Structuring emulsion gels with peanut protein isolate and fish oil and analyzing the mechanical and microstructural characteristics of surimi gel

Intermolecular interactions influenced the gelation and texture improvement of sturgeon surimi gels by walnut protein isolates

Intermolecular interaction is a key factor in the fortification of surimi gels by plant protein addition. Here, the effects of different intermolecular interactions, such as ionic, covalent and non-covalent interactions, on gel structure, gelation strength and water-holding properties were investigated, using sturgeon surimi fortified by three walnut isolates, including walnut meal (WM), protein isolate (WPI) and peptide (WP), as representatives. Quantitative creep-recovery analysis and soluble protein assay demonstrated that secondary bonds, mainly hydrophobic interaction and hydrogen bond, possibly played a dominant role in walnut protein-fortified surimi gels. Hydrophobic interaction and disulfide bond benefited gelation behavior and textural strengthening by supplementation of WM and WPI. However, 1-3 % addition of WPI and WP positively influenced water retention of surimi gels due to higher hydrogen bonding level. Structural integrity of surimi gel was not destroyed, while appropriate addition of walnut proteins especially WPI improved sensory quality of sturgeon surimi product.

Effect of different concentrations of kappa-carrageenan on gelation properties of walnut protein

Walnut protein (WP) possesses considerable nutritional and biological value, however, the 70% water-insoluble gluten composition constrains its applicability in commercial settings. The effect of different concentrations of kappa-carrageenan (KC) on the properties of WP gels was investigated in this study. The results suggested that hydrophobic interactions are the most important force when WP/KC gels are formed. Furthermore, structural analysis revealed that KC induces notable alterations in protein molecules' secondary and tertiary structures. Moreover, the critical gelation concentration of WP decreased from 10% (w/v) to 6% (w/v) in the addition of KC. As the amount of KC increased, the rheological properties, texture properties, and physical stability of gels were enhanced. Specifically, when the addition of carrageenan increased to 2.0% (w/v), hardness increased from 25.06 g to 139.07 g, and the water-holding capacity reached 99.75%. These results provide theoretical support for the diversification of potential uses of WP/KC complexes in the plant-based protein classes.

Impact of Saturated and Unsaturated Oils on the Nonlinear Viscoelasticity, Microstructure, and 3D Printability of Fish Myofibrillar-Protein-Based Pastes and Gels

The effect of oil incorporation (soybean oil [SO] and coconut oil [CO] at 0, 1, 3, and 5 g/100 g) on the rheological, structural, and 3D printing properties of fish myofibrillar protein (MP, also known as surimi) paste and gel was investigated. Small-amplitude oscillatory shear (SAOS) tests showed that increasing oil concentration reduced the storage modulus (G'), weakening the gel network. Large-amplitude oscillatory shear (LAOS) analysis revealed strain-stiffening shifts and nonlinearity at γ = 5%. CO-containing gels exhibited higher hardness and gumminess, particularly at lower concentrations, due to enhanced protein-lipid interactions. In contrast, SO-containing gels showed reduced strength at higher concentrations, indicating phase separation. SEM confirmed that CO promoted a denser network, while SO led to a more porous structure, especially at 5% oil. Three-dimensional printing analysis demonstrated that both oils improved extrusion flowability by reducing nozzle friction. However, CO-containing samples maintained post-extrusion stability at 85% moisture, whereas SO-containing samples collapsed after multiple layers due to excessive softening. These findings highlight oil's dual role in MP gels, enhancing lubrication and flowability while compromising rigidity. The results offer valuable insights for developing soft, texture-controlled foods using 3D printing, especially for personalized nutrition applications such as elderly care or dysphagia-friendly diets.

Enhancing the nutritional value and caliber of silver carp surimi by adding β-carotene: Insights into the gel characteristics, protein structure, and digestive properties

To investigate the effects of β-carotene on the gelling and digestion properties of surimi gels and the underlying molecular mechanisms, the gel properties, moisture distribution, rheological properties, secondary structure and microstructure were determined at different β-carotene concentrations (0 % ∼ 0.1 %). The results indicated that β-carotene levels from 0.02 % to 0.06 % were positively correlated with gel properties, and the storage modulus (G') gradually increased during heating. This was attributed primarily to the conversion of α-helix to β-sheet structures and the intensification of hydrophobic interactions, resulting in a more compact microstructure. Most importantly, at an additional level of 0.06 %, the digestibility did not significantly decrease with increasing gel properties. Moreover, the antioxidant activity of the hybrid gels subjected to gastrointestinal digestion was also enhanced. The present study provides a theoretical foundation for incorporating β-carotene into surimi which will provide more nutritious products.

Effect of K2CO3 on konjac glucomannan/κ-carrageenan-based camellia oil Pickering emulsion gel for the development of fat analogs

Konjac glucomannan (KGM) undergoes deacetylation in alkaline conditions, while κ-carrageenan (CRG) is sensitive to potassium ions. This study examines the influence of K2CO3 on the mechanical properties of KGM/CRG-based camellia oil Pickering emulsion gels. Texture analysis and rheological testing revealed that the addition of K2CO3 significantly enhanced the mechanical properties of emulsion gels. Texture parameters, such as the hardness, gumminess, and chewiness of the gel, were closer to those of pork back fat when the K2CO3 concentration was 0.2 M. The addition of K2CO3 enhance the intermolecular crosslinking within the gel and formed a more uniform and dense gel network, promoting gelation and structural stability, which were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, and microstructural analysis. Besides, low-field nuclear magnetic resonance and thermogravimetric analyses indicated that the addition of K2CO3 reduced the water mobility of the gel and improved its thermal stability. Physicochemical and color analysis results showed that the energy value of the camellia oil Pickering emulsion gel was only 15.9 % that of pork back fat, and its appearance was closer to that of pork back fat than hydrogels. This study provides technical support for the use of KGM/CRG-based camellia oil Pickering emulsion gels as fat analogs.

