Effect of the number of freeze-thaw cycles number on the quality of Pacific white shrimp (Litopenaeus vannamei): An emphasis on moisture migration and microstructure by LF-NMR and SEM

Effect of pectin with different esterification degree on the freeze-thaw stability of gluten protein: Structures, functional properties, and Cryoprotective mechanism

The effect of degree of esterification (DE) on the cryoprotective function of pectin against the frozen deterioration of gluten protein is still unclear. Here, NMR, HPSEC-MALLS, HPGPC and optical microscrope were applied to determine the structure and ice recrystallization inhibition (IRI) activity of pectin with varying DE. The effect on structure, physicochemical properties and molecular interaction of gluten supplemented with pectin were investigated. Results suggested that low-ester pectin (LEP) exhibited higher IRI activity than that of high-ester pectin (HEP), and reduced the damage of gluten during freezing storage. Moreover, SEM and low field-NMR revealed that LEP effectively helped to maintain the network structure and inhibited the water migration of gluten. Besides, molecular docking results suggested higher affinity between LEP and gluten protein than that of HEP. These results illustrated better cryoprotective effects of LEP than that of HEP through pathways including IRI activity, water migration, and possible molecular interaction.

Screening and characterization of an antifreeze peptide from sea cucumber intestinal protein hydrolysates

Protein deterioration caused by ice crystals is an important factors affecting the frozen storage of fish. In this study, antifreeze peptides extracted from hydrolysates of sea cucumber intestinal protein with inhibition of protein denaturation were screened and characterized. The peptide Leu-Pro-Glu-Phe-Thr-Glu-Glu-Glu-Lys (LPEFTEEEK), derived from neutral protease hydrolysates of sea cucumber intestinal protein, was investigated for its potential to enhance the quality of salmon fillets during three freeze-thaw cycles. The results showed that the application of LPEFTEEEK effectively maintained the texture of fish fillets, as well as the oxidative and conformation stability of myofibrillar protein during the freezing process. Additionally, molecular dynamics simulations verified that LPEFTEEEK could bind to ice crystals and inhibit their recrystallization, thus preventing organisms from being damaged by freezing. This suggests that LPEFTEEEK holds significant promise as a novel cryoprotective agent for marine-derived antifreeze peptides.

Protective effects and molecular mechanisms of Litopenaeus vannamei treated with l-arginine/l-lysine against myofibrillar proteins oxidation and quality degradation during freeze-thaw cycles

The storage and processing of Litopenaeus vannamei are often challenged by the freeze-thaw (F-T) cycle phenomenon. This study delved into the influence of pretreatment with l-arginine (Arg) and l-lysine (Lys) on the myofibrillar proteins oxidation and quality of shrimp subjected to F-T cycles. Arg and Lys pretreatment notably improved water-holding capacity (WHC), textural integrity as well as the myofibrillar structure of the shrimps. A lesser reduction in the amounts of immobile and bound water was found in the amino acid-treated groups, and the oxidation of lipids and proteins were both decelerated. Molecular simulation results indicated that Arg and Lys could form hydrogen and salt-bridge bonds with myosin, enhancing the stability of Litopenaeus vannamei. The study concludes that Arg and Lys are effective in alleviating the adverse effects of F-T cycles on the quality of Litopenaeus vannamei, and provides a new solution for the quality maintenance during storage and processing.

Influence of beeswax-based fish oil oleogels on the mechanism of water and oil retention in Pacific white shrimp (Litopenaeus vannamei) meat emulsion gels: Filling, emulsification and phase transition

Oleogels have been used in the gelled surimi products to replace animal fats due to its structure characteristics. The effect of structure characteristics in fish oil oleogels on the mechanism of oil/water retention was investigated in meat emulsions. Beeswax assembly improved the oil and water retention. The unsaturation degree of fatty acids lowered the mobility of bound water, immobilized water as well as bound fat in the fish oil oleogel, but enhanced the mobility of free water and protons of unsaturated fatty acids. Beeswax addition and oil phase characteristics could enhance β-sheets, disulfide bonds and hydrophobic force to improve the viscoelasticity, gel strength and oil/water retention. Beeswax assembly facilitated the tight micro-sol network and filling effect, and high unsaturation degree promoted the emulsification effect, thus reducing phase transition temperature and juice loss. The study could lay the foundation for development of gelled shrimp meat products with EPA and DHA.

Effect of whey protein hydrolysate on the structural and functional stability of surimi myofibrillar protein gels during freeze-thaw cycles

This study investigates the effects of varying concentrations of whey protein hydrolysate (WPH) (5 %, 10 %, 15 %) on surimi myofibrillar protein gels subjected to freeze-thaw (FT) cycles. With an increase in the number of FT cycles, there was a decrease in both ionic and hydrogen bonding, resulting in reduced chewiness and elasticity. At the same time, hydrophobic interactions were strengthened, leading to disruptions in protein secondary structures. In contrast, the addition of WPH significantly improved and stabilized the gels' intermolecular interactions and textural properties, particularly at the 15 % concentration, which demonstrated superior effects compared to both the untreated control and the positive control treated with 0.02 % butylated hydroxyanisole (BHA) (P < 0.05). Furthermore, 15 % WPH effectively preserved the gel's secondary structure and water-holding capacity, significantly outperforming the 0.02 % BHA positive control group (P < 0.05). These findings highlight the potential of WPH to enhance intermolecular interactions and preserve the structural integrity of myofibrillar protein gels during FT cycles, indicating its promising application in food science.

