A mechanistic investigation of the effect of dispersion phase protein type on the physicochemical stability of water–in–oil emulsions

Modification of soy protein isolate and pea protein isolate by high voltage dielectric barrier discharge (DBD) atmospheric cold plasma: Comparative study on structural, rheological and techno-functional characteristics

The modification in structural, rheological, and techno-functional characteristics of soy and pea protein isolates (SPI and PPI) due to dielectric barrier discharge cold plasma (DBD-CP) were assessed. The increased carbonyl groups in both samples with cold plasma (CP) treatment led to a reduction in free sulfhydryl groups. Moreover, protein solubility of treated proteins exhibited significant improvements, reaching up to 59.07 % and 41.4 % for SPI and PPI, respectively, at 30 kV for 8 min. Rheological analyses indicated that storage modulus (G') was greater than loss modulus (G″) for CP-treated protein gels. Furthermore, in vitro protein digestibility of SPI exhibited a remarkable improvement (4.78 %) at 30 kV for 6 min compared to PPI (3.23 %). Spectroscopic analyses, including circular dichroism and Fourier Transform-Raman, indicated partial breakdown and loss of α-helix structure in both samples, leading to the aggregation of proteins. Thus, DBD-CP induces reactive oxygen species-mediated oxidation, modifying the secondary and tertiary structures of samples.

Construction and Properties of Oil-Loaded Soybean Protein Isolate/Polysaccharide-Based Meat Analog Fibers

Rationally designing the fibrous structure of artificial meat is a challenge in enriching the organoleptic quality of meat analogs. High-quality meat analog fibers have been obtained by wet-spinning technique in our previous study, whereas introducing oil droplets will further achieve their fine design from the insight of microstructure. Herein, in this current work, oil was introduced to the soybean protein isolate/polysaccharide-based meat analog fibers by regulating the oil droplets' size and content, which, importantly, controlled the spinning solution characterization as well as structure-related properties of the meat analog fiber. Results showed that the oil dispersed in the matrix as small droplets with regular shapes, which grew in size as the oil content increased. Considering the effect of oil droplets' size and content on the spinnability of the spinning solution, the mechanical stirring treatment was chosen as the suitable treatment method. Importantly, increasing the oil content has the potential to enhance the juiciness of meat analog fibers through improvements in water-holding capacity and alterations in water mobility. Overall, the successful preparation of oil-loaded plant-based fiber not only mimicked animal muscle fiber more realistically but also provided a general platform for adding fat-soluble nutrients and flavor substances.

Effects of Maillard reaction of different monosaccharide-modified on some functional properties of fish gelatin

In this work, the effects of Maillard reaction of different monosaccharide-modified fish gelatin were studied. The changes of gel properties, rheology and structure of fish gelatin before and after modification were compared and analyzed, and oil-in-woter emulsions were prepared. The results showed that the five-carbon monosaccharide had stronger modification ability than the six-carbon monosaccharide, which was mainly due to the different steric hindrance of the amino acids in the nuclear layer and the outer layer to the glycosylation reaction. With the progress of the Maillard reaction, the color of fish gelatin gradually became darker. The attachment of sugar chains inhibited the gelation process of fish gelatin, decreased the gelation rate, changed the secondary structure, increased the content of β-turn or α-helix, increased the degree of fluorescence quenching, and enhanced the emulsifying properties and emulsion stability. This study provides useful information for the preparation of different types of monosaccharide-modified proteins and emulsions.

The effect of subzero temperatures on the properties and structure of soy protein isolate emulsions

Different freezing temperatures (-5, -20, -40 and -80 ℃) could change soy protein isolate (SPI) structure and emulsion properties. After freezing at -5 ℃ and -20 ℃, the structure of the SPI loosened, the fluorescence intensity was red shifted, and the proportion of Phe, Tyr and Trp exposed increased. With decreasing temperature, the surface hydrophobicity (H0 × 100), the number of sulfhydryl groups and the number of disulfide bonds all rose, then fell (-40 ℃), and rose again (-80 ℃). The β-sheet content in the protein secondary structure increased from 32.71% (control) to 50.66% (-40 ℃) and then decreased to 37.05% (-80 ℃), while the β-turn and random coil contents showed the opposite pattern, which also confirmed aggregation. The emulsification performance of SPI after freezing treatment was decreased. The results of this study provide theoretical support for future production of frozen foods with added SPI.

