reaction in the microwave field. In this study, the electromagnetic properties of glucose, lysine solution and their 1 : 1 mixture were determined at frequencies of 1.7–2.6 GHz. The results show that the dielectric loss factors gradually increased. Reflection loss gradually decreased with concentration in the order of glucose > mixture > lysine. The heating rates gradually increased at low concentrations (≤5%) and slowly changed at high concentrations (≥10%). These results indicate that the effect of electromagnetic properties on the heating rate is related to concentration. The heating rates depended on the dielectric properties at low concentrations (≤5%), whereas microwave-absorption properties dominated at high concentrations (≥10%).

The influences of glucono-δ-lactone (GDL) on the structural characteristics of red seabream (Pagrosomus major) surimi gel were studied in terms of protein components, secondary structure and aggregation of protein under pasteurisation conditions. The results showed that most of the salt-soluble protein form a gel, and a small amount of water-soluble protein plays a role in the addition of GDL under low-temperature heating conditions during surimi gel formation. The active sulfhydryl content of actomyosin increased but the total sulfhydryl content decreased as the content of GDL increased. The percentage of β-folds increase and that of α-helices decreased as the content of the GDL increased. SDS-PAGE results suggest that adding GDL can induce more MHC cross-linking and that the degree of cross-linking is higher than that in the high-temperature treatment samples.

In this study, the textural properties and micromechanism of yellowtail seabream (Parargyrops edita, Sparidae) surimi, with and without Chinese oak silkworm pupa homogenate (SPH), were investigated at different levels. The fresh, freeze-dried, and oven-dried SPH all showed a gel-enhancing ability in suwari (40/90 °C) and modori (67/90 °C) gels, in a concentration-dependent manner. Though the drying treatments can improve the storability of SPH, compared with fresh, the effect of the active substance was weakened. Suwari and modori gels added with 5%(w/w, whole product) fresh SPH had the increase in breaking force and deformation by 37.39% and 47.98%, and 85.14% and 78.49%, respectively, compared with the control gel (without SPH addition). The major myofibrillar protein, especially myosin heavy chain (MHC), was better retained by the addition of SPH. Compared the control group, a finer, denser, and more ordered 3-dimensional gel network microstructure was obtained, and different Df (Fractal dimension) was analyzed by using the box count method. This was found in all samples from 2.838 to 2.864 for suwari gels and 2.795 to 2.857 for modori gels, respectively. Therefore, the modori of yellowtail seabream surimi, linked with endogenous proteases, could be retarded in the presence of SPH, leading to an increase in gel strength.

The present study was conducted to elucidate the gelation mechanism of surimi protein-fish oil composite gels heated by microwave. Changes in chemical interactions, secondary structures, protein profiles and microwave-absorbing ability were investigated. The results clearly indicated that microwave heating could markedly (P

The evaluation of food cooking process is an important way to understand the heat-induced quality changes and optimize the heating process. To understand the quality changes in crayfish tail heated by microwave (MW) and boiling water (BW), the protein denaturation, cooking uniformity and overheating degree of tails were visually evaluated based on the theories of reaction kinetics and maturity value in this work. Protein denaturation analysis showed that heat-induced protein denaturation in crayfish tails heated by MW and BW followed first-order reaction kinetics and had similar one-dimensional denaturation patterns and temperatures, but their distributions were non-uniform and with reverse trends. Moreover, strong correlations between protein denaturation degree and heat-induced qualities changes were observed in crayfish tail during heating. The cooking uniformity and overheating degree of crayfish tail heated by MW and BW were evaluated by the maturity value (Mv) and overheating value (Ov), respectively. Evaluations showed that the profiles of Mv and Ov in the crayfish tail were non-uniform and with reverse trends, and there was lower ΔMv and O ¯ v for crayfish tail heated by MW than by BW, but higher Ov occurred in the centre, which corresponded to the texture of crayfish tails heated by MW was more susceptible than by BW when proteins had completely denatured. Industrial relevance The general patterns of cooking process in crayfish tail during microwave heating and boiling have been visually evaluated and compared based on the theories of reaction kinetics and maturity value, which enriched the knowledge for the application of microwave in the industrial thermal processing of crayfish and reaction kinetics in the analysis of cooking (especially microwave heating). Furthermore, the theory of maturity value was introduced into the evaluation of the cooking uniformity and overcooked degree in crayfish tail during the heating, which provided a new strategy for the cooking evaluation of food.

This study was aimed to investigate the effect of microwave heating (MWH) on the activity and conformation of cathepsin L (Cat L) compared to traditional conduction heating during surimi gel degradation stage. The gel properties and SDS-PAGE analysis showed that hydrolysis of myosin heavy chain was prevented by microwave. The activity of Cat L was affected by microwave power and heating time, which inhibited by MWH mainly due to the changes of conductivity caused by the vibration of polar groups under MWH. In addition, the reduction of total sulfhydryl group of Cat L during microwave irradiation led to conformation changes of Cat L. Significant decrease (P

Refrigeration is commonly used in the processing and storage of surimi products. However, refrigerated surimi products are susceptible to microbial contamination, which leads to deterioration of the products and shortens their shelf life. The aims of the present study were therefore to evaluate the effects of ?-polylysine (?-PL) on spoilage bacteria in surimi products, and to investigate the antibacterial mechanism of Bacillus cereus, which is the dominant spoilage bacterium. RESULTS ?-Polylysine with a high degree of polymerization (20?30K) proved able to decrease the total number of colonies in surimi products and showed an obvious antibacterial effect against B. cereus. After ?-PL treatments, the distinct broken areas on the bacterial surfaces and the aggregations of cells were observed by scanning electron microscope (SEM). The intracellular materials, such as small molecules, soluble proteins, and deoxyribonucleic acids in the cells were analyzed, which revealed the destructive effects of ?-PL on bacterial cells. Experiments with propidium iodide (PI) infiltration experiments verified that the permeability of cell membranes was enhanced by ?-PL treatment. CONCLUSION These results indicated that ?-PL could destroy the cell membranes and change the permeability of B. cereus, and subsequently the cell contents leaked out to achieve antibacterial effects. ? 2018 Society of Chemical Industry

