Insight into the Gel Properties of Antarctic Krill and Pacific White Shrimp Surimi Gels and the Feasibility of Polysaccharides as Texture Enhancers of Antarctic Krill Surimi Gels

The mechanism of egg white protein to enhance the thermal gel properties of giant squid (Dosidicus gigas) surimi

In this paper, the interaction between egg white protein (EWP) and giant squid surimi was regulated by changing the ratio of surimi to EWP, and the mechanism of EWP on the gel properties of giant squid surimi was analyzed. The results showed that when the proportion of EWP was 16: 1, the hardness and springiness of surimi gel were the highest, reaching 645.5 g and 1.258, respectively. The gel strength reached 0.634 kg, the cooking yield of surimi gel increased by 27 % and the water loss decreased to less than 10 %. A significant increase in the proportion of fixed water and a decrease in the proportion of free water indicated that mixed surimi improved the "trapping" ability of water molecules, induced the formation of a more ordered "cage"-like structure, and significantly increased the water holding capacity and whiteness of surimi gels.

Decoding the textural deterioration of ready-to-eat shrimp: Insights from dynamic myofibrillar protein changes during thermal sterilization

Previous research has indicated a noticeable decline in the textural properties of ready-to-eat shrimp after thermal sterilization. However, the specific deterioration pattern of these textural properties during thermal sterilization remains unclear. This study investigated the dynamic changes of myofibrillar protein during thermal sterilization and their relationship with the textural properties of ready-to-eat shrimp. The primary textural attributes, including hardness, cohesiveness, chewiness, and responsiveness, initially decreased, followed by an increase and a subsequent decrease during sterilization. With the extension of sterilization time, protein oxidation increased, leading to protein unfolding, cross-linking, and aggregate formation. The content of ordered α-helix decreased by 22.35 %, and the content of random coil increased by 21.5 %, indicating the re-degradation of protein aggregates during the final stage of thermal sterilization. Observations from fluorescence microscopy and atomic force microscopy confirmed significant aggregation and degradation of protein particles during sterilization. Therefore, the aggregation and degradation of myofibrillar protein are the primary factors contributing to the changes in the textural properties of the shrimp during thermal sterilization. These findings provide valuable insights for quality control measures in processing ready-to-eat shrimp.

Effect of dense phase carbon dioxide on the digestive properties of shrimp surimi gels: Insight from digestive kinetic

Understanding the protein digestion rate and the release of nutrients in the gastrointestinal tract is critical to designing novel food products with enhanced functionalities. The digestion characteristics of untreated shrimp surimi and surimi gels induced by water-bath heating (WB) and different dense phase carbon dioxide (DPCD) treatment (L, M, and H crosslink degree) groups were studied. With the increasing crosslink, the protein digestibility increased and the average particle size decreased. The DPCD treatment condition (25 MPa, 50 °C, 60 min) induced H crosslink showed higher digestibility (91.31 %), compared to those other groups (P < 0.05). An increase in fluorescence intensity with redshift was shown in the gastric phase, while a decrease in fluorescent intensity with blueshift was displayed in the gastrointestinal phase. The MHC and actin bands were progressively degraded and disappeared with increasing digestion, and the intensity of low molecular weight < 10 kDa became obvious in late digestion. According to the digestive kinetic results, the H group showed that free amino acids decreased (325.77 ± 1.58 μmol/L) and then increased (789.18 ± 8.13 μmol/L) in the gastric phase, reaching a maximum value (5.86 ± 0.034 mmol/L) at the end of GI digestion phase (P < 0.05). The results suggested that the proper crosslink structure would provide a sustainable release of the nutritional value of shrimp surimi gels. This study provides the underlying mechanisms of surimi protein digestion and nutrient release in the GI tract.