Influence of varying oil phase volume fractions on the characteristics of flaxseed-derived diglyceride-based Pickering emulsions stabilized by modified soy protein isolate

This research aimed to create Pickering emulsions using modified soy protein isolate (SPI) as a stabilizer and flaxseed-derived diglyceride (DAG) as an oil phase. The SPI was modified through a process involving both heating and ultrasound treatment. The result indicated that the droplet size of emulsions increased with the increase in oil content (p < 0.05). For instance, the largest droplet size (23 µm) was observed at an oil-to-SPI dispersion ratio of 4:1 ratio (φ = 80), whereas the smallest droplet size (6.39 µm) was noticed at the 1:4 ratio. During the 7-day storage period, the emulsions with a 4:1 ratio (φ = 80) showed the lowest droplet size increase (from 23 µm to 25.58 µm). In contrast, the emulsions with a 1:1 ratio displayed the highest increase (from 19.39 µm to 74.29 µm). Creaming index results revealed that emulsions with a 4:1 ratio (φ = 80) showed no signs of creaming and phase separation than all other treatments (p < 0.05). Backscattering fluctuations (ΔBS) and turbiscan stability index (TSI) showed that emulsions with 4:1, 2:1, and 1:1 oil-to-SPI dispersion ratios had consistent ΔBS curves with higher and TSI curves with lower values. Optical microscopy, confocal laser scanning, and cryo-scanning electron microscopy revealed that emulsions with oil-to-SPI dispersion ratios of 4:1 and 2:1 had well-organized structures with no visible coalescence. Macromorphological and microrheological investigations demonstrated that emulsions with 80% oil content had the highest viscosity, both moduli, elasticity index, macroscopic viscosity index, and the lowest fluidity index and solid-liquid balance values. Moreover, these emulsions were more resistant to centrifugation and storage environments. In conclusion, the study determined that flaxseed-derived DAG-based high internal phase Pickering emulsions (φ = 80) had superior stability, improved viscoelasticity, and better rheological properties.

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.

Effects of the Combination of Protein in the Internal Aqueous Phase and Polyglycerol Polyricinoleate on the Stability of Water-In-Oil-In-Water Emulsions Co-Encapsulating Crocin and Quercetin

This study aimed to diminish the reliance on water-in-oil-in-water (W/O/W) emulsions on the synthetic emulsifier polyglycerol polyricinoleate (PGPR). Considering the potential synergistic effects of proteins and PGPR, various protein types (whey, pea and chickpea protein isolates) were incorporated into the internal aqueous phase to formulate W/O/W emulsions. The effects of the combination of PGPR and protein at different ratios (5:0, 4:1, 3:2, 1:1 and 2:3) on the stability and encapsulation properties of W/O/W emulsions co-encapsulating crocin and quercetin were investigated. The findings indicated that the combination of PGPR and protein resulted in a slight reduction in the encapsulation efficiency of the emulsions, compared to that of PGPR (the control). Nonetheless, this combination significantly enhanced the physical stability of the emulsions. This result was primarily attributed to the smaller droplet sizes and elevated viscosity. These factors contributed to increased retentions of crocin (exceeding 70.04%) and quercetin (exceeding 80.29%) within the emulsions after 28 days of storage, as well as their improved bioavailability (increases of approximately 11.62~20.53% and 3.58~7.98%, respectively) during gastrointestinal digestion. Overall, combining PGPR and protein represented a viable and promising strategy for reducing the amount of PGPR and enhancing the stability of W/O/W emulsions. Notably, two plant proteins exhibited remarkable favorability in this regard. This work enriched the formulations of W/O/W emulsions and their application in the encapsulation of bioactive substances.

