Fabrication, characterization and application of Pickering emulsion gels stabilized by defatted grape seed powder.

The feasibility of defatted grape seed powder (DGSP) stabilizing Pickering emulsion gels as butter substitute was investigated. The Pickering emulsion gel was constructed using DGSP through high-speed homogenization, and the effects of particle concentration (c) and oil-phase (Medium chain triglyceride) volume fraction (φ) on its structure and properties were investigated. Its application as a butter substitute was also evaluated. The results showed that DGSP had various particle shapes, a wide particle size distribution (3-130 µm), and a three-phase contact angle of 128.9 ± 2.3°. The O/W Pickering emulsion gels with φ ≥ 60% could be obtained at c ≥ 2%. The droplet diameter was negatively correlated with c and positively correlated with φ, while the gel strength was positively related to c and φ. The resulting emulsion gel demonstrated solid-like viscoelastic behavior and pseudoplasticity, and had the potential to serve as a butter substitute. The results can promote the application of grape seeds in food.

The Effect of Acid Hydrolysis on the Pickering Emulsifying Capacity of Tartary Buckwheat Flour.

The effect of sulfuric acid hydrolysis on the Pickering emulsifying capacity of Tartary buckwheat flour (TBF) rich in starch was evaluated for the first time. The results indicate that the sulfuric acid concentration and hydrolysis time had a significant impact on the Pickering emulsifying capacity of acid-hydrolyzed Tartary buckwheat flour (HTBF). A low sulfuric acid concentration (1-2 mol/L) could reduce the particle size of HTBF, but it also decreased the Pickering emulsifying ability. At a sulfuric acid concentration of 3 mol/L, appropriate treatment time (2 and 3 days) led to particle aggregation but significantly improved wettability, thereby resulting in a rapid enhancement in emulsifying capacity. Under these conditions, the obtained HTBF (HTBF-D2-C3 and HTBF-D3-C3) could stabilize medium-chain triglyceride (MCT)-based Pickering high-internal-phase emulsions (HIPEs) with an oil-phase volume fraction of 80% at the addition amounts (c) of ≥1.0% and ≥1.5%, respectively. Its performance was significantly superior to that of TBF (c ≥ 2.0%). Furthermore, at the same addition amount, the droplet size of HIPEs constructed by HTBF-D3-C3 was smaller than that of HTBF-D2-C3, and its gel strength and microrheological performance were also superior to those of HTBF-D2-C3, which was attributed to the higher wettability of HTBF-D3-C3. The findings of this study can facilitate the in-depth application of Tartary buckwheat and provide references for the development of novel Pickering emulsifiers.

Effect of sulfuric acid hydrolysis on the structure and Pickering emulsifying capacity of acorn starch.

The acid-hydrolyzed acorn starch samples (HAS-1, HAS-2, HAS-3, and HAS-4) were prepared from natural acorn starch (NAS) at sulfuric acid concentrations of 1, 2, 3, and 4 mol/L for 2 d. The particle characteristics and structures of HAS were investigated, and Pickering high internal phase emulsions (HIPEs) based on HAS were constructed and characterized. The results showed that with an increase in sulfuric acid concentration, the size, yield, amylose content, molecular weight, and amylopectin chain length of HAS gradually decreased. HAS retained an A-type crystal structure, and its relative crystallinity and short-range order degree gradually increased with increasing sulfuric acid concentration. Acid hydrolysis treatment improved the wettability of NAS, and its effect was positively correlated with the sulfuric acid concentration. HAS-3 and HAS-4 could stabilize the Pickering HIPEs with an oil phase volume fraction of 80% at c ≥ 1.5%. The mechanical properties of the HIPEs were positively correlated with c.

Ultrasound-assisted fabrication and stability evaluation of okra seed protein stabilized nanoemulsion.

