This study aims to explore the effects of radio frequency-assisted hot air drying (RF-HAD) on the drying characteristics and physicochemical properties of Litopenaeus vannamei (L. vannamei). Hot air drying (HAD) at 60 ℃ was taken as the control. A systematic investigation was also made to clarify the impacts on drying characteristics, water distribution, color, texture, astaxanthin content, antioxidant capacity, protein secondary structure, and microstructure under various drying temperatures (60, 70, and 80 ℃), and electrode gaps (107, 117, and 127 mm). The results showed that there was a dynamic variation in the internal temperature of L. vannamei during drying. The transverse relaxation time was adjusted to shorten the drying time by 47.22%-72.22%, compared with the HAD. The L. vannamei contained a high amount of the free water initially, and then evaporated, as the drying proceeded, leading to a great reduction in the free water content. At the last stage of drying, the bound water was the main component of the moisture in the L. vannamei, which was more difficult to remove. Therefore, the drying rate decreased, as the drying time increased. The relaxation time of strongly bound water T_2b value was significantly reduced (P<0.05) under the RF-HAD treatment, compared with the HAD. The RF-HAD L. vannamei tissue shared a stronger binding to water. The moisture of each component was removed continuously. At the same time, the immobile water was converted into bound water during RF-HAD. Additionally, the drying rate increased with the decrease of the electrode gap at the same RF-HAD temperature. There was a large proportion of the peak area that was occupied by bound water. Specifically, 107 mm treatment was more conducive to improving the drying efficiency. Besides, the L* value increased by 17.39%-21.70%, compared with the HAD. The RF-HAD treatment has enhanced the brightness of L. vannamei. Specifically, the L. vannamei dried at 60 ℃ with an electrode gap of 117 mm shared a higher L* value (51.23) and lower ∆E value (7.64), in order to better preserve the color of L. vannamei. The cohesiveness and chewiness of the L. vannamei after RF-HAD treatment were reduced by 34.88%-74.48% and 35.75%-79.49%, respectively, compared with the HAD, indicating improved palatability. Furthermore, the higher content of astaxanthin was observed at the same temperature of the RF-HAD, when the electrode gap was 117 mm, compared with 107 or 127 mm. The content of astaxanthin in the RF-HAD treatment groups at 70 and 80 ℃ was lower than that at 60 ℃. Specifically, the L. vannamei dried at 60 ℃ with an electrode gap of 117 mm shared the highest astaxanthin content (20.70 μg/g), indicating the slow degradation of astaxanthin. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging increased by 42.36% and 58.33%, respectively, at 60 ℃ with the electrode gap of 117 mm, compared with the 107 and 127 mm treatments, indicating the stronger antioxidant capacity and protein thermal stability. Scanning electron microscope (SEM) images revealed that the muscle fibers varied more outstandingly at the higher temperature and lower electrode gap. Moreover, the fractal dimension (1.923 0) at 60 ℃ with an electrode gap of 117 mm was quite lower, compared with the 107 and 127 mm treatments. The microstructure of the L. vannamei dried was relatively simple. Pearson’s correlation analysis showed that there was a correlation between the color and texture. Besides, the astaxanthin content was highly significantly positively correlated with the elasticity (P<0.01), although it was highly significantly negatively correlated with the hardness (P<0.01). Meanwhile, there was a significant positive correlation between DPPH scavenging and elasticity (P<0.05). This finding can provide the theoretical reference and technical assistance for the deep processing of the L. vannamei.

Pseudomonas fluorescens is a widespread spoilage bacterium in food, and its spoilage characteristics and biofilm formation are regulated by N-acyl-homoserine lactone (AHLs) quorum sensing (QS) system. Quorum quenching (QQ) is considered as an effective strategy to control the spoilage bacteria. Therefore, this study revealed a new QQ bacteria Lactiplantibacillus plantarum YP4-1-2. Notably, the crude cell extract (CCE) from L. plantarum YP4-1-2 showed strongly QQ activity against the AHLs of P. fluorescens. The degradation rate of AHLs (N-octanoyl-L-homoserine lactone) reached 25.90%, 78.57% and 100% at the CCE protein concentrations of 57, 86 and 114 μg/mL, respectively. In addition, the CCE could drastically reduce the formation of biofilm, bacterial motility (swimming and swarming), and the release of extracellular protease and biogenic amines of P. fluorescens. Real-time polymerase chain reaction (PCR) results revealed that the CCE downregulated QS-related genes (rhlI, rhlR, aprX, algA, orm, flgA, and ldcA). Finally, using whole-genome sequencing analysis, the active substance in the CCE was identified to be penicillin V acylase (PVA) and named LpPVA. Meanwhile, homologous modeling and molecular docking analysis showed that the binding effect of LpPVA on long-chain AHLs was better than that on short-chain AHLs. This study demonstrated that L. plantarum YP4-1-2 could be considered as a promising QS inhibitor and antibiofilm agent against foodborne spoilage bacteria.