Analytics and applications of polyglycerol polyricinoleate (PGPR)-Current research progress

Polyglycerol polyricinoleate (PGPR) is a synthetic food additive containing a complex mixture of various esters. In recent years, there has been a growing trend to use PGPR-stabilized water-in-oil (W/O) emulsions to replace fat in order to produce low-calorie food products. In this respect, it is essential to comprehensively characterize the PGPR molecular species composition, which might enable to reduce its required amount in emulsions and foods based on a better understanding of the structure-activity relationship. This review presents the recent research progress on the characterization and quantitative analysis of PGPR. The influencing factors of the emulsifying ability of PGPR in W/O emulsions are further illustrated to provide new insights on the total or partial replacement of PGPR. Moreover, the latest progress on applications of PGPR in food products is described. Current studies have revealed the complex structure of PGPR. Besides, recent research has focused on the quantitative determination of the composition of PGPR and the quantification of the PGPR concentration in foods. However, research on the quantitative determination of the (poly)glycerol composition of PGPR and of the individual molecular species present in PGPR is still limited. Some natural water- or oil-soluble surfactants (e.g., proteins or lecithin) have been proven to enable the partial replacement of PGPR in W/O emulsions. Additionally, water-dispersible phytosterol particles and lecithin have been successfully used as a substitute of PGPR to create stable W/O emulsions.

Improving the Stability of Water-in-Oil Emulsions with Medium Internal Phase by the Introduction of Gelatin

The water-in-oil (W/O) emulsion with a medium aqueous phase may be limited in food and cosmetics due to its poor stability and high cost. Herein, this work proposed a facile strategy to improve the W/O emulsion stability by introducing gelatin. The influence of different gelatin concentrations (0, 0.5%, 1.0%, 2.0%, and 4.0%) on the stability and properties of W/O emulsions was mainly investigated. Results showed that the obtained emulsions still belonged to W/O emulsions after adding gelatin to the aqueous phase. As the gelatin concentration increased (0~4.0%), the interfacial tension decreased, which is conducive to promoting the interface adsorption of polyglycerol polyricinoleate (PGPR). Furthermore, introducing gelatin also improved the water-holding capacity (WHC) (33.50~6.32%) and viscosity of W/O emulsions and reduced the droplet size (37.47~8.75 μm) of emulsions. The enhanced interfacial adsorption and aqueous gelation induced by gelatin addition promoted the formation of a tight overall emulsion network structure by the interaction between the interfacial adsorbed PGPR, as well as PGPR and gelatin in the aqueous phase. The enhancement of the overall network effectively improved the storage stability (35 d), thermal stability (20 min, 80 °C), and freeze-thaw stability (10 cycles) of emulsions, especially at 4.0% gelatin concentration. Hence, this study can provide guidance for the improvement and regulation of the stabilities of W/O emulsions.

Dodecenylsuccinic anhydride-modified oxalate decarboxylase loaded with magnetic nano-Fe3O4@SiO2 for demulsification of oil-in-water emulsions

The inability to demulsify oil-in-water emulsions via green and efficient processes is a challenging problem in many industrial processes. As a novel biodemulsifier, protein demulsifiers display excellent dispersibility and stability, but their demulsification mechanisms are not clear, which severely restricts their large-scale production and application. In this study, the demulsification mechanism of the high-efficiency protein biodemulsifier oxalate decarboxylase (Bacm OxdC), which is secreted by the Bacillus mojavensis XH1 strain, for an oil-in-water emulsion was analyzed. The results showed that Bacm OxdC was spontaneously adsorbed at the oil-water interface and turned its hydrophobic amino acids outward to increase its hydrophobicity and break the emulsified system. Furthermore, it effectively reduced the oil-water interfacial tension and interfacial film strength, thereby reducing the oil-water interfacial energy and finally enabling demulsification. To further improve the demulsification efficiency and reusability, Fe₃O₄@SiO₂@OxdC-DDSA was prepared. This method provided a magnetic response for Bacm OxdC and enabled efficient demulsification. The demulsification rate of Fe₃O₄@SiO₂@OxdC-DDSA reached 98.1% at 24 h, which was 30.7% higher than that of the original Bacm OxdC. After three cycles, the demulsification rate still reached 89.3%, proving it has excellent recyclability. This work is the first study on the demulsification mechanism of protein biodemulsifiers and provides useful insights into the demulsification mechanism of biodemulsifiers for oil-in-water emulsions. In addition, a promising high-efficiency modification technique for protein biodemulsifiers was proposed, which provided information for the development of biodemulsifiers for oil-water separation.