Microwave (MW) heating improved the activity of transglutaminase (TGase) by inducing conformational changes due to structural modification. However, when TGase and myofibrillar protein were heated, the solubility and degree of crosslinking were similar. Further, the gel properties of the mixed solution pre-gelled by MW heating were lower than that obtained with water bath (WB) pre-gelling. We compared the effects on myofibrillar proteins at the same heating rate, our results showed that MW promoted aggregation, as the particle distribution tended toward larger molecular size. The increase of random coil as investigated by circular dichroism (CD) indicated that WB induced the unfolding of myofibrillar protein. MW enhanced intermolecular forces by engendering more disulfide bonds, which hindered the catalysis by TGase. Finally, SDS-PAGE indicated that the myosin molecules had more head crosslinking during MW treatment. MW and WB cause different response behaviors of myofibrillar protein, thereby affecting the catalytic effect of TGase.

This study investigated the effect of glucose oxidase on the gel properties of threadfin bream surimi. The gel strength of surimi increased with the addition of 0.5‰ glucose oxidase after two-step heating. Based on the results of the chemical interactions, the hydrophobic interaction and disulfide bond of glucose oxidase-treated surimi samples increased compared with the control samples at the gelation temperature and gel modori temperature. The surface hydrophobicity of samples with glucose oxidase and glucose increased significantly ( p

This study investigated the effect of overdrying potato starches on surimi products. The chemical composition of protein and chemical interactions, gel solubility, and protein conformation of the mixture of surimi gel protein, respectively, with 8% native potato starch and with 8% overdrying potato starch were investigated. The results show that the starch increased the insoluble protein content. In terms of the chemical interactions, the overdrying potato starch increased the amount of hydrogen bond and nondisulfide covalent bond and decreased the amount of ionic bond, which might stabilize the network structure of protein gel. The analysis of Raman Spectroscopy shows that more α-helices turn into random coin structure after the starch was added, which is conducive to higher strength and a better water retention ability of the surimi product.

Although it is well known that structural variations occur in starch during gelatinisation, little is known about how the structure of starch changes at subgelatinisation levels. The objective of this study was to investigate structural variations of rice starch ascribed to the temperature during microwave heating. Rapid conduction heating was used to imitate the high microwave heating rate through oil bath, which was then compared with traditional conduction heating. Structural changes due to temperature increases were investigated using thermogravimetry and differential scanning calorimetry while the distinct lamellar organisation of starch was obtained through small-angle X-ray scattering. The results showed that the structure of starch responds non-monotonically to temperature rising before gelatinisation, which was also affected by heating rates. The samples treated by microwave and rapid conduction heating essentially underwent the same thermal property changes and the molecular vibration of the microwaves did influence the submicroscopic lamellar structure.

Adding microbial transglutaminase (MTGase) to frozen surimi to enable the surimi to be sold as a higher-grade product at a higher price defrauds surimi product manufacturers and undercuts legitimate industry prices. Therefore, it is important to develop an accurate method of detecting the presence of MTGase in surimi. In this study, an immunochromatographic strip assay with a colloidal gold antibody probe was successfully developed and used to rapidly and qualitatively detect MTGase in surimi samples. The results were obtained in less than 10 min. The limit for the qualitative detection of MTGase using the immunochromatographic strip assay was identified as 1.0 μg/mL. The results of the immunochromatographic strip analysis of frozen surimi samples were verified by comparison with the results of a sandwich enzyme-linked immunosorbent assay. The colloidal gold probe-based immunochromatographic strip assay was thus found to be a rapid, economical, and user friendly method of detecting MTGase in surimi.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, P. R. ChinaFTIR and confocal laser micro-Raman spectroscopy methods were used to investigate thedifferences in chemical bond types, bond energy, and skeleton connection system betweenrice starch heated in a microwave and rice starch heated rapidly using a traditional method.The temperature of the peak absorption position of C–H mode vibration of microwavedsample was lower and the temperature of peak position of C–O related mode vibration onskeleton of microwaved sample werehigher than those of the rapid heating sample, but therewere no changes to other skeletal mode vibrations such as glycosidic linkage and pyranosering. Overall, microwave-heat treatment did not change the type of chemical groups in starchmolecules, and induce the formation of new chemical group bonds, or change the way thatthey interact with each other in rice starch. Furthermore, the vibrational energy of thechemical-bond of microwave-treated rice starch changes gradually during the heatingprocess.

The effects of microwave heating on the double helices, single helix and amorphous structures and the relative crystallinity of rice starch were studied by 13C CP/MAS NMR method, with rapid heating in an oil bath and conventional slow heating as controls. The results indicated that compared with rapid heating, microwave heating did not significantly change the ordered and disordered structures. All of the heating methods exhibited similar content changes to the double helices, V-type single helix and amorphous structures with rising temperature. The rapid heating effects caused by microwave and oil bath accelerated the destruction of the V-type single helix in the starch granules. The electromagnetic effect of microwave heating did not affect the decrease of the double helices or the amorphous content of the starch.