Enhancing gel and 3D printing performance of lipid-enhanced skipjack tuna (Katsuwonus pelamis) surimi via Pickering high internal phase emulsion

This study explored the effect of lactoferrin (LF)-stabilized fish oil Pickering high internal phase emulsions (HIPPEs) on the gel property and 3D printing performance of skipjack tuna surimi compared with directly added fish oil. Based on the various environmental stress stability, HIPPEs could remain relatively stable when added to surimi gels. The luminance and whiteness of skipjack tuna surimi gel were significantly (p < 0.05) elevated after adding HIPPEs. Compared with directly added fish oil, the texture properties, gel strength and water holding capacity of surimi gels were notably (p < 0.05) increased after adding HIPPEs, and more free water changed into bound water and non-fluidizable water. Moreover, more α-helix turned into β-sheet, and the disulfide bond content was increased. The microstructure indicated that the tiny oil droplets of HIPPEs were more evenly distributed in the surimi gel network, while directly added fish oil caused the larger droplets aggregation and damaged the gel network structure. Higher viscoelastic modulus and apparent viscosity endowed surimi with better 3D printing accuracy and stability. Consequently, HIPPEs improved the quality of skipjack tuna surimi gel, which could provide a direction for developing of new skipjack tuna products.

Plant proteins in structuring gelled emulsions for saturated fat substitutes: Challenges and opportunities

Gelled emulsions are promising alternatives to saturated fats, offering the ability to mimic the solid-like behavior of fat while incorporating healthier oils. Polysaccharides and proteins, known for their emulsifying and gelling properties, are commonly used in such systems. Recently, plant proteins have gained increasing attention due to the growing demand for alternative proteins and the rise of flexitarian and vegetarian diets. This review explores the use of plant proteins to structure gelled emulsions as potential substitutes for saturated fats, highlighting the challenges and opportunities of this approach. Physical treatments such as heating, sonication, and high pressure have been used to enhance the functional properties of plant proteins, improving their performance as gelling and emulsifying agents. These treatments have resulted in gelled emulsions with improved properties, such as higher G', increased yield stress, lower tan δ, and improved water absorption. Additionally, applying these physical treatments during emulsification has been shown to enhance system interactions. Incorporating polysaccharides into the protein network can result in a segregative or aggregative relation, potentially leading to a stiffer microstructure. Recent studies demonstrated that the combination of biopolymers resulted in structures with texture characteristics similar to those of fat, such as hardness, chewiness, and lubricity. Finding new correlations between structural properties and sensory aspects through tribological, rheological, and fundamental texture analyses could provide valuable information on the sensory perception of fat.

Unveiling the protein-lipid interaction mechanism: How the sturgeon lipids diminish the surimi gel properties

Sturgeon, with 4 times higher lipid content than silver carp (ubiquitously applied for surimi production in China), affects surimi gelling properties. However, how the flesh lipids affect gelling properties remains unclear. This study investigated how flesh lipids impact surimi gelling properties and elucidated the interaction mechanism between lipids and proteins. Results revealed yellow meat contains 7 times higher lipids than white meat. Stronger ionic protein-protein interactions were replaced by weaker hydrophobic forces and hydrogen bonds in protein-lipid interaction. Protein-lipid interaction zones encapsulated lipid particles, changing protein structure from α-helix to β-sheet structure thereby gel structure becomes flexible and disordered, significantly diminishing surimi gel strength. Docking analysis validated fatty acid mainly binding at Ala577, Ile461, Arg231, Phe165, His665, and His663 of myosin. This study first reported the weakened surimi gelling properties from the perspective of free fatty acids and myosin interactions, offering a theoretical basis for sturgeon surimi production.

Factors influencing surimi gelling properties and natural additive-based gel fortification strategies: A review

Gelation and gel properties are crucial to surimi-based seafood products, and many factors significantly influence surimi gel quality. Although physical and chemical modifications can improve surimi gel performance, challenges such as high cost, difficulties in industrialization and environmental pollution pose significant barriers to their practicality. Natural additives offer a promising alternative by reinforcing and improving the characteristics of surimi gel through mechanisms such as protein conformational transformation, protein denaturation, and altered chemical forces. By incorporating different substances into surimi gel, it is possible to tune the interaction between the additives and the myofibrillar proteins, thus enhancing the gelation process and achieving the desired textural profiles. This review comprehensively explored the factors influencing the surimi gelation chemistry, with a focus on how the natural additives such as proteins, lipids, polysaccharides, salts, enzymes, and extracts impact the surimi gel properties. It elucidated the reinforcing mechanisms of these additives and proposed a general interaction model between natural substance and myofibrillar proteins. Furthermore, this review well established the interrelation between the performance and mechanism of enhancement effects of typical natural substances on surimi gels and provided new insights on tuning surimi gelation and gel properties by adding natural additives with specific physicochemical properties, thus facilitating the production of high-quality surimi products with satisfactory gel characteristics in food industry.

The Effects of Cooking Methods on Gel Properties, Lipid Quality, and Flavor of Surimi Gels Fortified with Antarctic Krill (Euphausia superba) Oil as High Internal Phase Emulsions

In this study, silver carp surimi products enriched with Antarctic krill oil high internal phase emulsions (AKO-HIPEs) were cooked using steaming (STE), microwave heating (MIC), and air-frying (AIR), respectively. The gel and flavor properties, lipid quality and stability were investigated. Compared to the MIC and AIR groups, the STE surimi gel added with HIPEs had better texture properties, exhibiting higher water-holding capacity and a more homogeneous structure, while the air-frying treatment resulted in visually brighter surimi products. The degree of lipid oxidation during cooking was in an order of STE < MIC < AIR as determined by electron paramagnetic resonance spectrometer and thiobarbituric acid reactive substances. HIPE-added surimi gels retained more nutrients and flavor when cooked by AIR compared to STE and MIC. Results imply that the texture properties and lipid stability of surimi products fortified with AKO-HIPEs were better than those of the oil group under any cooking method. In conclusion, surimi products added with AKO-HIPEs had better gel properties and retained more fatty acids and flavor than AKO-SO.

Rice bran oil-in-water emulsion stabilized by Amur catfish myofibrillar protein: Characteristics and its application in surimi gels

The objective of this investigation was to isolate amur catfish myofibrillar protein (AMP), emulsify it with rice bran oil, and assess its application in the silver carp surimi gel. The proportion and addition of AMP/rice bran oil emulsion on the gel properties were compared. The emulsion stabilized by 3 % AMP was stable when an oil/water ratio of 0.70 and 0.75 was employed, as evidenced by its appearance, microstructure, and rheological characteristics. The L*, a* and whiteness values of gels observably elevated when the emulsion blended (p < 0.05). The mechanical capacities (texture and rheology indicators) of surimi gels were dramatically improved with 5 % emulsion added (p < 0.05). However, the addition of excessive emulsion (up to 15 %) impeded the formation of surimi protein network and lowered water retention ability of surimi gels. Moreover, 5 % emulsion was distributed uniformly throughout the gel matrix, giving rise to the development of a dense and uniform network with high water binding capacity. Furthermore, the study on protein solubility expressed that the addition of the emulsion facilitated protein-protein interactions in surimi gels. In summary, the addition of 5 % AMP stabilized rice bran oil emulsion could yield a stronger surimi gel with increased whiteness. The resulting gels could serve as healthy fat-rich surimi-based products.

