Effects of compound emulsifiers on the characteristics and stability of nano-emulsions from pollock bones.

To improve the stability of pollock bone broth, compound emulsifiers were employed and evaluated in nano-emulsions from pollock bones (PBNs). The microstructure, creaming index, particle size, zeta potential, and viscosity of PBNs were characterized and the stability of PBNs was investigated. It revealed that the concentration of compound emulsifiers is one of the principal factors for particle size, zeta potential, and viscosity of PBNs, and 0.9% of sodium caseinate and sucrose fatty acid ester (CS-SE) can make the PBN display good stability. Its particle size changed from 81.17 ± 1.33 nm to 19.62 ± 0.21 nm when the temperature ranged from 40 °C to 80 °C, and its creaming index could reach a maximum (90.83%) among all PBNs in 4 months of freeze-thaw assays. PBN stability could be improved by the compound emulsifier (CS-SE), which offers a theoretical basis for the application of pollock bone broth.

Freeze-thaw stability of high-internal-phase emulsion stabilized by chickpea protein microgel particles and its application in surimi.

BACKGROUND: Future applications of high-internal-phase emulsions (HIPEs) are highly regarded, but poor freeze-thaw stability limits their utilization in frozen products. This study aimed to characterize the structure of chickpea protein microgel particles (HCPI) induced by NaCl and to assess its impact on the freeze-thaw stability of HIPEs. RESULTS: The results showed that NaCl induction (0-400 mmol L-1) increased the surface hydrophobicity (175.9-278.9) and interfacial adsorbed protein content (84.9%-91.3%) of HCPI. HIPEs prepared with HCPI induced by high concentration of NaCl exhibited superior flocculation index and centrifugal stability, and their freeze-thaw stability was better than that of natural chickpea protein. The increase in NaCl concentration reduced the droplet aggregation and coalescence index of the freeze-thaw emulsions, diminishing the precipitation of oil from the emulsion. Linear and nonlinear rheology showed that the strengthened gel structure (higher G' values) restricted water flow and counteracted the damage to the interfacial film by ice crystals at 100-400 mmol L-1 NaCl, thus improving the viscoelasticity of the freeze-thaw emulsions. Finally, the thawing loss of surimi gel with HCPI-200 HIPE was reduced by 2.04% compared to directly adding oil. CONCLUSION: This study provided a promising strategy to improve the freeze-thaw stability of HIPEs and reduce the thawing loss of frozen products. © 2024 Society of Chemical Industry.

Stimuli-responsive antioxidant Pickering emulsions stabilized by functionalized cellulose nanocrystals.

Stimuli-responsive antioxidant Pickering emulsions play crucial role in many industrial areas. This study demonstrated for the first time oil-in-water Pickering emulsions with outstanding antioxidation and responsive demulsification stabilized by functionalized cellulose nanocrystals (CNCs). Dialdehyde cellulose nanocrystals (DACs) were first prepared through the oxidation of CNCs with periodate, followed by the grafting of p-aminophenols (PAPs) onto their surfaces through Schiff base reaction, affording PAP grafted DACs (DAC-g-PAP) via dynamic covalent linkage. The degree of the oxidation (DO) of DACs had a significant effect on the yield of the targeting DAC-g-PAP nanoparticles. High DO (≥40 %) potentially led to the degradation of DACs during the grafting of PAP. The introduced PAP endowed DACs with excellent radical scavenging capability, thereby providing antioxidant properties while improving the hydrophobicity. DAC-g-PAP nanoparticles were then applied as Pickering emulsifiers to prepare oil-in-water Pickering emulsions. The resultant Pickering emulsions indicated exceptional antioxidant and pH-responsiveness together with good freezing-thaw stability. The structures of DAC-g-PAP nanoparticles were thoroughly characterized in this study.

High freeze-thaw stability of Pickering emulsion stabilized by SPI-maltose particles and its effect on frozen dough.

