Preservation strategies for processed grass carp products: Analyzing quality and microbial dynamics during chilled and ice temperature storage.

This study investigated the impact of ice temperature storage on quality and bacterial composition of processed fish paste products (PFP). Freezing curve revealed the ice temperature was -1 °C. Electric nose (e-nose) showed significant changes in volatile components within 8 days. Results of total volatile basic nitrogen (TVB-N) showed that PFP stored at 4 °C reached its limit after 2 days, whereas PFP stored at ice temperature remained stable for 6 days. Thiobarbituric acid reactive substances (TBARS) demonstrated delayed oxidation in PFP stored at ice temperature compared to 4 °C. TCA-soluble peptides indicated that the protein degradation was suppressed by ice temperature. Additionally, ice temperature inhibited microbial growth and altered bacterial composition. High-throughput sequencing revealed that Pseudomonas, Brochothrix, Carnobacterium were dominant at 4 °C, while Acinetobacter, Pseudomonas, Janthinobacterium and Brochothrix were dominant at ice temperature. In summary, ice temperature might be a potential method for maintaining the freshness of PFP.

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 ß-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.

Investigation on 3D printing of shrimp surimi under different printing parameters and thermal processing conditions.

Improving the printing accuracy and stability of shrimp surimi and finding appropriate printing parameters and suitable thermal processing method can help to develop high value-added 3D printing products of shrimp surimi. It was found that in order to make the 3D printing products of shrimp surimi have higher printing adaptability (printing accuracy and printing stability reach more than 97%), by choosing nozzle diameter of 1.20 mm and setting the printing height of the nozzle to 2.00 mm, the layers of the printed products were better fused with each other, and the printing accuracy of the products could be greatly improved; there was no uneven discharge and filament breakage when the nozzle moved at the speed of 30 mm/s; and the products were internally compact and had good stability when the printing filling rate was 80%. In addition, the deformation rates of steamed, boiled and deep-fried shrimp surimi products were significantly higher than those of oven-baked and microwaved shrimp surimi products (P < 0.05). Microwave heating had a greater effect on the deformation and color of shrimp surimi products, and was not favored by the evaluators. In terms of deformation rate, sensory score, and textural characteristic, the oven-baked thermal processing method was selected to obtain higher sensory evaluation scores and lower deformation rates of shrimp surimi 3D printed products. In the future, DIY design can be carried out in 3D printing products of shrimp surimi to meet the needs of different groups of people for modern food.

Insight into the correlation of key taste substances and key volatile substances from shrimp heads at different temperatures.

This study aimed to investigate taste substances of shrimp heads stored at 20 °C, 4 °C, -3 °C, and - 18 °C, and the correlation between taste substances and 25 key volatile substances. Notably, samples stored at 20 °C showed significant changes in bitter amino acids and hypoxanthine, and quickly deteriorated. Samples stored at 4 °C for 14 d or - 3 °C for 30 d facilitated the development of umami amino acids, sweet amino acids, and IMP. Furthermore, samples stored at -18 °C for 30 d demonstrated no significant changes in taste profile. Changes in taste substances through quantitative analysis were consistent with changes in taste profile through e-tongue analysis. Based on the results of O2PLS (VIP > 1), Cys, Arg, Glu, Ser, Val, Ala, Ile, ADP, and IMP were correlated with 25 key volatile substances. This study provides fundamental data for the storage, transportation, and value-added utilization of shrimp heads.

Bactericidal efficacy of plasma-activated water against Vibrio parahaemolyticus on Litopenaeus vannamei.

In this study, the antimicrobial mechanism of plasma-activated water (PAW) against Vibrio parahaemolyticus and the effectiveness of PAW in artificially contaminated Litopenaeus vannamei were investigated. The results demonstrated a significant reduction (p < 0.05) in viable counts of V. parahaemolyticus with increasing plasma discharge time (5, 10, 20, and 30 min) and PAW immersion time (3, 5, 10, 20, and 30 s). Specifically, the count of V. parahaemolyticus decreased by 2.1, 2.7, 3.3, and 4.4 log CFU/mL after exposed to PAW 5, PAW 10, PAW 20, and PAW 30 for 30 s, respectively. Significant cell surface wrinkling, accompanied by notable nucleic acid and protein leakage were observed after treatment with PAW. The permeability of the inner and outer cell membranes was significantly increased (p < 0.05), along with an increase in electrical conductivity (p < 0.05). The reactive oxygen species (ROS) within V. parahaemolyticus cells were significantly increased (p < 0.05), while superoxide dismutase (SOD) activity, and the relative expression of the ompW, emrD, and luxS genes were significantly decreased (p < 0.05). A reduction number of 1.3, 1.8, 2.1, and 2.2 log CFU/g of V. parahaemolyticus in artificially contaminated L. vannamei was obtained with PAW for 5 min. The study elucidated that PAW could destroy cell membranes, leading to cell death. The findings would strengthen strategies for V. parahaemolyticus control and provide a potential application of PAW for preserving aquatic products.