Protein-based Emulsion Hydrogels and Their Application in the Development of Sustainable Food Products

Consumers have become more conscious of their diet, resulting in an increased demand for low-calorie and nutrient-rich food. Therefore, finding alternative ways to develop food products with improved nutritional values has become necessary without compromising the textural and sensorial properties. In the last few years, emulsion gels have gained much popularity for oil structuring, delivery of bioactive compounds, and development of nutritious food products. Protein-stabilized emulsion hydrogels have the most significant potential to be utilized in the food industry as they contain natural ingredients that help with clean label tags. Different gelation methods can be used to fabricate emulsion gels depending on the requirements of end products. Emulsion hydrogels' rheological, textural, mechanical, and structural properties can be modified by altering their composition, oil concentration, gelation method, and gelling environment, such as pH, temperature, etc. This review addresses using protein-based emulsion gels to develop novel food products with reduced-calorie and nutrition-rich content.

Effect of α-tocopherol, soybean oil, and glyceryl monostearate oleogel on gel properties and the in-vitro digestion of low-salt silver carp (Hypophthalmichthys molitrix) surimi

To improve nutritional health, a low-salt (0.5 %) silver carp (Hypophthalmichthys molitrix) surimi gel with α-tocopherol, soybean oil, and glyceryl monostearate oleogel was fabricated and evaluated for textural qualities, lipid oxidation, and in-vitro digestion analysis. Based on the texture profile analysis, gel strength, water holding capacity (WHC), rheological, protein secondary structure, and microstructural examination, 5 % oleogel addition to low-salt surimi exhibited similar physicochemical properties to regular-salt surimi gels. By crosslinking myosin and filling protein network voids, the oleogel increased surimi gel density. Increasing oleogel content improved the physicochemical qualities of heat-induced surimi, causing protein aggregation during digestion and reducing digestibility. The presence of oleogel altered protein secondary structure, reducing α-helix content and increasing β-sheet and other structures, enhancing WHC and gel strength of low salt surimi. Adding oleogel improved the antioxidant activity of digestive solutions. This study will help understand myosin-oleogel interaction and the development of sustainable and nutritious surimi-based foods.

Effect and mechanism of different exogenous biomolecules on the thermal-induced gel properties of surimi: A review

Surimi products are favored by domestic and foreign consumers due to their distinctive gelatinous texture, rich nutrition, and convenient consumption. Gel properties are key evaluation indicators for the quality of surimi products, which was mainly determined by the gel-forming ability of the myofibrillar protein (MP). In recent years, the surimi processing industry has faced challenges in product quality that limits the further development, and how to effectively improve the gel properties of surimi products has become one of the key scientific problems to be solved in surimi processing industry. A viable strategy for improving the product quality involves combining surimi with exogenous additives, such as proteins, polysaccharides, and lipids, to enhance the gel-forming ability of MP. At present, there is limited literature review to systematically investigate the role of these exogenous additives in interacting with MPs in surimi gel system and their effect on the gel properties of heat-induced surimi. Therefore, in this review, we systematically discussed the formation mechanism and influencing factors of surimi gel, the interactions of exogenous biomolecules (proteins, polysaccharides, and lipids) with surimi protein, as well as their effects on the gel properties of surimi product. The aim of this review was to help us with a better understanding for the intrinsic action mechanisms of complex surimi system and provide some theoretical guidance for the improvement of gel quality and development of surimi products.

A comparative study of different soybean oil forms on the physicochemical properties of surimi myofibrillar protein gel: The role of soybean protein isolate and κ-carrageenan

Natural soybean oil, Pickering emulsion, high-internal-phase emulsion (HIPE), and emulsion gel were prepared to investigate their effects on the physicochemical properties of surimi myofibrillar protein gels. Their effects on gel strength ranked as: emulsion gel > Pickering emulsion > HIPE > soybean oil. At the same oil content, the emulsion gel exhibited higher G' than the other forms whereas natural oil exhibited the lowest G', and T22 was smaller in the emulsion gel group, indicating that the emulsion gel enhanced the interaction between water molecules and protein macromolecules. FT-IR testified that 9 % natural oil reduced the β-sheet content to 26.34 %, whereas Pickering emulsion, HIPE, and emulsion gel recovered the β-sheet content to 31.30 %, 36.17 %, and 32.69 %, respectively. Emulsion gel led to fewer voids, and the oil droplets in emulsion gel were more regularly spherical and homogeneously dispersed in the gel matrix, which might be attributed to the filling effects as well as "bridging action" of soybean protein isolate and κ-carrageenan within surimi proteins. In conclusion, we demonstrated emulsion gel as a good replacer to mitigate the negative effect of oil on the texture and structure of surimi gels, which would be a promising approach for oil supplementation in surimi production.

Preparation of cod protein composite gels for dysphagia by high-pressure homogenization: Egg white microgels-based high-phase emulsion as a texture modifier

The rising prevalence of dysphagia among the aging population presents significant challenges in developing specialized diets that combine soft textures with high nutritional value. This study investigates the formulation of cod protein composite gels (CPCGs) using egg white based microgels-high internal phase emulsions (HIPEs, 5-25 %). The CPCGs were prepared via high-pressure homogenization at 400 bar for 10 min. The texture, water retention, rheological properties, and network structure of the CPCGs were analyzed. Results demonstrated that incorporating HIPEs increased the hardness and whiteness of CPCGs. The water holding capacity peaked at 98.52 % with 15 % HIPEs. Additionally, as the concentration of HIPEs increased, the apparent viscosity, support properties, and thermal stability of CPCGs improved, although the critical strain point decreased from 475.33 % (control) to 199.33 % (25 % HIPEs). The network structure of CPCGs became denser and more uniform with higher HIPE concentrations, with noticeable changes in the gel skeleton when HIPEs exceeded 15 %. According to the International Dysphagia Diet Standardization Initiative (IDDSI) tests, all CPCG formulations met Level 6 - soft and bite-sized criteria. This study offers valuable insights into the development of fish protein-based dysphagia diets that are both nutritious and safe for swallowing.