Pickering emulsions with good freeze-thaw stability are essential in frozen food applications. This study developed a high freeze-thaw stabilized soy protein isolate (SPI)-maltose (M) Pickering emulsion and applied it to frozen doughs to investigate and reveal its impacts on the processing properties of the frozen dough. The results showed that after the freeze-thaw cycle, with a volume ratio of 1:2 of SPI to M, the appropriate amount of M changed the structure of SPI. This resulted in the Pickering emulsion prepared by the SPI exhibiting the least droplet coalescence and the best freeze-thaw stability. The results of dough rheological properties, textural properties, and binding capacity with water demonstrated that Pickering emulsions effectively inhibited the loss of gluten protein network structure in the dough after freeze treatment and increased the binding capacity of gluten proteins with starch and water in the dough. The best results were obtained with the incorporation of 3 % SPI-M high freeze-thaw stability, where the amount of bound water following three freeze-thaw cycles was 4.27 times higher than in doughs without Pickering emulsion. Overall, this study is significant for enhancing the freeze-thaw stability of Pickering emulsions stabilized by proteins and providing a new application route for Pickering emulsions.

Soybean protein isolate-sodium alginate double network emulsion gels: Mechanism of formation and improved freeze-thaw stability.

Soybean protein isolate (SPI) is widely used in the food industry. However, SPI-based emulsion gels tend to aggregate and undergo oiling-off during freeze-thawing. In this study, emulsion gels were prepared by a combination of heat treatment and ionic cross-linking using SPI and sodium alginate (SA) as raw materials. The focus was on exploring the mechanistic effects of the SPI-SA double network structure on the freeze-thaw stability of emulsion gels. The results showed that the addition of SA could form different types of network structures with SPI, due to different degrees of phase separation. In addition, SA appearing on the SPI network indicated that the addition of Ca2+ shielded the electrostatic repulsion between SPI and SA to form SPI-SA complexes. The disappearance of the characteristic peaks of SA and SPI in Fourier transform infrared spectroscopy analysis also confirmed this view. Low-field nuclear magnetic resonance data revealed that SA played a role in restricting water migration within the emulsion gels, increasing bound water content, and thereby improving the water-holding capacity of the emulsion gels. Therefore, the incorporation of SA improved the freeze-thaw stability of SPI emulsion gels. These findings offer a theoretical basis and technical support for SPI application in frozen products.

Salt ions improve soybean protein isolate/curdlan complex fat substitutes: Effect of molecular interactions on freeze-thaw stability.

Although emulsion gels show significant potential as fat substitutes, they are vulnerable to degreasing, delamination, and other undesirable processes during freezing, storage, and thawing, leading to commercial value loss in terms of juiciness, flavor, and texture. This study investigated the gel strength and freeze-thaw stability of soybean protein isolate (SPI)/curdlan (CL) composite emulsion gels after adding sodium chloride (NaCl). Analysis revealed that adding low salt ion concentrations promoted the hardness and water-holding capacity (WHC) of fat substitutes, while high levels displayed an inhibitory effect. With 40 mM NaCl as the optimum concentration, the hardness increased from 259.33 g (0 mM) to 418.67 g, the WHC increased from 90.59 % to 93.18 %, exhibiting good freeze-thaw stability. Confocal laser scanning microscopy (CLSM) and particle size distribution were used to examine the impact of salt ion concentrations on protein particle aggregation and the damaging effect of freezing and thawing on the proteoglycan complex network structure. Fourier-transform infrared spectroscopy (FTIR) and protein solubility evaluation indicated that the composite gel network structure consisted of covalent contacts between the proteoglycan molecules and hydrogen bonds, playing a predominant role in non-covalent interaction. This study showed that the salt ion concentration in the emulsion gel affected its molecular interactions.

Fabrication and Stability Improvement of Monoglyceride Oleogel/Polyglycerol Polyricinoleate-Stabilized W/O High Internal Phase Pickering Emulsions.

To decrease the lipid content in water-in-oil (W/O) emulsions, high internal phase Pickering W/O emulsions (HIPPE) were fabricated using magnetic stirring using a combination of monoglyceride (MAG) oleogel and polyglycerol polyacrylate oleate (PGPR) as stabilizers. Effects of MAGs (glyceryl monostearate-GMS, glycerol monolaurate-GML and glycerol monocaprylate-GMC) and internal phase components on the formation and properties of HIPPEs were investigated. The results showed that milky-white stabilized W/O HIPPE with up to 85 wt% aqueous phase content was successfully prepared, and the droplet interfaces presented a network of MAG crystals, independent of the MAG type. All HIPPEs exhibited great stability under freeze-thaw cycles but were less plastic. Meanwhile, GML-oleogel-based HIPPEs had larger particle size and were less thermal stable than GMS and GMC-based HIPPEs. Compared to guar gum, the internal phase components of sodium chloride and sucrose were more effective in reducing the particle size of HIPPEs, improving their stability and plasticity, and stabilizing them during 100-day storage. HIPPEs presented great spreadability, ductility and plasticity after whipping treatment. This knowledge provides a new perspective on the use of oleogels as co-stabilizers for the formation of W/O HIPPEs, which can be used as a potential substitute for creams.