Konjac glucomannan-assisted fabrication of stable emulsion-based oleogels constructed with pea protein isolate and its application in surimi gels.

Konjac glucomannan (KGM) is widely used as a stabilizer for the structuring of highly unsaturated oils. This study aimed to investigate the changes in structure and functional properties of soybean oil - based oleogels (emulsion template method) prepared with different amounts of KGM-modified pea isolate protein (PPI). The findings revealed that the oleogels formed three - dimensional networks through van der Waals interactions and hydrogen bonding between the stretched PPI and KGM. As the amount of KGM increased, the oil droplets were more uniformly dispersed within the continuous PPI - KGM rigid network, especially when the ratio of PPI to KGM was 4:1. This formulation also showed the highest thixotropy (73.2 %) and the best oil binding capacity (94 %). Cryo - SEM revealed that the oleogel - prepared surimi gels successfully enclosed oil droplets in a dense matrix through a dual stabilization mechanism. Additionally, the incorporation of oleogels significantly improved the textural properties of surimi in comparison to directly adding oil.

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

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

Tracking protein aggregation behaviour and emulsifying properties induced by structural alterations in common carp (Cyprinus carpio) myofibrillar protein during long-term frozen storage.

The effect of ultrasound-assisted immersion freezing (UIF), air freezing (AF), and immersion freezing (IF) on the protein structure, aggregation, and emulsifying properties of common carp (Cyprinus carpio) myofibrillar protein during frozen storage were evaluated in the present study. The result showed that, compared with AF and IF samples, UIF sample had higher reactive/total sulfhydryl, protein solubility, and lower protein turbidity (P < 0.05), indicating that UIF was beneficial to inhibit protein oxidation and aggregation induced by frozen storage. UIF inhibited the alteration of secondary structure and tertiary structure during frozen storage. Meanwhile, UIF sample had higher emulsifying activity index, and smaller emulsion droplet diameter than AF and IF samples (P < 0.05), suggesting that UIF was beneficial for maintaining the emulsifying properties of protein during storage. In general, UIF is a potential and effective method to suppress the decrease in protein emulsifying properties during long-term frozen storage.

Oxidized myoglobin: Revealing new perspectives and insights on factors affecting the water retention of myofibrillar proteins.

The impact of oxidized myoglobin (Mb) on myofibrillar protein (MP) oxidation and water retention was investigated. Results showed that the oxidation of Mb increased with increasing concentration of oxidized linoleic acid (OLA). In the presence of 100 mmol/L OLA, hemin iron decreased by 62.07 % compared to the control group. Further investigation showed that mild oxidation of Mb (≤10 mmol/L OLA) increased the water retention and the absolute value of the zeta potential of MP, whereas excessive oxidation (>10 mmol/L OLA) decreased these properties. With the increase of Mb oxidation, the carbonyl content in MP increased, and α-helices changed to random helix. And the tertiary structure changed. Pearson correlation analysis suggested that oxidized Mb affected the water retention of MP, which was closely related to hemin iron and non-hemin iron. In conclusion, OLA induced Mb oxidation, further promoted MP oxidation and affected its water retention.

Effect of MDA-mediated oxidation on the protein structure and digestive properties of golden pomfret.

In this study, golden pomfret myofibrillar protein (MP) was used as the research object, and the oxidation system of malondialdehyde (MDA) as an inducer and the static digestion model in vitro was established for the analysis of the changes in protein structure and molecular morphology during oxidation and digestion. Subsequently, the effects of MDA-mediated oxidation on the structure and digestive properties of golden pomfret myofibrillar fibrillar protein were determined. The results showed that the hydrolysis degree and digestion rate of MP were inhibited with the increase in MDA concentration (0, 0.5, 1, 2, 5, 10 mmol/L), and the carbonyl group, surface hydrophobicity, irregular curling, and MDA content increased significantly (P < 0.05), whereas the total sulfhydryl groups, α-helices, free amino groups, hydrolysis degree, and MDA incorporation decreased significantly (P < 0.05), The molecular particle size was significantly reduced (P < 0.05), and the molecular morphology and molecular structure were analyzed (P >0.05). Finally, the molecular size and cross-linking degree gradually increased. In conclusion, MDA can alter the structure and morphology of proteins, resulting in a decrease in hydrolysis and digestion rate. This study can provide theoretical support and reference for the regulation of protein digestion.