Development and characterization of defatted coconut flour based oleogels: A fat substitute for application in oil-fortified surimi

This research examined the impact of defatted coconut flour (DCF)-based oleogels on the quality of surimi. Microscopic analysis indicated that the dietary fiber present in DCF could act as the main structure of the oleogels network. The formation of the oleogels network primarily relies on the tensile intramolecular or intermolecular hydrogen bonds between DCF and corn oil. The oleogels displayed oil binding capacity of up to 96.95% and exhibited favorable mechanical and rheological properties. Efforts were undertaken to integrate the acquired oleogels into silver carp surimi to create oil-fortified surimi products. Adding oleogels significantly enhanced the gel strength, texture, and water-holding capacity of surimi compared to adding corn oil. Especially, oleogels containing 5.0 % (w/v) DCF concentration elevated the lipid content in the surimi and preserved the gel and texture properties. Therefore, incorporating oleogels in surimi presents a potential solution for enhancing the nutritional content of surimi products.

Effect of modified cellulose-based emulsion on gel properties and protein conformation of Nemipterus virgatus surimi

Microcrystalline cellulose was modified by TEMPO oxidation combined with ultrasound to prepare modified cellulose-based emulsion. The effect of different emulsion concentration on gel properties and protein conformation of surimi was investigated. The results showed the length and width of microcrystalline cellulose were reduced, and a large amount of -COOH was introduced into modified cellulose. Direct addition of flaxseed oil decreased the gel strength and WHC from 3640.49 g·mm and 76.94% to 2702.95 g·mm and 75.89%, respectively, while 5% modified cellulose-based emulsion could improve the gel properties of surimi. Surimi gel containing 5% emulsion had the highest hydrophobic interaction, disulfide bond and β-sheet content. Moreover, protein network structure was the densest in 5% emulsion group. Therefore, modified cellulose-based emulsion could be used to compensating for the negative impact of direct addition of flaxseed oil on surimi, which provided a new idea for the development of healthy and new emulsified surimi products.

Performance and protein conformation of thermally treated silver carp (Hypophthalmichthys molitrix) and scallop (Argopecten irradians) blended gels

BACKGROUND

The quality of surimi-based products can be improved by combining the flesh of different aquatic organisms. The present study investigated the effects of incorporating diverse ratios of unwashed silver carp (H) and scallop (A) and using various thermal treatments on the moisture, texture, microstructure, and conformation of the blended gels and myofibrillar protein of surimi.

RESULTS

A mixture ratio of A:H = 1:3 yielded the highest gel strength, which was 60.4% higher than that of scallop gel. The cooking losses of high-pressure heating and water-bath microwaving were significantly higher than those of other methods (P < 0.05). Moreover, the two-step water bath and water-bath microwaving samples exhibited a more regular spatial network structure compared to other samples. The mixed samples exhibited a microstructure with a uniform and ordered spatial network, allowing more free water to be trapped by the internal structure, resulting in more favorable gel properties. The thermal treatments comprehensively modified the tertiary and quaternary structures of proteins in unwashed mixed gel promoted protein unfurling, provided more hydrophobic interactions, enhanced protein aggregation and improved the gel performance.

CONCLUSION

The findings of the present study improve our understanding of the interactions between proteins from different sources. We propose a new method for modifying surimi's gel properties, facilitating the development of mixed surimi products, as well as enhancing the efficient utilization of aquatic resources. © 2024 Society of Chemical Industry.

Developing fish oil emulsion gel enriched with Lentinula edodes single cell protein and its effect on controlling the growth of Acinetobacter baumannii

In this study, the characterization of fish oil (FO) emulsion gel (EGEL) containing single cell protein (SCP) produced from Lentinula edodes (L. edodes) and its potential inhibition against Acinetobacter baumannii (A. baumannii) were investigated. Oil extracted from the fish liver was emulsified with tween 80 and water, and then gelled using gelatin with the assistance of an ultrasonic homogenizer. The characteristics and surface analysis of SCP-EGEL were examined using FTIR (Fourier-transform infrared spectroscopy) and SEM (Scanning electron microscope). The particle size distribution and zeta potential of SCP-EGEL were measured using a Malvern Zetasizer. When SCP-EGEL was applied to the surface of the medium inoculated with A. baumannii, the inhibition zone (IZ) was 8.2 mm. An expansion of the IZ was observed (10.2 mm) when SCP-EGEL was applied to a fish skin (FS) surface prepared in the shape of a 6-mm diameter disc. In the SEM images, when SCP was added to lipo gel, the gel structure appeared flattened or swollen in some areas. The appearance of SCP cells being covered with gel gave the impression that they have a secondary wall. Therefore, the resulting complex can potentially be used as an additive in animal and human nutrition, in functional food coatings to suppress A. baumannii, and in fish feed to enrich it with protein.

Effect of a collagen peptide-fish oil high internal phase emulsion on the printability and gelation of 3D-printed surimi gel inks

The effect of a high internal phase emulsion (HIPE) on three-dimensional-printed surimi gel inks was studied. Increasing the concentration of collagen peptide decreased the particle size of HIPE droplets and improved the viscoelasticity and stability. For example, when the collagen peptide concentration was 5 wt%, the viscoelasticity of the HIPE was high, as indicated by the presence of small and uniform particles, which formed a monolayer in the outer layer of the oil droplets to form stable a HIPE. A HIPE was used as the filling material to fill the surimi gel network, which reduced the porosity of the network. Surimi protein and peptides have dual emulsifying effects on the stabilization of oil. After adding the emulsion, the texture, gel properties and rheological properties of the surimi were reduced, and its printing adaptability was improved. This study provides new ideas for the production of surimi and its application in 3D printing.

Effects of sturgeon oil and its Pickering emulsion on the quality of sturgeon surimi gel

This study aimed to extract sturgeon oil (SO) from the sturgeon head and apply it to sturgeon meat to produce surimi gel. The effects of SO and its Pickering emulsion on the qualities of surimi gel were investigated. The results demonstrated that Pickering emulsions improved the quality deterioration of the gel caused by the direct addition of SO, especially the soy isolate protein (SPI) emulsion and the pea isolate protein (PPI) emulsion. Pickering emulsions contributed to a more uniform and compact network structure of the gel, improved the texture properties, enhanced the freeze-thaw stability, and reduced lipid oxidation. Additionally, compared to the addition of exogenous lipids such as peanut oil and linseed oil, SO and its Pickering emulsion better maintained the characteristic flavor of sturgeon surimi gel. This study provides valuable data and feasible ideas for expanding the utilization of sturgeon by-products and developing new types of surimi gel products.