Enzymatic modification lowers syneresis in corn starch gels during freeze-thaw cycles through 1,4-α-glucan branching enzyme.

The current research in the food industry regarding enzymatic modification to enhance the freeze-thaw (FT) stability of starch is limited. The present study aimed to investigate the FT stability of normal corn starch (NCS) modified using 1,4-α-glucan branching enzyme (GBE) derived from Geobacillus thermoglucosidans STB02. Comprehensive analyses, including syneresis, scanning electron microscopy, and low-field nuclear magnetic resonance, collectively demonstrated the enhanced FT stability of GBE-modified corn starch (GT-NCS-30) in comparison to its native form. Its syneresis was 66.4 % lower than that of NCS after three FT cycles. Notably, GBE treatment induced changes in the pasting properties and thermal resistance of corn starch, while simultaneously enhancing the mechanical strength of the starch gel. Moreover, X-ray diffractograms and microstructural assessments of freeze-thawed gels indicated that GBE treatment effectively hindered the association of corn starch molecules, particularly amylose retrogradation. The enhanced FT stability of GBE-modified starch can be attributed to alterations in the starch structure induced by GBE. This investigation establishes a foundation for further exploration into the influence of GBE treatment on the FT stability of starch and provides a theoretical basis for further research in this area.

Enhanced gelling property and freeze-thaw stability of potato, tapioca and corn starches modified by mild heating in aqueous ethanol solution.

BACKGROUND: Physically modified starches can be classified as natural ingredients on food labels and clean label products. Thus, the market demand for physically modified starch is increasing. Potato, tapioca and corn starches were physically modified by mild heat treatment in an alcoholic solution to enhance their gelling property and freeze-thaw stability. RESULTS: During mild heating of starch suspension (40% w/w) in 10% ethanol solution at the onset gelatinization temperature, granular swelling of starch occurred, followed by amylose leaching with medication of the surface structure of the starch granules. All treated starches exhibited increased gelatinization and pasting temperatures and decreased breakdown for pasting as a result of improved stability against shear and heat. The treated starches had higher hardness, cohesiveness and springiness of gel than the respective native starches, and these gel properties were more pronounced in potato starch than in tapioca and corn starches. The treated starches showed substantially reduced gel syneresis during freeze-thawing. CONCLUSION: Physical modification of starch by mild heat treatment in an alcoholic solution substantially improved its gelation ability and freeze-thaw stability. © 2024 Society of Chemical Industry.

Investigating Texture and Freeze-Thaw Stability of Cold-Set Gel Prepared by Soy Protein Isolate and Carrageenan Compounding.

In this study, the purpose was to investigate the effects with different concentrations of carrageenan (CG, 0-0.30%) on the gel properties and freeze-thaw stability of soy protein isolate (SPI, 8%) cold-set gels. LF-NMR, MRI, and rheology revealed that CG promoted the formation of SPI-CG cold-set gel dense three-dimensional network structures and increased gel network cross-linking sites. As visually demonstrated by microstructure observations, CG contributed to the formation of stable SPI-CG cold-set gels with uniform and compact network structures. The dense gel network formation was caused when the proportion of disulfide bonds in the intermolecular interaction of SPI-CG cold-set gels increased, and the particle size and zeta potential of SPI-CG aggregates increased. SG20 (0.20% CG) had the densest gel network in all samples. It effectively hindered the migration and flow of water, which decreased the damage of freezing to the gel network. Therefore, SG20 exhibited excellent gel strength, water holding capacity, freeze-thaw stability, and steaming stability. This was beneficial for the gel having a good quality after freeze-thaw, which provided a valuable reference for the development of freeze-thaw-resistant SPI cold-set gel products.