The effects of different concentrations (0.05%, 0.1%, 0.15%, 0.2%, and 0.25%) of resveratrol (RE) on the structural properties, rheological properties and gel properties (gel strength, water retention, water mobility, whiteness and microstructure) of silver fish myofibrillar protein were investigated. RE was found to combine with myofibrillar protein molecules, resulting in an increase in the particle size. Ultraviolet (UV) absorption spectra and intrinsic fluorescence spectra showed that the addition of RE changed the spatial conformation of myofibrillar protein and reduce its fluorescence intensity. The rheological results showed that the addition of RE increased the storage modulus and loss modulus of myofibrillar protein. As the amount of added RE increased, the gel strength first increased and then decreased. The addition of 0.15% of RE increased it by 38.43% compared with the control group. In addition, the addition of RE also improved the texture properties of the gel and increased the whiteness. Low-field nuclear magnetic resonance (LF-NMR) analysis showed that the addition of RE transformed part of the free water into immobilized water, enhancing the water-binding capacity of the gel. Scanning electron microscopy (SEM) showed that the addition of RE promoted the formation of a denser gel network. These results show that when added at an appropriate level, RE could interact with silver carp myofibrillar protein to change its conformation, thereby enhancing the gel properties of myofibrillar protein and forming a dense gel network structure. The results of this study can provide a reference for improving the gel properties of freshwater fish surimi and the quality of surimi products.

In order to explore the effects of different drying methods on the physicochemical properties and microstructure of Penaeus vannamei, the drying characteristics, color, texture, water distribution, astaxanthin content, antioxidant capacity and microstructure of P. vannamei were analyzed after medium-short wave infrared drying (MSWID) or hot air drying (HAD). The results showed that with the increase in drying temperature, the moisture content of P. vannamei decreased gradually, and MSWID could reduce the drying time of P. vannamei by 16.67% and make its color brighter compared with HAD at 70 ℃. The hardness, gumminess and chewiness of P. vannamei were significantly increased with increasing drying temperature (P < 0.05), but the springiness was not significantly affected by drying temperature (P > 0.05). According to magnetic resonance imaging (MRI) results, the rate of water migration during MSWID was faster than that during HAD. Besides, the results of microstructure observation indicated that the muscle fiber of P. vannamei became looser and more porous after MSWID compared with HAD. For both drying treatments, the α-helix relative content of shrimp proteins first increased and then decreased, and the β-fold relative content showed a contrary trend. The astaxanthin content of MSWID dried shrimp was lower than that of HAD dried shrimp, and so was the antioxidant capacity. The quality of MSWID dried P. vannamei was better than that of HAD dried P. vannamei, indicating MSWID to be a promising drying method for P. vannamei.