Insight into the allergenicity and structure changes of parvalbumin from Trachinotus ovatus induced by dense-phase carbon dioxide.

Parvalbumin (PV) is a major allergen in fish, and traditional treatments cannot reduce its sensitization. The effects of dense-phase carbon dioxide (DPCD) treatment on the sensitization and spatial structure of PV in Trachinotus ovatus were evaluated in this study. Western blotting and indirect ELISA were used to determine the allergenicity changes and spatial conformations of PV treated by DPCD. Tris-tricine-SDS-PAGE, circular dichroism, surface hydrophobicity, endogenous fluorescence, UV spectrophotometry, free amino group, total sulfhydryl group and SEM analyses were applied to characterize PV structure. The results showed that DPCD treatment (15 MPa, 30 min, 50 °C) could reduce PV-induced allergic reactions by 39-41 %, which destroyed the normal conformational epitopes and reduced the risk of PV-induced allergy. The secondary structure changed from ordered to disordered with a decreased content of α-helical groups, while the internal hydrophobic groups were exposed. The total sulfhydryl group content decreased significantly (P < 0.05). The surface hydrophobicity and ultraviolet absorption spectrum were enhanced, and the endogenous fluorescence peak shifted to a long wavelength. Meanwhile, the content of free amino groups increased significantly (P < 0.05). This study could provide a theoretical basis and a promising technical approach for reduction of PV allergenicities.

Effect of static magnetic field-assisted freezing at different temperatures on muscle quality of pacific white shrimp (Litopenaeus vannamei).

The effect of static magnetic field-assisted freezing (MF) at different temperatures (-35, -30, -25, and -20 °C) on the muscle quality of pacific white shrimp (Litopenaeus vannamei) was evaluated to investigate the possibility of energy saving by MF. The results showed that the -35 °C MF treatment increased the water-holding capacity of shrimp muscle, and maintained the wholeness of the microstructure compared to -35 °C immersion freezing (control group, IF). With the increase in freezing temperature in the MF treatments, the size of ice crystals gradually increased, and the sensory properties of shrimp decreased. The water-holding capacity, sensory properties, and water distribution of shrimp muscle subjected to MF at -25 °C were still no significantly different from those of the IF at -35 °C (P > 0.05). In summary, the utilization of MF enhanced the quality of frozen pacific white shrimp, which has the potential to provide energy saving benefits.

Effect of protein structure changes during different power ultrasound thawing on emulsification properties of common carp (Cyprinus carpio) myofibrillar protein.

The impact of ultrasound thawing (UT) at different power (0 W, 100 W/0.132 W·cm-2, 300 W/1.077 W·cm-2, and 500 W/1.997 W·cm-2, namely WT, UT-100, UT-300, and UT-500) on protein structure, aggregation, and emulsifying properties of common carp (Cyprinus carpio) myofibrillar protein were investigated in the present study. The result showed that the reactive sulfhydryl content, total sulfhydryl content, protein solubility, and absolute potential of UT-300 samples were obviously higher than those of other thawed samples, while the turbidity of UT-300 samples was lower (P < 0.05), which indicated that proper UT power was beneficial to inhibit protein aggregation caused by thawing, while too low (100 W) or too high (500 W) ultrasonic power had poor effect. The Ca2+-ATPase activity and thermal stability of UT-300 samples were much higher than those of other thawed samples (P < 0.05), indicating that UT-300 inhibited myosin denaturation and thermal stability reduction of thawed products. The α-helix content of UT-300 samples was higher than that of other thawed samples, while the ß-sheet content was significantly lower than that of other thawed samples (P < 0.05). The fluorescence intensity of UT-300 samples was higher than that of other thawed samples, and the λmax of UT-300 samples and UT-100 samples were lower than that of other thawed samples, which indicated that UT-300 could effectively inhibit the alteration of protein secondary structure and tertiary structure during thawing. The emulsifying activity of UT-300 samples was significantly higher than that of WT samples, and the droplet diameter of UT-300 samples was also lower than that of WT samples (P < 0.05), which indicated that UT-300 inhibited the decrease of emulsifying property during thawing. Overall, moderate ultrasonic power (300 W) could effectively inhibit the protein aggregation and structural changes during thawing, led to the decrease of emulsifying activity.

