One-step high efficiency separation of prolyl endopeptidase from Aspergillus niger and its application.

Prolyl endopeptidase from Aspergillus niger (An-PEP) is an enzyme that recognizes C-terminal peptide bonds of amino acid chains and cleaves them by hydrolysis. An aqueous two-phase system (ATPS) was used to separate An-PEP from fermentation broth. Through single factor experiments, the ATPS containing 16 % (w/w) PEG2000 and 15 % (w/w) (NH4)2SO4 at pH 6.0 obtained the recovery of 79.74 ± 0.16 % and the purification coefficient of 7.64 ± 0.08. It was then used to produce soy protein isolate peptide (SPIP) by hydrolysis of soy protein isolate (SPI), and SPIP-Ferrous chelate (SPIP-Fe) was prepared with SPIP and Fe2+. The chelation conditions were optimized by RSM, as the chelation time was 30 min, chelation temperature was 25 °C, SPIP mass to VC mass was two to one and pH was 6.0. The obtained chelation rate was 82.56 ± 2.30 %. The change in the structures and functional features of SPIP before and after chelation were investigated. The FTIR and UV-Vis results indicated that the chelation of Fe2+ and SPIP depended mainly on the formation of amide bonds. The fluorescence, SEM and amino acid composition analysis results indicated that Fe2+ could induce and stabilize the surface conformation and change the amino acid distribution on the surfaces of SPIP. The chelation of SPIP and Fe2+ resulted in the enhancement of radical scavenging activities and ACE inhibitory activities. This work provided a new perspective for the further development of peptide-Fe chelates for iron supplement.

Ultrasonic-microwave synergistic supramolecular solvent liquid-liquid microextraction of trace biogenic amines in fish and beer based on solidification of floating organic droplet.

It is important to detect the presence of biogenic amines (BAs) as indicators of food freshness. The purpose of this study was to develop a novel ultrasonic-microwave synergistic supramolecular solvent liquid-liquid microextraction based on solidification of floating organic droplet (UMS-SUPRAS-SFO-LLME) combined with high-performance liquid chromatography for the determination of BAs. The physical properties and microstructure of SUPRAS based on 1-dodecanol and tetrahydrofuran were studied, and the extraction conditions such as the SUPRAS volume, the UMS process, and the centrifugal conditions were optimized. The results for the extraction kinetics and thermodynamics showed that UMS-SUPRAS-SFO-LLME is a spontaneous, endothermic diffusion process. The linear ranges of this method are 0.1-2.0 × 105 ng·mL-1 (R2 > 0.994), the limits of detection are 4.0 × 10-3-6.0 × 10-2 ng·mL-1, and the recoveries were 96.28-103.15%. Compared with existing analysis methods, UMS-SUPRAS-SFO-LLME is a sensitive, green and economical sample pretreatment method for analyzing the enrichment of BAs in beer and fish.

Structural characteristics and biological activity of lactic acid bacteria exopolysaccharides separated by ethanol/(NH4)2SO4 ATPS.

Exopolysaccharides (EPS) from lactic acid bacteria (LAB) as edible and safe bioproducts with health benefits have become an interesting topic. In this study, aqueous two-phase system (ATPS) was established using ethanol and (NH4)2SO4 as phase-forming substances to separate and purify LAB EPS from Lactobacillus plantarum 1.0665. The operating conditions were optimized by a single factor and response surface method (RSM). The results indicated that an effectively selective separation of LAB EPS was achieved by the ATPS consisted of 28 % (w/w) ethanol and 18 % (w/w) (NH4)2SO4 at pH 4.0. Under optimized conditions, the partition coefficient (K) and recovery rate (Y) were well matched with the predicted value of 3.83 ± 0.019 and 74.66 ± 1.05 %. The physicochemical properties of purified LAB EPS were characterized by various technologies. According to the results, LAB EPS was a complex polysaccharide with a triple helix structure mainly composed of mannose, glucose and galactose in the molar ratio of 1.00: 0.32: 0.14, and it proved that the ethanol/(NH4)2SO4 system had good selectivity for LAB EPS. In addition, LAB EPS displayed excellent antioxidant activity, antihypertension activity, anti-gout capacity and hypoglycemic activity in vitro analysis. The results suggested that LAB EPS could be a dietary supplement applied in functional foods.

A Novel Intelligent Indicator Film: Preparation, Characterization, and Application.