Interfacial crystallized oleogel emulsion with improved freeze-thaw stability and tribological properties: Influence of cooling rate.

In this study, the influence of cooling rate on the freeze-thaw stability, rheological and tribological properties of interfacial crystalized oleogel emulsion was investigated. Results showed that slower cooling rate could promote formation of larger crystals and stronger network in oleogels. Additionally, oleogel emulsions showed higher freeze-thaw stability than those stabilized solely by emulsifiers. The slower cooling rate resulted in larger crystals adsorbed at the droplet surface. This led to greater steric hindrance that prevented the migration of oil droplets with higher resistance to disruption by ice crystals. The rheological and tribological measurements suggested that with appropriate amount of crystals, the tribological properties were better maintained for emulsions prepared at slow cooling rate after freeze-thaw treatment. This strategy greatly enriched oleogel emulsion formulations and provided important clues for potential applications in food products involved with freeze-thaw treatment.

Improved physicochemical stability of fish oil nanoemulsion via a dense interfacial layer formed by hyaluronic acid-poly(glyceryl)10-stearate.

This study aimed to synthesize a novel emulsifier, hyaluronic acid-poly(glyceryl)10-stearate (HA-PG10-C18), and employ it for the fabrication of nanoemulsions incorporating deep-sea fish oil to improve their apparent solubility and physicochemical stability. 1H NMR and FT-IR analyses indicated successful synthesis of HA-PG10-C18. Nanoemulsions of deep-sea fish oil loaded with HA-PG10-C18 (HA-PG10-C18@NE) were successfully fabricated by ultrasonic emulsification. The fixed aqueous layer thickness (FALT) of PG10-C18@NE and HA-PG10-C18@NE was determined and the FALT of both nanoemulsions was similar, while the surface density of HA-PG10-C18@NE (4.92 × 10-12 ng/nm2) is 60 % higher than that of PG10-C18@NE (3.07 × 10-12 ng/nm2). Notably, HA-PG10-C18@NE demonstrated an exceptional physicochemical stability when exposed to various stressed environmental conditions, especially its freeze-thaw stability. Moreover, after simulated in vitro digestion, the HA-PG10-C18@NE exhibited a comparatively greater liberation of free fatty acids (94.0 ± 1.7 %) when compared to the release observed in PG10-C18@NE (85.5 ± 2.2 %).

High-temperature glycosylation of saccharides to modify molecular conformation of egg white protein and its effect on the stability of high internal phase emulsions.

This paper investigates the freeze-thaw stability of oil-in-water emulsions stabilized by high-temperature wet heating glycosylation products. Glucose (Glu), D-fructose (Fru), xylose (Xyl), maltodextrin (MD), oligofructose (FO), and oligomeric isomaltulose (IMO) were chosen as sugar sources for the glycosylation reaction with egg white proteins (EWPs) at 120 °C to prepare the GEWPs. The study reveals that the type of sugar significantly influences the Maillard reactions with EWPs. The degree of glycosylation was highest in the Xyl group with the greatest reducing capacity and lowest in the MD, FO, and IMO groups. High-temperature wet glycosylation treatment induced changes in the secondary and tertiary structures of EWP. Elevated temperature exposed hydrophobic groups within the protein, while covalent binding of hydrophilic carbohydrates via the Maillard reaction decreased the protein's H0 value. Improved foaming and emulsifying properties were attributed to the increase in α-helix content, disulfide bond formation, and reduced surface tension. Emulsions prepared from GEWPs exhibited higher apparent viscosity and G' compared to those from natural EWPs, with the GEWP/Xyl group showing the highest values. After freeze-thaw treatment, the GEWP/Fru and GEWP/FO groups demonstrated superior stability and reduced freezing point, along with minimal microstructural alterations. These findings underscore the importance of sugar type in the stability of high internal phase emulsions (HIPEs) stabilized by GEWPs, indicating that a tailored Maillard reaction can yield stabilizers with exceptional freeze-thaw stability for emulsions.

Pickering emulsion with high freeze-thaw stability stabilized by xanthan gum/lysozyme nanoparticles and konjac glucomannan.