Effect of water migration on changes of quality and volatile compounds in frozen Penaeus monodon

The purpose of this study was to clarify effects of water changes on the quality and volatile compounds of Penaeus monodon during frozen storage. The content of immobilized water decreased significantly while the bound water and free water increased significantly. Total sulfhydryl content, and Ca2+-ATPase activity decreased significantly to 68.31 μmol/g and 0.127 U/mg, meantime, carbonyl content and MFI value increased significantly to 2.04 μmol/g prot and 55.10. Total of 50 volatile compounds were identified. Nonanal (M & D), 2-nonanone and octanal were only detected in fresh samples, while 3-hydroxy-2-butanone and 1-hydroxy-2-propanone were only found in the samples after 20 days of storage. Correlation analysis revealed that 6 of the volatile compounds were associated with the change of free water. Total of 28 and 17 volatile compounds showed significant correlations with the immobilized water and bound water, respectively. Four volatile compounds have the potential to be used as the flavor marker.

Effects of Different Roasting Methods on the Quality of Roasted Large Yellow Croaker (Larimichthys crocea)

This study investigated the effects of different roasting methods (45% light wave and 55% microwave roasting, 70% light wave and 30% microwave roasting, 100% light wave roasting, far-infrared roasting, and oven roasting) on the quality of roasted large yellow croaker. The quality was evaluated using sensory evaluation, texture characteristics, color differences, moisture content, and volatile flavor substances. In this context, different roasting methods can affect the color, taste, and flavor of large yellow croaker fish, significantly improving the overall acceptance of roasted fish. The results showed that after 45% light wave and 55% microwave roasting, the elasticity of fish meat was maintained, the hardness of fish meat was reduced, the moisture content and distribution were changed, and the taste was the best. Far-infrared roasting and 45% light wave and 55% microwave roasting had a significant effect on the color of large yellow croaker samples and improved the sensory evaluation score. Forty-six volatile compounds were detected using gas chromatography-mass spectrometry. After roasting, the oxidation and Maillard reactions of lipids and proteins were increased, with the 45% light wave and 55% microwave roasting giving the highest variety of volatile flavor substance products.

3D printing of prawn mimics with faba proteins: The effects of transglutaminase and curdlan gum on texture

With its capability for automated production of high-resolution structures, 3D printing can develop plant-based seafood mimics with comparable protein content. However, the challenge lies in solidifying 3D printed products to achieve the firmness of seafood. Targeting prawn, texturisation of its 3D printed mimic by curdlan gum was compared against incubation with a protein cross-linking enzyme, microbial transglutaminase. Faba bean protein extract (FBP) was selected for its lightest colour. To confer structural stability to the FBP-based ink without hindering extrudability, adding 1 % xanthan gum was optimal. Printed curdlan-containing mimics were steamed for 9 min, while printed transglutaminase-containing mimics were incubated at 55 °C before steaming. Either adding 0.0625 % or 0.125 % w/w curdlan or, incubating the transglutaminase-containing mimics for an hour achieved chewiness of 818.8-940.6 g, comparable to that of steamed prawn (953.13 g). Curdlan hydrogel penetrated and reinforced the FBP network as observed under confocal imaging. Whereas incubation of transglutaminase-containing mimics enhanced microstructural connectivity, attributable to transglutaminase-catalysed isopeptide cross-linkages, and the consequent increase in disulfide bonding and β-sheet. Ultimately, transglutaminase treatment appeared more suitable than curdlan, as it yielded mimics with cutting strength comparable to steamed prawn. Both demonstrated promising potential to broaden the variety of 3D printed seafood mimics.

Fluctuation of flavor quality in roasted duck: The consequences of raw duck preform's repetitive freeze-thawing

This study aimed to investigate the changes in flavor quality of roasted duck during repetitive freeze-thawing (FT, -20 ℃ for 24 h, then at 4 ℃ for 24 h for five cycles) of raw duck preforms. HS-SPME/GC-MS analysis showed that more than thirty volatile flavor compounds identified in roasted ducks fluctuated with freeze-thawing of raw duck preforms, while hexanal, nonanal, 1-octen-3-ol, and acetone could as potential flavor markers. Compared with the unfrozen raw duck preforms (FT-0), repetitive freeze-thawing increased the protein/lipid oxidation and cross-linking of raw duck preforms by maintaining the higher carbonyl contents (1.40 ∼ 3.30 nmol/mg), 2-thiobarbituric acid reactive substances (0.25 ∼ 0.51 mg/kg), schiff bases and disulfide bond (19.65 ∼ 30.65 μmol/g), but lower total sulfhydryl (73.37 ∼ 88.94 μmol/g) and tryptophan fluorescence intensity. Moreover, A lower protein band intensity and a transformation from α-helixes to β-sheets and random coils were observed in FT-3 ∼ FT-5. The obtained results indicated that multiple freeze-thawing (more than two cycles) of raw duck preforms could be detrimental to the flavor quality of the roasted duck due to excessive oxidation and degradation.

Effect of ultrasound combined with pineapple protease treatment on the tenderness of dried shrimp

BACKGROUND

In order to improve the tenderness of dried shrimp products as well as to reduce the hardness of the meat during the drying process, shrimp were treated with ultrasound combined with pineapple protease and the tenderization condition was optimized by measuring the texture and shear force of dried shrimp. In addition, the sulfhydryl content, myofibril fragmentation index (MFI) and microstructure were also examined to clarify the mechanisms of shrimp tenderization.