Effect of Liquid Nitrogen Freezing Temperature on the Muscle Quality of Litopenaeus vannamei.

The implications of different liquid nitrogen freezing (LNF) temperatures (-35 °C, -65 °C, -95 °C, and -125 °C) on the ice crystal and muscle quality of white shrimp (Litopenaeus vannamei) were investigated in this essay. The results showed that better muscle quality was maintained after LNF treatment compared to that after air blast freezing (AF) treatment. As the freezing temperature of liquid nitrogen decrease, the freezing speed accelerated, with the freezing speed of LNF at -125 °C being the fastest. However, an excessively fast freezing speed was not conducive to maintaining the quality of shrimp. Among all the freezing treatments, LNF at -95 °C led to the lowest thawing losses and cooking losses, and the highest L* values, indicating that LNF at -95 °C could keep the water holding capacity of frozen shrimp better than that with other freezing methods. At the same time, LNF at -95 °C resulted in higher water holding capacity, and hardness values for shrimps than those with other frozen treatments (p < 0.05). In addition, the results of the water distribution of shrimps showed that treatment with a -95 °C LNF reduced the migration rate of bound and free water. Meanwhile, the microstructural pores of shrimps in the -95 °C LNF group were smaller, indicating that the ice crystals generated during -95 °C LNF were relatively smaller than those generated via other frozen treatments. In conclusion, an appropriate LNF temperature (-95 °C) was beneficial for improving the quality of frozen shrimp, and avoiding freezing breakage.

Quantitative analysis of the correlation between gel strength and microstructure of shrimp surimi gel induced by dense phase carbon dioxide.

The impact of treatment pressure, temperature and time of DPCD on the Pacific White Shrimp (Litopenaeus vannamei) surimi gel properties was studied and compared with the conventional heat treatment. The gel strength, crosslinking degree, and microstructure of shrimp surimi gels were investigated. Quantitative microstructural characteristics were investigated to elucidate the changes in microstructure during the formation of gel induced by DPCD. With increased DPCD treatment setting conditions, the gel strength and crosslinking degree of shrimp surimi gel significantly improved (P < 0.05) with similar variation trends. Quantitative microstructural analysis revealed that the fractal dimension (Df) and the pore equivalent diameter of gel microstructure increased with the increase of DPCD treatment conditions. The lacunarity decreased and then increased, whereas pore number increased and decreased. According to the microstructural characteristics results, the surimi gel with 51.48 % degree of crosslinking induced at 25 MPa, 50˚C, and 60 min showed the most complex and homogeneous microstructure with the highest (Df), smaller lacunarity, an average pore equivalent diameter, and a larger pore number. The correlation analysis demonstrated that the crosslinking degree was strongly positively correlated with the gel strength. The Df, pore equivalent diameter and number of pores significantly positively correlated with the crosslinking degree, whereas the lacunarity strongly negatively correlated with the crosslinking degree. The present study showed that the DPCD treatment with a crosslinking degree of 51.48 % is the most optimum condition for better gel formation. The study could provide a theoretical basis for processing shrimp surimi with improved gel properties.

Insight into the microorganisms, quality, and protein structure of golden pompano (Trachinotus ovatus) treated with cold plasma at different voltages.

Cold plasma (CP) is a non-thermal novel technology for the processing of heat-sensitive food products, but there is concern regarding its impact on food quality. Voltage is one of the most direct factors affecting the bacteriostatic effect of CP. Golden pompano (Trachinotus ovatus) was treated with CP at different voltages (10, 20, and 30 kV). The total viable count decreased as the CP voltage increased, reaching a maximum reduction of 1.54 lg CFU/g on golden pompano treated at 30 kV. No effects on water-holding capacity, pH, total volatile base nitrogen, and T2b relaxation time were observed, indicating that all CP treatments retained the freshness and bound water of the samples. However, as the CP voltage increased, peroxide value and thiobarbituric acid-reactive substances of golden pompano gradually increased, the protein tertiary structure unfolded, and α-helices converted to ß-sheets, indicating inevitable lipid and protein oxidation caused by excessive CP voltage. Therefore, a suitable voltage of CP should be selected to inhibits the growth of microorganisms, which avoids deterioration of sea-foods quality.

Regulation of the Colour Change of 3D-Printed Mackerel Mince (Scomber scombrus) Based on Purple Potato Powder and Citric Acid.