The structure and functional properties of okra seed protein (OSP) were characterized, the ultrasonic homogenization process of OSP nano-emulsion was optimized by response surface methodology (RSM), and its stability was also evaluated in this study. The results suggested that OSP was a high-quality plant protein, rich in glutamic acid. The molecular weight of its main subunits distributed in the range of 10-55 kDa, and some subunits were connected by disulfide bonds. Although the water and oil holding capacities of OSP were inferior to those of soy protein isolate (SPI), its emulsifying ability was superior to that of SPI. And the OSP concentration, ultrasonic time and ultrasonic power had obvious effects on the droplet size of nanoemulsion. The optimum process of OSP emulsion was determined as follows: OSP concentration 2.4 %, ultrasonic power 600 W, ultrasonic time 340 s. Under these conditions, the median droplet size of the nanoemulsion was 192.03 ± 3.48 nm, close to the predicted value (191.195 nm). And the obtained nano-emulsion exhibited high stability to the changes of pH, temperature and ionic strength in the environment. Our results can provide reference for the application of OSP, and promote the development of plant protein-based nanoemulsions.

Interaction mechanism of okra (Abelmoschus esculentus L.) seed protein and flavonoids: Fluorescent and 3D-QSAR studies.

The binding capacity of 10 flavonoids with okra seed protein (OSP) was studied by fluorescence spectroscopy. The structure of flavonoids had an obvious impact on binding performance. The binding ability of flavanone was lower than that of flavone, isoflavone and dihydrochalcone. The binding capacity of flavonoid glycoside was superior to that of the corresponding flavonoid aglycone. The binding ability was positively correlated with the number of phenolic hydroxyl groups on the B ring. The steric field and electrostatic field model constructed by 3D-QSAR method could well explain the above interaction behavior. Thermodynamic analysis suggested that the quenching mechanism of OSP caused by flavonoids was static quenching, and the binding-site number was 1. In addition, hydrogen bonding and van der Waals force dominated this interaction. The 3D and synchronous fluorescence spectra showed that there was no significant change in the polarity of the environment around tryptophan and tyrosine residues during binding.

Characterization of Wei Safflower Seed Oil Using Cold-Pressing and Solvent Extraction.

Wei safflower seed oil (WSO) prepared by the cold pressing method and organic solvent extraction method was characterized in this study. The yield of cold-pressed WSO (CP-WSO) was inferior to that of n-hexane-extracted WSO (HE-WSO). The physicochemical properties (refractive index, density, iodine value, insoluble impurities) and fatty acid compositions were similar, and both were rich in linoleic acid. However, CP-WSO had better color and less solvent residue. The type and content of vitamin E in CP-WSO was also superior to that in HE-WSO, which explained the high oxidative stability of CP-WSO in the Rancimat test. Our results provide a reference for the development of Wei safflower seed oil.

Characterization of polysaccharide from Lonicera japonica Thunb leaves and its application in nano-emulsion.

The polysaccharides in honeysuckle leaves (PHL) were separated and characterized for the first time. The nano-emulsion stabilized by PHL and whey protein isolate (WPI) were also fabricated based on the ultrasonic method. The results indicated that PHL was mainly composed of glucose (47.40 mol%), galactose (19.21 mol%) and arabinose (20.21 mol%) with the weight-average molecular weight of 137.97 ± 4.31 kDa. The emulsifier concentration, WPI-to-PHL ratio, ultrasound power and ultrasound time had significant influence on the droplet size of PHL-WPI nano-emulsion. The optimal preparation conditions were determined as following: emulsifier concentration, 1.7%; WPI/PHL ratio, 3:1; ultrasonic power, 700 W; ultrasonic time, 7 min. Under the above conditions, the median diameter of the obtained nano-emulsion was 317.70 ± 5.26 nm, close to the predicted value of 320.20 nm. The protective effect of PHL-WPI emulsion on ß-carotene against UV irradiation was superior to that of WPI emulsion. Our results can provide reference for the development of honeysuckle leaves.

Characterization of a Dihydromyricetin/α-Lactoalbumin Covalent Complex and Its Application in Nano-emulsions.

A dihydromyricetin (DMY)/α-lactoalbumin (α-La) covalent complex was prepared and characterized, and its application in nano-emulsions was also evaluated in this study. The results suggested that the covalent complex could be obtained using the alkaline method. The UV and IR spectra confirmed the formation of the covalent complex, and the amount of DMY added was positively correlated with the total phenol content of the complex. The complex had an outstanding 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-radical-scavenging ability, reducing power and α-glucosidase inhibitory activity, which were positively related to its total phenol content. The complex could be used as an emulsifier to stabilize the ß-carotene-loaded nano-emulsion. The stability and ß-carotene-protective capacity of the nano-emulsion stabilized by the complex were also positively related to the total phenol content of the complex, being higher than those of the nano-emulsion developed using α-La. Our results provide a reference for the construction of a new food delivery system and extend the applications of α-La and DMY in foods.