RESULTS

The results showed UB1 group with ultrasonic power of 100 W, heating temperature of 50 °C and pineapple protease concentration of 20 U mL-1 were the optimum tenderization conditions, where shrimp showed the lowest hardness (490.76 g) and shear force (2006.35 gf). Microstructure as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis results suggested that during the tenderization process the muscle segments of shrimps were broken, degradation of myofibrillar proteins occurred, and MFI values and total sulfhydryl content increased significantly (P < 0.05) (MFI value = 193.6 and total sulfhydryl content = 93.93 mmol mg-1 protein for UB 1 group).

CONCLUSION

Ultrasound combined with bromelain could be used as a simple and effective tenderization method for the production of tender dried shrimp. The best conditions were 100 W ultrasonic power, 50 °C ultrasonic temperature, and 20 U mL-1 bromelain. © 2024 Society of Chemical Industry.

Effect of Freeze-Thaw Cycles on the Freshness of Prepackaged Penaeus vannamei

The effect of temperature fluctuations on the freshness of shrimp in simulated trays was investigated by setting a freeze-thaw (F-T) cycle of 12 h after freezing at -20 °C and thawing at 1 °C under refrigeration. The results showed that the shrimp's physicochemical properties deteriorated to different extents with the increase in F-T cycles. The total colony count of shrimp was 6.07 lg CFU/g after 21 cycles, and the volatile saline nitrogen content reached 30.36 mg/100 g, which exceeded the edible standard. In addition, the sensory quality and textural properties (hardness, elasticity, chewiness, and adhesion) declined to different degrees with increased F-T cycles. LF-NMR and protein property measurements showed that F-T cycles resulted in reduced water holding capacity and protein denaturation, which were the main factors leading to the deterioration of shrimp quality. Furthermore, flavor changes were analyzed using an electronic nose sensor to establish a freshness model. The W1W, W1S, W2S, and W5S sensors were correlated with the quality changes in shrimp and used as the main sensors for detecting the freshness of Penaeus vannamei. As a result, to better maintain the overall freshness, temperature fluctuations should be minimized in sales and storage, and fewer than 8 F-T cycles should be performed.

Coexisting with Ice Crystals: Cryogenic Preservation of Muscle Food─Mechanisms, Challenges, and Cutting-Edge Strategies

Cryopreservation, one of the most effective preservation methods, is essential for maintaining the safety and quality of food. However, there is no denying the fact that the quality of muscle food deteriorates as a result of the unavoidable production of ice. Advancements in cryoregulatory materials and techniques have effectively mitigated the adverse impacts of ice, thereby enhancing the standard of freezing preservation. The first part of this overview explains how ice forms, including the theoretical foundations of nucleation, growth, and recrystallization as well as the key influencing factors that affect each process. Subsequently, the impact of ice formation on the eating quality and nutritional value of muscle food is delineated. A systematic explanation of cutting-edge strategies based on nucleation intervention, growth control, and recrystallization inhibition is offered. These methods include antifreeze proteins, ice-nucleating proteins, antifreeze peptides, natural deep eutectic solvents, polysaccharides, amino acids, and their derivatives. Furthermore, advanced physical techniques such as electrostatic fields, magnetic fields, acoustic fields, liquid nitrogen, and supercooling preservation techniques are expounded upon, which effectively hinder the formation of ice crystals during cryopreservation. The paper outlines the difficulties and potential directions in ice inhibition for effective cryopreservation.

The Sous Vide Cooking of Mediterranean Mussel (Mytilus galloprovincialis): Safety and Quality Assessment

This study involves an investigation of the effects of various cooking temperatures, freeze-thaw processes, and food preservatives on the quality and shelf-life of sous vide Mediterranean mussels. Cooking temperatures of 80 °C or above significantly improved the microbiological quality, with bacterial counts remaining within the acceptability range for human consumption even after 21 days of refrigerated storage. Fast freezing followed by slow thawing preserved the highest moisture content, potentially improving texture. Sensory analysis revealed that refrigerated sous vide mussels maintained a comparable taste to freshly cooked samples. Frozen samples reheated via microwaving exhibited more intense flavour than pan-reheated or fresh mussels. Food additives, including citric acid, potassium benzoate, and potassium sorbate, alone or in combination with grape seed oil, significantly reduced total volatile basic nitrogen and thiobarbituric acid-reactive substances during 28 days of storage, indicating decreased spoilage and lipid oxidation. Mussels with a combination of these additives registered a nitrogen content as low as 22 mg of N/100g after 28 days, well below the limit of acceptability (<35 mg of N/100g). Food additives also inhibited bacterial growth, with mesophilic bacteria count below 3.35 Log CFU/g after 28 days, compared with 5.37 Log CFU/g in control samples. This study provides valuable insights for developing optimal cooking and preservation methods for sous vide cooked seafood, underscoring the need for further research on optimal cooking and freeze-thaw protocols for various seafood types.

Progress in the application of novel cryoprotectants for the stabilization of myofibrillar proteins

In this review, the physicochemical and conformational changes of myofibrillar proteins (MPs) of freeze-induced mince-based aquatic foods were comprehensively summarized in depth. Studies have demonstrated that temperature fluctuation and long-time freezing negatively affect food quality, resulting in texture alteration, drip fluid, flavor degradation, and nutrition loss due to MPs denaturation, aggregation, and oxidation. Attempts have been made in ice-recrystallization inhibition, freezing point depression, and ice shape and growth control for better cryopreservation. Moreover, to further minimize the quality deterioration, cryoprotectants were acknowledged to reduce the denaturation and aggregation of the MPs effectively. Recently, interest in novel functional ingredients, including oligosaccharides, protein hydrolysates, and natural polyphenols demonstrated excellent cryoprotective effects while avoiding health concerns and undesirable flavor caused by traditional sugar-based or phosphates-based cryoprotectants. Therefore, the present review provides a systematic overview of these low molecular weight multifunctional substances with a particular sequence and highlights their underlying mechanism in the inhibition of ice recrystallization the stabilization of MPs.