Here air impingement drying (AID) was introduced to dry the desalted sea cucumber for less drying time and better quality of dried products. A systematic investigation was implemented to clarify the impacts of AID temperature (50, 60, and 70 ℃) and air velocity (4, 6, and 8 m/s) on the moisture distribution, moisture state, microstructure, hardness, and saponin content of desalted sea cucumber. Conventional hot air drying (HAD) was also taken as a control. The results revealed that the drying rate of desalted sea cucumbers increased significantly, as the drying temperature increased. The drying time of desalted sea cucumber was also reduced by 6.67%-33.33% at 6 m/s air velocity and various AID temperatures, compared with the HAD at 60 °C. The air velocity shared an insignificant effect on the drying time of desalted sea cucumbers (P>0.05) at the same temperature (60 ℃), particularly for the extended drying time (12-13 h) with the increased air velocity (4-8 m/s). The microstructure showed that the high AID temperature was beneficial to increase the porous structure of the material surface, leading to accelerated water migration. More and larger porous structures were observed on the surface of AID sea cucumber samples under the same conditions (the temperature was 60 ℃ and the air velocity was 6 m/s), compared with the HAD ones. As such, the AID drying rate was accelerated as well. However, the high air velocity was used to prevent the surface deformation (such as crusting) of desalted sea cucumber, thus reducing the structure porosity, which hindered the water migration and lowered the drying rate. The relaxation time of immobilized water in the AID sea cucumbers moved faster toward the short relaxation time, and then the peak amplitude decreased significantly, compared with the HAD. The low freedom of water molecules also led to a decrease in drying rate, with the extension of drying time. There was a weaker signal of proton density in the AID sea cucumbers. The water content was lower under the same conditions (drying time was 6 h). The water migration rate of AID sea cucumbers was higher than that of HAD, indicating that the AID was beneficial in shortening the drying time. The hardness of dried sea cucumber increased first and then decreased, with the increase in AID temperature and air velocity. The maximum hardness (494.25 N) was recorded at an AID temperature of 60 ℃ and 6 m/s air velocity. The saponin content (1.36-1.79 μg/g dry matter) of AID sea cucumbers increased with the increase in temperature, while there was no significant change in the air velocity. The saponin content of AID sea cucumber samples increased by 50% under the same conditions, compared with HAD. The temperature of 70 ℃ and the air velocity of 6 m/s were the better conditions for the AID sea cucumbers, in terms of drying efficiency and quality. The AID can be expected to improve the drying efficiency and ingredient retention rate of desalted sea cucumbers. The finding can provide theoretical reference and technical support for better drying quality.

This study investigated the protective and reparative effects of sea cucumber intestinal peptides (SCIPs) against ethanol-induced damage in human gastric mucosal epithelial cells (GES-1 cells) and explored the underlying mechanisms. SCIPs alleviated oxidative stress by reducing ROS levels, increasing SOD activity, and inhibiting MDA overproduction. Using a protein purification instrument and LC-MS/MS technology, peptides with a molecular weight of less than 1 kDa in the sea cucumber intestine were separated, purified, and identified, yielding a total of 91 peptide sequences. Using bioinformatics methods, the peptide PPPP with the best activity and drug-like properties is selected. Network pharmacology revealed that PPPP mainly exerts its biological functions by acting on core targets AKT1, EGFR, MAPK10, MAPK8, and IGF1R, regulating cancer pathways, PI3K-Akt signaling pathway, and lipid and atherosclerosis. Molecular docking and molecular dynamics simulations have confirmed that PPPP binds tightly to AKT1 through hydrogen bonds and hydrophobic interactions. The PPPP-AKT1 complex exhibits good stability, thereby effectively demonstrating its protective and reparative effects on the gastric mucosa. This study confirmed the protective and reparative effects of sea cucumber intestinal peptides on gastric mucosa and elucidated their underlying mechanisms, offering new insights for developing novel functional foods or pharmaceuticals.