Effect of Ultrasonic Treatment on Structure and Physicochemical Properties of Pea Starch.

The effects of ultrasonic treatment on the structure and physicochemical properties of pea starch were investigated in this study. The results showed that ultrasonic treatment increased the hydrolysis rate and particle size of pea starch. In the process of treatment, there were some depressions and pores on the surface of pea starch granules. Although the crystallization type of starch was retained, its crystallinity decreased. The pasting temperature of pea starch remained stable after ultrasonic treatment, but its peak viscosity, trough viscosity, cold viscosity, breakdown viscosity and setback viscosity all declined significantly. The transparency of starch paste decreased, but proper ultrasonic treatment could improve the strength of starch gel. The obtained results can provide a reference for the physical modification of pea starch.

The physicochemical properties and Pickering emulsifying capacity of acorn starch.

In this work, the granule characteristics, functional properties, in-vitro digestibility, antioxidant capacity, and phenolic composition of acorn starch were investigated and compared to those of potato starch and corn starch, and its Pickering emulsifying ability was also evaluated. The results showed that the acorn starch granules were spherical and oval in shape, with a smaller particle size, and the amylose content and crystallinity degree were similar to those of corn starch. However, the acorn starch was difficult to swell, with poor aqueous solubility, though it had a strong gel strength and setback viscosity. Because acorn starch contained more free and bound polyphenols, its resistant starch content after cooking and ABTS and DPPH radical scavenging activities were significantly higher than those of potato starch and corn starch. Acorn starch also exhibited outstanding particle wettability and could stabilize Pickering emulsions. The assessed emulsion showed an outstanding effect for protecting ß-carotene against ultraviolet irradiation and was positively correlated with the acorn starch addition amount. The obtained results may serve as a reference for the further development of acorn starch.

Cytochalasans from the Endophytic Fungus Aspergillus sp. LE2: Their Structures, Antibacterial and NO Production Inhibitory Activities.

Six new cytochalasans-namely, aspergicytochalasins A-F (1-6)-together with five known analogs were isolated and characterized from the endophytic fungus Aspergillus sp. from the medicinal plant Lonicera japonica. The structures of the new compounds were established by NMR and MS methods as well as single crystal X-ray diffractions. Compounds 3 and 4 showed weak antibacterial activities to Staphylococcus aureus, with MIC values of 128 and 64 µg/mL, respectively. Compounds 1, 3, 5 and 6 showed inhibitory activities on NO production, with IC50 values less than 40 µM.

Formation mechanism of Pickering emulsion gels stabilized by proanthocyanidin particles: Experimental and molecular dynamics studies.

The feasibility of constructing a Pickering emulsion gel with proanthocyanidin particles (PAP) was evaluated in this study, and the related mechanism was revealed by combining instrumental characterization with molecular dynamics simulation. The results showed that PAP was composed of nano/micron spherical particles or their fragments, which had excellent wettability. Suitable PAP addition amount (w, ≥1%) and oil volume fraction (φ, 40-90 %) were beneficial to the formation of stable Pickering emulsion gel. The oil droplet size of gel was inversely proportional to w and φ. The mechanical parameters (gel strength, loss modulus, and storage modulus) were positively correlated with w and φ. Molecular dynamics simulation indicated that the proanthocyanidin molecules in the oil-water system could spontaneously reside and aggregate at the interface, and their interactions with water and oil reduced interfacial tension, which was consistent with the experimental results. This study provides a reference for other polyphenol-based Pickering emulsions.

An investigation on pickering nano-emulsions stabilized by dihydromyricetin/high-amylose corn starch composite particles: Preparation conditions and carrier properties.