Analysis of the water state and microfractal dimension of tilapia fillets during freezing and thawing

To study the effects of freezing and thawing times and freezing temperatures on the water state and microstructure of tilapia fillets, experiments on tilapia fillets were carried out at -4 and -18°C with one to four freezing and thawing cycles (FTCs). Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to observe the water state after different treatments, and scanning electron microscopy (SEM) and frozen sections were used to observe the microstructure changes. Fractal dimension (FD) was used to quantitatively characterize the microstructure of the fish tissue, and the correlation between FD and fish fillet quality parameters was studied by principal component analysis (PCA). The findings showed that with the increase of FTCs, the thawing loss increased, and the water holding capacity (WHC) fell. FTCs cause a decrease in immobilized water and an increase in free water in the fillet. This indicates the migration of immobilized water to free water. SEM and frozen slice images showed that the growth of ice crystals led to the destruction of myogenic fibers. A decrease in freezing temperature inhibited ice crystal growth. The FD value dropped in accordance with an increase in FTCs. PCA demonstrated that the WHC, NMR data, and FD value had a strong correlation with the quality changes in the tilapia fillets. Therefore, FD and water state can reflect the quality characteristics of tilapia fillets. PRACTICAL APPLICATION: The water migration in tilapia fillets is detected with LF-NMR, and the microscopic image may be quantified using the FD value. Both approaches can offer fresh perspectives on how to assess the quality of tilapia fillets and reflect changes in their quality.

Integrating transcriptomic and metabolomic analysis to understand muscle qualities of red swamp crayfish (Procambarus clarkii) under transport stress

This study investigated the transport stress (crowding stress and duration) on the physicochemical properties, energy metabolism and antioxidant enzyme activities of the red swamp crayfish (Procambarus clarkii) tail muscle (CTM). Besides, transcriptomic and metabolomic were conducted to elucidate the possible mechanism of CTM alternations during transport stress. The survival rate of crayfish gradually decreased with the external crowding stress and crowding time increasing. The transport stress also led to the increased distance among muscle fibers, water mobility and energy consumption, and the decreased of water holding capacity (WHC), hardness of CTM. The hepatopancreas exhibited more sensitive to crowding stress than muscle. The multi-omics analysis revealed that transport stress could interfere the translation and protein folding functions of ribosomal proteins, fatty acid metabolism and degradation, physiological functions of mitochondria in CTM. This study could provide critical information to increase the understanding of the regulation mechanism of crayfish when subjected to transport stress.

Effect of freezing-thawing on the quality changes of large yellow croaker treated by low-salt soaking during frozen storage

Introduction

The production of the large yellow croaker has seasonal and regional characteristics, which is typically preserved on ice, possibly leading to its deterioration in a short time. Therefore, in this study, we focused on the effect of temperature fluctuation on the quality changes of the large yellow croaker during frozen storage.

Methods

In this experiment, the large yellow croaker was soaked in a low-salt solution, and physical and chemical properties, water-holding capacity, color, and protein characteristics of the muscle were investigated after repeated freeze-thaw (F-T) cycles and frozen storage.

Results and discussion

The results show the deterioration of muscle quality of large yellow croaker after low-salt treatment was lower than that of the salt-free soaking group. The salting treatment significantly (P < 0.05) enhanced the yield of large yellow croaker, which was 24.3% greater than the salt-free soaking group after 6 weeks of frozen storage. The microstructure of the salted muscle was more stable and maintained its cellular structure after F-T cycles and frozen storage. The b* value of the salt-free soaking group increased from b* value of the low-salt soaking group decreased from acceptable range. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicates the content of 17 kDa peptide decreased in the low-salt soaking group, and the peptides at 21 and 24 kDa increased during frozen storage. The results of the present study provide guidance for the optimal processing, transport, and storage of large yellow croaker, but the effect of salting on lipid oxidation and protein oxidation requires further study.

Research progress on quality deterioration mechanism and control technology of frozen muscle foods

Freezing can prolong the shelf life of muscle foods and is widely used in their preservation. However, inevitable quality deterioration can occur during freezing, frozen storage, and thawing. This review explores the eating quality deterioration characteristics (color, water holding capacity, tenderness, and flavor) and mechanisms (irregular ice crystals, oxidation, and hydrolysis of lipids and proteins) of frozen muscle foods. It also summarizes and classifies the novel physical-field-assisted-freezing technologies (high-pressure, ultrasound, and electromagnetic) and bioactive antifreeze (ice nucleation proteins, antifreeze proteins, natural deep eutectic solvents, carbohydrate, polyphenol, phosphate, and protein hydrolysates), regulating the dynamic process from water to ice. Moreover, some novel thermal and nonthermal thawing technologies to resolve the loss of water and nutrients caused by traditional thawing methods were also reviewed. We concluded that the physical damage caused by ice crystals was the primary reason for the deterioration in eating quality, and these novel techniques promoted the eating quality of frozen muscle foods under proper conditions, including appropriate parameters (power, time, and intermittent mode mentioned in ultrasound-assisted techniques; pressure involved in high-pressure-assisted techniques; and field strength involved in electromagnetic-assisted techniques) and the amounts of bioactive antifreeze. To obtain better quality frozen muscle foods, more efficient technologies and substances must be developed. The synergy of novel freezing/thawing technology may be more effective than individual applications. This knowledge may help improve the eating quality of frozen muscle foods.