The present study evaluates the effect of purple potato (PP) powder and citric acid (CA) on the regulation of the colour change of 3D (three-dimensional) printed mackerel mince (Scomber scombrus). In addition, the effects of PP and CA content on the 3D-printability and quality of mackerel mince were also investigated. The results showed that an increase in PP and CA concentrations gradually brightened the product colour and turned it pink. Furthermore, an increase in PP concentration and added CA reduced the fluidity and loss of water in mackerel mince. Proper PP and CA concentrations moderately increased the storage modulus (G'), loss modulus (G″), and yield stress of mackerel mince, making it suitable for 3D printing. At the same time, an increase in PP and CA concentrations enhanced the umami and sweet taste of mackerel mince but reduced the fishy and sour taste, and the degree of preference was within the acceptable range, except for PP1%-CA0%. It was found that, when the 3D-printing accuracy of mackerel-mince samples reached more than 97% and was acceptable, the optimal PP and CA concentrations for realizing the regulation of L*, a*, and b* were 1.00~3.00% and 0.09~0.32%, respectively.

Correlation between Water Characteristics and Gel Strength in the Gel Formation of Golden Pompano Surimi Induced by Dense Phase Carbon Dioxide.

The relationship between the gel quality of golden pompano surimi treated with dense phase carbon dioxide (DPCD) and changes in water characteristics was evaluated. Low-field nuclear magnetic resonance (LF-NMR) and nuclear magnetic resonance imaging were used to monitor changes in the water status of surimi gel under different treatment conditions. Whiteness, water-holding capacity and gel strength were used as the quality indicators of the surimi gel. The results showed that DPCD treatment could significantly increase the whiteness of surimi and the strength of the gel, while the water-holding capacity decreased significantly. LF-NMR analysis showed that, as the DPCD treatment intensity increased, the relaxation component T22 shifted to the right, T23 shifted to the left, the proportion of A22 decreased significantly (p < 0.05) and the proportion of A23 increased significantly (p < 0.05). A correlation analysis of water characteristics and gel strength showed that the water-holding capacity of surimi induced by DPCD was strongly positively correlated with gel strength, while A22 and T23 were strongly negatively correlated with gel strength. This study provides helpful insights into the quality control of DPCD in surimi processing and also provides an approach for the quality evaluation and detection of surimi products.

Physicochemical parameters and nutritional profile of back and abdomen muscle of fresh golden pompano (Trachinotus ovatus) and hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus).

Golden pompano (Trachinotus ovatus) and hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus) has widely been distributed in China and Southeast Asian countries with great commercial importance. In this study, the nutritional profiles, chemical and physical parameters of back and abdomen muscles were determined. Significantly different (p < .05) proximate compositions were found in two fish muscles. The contents of water-soluble protein, salt-soluble protein, and non-nitrogenous protein were higher in the golden pompano while salt-insoluble proteins were higher in the hybrid grouper. The main minerals found were K (3700.56-4495.57 µg/g) followed by P > Na > Mg > and Ca, respectively. Fatty acids contents consisted of polyunsaturated fatty acids ranging from 29.40% to 43.09% and saturated fatty acids 28.33% to 39.61%. The muscles were rich in n-3 PUFAs with n-6/n-3 ratio of 1.36%-2.96% in the back and abdomen. On the other hand, total amino acid and non-essential amino acid contents were found higher in the hybrid grouper while essential amino acid and delicious amino acid contents were higher in the golden pompano. Glutamic acid was the most predominant amino acid. The amino acid scores (AAS) of six amino acids were close to 1.00, whereas lysine showed the highest AAS while tryptophan was the most limited essential amino acid in all muscles, respectively. These results indicated golden pompano and hybrid grouper exhibited a varied nutritional composition and offered a good nutritional profile.

Insight into muscle quality of white shrimp (Litopenaeus vannamei) frozen with static magnetic-assisted freezing at different intensities.

The effects of magnetic field-assisted immersion freezing (MF) with different intensities (20, 40, 60, and 80 mT) on the freezing process and muscle quality of white shrimp (Litopenaeus vannamei) were studied in the present study. The results showed that, compared with immersion freezing (IF), 60 mT MF (MF-60) shortened the total freezing time, reduced thawing loss and cooking loss, and helped to maintain the water holding capacity and texture properties of frozen shrimp samples. In addition, the increase in the L* value of frozen shrimp samples was also inhibited by MF-60. The result of water distribution revealed that MF-60 reduced the mobility and loss of immobilized water and free water. The microstructure of MF-60 was characterized by smaller pores, indicating that MF-60 promoted the generation of fine ice crystals. Overall, MF-60 was beneficial in reducing ice crystal size and inhibiting the loss of shrimp muscle quality loss during the freezing process.