With dihydromyricetin (DMY)/high-amylose corn starch (HCS) composite particles as the emulsifier, Pickering nano-emulsions were fabricated by combining high-speed shearing and high-pressure homogenization. The effect of particle properties and processing conditions on the formation and physicochemical properties of the Pickering nano-emulsions was then investigated systematically. The results showed that the DMY content of the composite particles, the oil phase volume fraction of the emulsion, and the homogenization conditions had obvious effects on the droplet size of the emulsion, where appropriate DMY content in the composite particles (5-20%) contributed to the formation of stable Pickering nano-emulsions. The oil phase of the obtained emulsions exhibited good stability during high-temperature storage, and their ß-carotene protecting performance against UV irradiation was superior to the emulsion stabilized by Tween 20. The in vitro simulated digestion analysis indicated that the nano-emulsions developed by the composite particles could enhance the bioaccessibility of ß-carotene and inhibit starch hydrolysis.

Fabrication and characterization of Pickering high internal phase emulsions stabilized by Tartary buckwheat bran flour.

The abilities of Tartary buckwheat whole flour (TBWF), Tartary buckwheat core flour (TBCF), and Tartary buckwheat bran flour (TBBF) to directly construct Pickering high internal phase emulsions (HIPEs) were compared. The results indicated that these flours had a similar appearance and size distribution, but TBBF was rich in proteins, lipids, and rutin. As a result, its hydrophobicity and ability to reduce interfacial tension were superior to TBWF and TBCF. These flours could fabricate HIPEs with an oil phase volume fraction (φ) of 80 %, and the increase in the addition amount (c) was not only beneficial to the mechanical properties, but also accelerated gel formation. When c was constant, the HIPEs developed by TBBF exhibited the smallest droplet size and the highest gel strength. The sunflower oil-based HIPE developed by TBBF at φ = 80 % and c = 5 % could also partially replace butter for cake preparation, and improve antioxidant activity of cakes.

Effect of citric acid esterification on the structure and physicochemical properties of tigernut starch.

In this work, esterified tigernut starch with citric acid (ETSC) was prepared for the first time, and its structure, in vitro digestibility, and Pickering emulsifying capacity were investigated. The formation of ETSC was confirmed by SEM (Scanning electron microscopy), XRD (X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), and solid-state 13C NMR (Nuclear magnetic resonance), and the citric acid dosage in the preparation process was positively correlated with the degree of substitution (DS) of ETSC. With an increase in DS, the solubility and swelling power of ETSC decreased, the crystallinity degree declined, and the proportion of resistant starch (RS) increased rapidly. The increase in DS could also enhance the wettability of ETSC, thus improving the Pickering emulsifying ability of ETSC. The high ETSC concentration (c) and suitable oil phase volume ratio (φ) of the Pickering emulsion were beneficial to its formation and stability. Moreover, the macroscopic viscosity index (MVI) and elastic index (EI) of the emulsion were also positively related to the DS of ETSC.

The Fabrication and Characterization of Pickering Emulsion Gels Stabilized by Sorghum Flour.

Pickering emulsion gels have potential application as solid fat substitutes and nutraceutical carriers in foods, but a safe and easily available food-derived particle emulsifier is the bottleneck that limits their practical application. In this study, the function of sorghum flour as a particle emulsifier to stabilize the oil-in-water (O/W) Pickering emulsion gels with medium chain triglycerides (MCT) in the oil phase was introduced. Sorghum flour had suitable size distribution (median diameter, 21.47 µm) and wettability (contact angle, 38°) and could reduce the interfacial tension between MCT and water. The oil phase volume fraction (φ) and the addition amount of sorghum flour (c) had significant effects on the formation of Pickering emulsion gels. When c ≥ 5%, Pickering emulsion gels with φ = 70% could be obtained. Microstructure analysis indicated that sorghum flour not only played an emulsifying role at the O/W interface but also prevented oil droplets from coalescing through its viscous effect in the aqueous phase. With increases in c, the droplet size of the emulsion gel decreased, its mechanical properties gradually strengthened, and its protective effect on ß-carotene against UV irradiation also improved.

Ultrasound-Assisted Natural Deep Eutectic Solvent Extraction and Bioactivities of Flavonoids in Ampelopsis grossedentata Leaves.