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.

Effect of antifreeze proteins on the freeze-thaw cycle of foods: fundamentals, mechanisms of action, current challenges and recommendations for future work

Freezing is widely used in food preservation, but if not carried out properly, ice crystals can multiply (nucleation) or grow (recrystallization) rapidly. This also affects thawing, causing structural damage and affecting overall quality. The objective of this review is to comprehensively study the cryoprotective effect of antifreeze proteins (AFPs), highlighting their role in the freeze-thaw process of food. The properties of AFPs are based on their thermal hysteresis capacity (THC), on the modification of crystal morphology and on the inhibition of ice recrystallization. The mechanism of action of AFPs is based on the adsorption-inhibition theory, but the specific role of hydrogen and hydrophobic bonds/residues and structural characteristics is also detailed. Because of the properties of AFPs, they have been successfully used to preserve the quality of a wide variety of refrigerated and frozen foods. Among the limitations of the use of AFPs, the high cost of production stands out, but currently there are solutions such as the use the production of recombinant proteins, cloning and chemical synthesis. Although in vitro, in vivo and human studies have shown that AFPs are non-toxic, their safety remains a matter of debate. Further studies are recommended to expand knowledge about AFPs, to reduce costs in their large-scale production, to understand their interaction with other food compounds and their possible effects on the consumer.

Tandem mass tag-based proteomics analysis of protein changes in the freezing and thawing cycles of Trachurus murphyi

We investigated the proteome variations in Trachurus murphyi with different cycles of freezing and thawing (FT) under frozen storage. A total of 2,482 proteins were assessed quantitatively, of which 269 proteins were recognized as differential abundance proteins during the second FT cycle until the eighth FT cycle. Bioinformatics analysis on gene ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of Differential Analysis of Proteins (DAPs) indicated multiple DAPs engaged with the protein structure, metabolic enzymes, and protein turnover. In addition, some of the observed proteins were probably the underlying markers of protein oxidation (PO). The analysis of PO sites revealed the sites of PO, such as amino adipic semialdehydes, γ-glutamic semialdehydes, and Schiff bases. Bioinformatics analyses demonstrated the involvement of differentially expressed proteins in the Hippo signaling pathway (Ko04390), indicating strong protein degradation with greater numbers of FT cycles under frozen storage. It provides an insight into quality stability from a proteomics quality perspective at the molecular level. The results obtained have deepened our current understandings of the mechanisms that reveal variations in proteomes and quality, as well as help promote quality control of T. murphyi across the cold transportation chain. PRACTICAL APPLICATION: Temperature fluctuation is one of the core issues during frozen food storage and distribution faced by the frozen food industry. Fluctuation may result in microstructural changes, ice recrystallization, and protein change in frozen food products. Tandem mass tag-based methods were adopted to study proteome variations in Trachurus murphyi muscles under different cycles of freezing and thawing under frozen storage conditions in this paper. The results obtained have deepened our current understandings of the mechanisms that reveal variations in proteomes and quality, as well as help promote quality control of T. murphyi across the cold transportation chain.

Effects of repeated freezing and thawing on myofibrillar protein and quality characteristics of marinated Enshi black pork

Repeated freeze-thaw is one of the main reasons for quality deterioration of frozen meat products. The study focused on the changes of endogenous fluorescence, secondary structure, microstructure, and water retention and distribution in marinated and unmarinated Enshi black pork after 10 freeze-thaw cycles. The results revealed that marinated treatment significantly reduced the thaw and centrifugal loss (P < 0.05), and increased endogenous fluorescence intensity of samples. During the entire freeze-thaw process, free water was undetectable in marinated group. After the first 4 cycles, α-helix percentage in marinated group was higher than that in control group. Scanning electron microscopy results suggested that there was no obvious increase in muscle fiber gap until 8 cycles in marinated group. Conclusively, moderate marination could slow down the deterioration of myofibrillar protein and pork quality, but it would be better to limit freeze-thaw cycles within 4 to maintain the quality of marinated Enshi black pork.

Preparation of chitosan grafted caffeic acid coating and its effect on pompano (Trachinotus ovatus) preservation

BACKGROUND

The present study aimed to investigate the preservative effect of chitosan-caffeic acid grafts coating (CS-g-CA) on the quality and microbial characteristics of pompano (Trachinotus ovatus) during iced storage. CS-g-CA was prepared by a 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydro/N-hydroxysuccinimide coupling reaction. The grafting of CS-g-CA was confirmed by UV-visible and Fourier-transform infrared spectra. Samples were treated with distilled water (control), chitosan (CS), caffeic acid (CA) and CS-g-CA for 10 min, respectively. Microbiological [total viable count (TVC), H₂ S-producing bacteria count, Pseudomonas bacteria count], physicochemical indicators [water holding capacity (WHC), cooking loss, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), texture profile analysis, free amino acids] and sensory evaluation were investigated during ice storage at 4 °C for up to 27 days.

RESULTS

The results showed that the antioxidant and antibacterial activities of CS could be improved by grafting CA onto CS. CS-g-CA coating could greatly slow down the speed of water loss and maintain WHC. Furthermore, CS-g-CA coating showed superior antibacterial activities by inhibiting the growth of TVC, delayed the decline of flavor amino acids and reduced sensory change. In addition, CS-g-CA coating reduced lipid oxidation and protein degradation as indicated by the decrease in TBA and TVB-N, possibly as a result of the addition of CA into CS membrane significantly improving the antioxidant activity of CS.

CONCLUSION

Compared with the control group, CS-g-CA coating had the optimal effect and could enhance the shelf-life of Trachinotus ovatus for at least another 9 days. © 2021 Society of Chemical Industry.