Effect of starch and peanut oil on physicochemical and gel properties of myofibrillar protein: Amylose content and addition form

Starch and peanut oil (PO) were widely used to improve the gel properties of surimi, however, the impact mechanism of addition forms on the denaturation and aggregation behavior of myofibrillar protein (MP) is not clear. Therefore, the effect of starch, PO, starch/PO mixture, and starch-based emulsion on the physicochemical and gel properties of MP was investigated. The results showed that amylose could accelerate the aggregation of MP, while amylopectin was conducive to the improvement of gel properties. The addition of PO, starch/PO mixture, or starch-based emulsion increased the turbidity, solubility, sulfhydryl content of MP, and improved the gel strength, whiteness, and texture of MP gel. However, compared with starch/PO mixture group, the gel strength of MP with waxy, normal and high amylose corn starch-based emulsion increased by 22.68 %, 10.27 %, and 32.89 %, respectively. The MP containing emulsion had higher storage modulus than MP with starch/PO mixture under the same amylose content. CLSM results indicated that the oil droplets aggregated in PO or starch/PO mixture group, while emulsified oil droplets filled the protein gel network more homogeneously. Therefore, the addition of starch and PO in the form of emulsion could effectively play the filling role to improve the gel properties of MP.

Characteristics of hairtail surimi gels treated with myofibrillar protein-stabilized Pickering emulsions

BACKGROUND

Hairtail (Trichiurus haumela) surimi exhibits poor gelation properties and a dark gray appearance, which hinder its utilization in high-quality surimi gel products. The effect of Pickering emulsions stabilized by myofibrillar proteins (MPE) on the gel properties of hairtail surimi has been unclear. In particular, the impact of MPE under NaCl and KCl treatments on the quality of hairtail surimi gels requires further elucidation.

RESULTS

Pickering emulsions stabilized by myofibrillar proteins and treated with NaCl or KCl (Na-MPE, K-MPE) were added to hairtail surimi in amounts of 10-70 g kg-1. The addition of 50 g kg-1 Na-MPE and K-MPE improved the gel strength, textural properties, whiteness, and water-holding capacity (WHC) of hairtail surimi. The relative content of β-turn and β-sheet in the surimi gels increased and the relative content of random coils and α-helix decreased with the addition of oil. The addition of Na-MPE and K-MPE did not affect the secondary structure of surimi gels but stimulated the gelation of hairtail surimi gels. Hairtail surimi containing K-MPE demonstrated similar performance in terms of hardness, microstructure, and WHC compared with the addition of Na-MPE.

CONCLUSION

The quality of hairtail surimi gels can be improved by the addition of Na-MPE or K-MPE. The K-MPE proved to be an effective option for enhancing the properties of hairtail surimi gels at 50 g kg-1 to replace Na-MPE. © 2024 Society of Chemical Industry.

Inhibition performance of almond shell hydrochar-based fish oil emulsion gel on Klebsiella pneumonia inoculated fish skin and its characteristics

In this study, the inhibition potential against Klebsiella pneumoniae (K. pneumoniae) and the characterization of fish oil (FO) emulsion gel (EGE) containing almond shell hydrochar (AH) were investigated. Oily water of mullet liver was emulsified using tween 80, then gelled using gelatin and finally immobilized into hydrochar using an ultrasonic homogenizer. Characteristics and surface analysis of hydrochar-based emulsion gel (HEGE) were examined using FTIR and SEM. Stability, particle size distribution and zeta potential of HEGE were measured. In this study, a zeta potential of -18.46 indicated that HEGE was more stable than EGE (35.7 mV). The addition of hydrochar to the emulsion gel containing micro-droplets enabled the structure to become fully layered and stable. Time-dependent inactivation of K. pneumoniae exposed to HEGE and fixed in 6 mm-fish skin was evaluated for the first time in this study. While the highest log reduction and percent reduction in the bacterial count were achieved within 5 min with 0.87 CFU/cm2 and 86.60% with EGE, the lowest log reduction and percent reduction were achieved with 0.003 CFU/cm2 and 0.082% with HEGE in 30 min. In conclusion, the almond shell hydrochar-immobilized emulsion gel is a functional adsorbent that can inhibit K. pneumonia, and its stability and performance make it a unique candidate for further studies in this field.

Study on the interaction and gel properties of pork myofibrillar protein with konjac polysaccharides

BACKGROUND

Natural myofibrillar protein (MP) is sensitive to changes in the microenvironment, such as pH and ionic strength, and therefore can adversely affect the final quality of meat products. The aim of this study was to modify natural MP as well as to improve its functional properties. Therefore, the quality improvement effect of konjac polysaccharides with different concentrations (0, 1.5, 3, 4.5 and 6 g kg-1 protein) on MP gels was investigated.

RESULTS

With a concentration of konjac polysaccharides of 6 g kg-1 protein, the composite gel obtained exhibited a significant improvement of water binding (water holding capacity increased by 7.71%) and textural performance (strength increased from 29.12 to 37.55 N mm, an increase of 8.43 N mm). Meanwhile, konjac polysaccharides could help to form more disulfide bonds and non-disulfide covalent bonds, which enhanced the crosslinking of MP and maintained the MP gel network structure. Then, with the preservation of α-helix structure (a significant increase of 8.11%), slower protein aggregation and formation of small aggregates, this supported the formation of a fine and homogeneous network structure and allowed a reduction in water mobility.

CONCLUSION

During the heating process, konjac polysaccharides could absorb the surrounding water and fill the gel system, which resulted in an increase in the water content of the gel network and enhanced the gel-forming ability of the gel. Meanwhile, konjac polysaccharides might inhibit irregular aggregation of proteins and promote the formation of small aggregates, which in turn form a homogeneous and continuous gel matrix by orderly arrangement. © 2023 Society of Chemical Industry.

Transglutaminase-induced soybean protein isolate cold-set gels treated with combination of ultrasound and high pressure: Physicochemical properties and structural characterization

Soybean protein isolate (SPI) was treated by the combined exposure to ultrasound and high pressure and then subjected to transglutaminase (TGase)-catalyzed cross-linking to prepare SPI cold-set gels. The effects of combined treatments on physicochemical and structural properties of TGase-induced SPI cold-set gels were investigated. The combination of ultrasound and high pressure promoted the covalent disulfide bonds and ε-(γ-glutaminyl) lysine isopeptide bonds as well as non-covalent hydrophobic interactions, which further improved the gelation properties of SPI compared to ultrasound or high pressure alone. In particular, the 480 W ultrasound followed by high pressure treatment of gels led to higher strength (120.53 g), water holding capacity (95.39 %), immobilized water (93.92 %), lightness (42.18), whiteness (51.03), and elasticity (G' = 407 Pa), as well as more uniform and compact microstructure, thus resulting in the improved gel network structure. The combination of two treatments produced more flexible secondary structure, tighter tertiary conformation and higher denaturation degree of protein in the gels, leading to more stable gel structure. The structural modifications of SPI contributed to the improvement of its gelation properties. Therefore, the combined application of ultrasound and high pressure can be an effective method for improving the structure and properties of TGase-induced SPI cold-set gels.