In this study, freeze-thaw cycle experiments were conducted on food-grade Pickering emulsions co-stabilized with konjac glucomannan (KGM) and xanthan gum/lysozyme nanoparticles (XG/Ly NPs). The rheological properties, particle size, flocculation degree (FD), coalescence degree (CD), centrifugal stability, Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and microstructure of Pickering emulsion stabilized by KGM before and after freeze-thaw were characterized. It was found that as the concentration of KGM increased, the flocculation degree (FD) and coalescence degree (CD) of the emulsion decreased after the freeze-thaw cycle compared to the control sample, and the microscopic images showed that the droplets became smaller and less affected by the freeze-thaw cycles. The rheological and water-holding properties also confirmed that the KGM-added emulsions still had a strong gel network structure and prevented the separation of the continuous and dispersed phases of the droplets after freezing and thawing. Freeze-thaw treatments had a negative effect on the stable emulsion of XG/Ly NPs, while the addition of KGM improved the freeze-thaw stability of the emulsion, which provided a theoretical basis for the development of emulsion products with high freeze-thaw stability.

Freeze-thaw stability of transglutaminase-induced soy protein-maltose emulsion gel: Focusing on morphology, texture properties, and rheological characteristics.

In this study, soy protein isolate (SPI) and maltose (M) were employed as materials for the synthesis of a covalent compound denoted as SPI-M. The emulsion gel was prepared by transglutaminase (TGase) as catalyst, and its freeze-thaw stability was investigated. The occurrence of Maillard reaction was substantiated through SDS-PAGE. The analysis of spectroscopy showed that the structure of the modified protein was more stretched, changed in the direction of freeze-thaw stability. After three freeze-thaw cycles (FTC), it was observed that the water holding capacity of SPI-M, SPI/M mixture (SPI+M) and SPI emulsion gels exhibited reductions of 8.49 %, 16.85 %, and 20.26 %, respectively. Moreover, the soluble protein content also diminished by 13.92 %, 23.43 %, and 35.31 %, respectively. In comparison to unmodified SPI, SPI-M exhibited increase in gel hardness by 160 %, while elasticity, viscosity, chewability, and cohesion demonstrated reductions of 17.7 %, 23.3 %, 33.3 %, and 6.76 %, respectively. Concurrently, the SPI-M emulsion gel exhibited the most rapid gel formation kinetics. After FTCs, the gel elastic modulus (G') and viscosity modulus (G″) of SPI-M emulsion were the largest. DSC analysis underscored the more compact structure and heightened thermal stability of the SPI-M emulsion gel. SEM demonstrated that the SPI-M emulsion gel suffered the least damage following FTCs.

Freeze-thaw stability of Pickering emulsion stabilized by modified soy protein particles and its application in plant-based ice cream.

Pickering emulsions are of great interest to the food industry and their freeze-thaw stability important when used in frozen foods. Particles of soybean isolate (SPI) were heat treated and then crosslinked with transglutaminase (TG) enzyme to produce Pickering emulsions. The protein particles produced using unheated and uncrosslinked SPI (NSPI) was used as the benchmark. The mean particle size, absolute zeta potential, and surface hydrophobicity of protein particles produced using heat treatment and TG crosslinking (at 40 U/g) SPI (HSPI-TG-40) were the highest and substantially higher than those produced using NSPI. The thermal treatment of protein particles followed by crosslinking with TG enzyme improved the freeze-thaw stability of Pickering emulsions stabilized by them. The Pickering emulsions produced using HSPI-TG-40 had the lowest temperature for ice crystal formation and they had better freeze-thaw stability. The plant-based ice cream prepared by HSPI-TG-40 particle-stabilized Pickering emulsions had suitable texture and freeze-thaw stability compared to the ice cream produced using NSPI. The Pickering particles produced using heat treatment of SPI followed by crosslinking with TG (at 40 U/g) produced the most freeze-thaw stable Pickering emulsions. These Pickering particles and Pickering emulsions could be used in frozen foods such as ice cream.

Protection of Whey Polypeptide on the Lipid Oxidation, Color, and Textural Stability of Frozen-Thawed Spanish Mackerel Surimi.