Synergistic cryoprotective effects of mannan oligosaccharides and curdlan on the grass carp surimi

The cryoprotective effects of mannan oligosaccharides (MOS) and curdlan (CU) on the quality of grass carp surimi after freeze-thaw cycles (FTCs) were assessed using the response surface methodology. The optimal contents of MOS (6.79 %, w/w) and CU (0.45 %, w/w) produced minimum thawing losses and the highest gel strength of surimi after five times FTCs. MOS, CU, and their mixture demonstrated cryoprotective effects on grass carp surimi. Compared to MOS or CU alone, MOS-CU displayed synergistic cryoprotective effects, as evidenced by the better prevention of thawing losses of surimi, the superior retardation of the aggregation and denaturation of MP, the amelioration of the gel strength and WHC of surimi gel. Moreover, the MOS-CU mixture demonstrated cryoprotective effects equivalent to those of commercial cryoprotectant on grass carp surimi from zero to five times FTCs and even outperformed CC after seven times FTCs.

Ultrasound treatment improved gelling and emulsifying properties of myofibrillar proteins from Antarctic krill (Euphausia superba)

Antarctic krill is a promising source of marine proteins with abundant biomass and excellent nutritional profile, but has poor technological properties. Ultrasonic treatment at power levels of 0, 100, 200, 300, 400 and 500 W was applied to improve the technological properties of Antarctic krill meat, and the changes in physicochemical properties of myofibrillar proteins (MPs) were investigated. The results indicated that proper ultrasonic treatment significantly improved the gelling properties of Antarctic krill meat, in terms of a more uniform and stable gel texture and better water holding capacity, which were related to better cross-linking of MPs. Ultrasonic treatment promoted the conversion of MPs' secondary structures from α-helix and random coil to β-sheet and β-turn, thereby making the molecular structure soft and loose. In addition, at tertiary structure level, ultrasonic treatment exposed the hydrophobic groups and sulfhydryl groups within MPs, thereby improving the emulsifying properties by changing the intermolecular interactions and interface properties. Furthermore, the particle size of MPs decreased and exhibited a more uniform distribution, aligning with the enhanced interactions observed between MPs and oil. These results provide an insight into the efficient development of Antarctic krill by elucidating how the ultrasonic treatment improves the gelling and emulsifying properties based on structure modulation of myofibrillar proteins.

Evaluation of the texture characteristics and taste of shrimp surimi with partial replacement of NaCl by non‑sodium metal salts

Ionic strength plays a significant role in the aggregation behavior of myofibrillar proteins. The study investigated the effects of KCl or CaCl2 as substitutes for NaCl on the gel properties and taste of shrimp surimi at a constant ionic strength (IS = 0.51). Increased KCl substitution ratio resulted in a reduction in α-helix content and an increase in β-sheet content of myofibrillar proteins, thereby enhancing water holding capacity. Optimal KCl substitutions (1.5% NaCl +1.94% KCl) contributed to maintaining the desired taste and improving gel properties. CaCl2 facilitates the extraction and dissolution of myofibrillar proteins, resulting in an organized and dense gel network with significant water-holding capacity. However, excessive additions (>1.27%) resulted in a notable decrease in taste and gel strength due to excessive aggregation and precipitation of myofibrillar proteins. These findings provide a solid theoretical foundation for production of high-quality, low-salt shrimp surimi.

Effects of different thermal sterilization conditions on the quality of ready-to-eat shrimp based on specific sterilization intensity

The effects of different thermal sterilization conditions on the quality and digestibility of ready-to-eat (RTE) shrimp were investigated. Compared with the high-temperature (121 °C) and short-time (6 min and 8 min) sterilization, the low-temperature (110 and 115 °C) and long-time (>20 min) sterilization significantly promoted the Maillard and browning reactions and changed the color of the RTE-shrimp. The high sterilization temperature promoted shrimp protein oxidation, resulting in increased carbonyl group, disulfide bond, and free radical content, while the free sulfhydryl group content decreased. This oxidation and tissue destruction at high temperature led to reduced texture properties and altered water distribution within the shrimp's muscles. However, sterilized shrimp exhibited superior digestive properties in an in vitro simulated digestion experiment. High-temperature and short-time sterilization is more effective in mitigating the quality deterioration of RTE-shrimp compared to low-temperature and long-time sterilization.