Mixed whey and pea protein based cold-set emulsion gels induced by calcium chloride: Fabrication and characterization

The cold-set gels of oil-in-water emulsions stabilized by mixtures of whey protein isolate (WPI) and pea protein isolate (PPI) with mass ratios of 10:0, 7:3, 5:5, 3:7, and 0:10 were investigated to evaluate the possibility of pea protein to replace milk protein. Particle size and surface charge of emulsions increased and decreased with raised PPI content, respectively. The redness and yellowness of emulsion gels were strengthened with elevated pea protein percentage and independent of calcium concentration applied. Considerable differences in water holding capacity were observed between samples with different mixed proteins and high percentage of pea protein gave better water retaining ability. Gradual decreases in hardness and chewiness of emulsion gels were observed at three calcium levels with the increased PPI proportion. FT-IR spectra indicated no new covalent bonds were generated between samples with different whey and pea protein mass ratios. As PPI concentration elevated, the network structure of emulsion gels gradually became loose and disordered. The established cold-set calcium-induced whey/pea protein composite gels may have the potential to be utilized as a new material to encapsulate and deliver environment sensitive bio-active substances.

Comparative effects of W/O and O/W emulsions on the physicochemical properties of silver carp surimi gels

The comparative effects of water-in-oil (W/O) and oil-in-water (O/W) emulsions on the physicochemical characteristics of silver carp surimi gels were investigated. The breaking force of surimi gels was 188.72 g, which decreased with increasing W/O emulsion but remained constant by adding O/W emulsion. The hardness decreased with increasing W/O emulsion, while the other parameters to TPA maintained constant whether the W/O or O/W emulsion was added. The yellowness value of surimi gels was 1.30, which increased with increasing W/O emulsion while remained constant after adding O/W emulsion. The water-holding capacity of surimi gels was invariant when emulsions increased. After emulsions added to surimi gels, no changes in the surimi protein interactions were found in electrophoretic patterns and Fourier transform infrared spectra. The increasing W/O emulsion enlarged the droplet size of oil and then destroyed the surimi gel network structure, while the oil droplets were evenly dispersed with increasing O/W emulsion.

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.

Effects of pork fat and linseed oil as additives on gel quality of fish cake

Pork fat (PF) is a necessary ingredient in making traditional fish cakes (TFCs), which contains saturated fatty acids with potential health concerns. While linseed oil (LO) containing α-linolenic acid is a potential nutrient-enhancing fat substitute. In this study, the effect of pork fat and linseed oil level on gel quality, sensory characteristics, microstructure, and protein conformation of TFCs were characterized. Results showed that the TFCs with 30% pork fat (wt/wt) had the highest gel strength. Additionally, sensory evaluation determined that TFCs with 30% pork fat scored the best by a sensory panel with high gel strength, water-holding capacity, and fresh and sweet taste. The gel strength, chewiness, and hardness of nutrient-enriched fish cakes with 20% linseed oil replaced for pork fat were higher than that only with pork fat (wt/wt) without changing in tenderness and elasticity. Visual results showed that the network was uniform at a moderate level of linseed oil addition (20% LO/PF replacement ratio). The results of this study provided technical guidelines for standardizing the TFC manufacture processes, and useful insight for the development of fish cakes with reduced animal fat content for additional health benefits for consumers.

Use of soybean oil to modulate the gel properties of soybean protein isolation-wheat gluten composite with or without CaCl2

BACKGROUND

Plant protein is widely used in the study of animal protein substitutes and healthy sustainable products. The gel properties are crucial for the production of plant protein foods. Therefore, the present study investigated the use of soybean oil to modulate the gel properties of soybean protein isolation-wheat gluten composite with or without CaCl2 .

RESULTS

Oil droplets filled protein network pores under the addition of soybean oil (1-2%). This resulted in an enhanced gel hardness and water holding capacity. Further addition of soybean oil (3-4%), oil droplets and some protein-oil compounds increased the distance between the protein molecule chain. The results of Fourier transform infrared spectroscopy and intermolecular interaction also showed that the disulfide bond and β-sheet ratio decreased in the gel system, which damaged the overall structure of the gel network. Compared with the addition of 0 m CaCl2 , salt ion reduced the electrostatic repulsion between proteins, and local protein cross-linking was more intense at 0.005 m CaCl2 concentration. In the present study, structural properties and rheological analysis showed that the overall strength of the gel was weakened after the addition of CaCl2 .

CONCLUSION

The presence of appropriate amount of soybean oil can fill the gel pores and improve the texture properties and network structure of soy protein isolate-wheat gluten (SPI-WG) composite gel. Excessive soybean oil may hinder protein-protein interaction and adversely affect protein gel. In addition, the presence or absence of CaCl2 significantly affected the gelling properties of SPI-WG composite protein gels. © 2023 Society of Chemical Industry.

Antarctic krill (Euphausia superba) oil high internal phase emulsions improved the lipid quality and gel properties of surimi gel

In the study, high internal phase emulsions (HIPEs) prepared from Antarctic krill oil (AKO) were added into surimi and the effects on gel properties, lipid quality and stability were investigated. It is found that HIPEs-added groups exhibited higher gel strength and lower cooking loss than Oil-added counterparts. HIPEs-added groups had higher proportion of capillary water, and microstructure of HIPEs-added gels showed fewer large voids and small size droplets. HIPEs-added groups also showed less pronounced myosin heavy chain band. HIPEs- and Oil-added gels showed > 3500 mg/kg EPA + DHA and 0.4-0.8 mg/kg astaxanthin, and most HIPEs-added groups had higher levels of them but lower TBARS values. Results suggest AKO-HIPEs could reduce the intervention by lipids on myosin crosslinking during gelation, and protect fatty acids and asxtanthin from oxidation due to oxygen-isolation led by their high accumulation. Thus, AKO-HIPEs can be applied to fortify ω-3 PUFA and maintain good gel properties in surimi product.