Correlations between Texture Profile Analysis and Sensory Evaluation of Cured Largemouth Bass Meat (Micropterus salmoides)

Texture is an important factor in evaluating the quality of aquatic products. To evaluate the texture properties of cured large mouth bass, edible sodium chloride (0, 1.0, 2.0, and 3.0%) was smeared to the bass meat. Texture profile analysis (TPA) and sensory evaluation were performed to evaluate the quality of the cured samples, and the correlations of the indexes in the two methods were analyzed. Two principal components were obtained from the TPA indexes and sensory evaluation indexes, and the cumulative variance contribution rates were 73.87% and 72.99%, respectively. Results from the principal component analysis showed that the main indicators that affected the TPA were gumminess and springiness, while those that affected sensory evaluation were chewiness and adhesiveness. The TPA index and sensory evaluation could be effectively improved when the sodium chloride added to the bass meat was 1%. In the correlation analysis, sensory springiness was negatively correlated with TPA hardness ( $P<0.05$ , r = −0.553) but positively correlated with TPA chewiness ( $P<0.05$ , r = 0.596). After stepwise regression analysis, the prediction equation between the sensory springiness and TPA hardness was obtained as SSp=5.770−0.002Ha. These results provide a basis for predicting the quality of large mouth bass cured products.

Effect of freeze-thaw cycles on the physicochemical properties, water-holding status, and nutritional values of broiler chicken drumstick

This study aimed to determine the effects of multiple freeze-thaw (FT) cycles (0, 1, 2, and 4) on the physicochemical properties, water-holding status, and nutritional values of broiler drumsticks. The results showed that L* (lightness) and b* (yellowness) values, thiobarbituric acid-reactive substances, total volatile basic nitrogen, and total viable counts significantly increased but pH values, protein solubility, and sensorial acceptance decreased after four FT cycles (P ˂ 0.05). The decreases in moisture content thawing loss, centrifugation loss, drip loss, and cooking loss indicated that the water-holding capacities of samples subjected to multiple FT cycles were diminished. Results of cell microstructure analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the occurrence of ruptured muscle cells with decreased fiber diameters and changes in myosin heavy chain band intensity after multiple FT cycles (P ˂ 0.05). As the number of FT cycles increased, the content of total free amino acids and polyunsaturated fatty acids including linoleic (C18:2), linolenic (C18:3), eicosatetraenoic (EPA, C20:5), and docosahexaenoic (DHA, C22:6) acids decreased (P ˂ 0.05). In conclusion, four repeated FT cycles accelerated the deterioration of physiochemical properties, reduced the water-holding status, and considerably impaired sensory characteristics and nutritional values of chicken meat.

Effect of Locust Bean Gum-Sodium Alginate Coatings Combined with High CO2 Modified Atmosphere Packaging on the Quality of Turbot (Scophthalmus maximus) during Refrigerated Storage

This research was conducted to investigate the effect of active coatings composed of locust bean gum (LBG) and sodium alginate (SA) containing daphnetin emulsions (DEs) combined with modified atmosphere packaging (MAP) on the microbiological and physicochemical properties of turbot during 4 °C refrigerated storage for 32 days. The results revealed that LBG-SA-DE coatings together with high CO₂ MAP (60% CO₂/35% N₂/5% O₂) maintained the total viable count (TVC) of H₂S-producing bacteria in 4–6 lg CFU/g, which is lower than the limit (7 lg CFU/g). In addition, LBG-SA-DE coatings together with high CO₂ MAP (60% CO₂/35% N2/5% O₂) inhibited the production of odor compounds, including thiobarbituric acid (TBA), trimethylamine-nitrogen (TMA-N), K value, and total volatile basic nitrogen (TVB-N). The low-field NMR analysis (LF-NMR) and magnetic resonance imaging (MRI) indicated that LBG-SA-DE coatings together with high CO₂ MAP (60% CO₂/35% N₂/5% O₂) treatments could delay the release of water located in muscle fiber macromolecules or convert it into free water based on muscle fiber destruction, thus maintaining the water content and migration. The results of the sensory evaluation showed that turbot treated with LBG-SA-DE coatings together with MAP could maintain its freshness during refrigerated storage.

Effect of cellobiose on the myofibrillar protein denaturation induced by pH changes during freeze-thaw cycles

The aim of this study was to investigate myofibrillar protein (MFP) denaturation induced by pH changes during freeze-thaw (FT) cycles, and to propose an effective mitigation strategy. Owing to the selective crystallization of Na₂HPO₄·12H₂O and the consequent pH change, a pH change of 3.32 units was observed when the MFP solution were frozen. The surface hydrophobicity, particle size and confocal laser scanning microscopy showed that the protein molecules gradually unfolded and formed larger protein aggregation as the number of FT cycles increases. Additionally, protein degradation, secondary and tertiary structure alterations suggested that the FT cycle could disrupt structural integrity. The addition of cellobiose could maximize the inhibition of pH changes (decrease of ∼0.62 unit), no Na₂HPO₄·12H₂O crystallization was observed by X-ray diffraction. Cellobiose could minimize FT damage to myofibrillar protein, which was closest to the control. Thus, cellobiose can be used as a new and effective cryoprotectant.