Repeated freeze-thaw (FT) cycles can have an impact on surimi quality. In this study, we used 0.02% BHA as a positive control group. We examined the effects of different concentrations (0%, 5%, 10%, and 15%) of whey protein hydrolysate (WPH) on surimi, focusing on alterations in color metrics (L* for brightness, a* for red-green, b* for yellow-blue, and overall whiteness), textural characteristics, and antioxidant capacity during various freeze-thaw (FT) cycles. The results showed that the lipid oxidant values of surimi, as well as its a* and b* values, rose as the number of FT cycles increased; whereas the adhesiveness, resilience, gumminess, and shear force dropped, as did L* and the whiteness values, leading to an overall darkening of color and gloss. By contrast, the study found that the addition of WPH could effectively slow down the decrease of surimi textural stability after repeated freeze-thawing, with the textural stability of the group with 15% WPH being significantly superior to those of the other groups (p < 0.05). Under the same number of cycles, adding 15% WPH to the experimental group could successfully lower total volatile basic nitrogen (TVB-N) and effectively increase the antioxidant activity of surimi. This finding suggested that 15% WPH had the greatest effect on increasing surimi FT stability. To conclude, it was proved that WPH can be added to frozen surimi and improve its quality.

The freeze-thaw stability of flavor high internal phase emulsion and its application to flavor preservation and 3D printing.

Volatilization of flavor substances may reduce consumers' perception of flavor, and the research on preservation of flavor substances by high internal phase emulsions (HIPEs) under freeze-thaw conditions is still blank. Herein, flavor HIPEs prepared by adding more than 15% litsea cubeba oil in the oil phase could be used as food-grade 3D printing inks, and showed better stability after 5 freeze-thaw cycles, which could be interpreted as the reduced ice crystal formation, more stable interface layer, and more flexible gel-like network structure resulting from the protein binding to flavor substances. The constructed HIPEs system in this study could preserve the encapsulated flavor substances perfectly after 5 freeze-thaw cycles. Overall, this study contributes a food-grade 3D printing ink, and provides a new method for the preservation of flavor substances under freezing conditions and expands the application range of flavor HIPEs in food industry.

Quinoa protein Pickering emulsion improves the freeze-thaw stability of myofibrillar protein gel: Maintaining protein composition, structure, conformation and digestibility and slowing down protein oxidation.

In this work, the effects of quinoa protein Pickering emulsion (QPPE) on protein oxidation, structure and gastrointestinal digestion property of myofibrillar protein gels (MPGs) after freeze-thaw (F-T) cycles are revealed. SDS-PAGE results indicated that 5.0 %-10.0 % QPPE addition slowed down the protein degradation. Meanwhile, 5.0 %-7.5 % QPPE maintained the stability of the protein secondary and tertiary structure of MPGs after F-T cycles. The sulfhydryl group, disulfide bond and dityrosine content increased with QPPE supplementation. The conformations of disulfide bond changed from g-g-t and t-g-t to g-g-g after F-T cycles, and 5.0 %-7.5 % QPPE stabilized the changes of t-g-t conformation. Furthermore, the increase of dityrosine content after F-T cycles was significantly reduced with 7.5 % QPPE addition, indicating its effect to slow down protein oxidation of MPGs. In addition, MPGs with 5.0 % and 7.5 % QPPE showed noticeably higher zeta potential values than other groups, indicating the enhanced electrostatic repulsion and weakened aggregation caused by F-T damage. This work showed that 7.5 % QPPE improved the F-T stability of MPGs and reduced the protein denaturation and oxidation caused by F-T treatments, exerting no side effect on the digestion property of MPGs. QPPE can be used as a green and effective antifreeze in meat industry.

Effect of caseinate salt addition on the structural characteristics of kefiran systems.

Sodium caseinates-kefiran systems were studied to explore whether any potential interactions between them might exist. The study was performed using low-deformation rheological techniques, which were dynamic and creep tests. The systems were prepared under various experimental conditions such as heating and acidification. Besides, the structure development of the systems in relation to time was also monitored using oscillatory shear rheometry. The results indicated that the structural characteristics of the systems were mainly affected by the state of the caseinates such as the formation of aggregates and to a lesser degree by the interactions of kefiran molecules with the caseinates. Freeze-thaw treatment produced cryogels with good thermal stability and fairly satisfactory mechanical properties. The morphology of the caseinate-kefiran systems was also investigated by means of confocal laser scanning microscopy.