Effect of oat β-glucan on gel properties and protein conformation of silver carp surimi

BACKGROUND

Polysaccharides are the most widely used additives to enhance the quality of surimi gels. Oat β-glucan (OG), a functional polysaccharide, is known to affect the gelation characteristics of surimi. However, it has been rarely reported. Therefore, the effect of OG at different levels on gelling properties, protein conformation, and microstructures of silver carp surimi gels were investigated.

RESULTS

An increase in the OG content from 0 to 1.0% significantly improved the hardness, springiness, chewiness, puncture properties, storage modulus, and loss modulus of surimi gels. Moreover, the incorporation of OG (0-1.0%) facilitated the unfolding of proteins, resulting in the conformational transformation from α-helix to β-sheet and β-turn. Consequently, surimi-OG gels displayed a denser network structure with smaller and more uniform voids. Furthermore, partial free water in the gel network was converted into immobile water, increasing the water-holding capacity. However, a further increase in the OG concentration (1.0-2.0%) resulted in a looser and more uneven network structure with large and numerous cavities. In addition, the whiteness of composite gels decreased with increasing content of OG.

CONCLUSION

The addition of 1.0% OG dramatically improved the gelation performance of silver carp surimi, providing a theoretical foundation for the exploitation and manufacture of functional surimi products. © 2023 Society of Chemical Industry.

Preparation of plant-based meat analogs using emulsion gels: Lipid-filled RuBisCo protein hydrogels

RuBisCo from duckweed is a sustainable source of plant proteins with a high water-solubility and good gelling properties. In this study, we examined the impact of RuBisCo concentration (9-33 wt %) and oil droplet concentration (0 to 14 wt %) on the properties of emulsion gels designed to simulate the properties of chicken breast. The color (L*a*b*), water holding capacity (WHC), textural profile analysis, shear modulus, and microstructure of the emulsion gels were measured. The gel hardness and WHC increased significantly with increasing protein concentration, reaching values equivalent to chicken breast. The lightness of the emulsion gels was less than that of chicken breast, due to the presence of pigments (such as polyphenols) in the protein. Shear modulus versus temperature measurements showed that gelation began when the protein solutions were heated to around 40 °C and then the gels hardened appreciably when the temperature was further raised to 90 °C. The shear modulus of the gels then increased during cooling, which was attributed to the strengthening of hydrogen bonds at lower temperatures. The hardness of the gels increased slightly but then decreased when the oil droplet concentration was raised from 0 to 14 %. The lightness of the protein gels increased after adding the oil droplets, which was attributed to increased light scattering. Microstructure analysis showed that the RuBisCo proteins formed a particulate gel after heating, with the oil droplets being in the interstices between the particulates. In summary, RuBisCo proteins can be dissolved at high concentrations and can form strong emulsion gels. Consequently, they may be able to mimic the composition and textural attributes of real chicken.

Effects of pre-emulsified safflower oil with magnetic field modified soy 11S globulin on the gel, rheological, and sensory properties of reduced-animal fat pork batter

In this work, the differences in macrostructure and microstructure, rheology, and storage stability of pre-emulsified safflower oil (PSO) prepared by natural and magnetic field modified soy 11S globulin were analysised. It was concluded that the PSO with magnetic field modified soy 11S globulin (MPSO) has better emulsifying activity and physical stability. The changes in gel quality, oxidational sensitivity, rheological, and sensory properties of pork batters with different substitute ratios (0%, 25%, 50%, 75%, and 100%) of pork back-fat by MPSO with magnetic field modified soy 11S globulin were studied. Compared to the sample without MPSO, pork batter with MPSO showed higher emulsion stability, apparent viscosity, L^⁎ value, springiness, cohesiveness, and expressible moisture, while lower a^⁎ value and cooking loss. Moreover, added MPSO could be more uniformly distributed into the meat matrix with smaller holes. With the increase in the replacement proportion of pork back-fat, the hardness, water- and fat-holding capacity, and P₂₁ of pork batter significantly decreased (P < 0.05). As revealed by sensory evaluation and TBARS, using MPSO to substitute for pork back-fat decreased the lipid oxidational sensitivity of pork batter, and without negative effects on the appearance, juiciness and overall acceptability. Overall, it is feasible to apply MPSO as a pork-fat replacer to produce reduced-animal fat pork batter with excellent gel and sensory properties.

Impact of interactions between peanut protein isolate and cellulose nanocrystals on the properties of Pickering emulsions: Rheological properties and physical stabilities

The interactions between cellulose nanocrystals and proteins can regulate the interfacial properties of Pickering emulsions, which plays a leading role in the stabilities of Pickering emulsions. In this work, oil-in-water (O/W) Pickering emulsions with different oil-water ratios were prepared using peanut protein isolate modified by cellulose nanocrystals (PPI/CL-CNCs). The distributions of PPI/CL-CNCs at the oil-water interfaces and the microstructures of Pickering emulsions were observed by CLSM and cryo-SEM. The results showed that stable complexes PPI/CL-CNCs formed thick and dense interface layers on the surface of oil droplets. The results of rheological tests clarified that the Pickering emulsions showed an elastic and gel texture, and their gel strength could be enhanced by regulating the oil-water ratios from 3:7 to 7:3. In addition, after one month of storage, the EI of all emulsions remained above 92 % with no obvious phase separation or demulsification. These results suggested that the PPI/CL-CNCs-stabilized Pickering emulsions showed good physical stabilities. The study on the rheological properties and physical stabilities of PPI/CL-CNCs-based Pickering emulsions provided novel insights on developing highly stable Pickering emulsions.

Effect of multiple-frequency ultrasound-assisted transglutaminase dual modification on the structural, functional characteristics and application of Qingke protein

Qingke protein rich in restricted amino acids such as lysine, while the uncoordination of ratio of glutenin and gliadin in Qingke protein has a negative impact on its processing properties. In this study, the effect of multiple-frequency ultrasound combined with transglutaminase treatment on the functional and structural properties of Qingke protein and its application in noodle manufacture were investigated. The results showed that compared with the control, ultrasound-assisted transglutaminase dual modification significantly increased the water and oil holding capacity, apparent viscosity, foaming ability, and emulsifying activity index of Qingke protein, which exhibited a higher storage modulus G' (P < 0.05). Meanwhile, ultrasound combined with transglutaminase treatment enhanced the cross-linking degree of Qingke protein (P < 0.05), as shown by decreased free amino group and free sulfhydryl group contents, and increased disulfide bond content. Moreover, after the ultrasound-assisted transglutaminase dual modification treatment, the fluorescence intensity, the contents of α-helix and random coil in the secondary structure of Qingke protein significantly decreased, while the β-sheet content increased (P < 0.05) compared with control. SDS-PAGE results showed that the bands of Qingke protein treated by ultrasound combined with transglutaminase became unclear. Furthermore, the quality of Qingke noodles made with Qingke powder (140 g/kg dual modified Qingke protein mixed with 860 g/kg extracted Qingke starch) and wheat gluten 60-70 g/kg was similar to that of wheat noodles. In summary, multiple-frequency ultrasound combined with transglutaminase dual modification can significantly improve the physicochemical properties of Qingke protein and the modified Qingke proteins can be used as novel ingredients for Qingke noodles.