Effects of Freeze-Thaw Cycles on Water Migration, Microstructure and Protein Oxidation in Cuttlefish

This study was conducted to analyze the effects of multiple freeze-thaw (F-T) cycles on microstructural disruption, water migration, protein oxidation and textural properties of cuttlefish. Low-field nuclear magnetic resonance (LF-NMR) showed an increase in the proportion of free water in cuttlefish flesh. It was also observed by scanning electron microscopy (SEM) that multiple F-T cycles increased the gap between muscle fibers and disrupted the original intact and compact structure. The results of Fourier transform infrared spectroscopy, intrinsic fluorescence spectroscopy, Ca2+ATPase content, sulfhydryl content and free amino acid content indirectly prove that multiple F-T cycles can lead to the destruction of the a-helical structure of cuttlefish myofibril protein and the content of irregular curls increased, protein aggregation and degradation, and tryptophan oxidation. In addition, after repeated freezing and thawing, the water holding capacity, whiteness value, elasticity and chewiness of cuttlefish flesh decreased, the total volatile base nitrogen content increased. It can be concluded that the freeze-thaw cycles are very harmful to the quality of the frozen foods, so it is important to keep the temperature stable in the low-temperature food logistics.

Shelf-Life Extension of Refrigerated Turbot (Scophthalmus maximus) by Using Weakly Acidic Electrolyzed Water and Active Coatings Containing Daphnetin Emulsions

This research was to investigate the effect of weakly acidic electrolytic water (WAEW) treatments combining with the locust bean gum (LBG) and sodium alginate (SA) active coatings, containing daphnetin emulsions on microbiological, physicochemical, and sensory changes of turbot (Scophthalmus maximus) during refrigerated storage at 4°C for 24 days. Results showed that WAEW, together with LBG-SA coatings containing daphnetin emulsions treatments, could significantly lower the total viable count (TVC), H₂S-producing bacteria, pseudomonas spp., and psychrotrophic bacteria counts, and inhibit the productions of off-flavor compounds, including the total volatile basic nitrogen (TVB-N), inosine (HxR), and hypoxanthine (Hx). Furthermore, the treatments also prevented textural deterioration, delayed water migration, and had higher organoleptic evaluation results. Therefore, WAEW, together with LBG-SA coatings, containing daphnetin emulsions treatments, had the potential to improve the quality of turbot during refrigerated storage.

Effects of different thawing methods on the physicochemical changes, water migration and protein characteristic of frozen pompano (Trachinotus ovatus)

The effects of five thawing methods (ultrasonic thawing [UT], radiofrequency thawing [RFT], water immersion thawing [WIT], microwave thawing [MT], and cold storage thawing [CST]) on physicochemical properties, water migration, and protein characteristic of whole frozen pompano (Trachinotus ovatus) were investigated and compared with fresh samples (FS). The physicochemical changes of thawed pompano were analyzed based on pH, total volatile basic nitrogen (TVB-N), color difference. The protein aggregation, physicochemical properties and conformation of myofibrillar proteins (MPs) were evaluated by Sodium dodecyl sulfate polyacrylamide gel electrophoresis, differential scanning calorimetry, and Raman spectra, respectively. Water migration and MPs microstructure were measured by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM), respectively. The results showed that different thawing methods could accelerate the protein denaturation and decrease of quality in pompano, especially MT treatment causing more seriously local overheating phenomena. Among the samples with different thawing treatments, the changes of pH, TVB-N values, and color difference in RFT and UT were closed to that from FS. The MT had the shortest thawing time, but could produce the damage of structural muscle. RFT had desirable thermal stability and made the protein secondary structure more stable, the myofibril bundles were also straight and smooth by SEM observation. The content of bound water and free water had no significant changes by LF-NMR. Therefore, compared with other thawing methods, RFT is a desirable thawing method for maintaining the quality of thawed pompano. PRACTICAL APPLICATIONS: Before further processing of frozen pompano, the thawing process is an important part, which is highly associated with the quality of products. The damage of conformation and properties in aquatic protein caused by freeze-thaw process is very obvious in food processing industry. Compared to microwave thawing, ultrasonic thawing, and traditional methods, the radiofrequency thawing (RFT) could reduce changes in structure and properties of protein, and have higher thawing efficiency. The temperature distribution on the pompano surface was uniform during the radiofrequency process with higher strong penetration and less local overheating. The RFT is a desirable thawing method to maintain the quality and extend the shelf life of frozen pompano for application in food industry.

The Effect of Multiple Freeze-Thaw Cycles on the Microstructure and Quality of Trachurus murphyi

Temperature fluctuation in frozen food storage and distribution is the perpetual and core issue faced by the frozen food industry. Ice recrystallisation induced by temperature fluctuations under cold storage causes microstructural changes in fish products and irreversible damages to cells and tissues, which lower the frozen fish quality in the food chain. This study is intended to explore how repeated freezing-thawing affected the microstructure and quality of Trachurus murphyi during its frozen storage. The results showed the consistency between the increase in ice crystal diameter, volume, and porosity in frozen fish and the increase in centrifugal loss (from 22.4% to 25.69%), cooking loss (from 22.32% to 25.19%), conductivity (from 15.28 Ms/cm to 15.70 Ms/cm), TVB-N (from 16.32 mg N/100 g to 19.94 mg N/100 g), K-value (from 3.73% to 7.07%), and amino acid composition. The muscle structure change observed by Fourier-Transform Infrared spectroscopy (FT-IR) showed that the content of α-helix reduced from 59.05% to 51.83%, while the β-sheet fraction grew from 15.44% to 17.11%, β-turns increased from 5.45% to 7.58%, and random coil from 20.06% to 23.49%. Moreover, muscular structure exhibited varying degrees of deterioration with increasing cycles of freezing and thawing as shown by scanning electron microscopy (SEM). We studied the muscular morphology, which included the measurement of porosities (%) of pore that increased (from 1.4% to 4.3%) and pore distribution, by X-ray computed tomography (uCT). The cycles of the freeze-thaw resulted in structural changes, which seemed to be closely associated with ultimate quality of frozen fish products.