Effect of κ-carrageenan on the quality of crayfish surimi gels

The demand for crayfish surimi products has grown recently due to its high protein content. This study examined the effects of varying κ-carrageenan (CAR) and crayfish surimi (CSM) concentrations on the gelling properties of CAR-CSM composite gel and its intrinsic formation process. Our findings demonstrated that with the increasing concentration of carrageenan, the quality of CAR-CSM exhibited rising trend followed by subsequently fall. Based on the textural qualities, the highest quality CAR-CSM was achieved at 0.3% carrageenan addition. With the exception of chewiness, and the cooking loss of the gel system was 1.62%, whiteness was 82.35%, and the percentage of β-sheets increased to 57.18%. Further increase in CAR (0.4-0.5%) addition resulted in internal build-up of LCAR-CSM, conversion of intermolecular forces into disulfide bonds and gel breakage. This study exudes timely recommendations for extending the CAR application for the continuous development of crayfish surimi and its derivatives and its overall economic worth.

Exploring the versatility of carbohydrates in surimi and surimi products: novel applications and future perspectives

Carbohydrate is one kind of the most important additives in the production of surimi and surimi products, mainly due to its wide range of sources and superior functionality. In recent years, new carbohydrates (oligosaccharides and polysaccharides) have been gradually applied in the production of surimi and surimi products which is mainly driven by consumer requirement on nutritional and the flavors or taste quality and producer requirement on extending the shelf life, like low calorie intake, dietary fiber enrichment, rich taste and improvement of antioxidant properties. Besides anti-freezing and improvement in gelling ability, novel functionalities have been explored such as fat substitution, improving flavor, antibacterial effect, antioxidant effect and improving three-dimensional printability. With an in-depth study of the mechanism of carbohydrate improving the qualities of surimi and surimi products, the application of carbohydrates in surimi would be more effective. Therefore, this review summarizes the new carbohydrates applied in the processing of surimi and surimi products, and their novel functionalities. Additionally, progress of the research on the mechanism of carbohydrate improving the qualities of surimi is also reviewed. © 2023 Society of Chemical Industry.

Tapioca Starch Improves the Quality of Virgatus nemipterus Surimi Gel by Enhancing Molecular Interaction in the Gel System

The gel prepared using Nemipterus virgatus (N. virgatus) surimi alone still has some defects in texture and taste. Complexing with polysaccharides is an efficient strategy to enhance its gel properties. The main objective of this study was to analyze the relationship between the gel quality and molecular interaction of N. virgatus surimi gel after complexing with tapioca starch. The results make clear that the gel strength, hardness, and chewiness of surimi gel were increased by molecular interaction with tapioca starch. At the appropriate addition amount (12%, w/w), the surimi gel had an excellent gel strength (17.48 N), water-holding capacity (WHC) (89.01%), lower cooking loss rate (CLR) (0.95%), and shortened T2 relaxation time. Microstructure analysis indicated that the addition of tapioca starch facilitated even distribution in the gel network structure, resulting in a significant reduction in cavity diameter, with the minimum diameter reduced to 20.33 μm. In addition, tapioca starch enhanced the hydrogen bonding and hydrophobic interaction in the gel system and promoted the transformation of α-helix to β-sheet (p < 0.05). Correlation analysis showed that the increased physicochemical properties of surimi gel were closely related to the enhanced noncovalent interactions. In conclusion, noncovalent complexation with tapioca starch is an efficient strategy to enhance the quality of surimi gel.

Discovery of Potential Protein Markers Associated with Quality Characteristics of Antarctic Krill (Euphausia superba) Surimi Gel

Antarctic krill are a consumption resource with great exploitation potential. However, the poor gel properties of Antarctic krill meat seriously limit its high-value application. In the present study, the quality characteristics and proteome changes of the κ-/ι-carrageenan-Antarctic krill surimi gel were systematically analyzed and compared. In addition, the transcriptome sequencing of Antarctic krill was carried out, which filled the gap in the Antarctic krill database. Higher molecular forces (disulfide bond and hydrophobic interaction) and the degree of network cross-linking significantly promoted the formation of κ/ι-carrageenan-Antarctic krill surimi compared to that of Antarctic krill surimi. This is the first study to investigate and map potential protein markers for quality characteristics of Antarctic krill surimi based on mass spectrometry-based label-free quantitative proteomics. The results could provide a theoretical reference for the quality control of Antarctic krill during application.