This study aims to explore the effects of precision feedback microwave heating (PFMH) on the physicochemical properties of myofibrillar proteins (MPs) of Nemipterus virgatus. The MPs were collected from the Nemipterus virgatus as the research subject. Traditional water bath heating (40 ℃ for 30 min, and 90 ℃ for 20 min) was taken as the control. A systematic investigation was also made on the impacts of PFMH on the protein's turbidity, surface hydrophobicity, fluorescence intensity, ultraviolet (UV) absorbance thermal stability, gel electrophoresis patterns, surface morphology, and surimi gel chemical interactions under various temperatures and heating durations. Results showed that the turbidity and surface hydrophobicity of MPs significantly increased after PFMH treatment, compared with the control group. Both increases also indicated protein aggregation and denaturation, which were critical to understanding the variations in the internal structure of the protein. Specifically, the turbidity of MPs reached 0.78 when heated under S₈₅A conditions, which was an increase of 129.41%, compared with the control group (0.34). Meanwhile, the surface hydrophobicity increased to 177.45 μg, representing a 52.51% increase, compared with the control group (116.35 μg). As such, the PFMH treatment altered the tertiary structure of the protein. The lowest intensity of fluorescence was at S₈₅A, indicating that the PFMH treatment enhanced intermolecular interactions within the protein. Specifically, the PFMH treatment led to the dynamic fluorescence quenching of protein oxidative aggregates in the excited state, resulting in reduced fluorescence intensity. There was a higher fluorescence intensity of myofibrillar protein treated with PFMH at low temperatures (80 °C for 2 and 3 min), compared with the control. The reason was possibly that the rapid PFMH treatment caused some tryptophan residues to be buried within the MPs molecules. Conversely, the UV absorbance exhibited an upward trend, indicating that the PFMH heating induced the conformational changes in the protein structure. The exposure of more aromatic residues led to more effective UV light. Thermal stability was assessed using differential scanning calorimetry (DSC). The results showed that the PFMH treatment significantly enhanced the thermal stability of MPs. Furthermore, the degradation temperature (T_d) of the MPs under S₈₅A conditions reached the maximum of 62.20 ℃, an increase of 13.65%, compared with the control group (54.73 ℃). The enthalpy change (ΔH) decreased from 0.43 J/g in the control group to 0.03 J/g, representing a 93.02% reduction. As such, the PFMH treatment effectively prevented the thermal denaturation and degradation of MPs at elevated temperatures. Gel electrophoresis patterns and atomic force microscopy (AFM) images further revealed the structural changes induced by PFMH treatment. The MPs also unfolded to form a dense gel network structure under the S₈₅A condition. Additionally, the AFM images indicated that the size of MPs aggregates increased, while the quantities decreased after PFMH treatment at 90 °C. Chemical interactions revealed that the maximum content of hydrogen bond was 3.06 g/L after heating at S₈₅A conditions, which was 14.61% higher than that of the control group (2.67 g/L). Meanwhile, the hydrophobic interactions and disulfide bonds increased by 105.60% and 97.80%, respectively. However, the ionic bonds decreased after PFMH treatment, compared with the control group. The cross-linking and aggregation of MPs were promoted to form a more stable and compact protein structure. In conclusion, these findings demonstrated that the PFMH treatment significantly affected the physicochemical properties of MPs in Nemipterus virgatus. The protein denaturation and aggregation also induced the structural changes to enhance the thermal stability and the formation of dense gel networks. The heating processing of surimi products can also offer potential reference data for the future application of PFMH technology.

The effects of starch type and concentration, egg white powder concentration and surimi concentration on the gel properties, water-holding capacity, texture characteristics, whiteness and sensory score of precooked shrimp cake prepared from Penaeus vannamei meat were investigated. Based on the results of single factor experiments, the formulation of precooked shrimp cake was optimized by response surface methodology (RSM) with gel strength and sensory scores as response values. The results showed that compared with other starches, cassava phosphate starch could effectively improve the eating quality of shrimp cake. The optimal formulation was determined as follows: 0.5% salt, 1% sodium glutamate, 3% lard, 0.5% compound phosphate, 2% soy protein isolate, 0.5% ginger powder, 0.5% onion powder, 1% cooking wine, 10% water, 15% mixed vegetable granules, 5.98% starch, 4.80% egg white powder, and 30.22% surimi relative to the mass of shrimp. The sensory score and gel strength of shrimp cake prepared using the optimized formulation were 89.20 and 65.06 g·cm respectively, which were not significantly different from the predicted values.

A Pickering emulsion based on sodium starch octenyl succinate (SSOS) was prepared and its effects on the physicochemical properties of hairtail myofibrillar protein gels (MPGs) subjected to multiple freeze-thaw (F-T) cycles were investigated. The whiteness, water-holding capacity, storage modulus (G’) and texture properties of the MPGs were significantly improved by adding 1%–2% Pickering emulsion (P < 0.05). Me anwhile, Raman spectral analysis demonstrated that Pickering emulsion promoted the transformation of secondary structure, enhanced hydrogen bonds and hydrophobic interactions, and promoted the transition of disulfide bond conformation from g-g-g to g-g-t and t-g-t. At an emulsion concentration of 2%, the α-helix content decreased by 10.37%, while the β-sheet content increased by 7.94%, compared to the control. After F-T cycles, the structure of the MPGs was destroyed, with an increase in hardness and a decrease in whiteness and waterholding capacity, however, the quality degradation of MPGs was reduced with 1%–2% Pickering emulsion. These findings demonstrated that SSOS-Pickering emulsions, as potential fat substitutes, can enhance the gel properties and the F-T stability of MPGs.