The Relationship between Penetration, Tension, and Torsion for the Fracture of Surimi Gels: Application of Digital Image Correlation (DIC)

A standardized method to evaluate the material properties of surimi gels has to be updated because of the lack of accuracy and the repeatability of data obtained from conventional ways. To investigate the relationships between the different texture measurement methods used in surimi gels, 250 batches of different surimi gels were used. The textural properties of surimi gels made with or without whey protein concentrate (SG-WP), potato starch (SG-PS), or dried egg white (SG-EW) were measured under torsion, tensile, and penetration tests. The correlation between the textural properties related to the deformation and hardness of surimi gels without any added ingredients (SG) was linear (R2 > 0.85). However, the R2 values of the shear strain and tensile strain of SG-WP and SG-EW were significantly lower than that of SG. The strain distributions of surimi gels with and without added ingredients were estimated by digital image correlation (DIC) analysis. The results showed that the local strain concentration in SG-WP and SG-EW was significantly higher than that of SG in the failure ring tensile test and the torsion test (p < 0.05). DIC analysis was an effective tool for evaluating the strain distribution characteristics of surimi gels upon fracture from torsion, penetration, and tension.

Gel-type emulsified muscle products: Mechanisms, affecting factors, and applications

The gel-type emulsified muscle products improve fatty acid composition, maintain the oxidative stability, and achieve a better sensory acceptability. This review emphasizes the stabilization mechanisms of these emulsified muscle products. In particular, factors associated with the stability of the emulsified muscle systems are outlined, including the processing conditions (pH and heating), lipids, and emulsifiers. Besides, some novel systems are further introduced, including the Pickering emulsions and organogels, due to their great potential in stabilizing emulsified gels. Moreover, the promising prospects of emulsion muscle products such as improved gel properties, oxidative stability, freeze-thaw stability, fat replacement, and nutraceutical encapsulation were elaborated. This review comprehensively illustrates the considerations on developing gel-type emulsified products and provides inspiration for the rational design of emulsified muscle formulations with both oxidatively stable and organoleptically acceptable performance.

Evaluation of dual-frequency multi-angle ultrasound on physicochemical properties of tofu gel and its finished product by TOPSIS-entropy weight method

The effects of dual-frequency (40 + 20 kHz) and multi-angle ultrasound (0°, 30°, 45°) on the coagulation state, network structure, flavor and protein conformation of tofu gel were studied. The results showed that the gel flavor of 40 + 20 kHz 0° group was the best and fluorescence intensity was low. The gel flavor in the 40 + 20 kHz 30° group was better than the group without ultrasound, and hydrophobic interaction and disulfide bond content was the largest. Meanwhile, the degree of protein cross-link was increased. The gel in 40 + 20 kHz 45° group had tightly gel state, high thermal stability, but poor flavor. Combined with The Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy weight method, the 40 + 20 kHz 30° group, was the best ultrasonic treatment of gel. It can change the interaction between proteins, promote protein cross-link, and form a uniform and dense gel network. Finally, the hardness and moisture content of finished tofu were increased significantly, and the quality was improved.

Recent progress in fish oil-based emulsions by various food-grade stabilizers: Fabrication strategy, interfacial stability mechanism and potential application

Fish oil, rich in a variety of long-chain ω-3 PUFAs, is widely used in fortified foods due to its broad-spectrum health benefits. However, its undesired characteristics include oxidation sensitivity, poor water solubility, and fishy off-flavor greatly hinder its exploitation in food field. Over the past two decades, constructing fish oil emulsions to encapsulate ω-3 PUFAs for improving their physicochemical and functional properties has undergone great progress. This review mainly focuses on understanding the fabrication strategies, stabilization mechanism, and potential applications of fish oil emulsions, including fish oil microemulsions, nanoemulsions, double emulsions, Pickering emulsions and emulsion gels. Furthermore, the role of oil-water interfacial stabilizers in the fish oil emulsions stability will be discussed with a highlight on food-grade single emulsifiers and natural complex systems for achieving this purpose. Additionally, its roles and applications in food industry and nutrition field are delineated. Finally, possible innovative food trends and applications are highlighted, such as novel fish oil-based delivery systems construction (e.g., Janus emulsions and nutraceutical co-delivery systems), exploring digestion and absorption mechanisms and enhancing functional evaluation (e.g., nutritional supplement enhancer, and novel fortified/functional foods). This review provides a reference for the application of fish oil-based emulsion systems in future precision diet intervention implementations.

Physicochemical properties and microstructure of composite surimi gels: The effects of ultrasonic treatment and olive oil concentration

This study was conducted to evaluate the effects of extra virgin olive (EVO) oil incorporation on the physicochemical properties and microstructure of surimi gels subjected to ultrasound-assisted water-bath heating. As the oil content was increased from 0 to 5 g/100 g, the breaking force and gel strength of the surimi gels significantly decreased, while the whiteness level exhibited the opposite tendency irrespective of the heating method. Compared with the traditional water-bath heating method, the ultrasonic heating promoted the unfolding of the α-helix structure and intensified the formation of β-sheet content and non-covalent bonds (ionic bonds, hydrogen bonds, and disulfide bonds), especially disulfide bonds, which contributed to the further crosslinking of the proteins and to gelation, thereby improving the gels' strength. In addition, smaller cavities and compact microstructures were observed in the low-oil (≤3 g/100 g) surimi gels under ultrasonic treatment, which effectively prevented water migration in the gel network and resulted in a high water holding capacity and uniform water distribution. However, the ultrasonic treatment barely remedied the poor microstructures of the high-oil (>3 g/100 g) surimi gels owing to oil coalescence, which weakened the protein-protein interaction. In conclusion, ultrasonic treatment combined with water-bath heating significantly improved the gelation properties of the low-oil surimi gels, although it did not remarkably improve those of the high-oil gels. The choice of a suitable oil concentration could be of great importance for the production and functioning of surimi products via ultrasound-assisted treatments.