Exploring the Effect of Dehydration on Water Migrating Property and Protein Changes of Large Yellow Croaker (Pseudosciaena crocea) during Frozen Storage

This study aimed to explore the effect of dehydration on the water migrating property and protein changes of large yellow croaker during frozen storage. A freeze-dryer was used to accelerate experiments, which was isolated from oxygen and excluded the effects of protein oxidation. After dehydration time (3, 9, 18, and 30 h) for both fast- and slow-freezing samples, the results showed that the ice sublimation of samples containing small ice crystals was faster than that of samples containing large ice crystals in the early stages of dehydration, but in the latest stage, there was an opposite trend. The results indicated that dehydration reduced the water freedom degrees and water-protein interaction. At the same time, dehydration had a significant effect on protein secondary and tertiary structures. The significant increase in surface hydrophobicity and particle size indicated that dehydration exacerbated myofibrillar protein aggregation. The ΔH1 values (from 1.275 to 0.834 J/g for slow-freezing group and from 1.129 to 0.855 J/g for fast-freezing group) decreased gradually as the dehydration time extended, indicating the decrease in protein thermal stability. Additionally, significant protein degradation occurred when the water content of the sample decreased to a certain level. This study showed that ice crystal size had an important effect on the rate of ice sublimation, and the occurrence of dehydration during frozen storage accelerated the water loss and the decrease in protein stability.

Effects of slightly acidic electrolyzed water pretreatment combined with biopreservatives on the shelf life of refrigerated obscure pufferfish (Takifugu obscurus)

This study assessed the effects of ε-polylysine hydrochloride (ε-PLH) and rosemary extract (RE) combined with slightly acidic electrolyzed water (SAEW) on the shelf life of obscure pufferfish (Takifugu obscurus) during refrigerated storage at (4 ± 1 °C). The samples were first dipped in SAEW and then treated with sterilized water (CK) and other solutions (0.2% RE [RE], 0.3% ε-PLH [PLH], and 0.2% RE + 0.3% ε-PLH [RE+PLH], respectively). Afterwards, microbiological, physicochemical, water migration, and sensory attributes were periodically assessed. The results showed that compared with CK and RE groups, ε-PLH treatment could effectively inhibit microbial growth and delay the increase in total volatile base nitrogen (TVB-N). In addition, microbial indexes, TVB-N, thiobarbituric acid, and metmyoglobin value in the samples treated with RE+ε-PLH were lower than those with ε-PLH or RE alone during storage. Meanwhile, samples treated with RE+ε-PLH exhibited the best sensory properties and no effect on color parameters. Based on the results of microbiological analysis, the shelf life of obscure pufferfish treated with RE+ε-PLH was 14 days during refrigerated storage at (4 ± 1 °C). PRACTICAL APPLICATION: In our study, the combined application of ε-PLH, RE, and SAEW was effective to extend the shelf life of obscure pufferfish. Based on the results of total viable counts, the RE+PLH group had a shelf life of approximately 14 days. Accordingly, bio-preservatives combined with SAEW technology have a broad application potential in the storage of obscure pufferfish.

Effect of locust bean gum-sodium alginate coatings incorporated with daphnetin emulsions on the quality of Scophthalmus maximus at refrigerated condition

In this study, the microbiological, physicochemical, and flavor changes of turbot (Scophthalmus maximus) coated with a composite active coating of locust bean gum (LBG) and sodium alginate (SA) supplemented with daphnetin emulsions (0.16, 0.32, 0.64 mg·mL^-1) were determined during 18 days of refrigerated storage (4 ± 1 °C). Results showed that LBG-SA coatings containing 0.32 mg·mL^-1 daphnetin emulsions could significantly lower the total viable count (TVC), psychrophiles, Pseudomonas spp. and H₂S-producing bacteria counts, and inhibit the productions of off-flavor compounds including the total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and ATP-related compounds. 32 volatile compounds were identified by solid phase microextraction combined with gas chromatography-mass spectrometer method (SPME-GC/MS) during refrigerated storage and the treated turbot samples significantly lowered the relative content of fishy flavor compounds. Further, the LBG-SA coatings containing daphnetin could also delay the myofibril degradation of the turbot samples. These results indicated that the LBG-SA coatings with 0.32 mg·mL^-1 daphnetin were a potential alternative way to improve the quality of turbot during refrigerated storage.

Emerging Techniques for Differentiation of Fresh and Frozen-Thawed Seafoods: Highlighting the Potential of Spectroscopic Techniques

Fish and other seafood products have a limited shelf life due to favorable conditions for microbial growth and enzymatic alterations. Various preservation and/or processing methods have been developed for shelf-life extension and for maintaining the quality of such highly perishable products. Freezing and frozen storage are among the most commonly applied techniques for this purpose. However, frozen–thawed fish or meat are less preferred by consumers; thus, labeling thawed products as fresh is considered a fraudulent practice. To detect this kind of fraud, several techniques and approaches (e.g., enzymatic, histological) have been commonly employed. While these methods have proven successful, they are not without limitations. In recent years, different emerging methods have been investigated to be used in place of other traditional detection methods of thawed products. In this context, spectroscopic techniques have received considerable attention due to their potential as being rapid and non-destructive analytical tools. This review paper aims to summarize studies that investigated the potential of emerging techniques, particularly those based on spectroscopy in combination with chemometric tools, to detect frozen–thawed muscle foods.