We performed ultrasound-assisted extraction coupled with natural deep eutectic solvents (NADES) to achieve the green and efficient preparation of flavonoid extract from Ampelopsis grossedentata leaves. We then evaluated its antioxidant and antiproliferative activities. A NADES consisting of choline chloride and glucose at a molar ratio of 4:1 with 20% water was determined to be the most suitable solvent. The optimal extraction conditions were: a liquid-to-solid ratio of 30 mL/g, an ultrasonication power of 490 W, and an ultrasonication time of 6.5 min. The actual flavonoid yield was 83.93%, which was close to the predicted yield. Further, 86.75% of the flavonoids were recovered by adding the same volume of phosphate buffer saline (100 mM, pH of 7.0) to the extract solution. Although the chemical antioxidant activities of the flavonoid extract were slightly inferior to those of dihydromyricetin, the flavonoid extract could still effectively inhibit the proliferation of human breast MDA-MB-231 cells by inducing cell apoptosis, retarding the cell cycle, changing the mitochondrial membrane potential and scavenging intracellular reactive oxygen species (ROS). The obtained results can provide a reference in the development of plant-derived functional foods.

Computational Methods for the Interaction between Cyclodextrins and Natural Compounds: Technology, Benefits, Limitations, and Trends.

Cyclodextrins (CDs) have a hollow structure with a hydrophobic interior and hydrophilic exterior. Forming inclusion complexes with CDs will maximize the bioavailability of natural compounds and enable active components to be processed into functional foods, medicines, additives, and so forth. However, experimental methods cannot explain CD-guest binding at the atomic level. Different models have been recently developed to simulate the interaction between CDs and guests to study the binding conformation and analyze noncovalent forces. This review paper summarizes modeling methods of CD-natural compound complexes. The methods include quantitative structure-activity relationships, molecular docking, molecular dynamics simulations, and quantum-chemical calculations. The applications of these methods to enhance the solubility and bioactivities of guest molecules, assist material transportation, and promote compound extraction are also discussed. The purpose of this review is to explore interaction mechanisms of CDs and guests and to help expand new applications of CDs.

Fabrication of food-grade Pickering high internal phase emulsions (HIPEs) stabilized by a dihydromyricetin and lysozyme mixture.

This study evaluated the feasibility of fabricating food-grade HIPEs using a dihydromyricetin and lysozyme mixture. The effects of the oil phase volume fraction (φ), composition (lysozyme:dihydromyricetin, k), and addition amount (w) of the mixture on the formation and properties of the HIPEs were analyzed. Then, the interactions of dihydromyricetin and lysozyme were investigated. The results indicated that when w was 0.4%, HIPEs with φ value of 90% could be obtained. Furthermore, the k also affected the microstructure, mechanical properties, oil oxidation, and lutein protection ability of the HIPEs. However, the presence of dihydromyricetin did not affect lysozyme activity. Both isothermal titration calorimetry and molecular simulations proved that they did not form a typical host-guest complex. But, dihydromyricetin could absorb on the lysozyme surface. Therefore, we speculated that lysozyme and dihydromyricetin particles could overlap and form a 3D network structure to stabilize the HIPEs, which was consistent with the microstructure observations.

Effects of Tartary Buckwheat Bran Flour on Dough Properties and Quality of Steamed Bread.

Steamed bread is a traditional staple food of China. Replacing wheat flour (WF) with Tartary buckwheat is expected to improve the nutritional value of steamed bread. In this study, Tartary buckwheat flour (TBF), Tartary buckwheat bran flour (TBBF), and Tartary buckwheat core flour (TBCF) were prepared, their composition and physicochemical properties were compared. It was found that TBBF had higher protein and rutin contents, so its antioxidant activity and dough rheological properties were obviously superior to those of TBF and TBCF. When TBBF was mixed with WF, its weight proportion in the blend (Wbran) had a significant effect on the dough rheological properties. When Wbran was 30%, the dough had the optimal mixing tolerance, and when Wbran exceeded 30%, it caused dilution effect, weakening the gluten network. With the increase of Wbran, the color of the steamed bread developed by the TBBF-WF blend gradually darkened and yellowed, the specific volume declined, and its hardness, gumminess, and chewiness ascended gradually. The appropriate addition of TBBF (Wbran = 10% and 30%) was beneficial to cell diameter and volume of steamed bread, but the further rise of Wbran would destroy its gas retention ability. The predicted glycemic index (pGI) of steamed bread declined significantly with the increasing Wbran.