The development of intelligent indicator film that can detect changes in food quality is a new trend in the food packaging field. The WPNFs-PU-ACN/Gly film was prepared based on whey protein isolate nanofibers (WPNFs). Anthocyanin (ACN) and glycerol (Gly) were used as the color indicator and the plasticizer, respectively, while pullulan (PU) was added to enhance mechanical properties of WPNFs-PU-ACN/Gly edible film. In the study, the addition of ACN improved the hydrophobicity and oxidation resistance of the indicator film; with an increase in pH, the color of the indicator film shifted from dark pink to grey, and its surface was uniform and smooth. Therefore, the WPNFs-PU-ACN/Gly edible film would be suitable for sensing the pH of salmon, which changes with deterioration, as the color change of ACN was completely consistent with fish pH. Furthermore, the color change after being exposed to grey was evaluated in conjunction with hardness, chewiness, and resilience of salmon as an indication. This shows that intelligent indicator film made of WPNFs, PU, ACN, and Gly could contribute to the development of safe food.

Efficient imaging based on P - and N-codoped carbon dots for tracking division and viability assessment of lactic acid bacteria.

Assessment of lactic acid bacteria (LAB) activity plays a key role in the fermented food industry. Fluorescence imaging method based on dye is facile to detect LAB viability. However, it is difficult to obtain stable fluorescence, non-toxic and low-cost dyes. In this study, we prepare P- and N-doped carbon dots (PN-CDs) via microwave-assisted hydrothermal synthesis. The properties of high quantum yield (60.36%) and excitation dependence allowed for multicolor imaging of LAB (Lactobacillus plantarum [L.p] and Streptococcus thermophilus [S.t]). The abundant functional groups and positive charges (+2.34 mV) on the surface of PN-CDs facilitated their quickly integrated into cell wall of live LAB with obvious fluorescence or into dead cells. As a result, PN-CDs can not only be used to rapidly and efficiently monitor bacterial viability (one minute), but can also be used to visualize LAB division using fluorescence imaging. Importantly, the PN-CDs have potential to rapidly detect LAB activity in LAB-fermented juices.

Enhanced viability of probiotics encapsulated within synthetic/natural biopolymers by the addition of gum arabic via electrohydrodynamic processing.

To enhance the probiotics' viability, novel vehicles consisting of synthetic/natural biopolymers, i.e., polyvinyl alcohol (PVOH), polyvinylpyrrolidone, whey protein concentrate and maltodextrin, encapsulated with L. plantarum KLDS 1.0328 and gum arabic (GA) as a prebiotic were fabricated by electrohydrodynamic techniques. Inclusion of cells into composites caused an increase in conductivity and viscosity. Morphological analysis showed that cells were distributed along the electrospun nanofibres or distributed randomly in the electrosprayed microcapsules. Both intramolecular and intermolecular hydrogen bond interactions exist between biopolymers and cells. Thermal analysis revealed that the degradation temperatures (>300 °C) of various encapsulation systems have potential applications in heat-treatment foods. Additionally, cells especially immobilized in PVOH/GA electrospun nanofibres showed the highest viability compared with free cells after exposure to simulated gastrointestinal stress. Furthermore, cells retained their antimicrobial ability after rehydration of the composite matrices. Therefore, electrohydrodynamic techniques have great potential in encapsulating probiotics.

Covalent and Noncovalent Complexation of Phosvitin and Gallic Acid: Effects on Protein Functionality and In Vitro Digestion Properties.

To investigate the effects of different binding modes on the structure, function, and digestive properties of the phosvitin (Pv) and gallic acid (GA) complex, Pv was covalently and noncovalently combined with different concentrations of GA (0.5, 1.5, and 2.5 mM). The structural characterization of the two Pv-GA complexes was performed by Fourier transform infrared, circular dichroism, and LC-MS/MS to investigate the covalent and noncovalent binding of Pv and GA. In addition, the microstructure of the two Pv-GA complexes was investigated by super-resolution microscopy and transmission electron microscopy. The particle size and zeta potential results showed that the addition of GA increased the particle size and the absolute potential of Pv. The determination of protein digestibility, polyphenol content, SH and S-S group levels, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and antioxidant capacity of the digests indicated that noncovalent complexes had greater antioxidant and protective effects on polyphenols. Molecular docking revealed that GA was conjugated with Pv through hydrogen bond interactions.

B- and N-doped carbon dots by one-step microwave hydrothermal synthesis: tracking yeast status and imaging mechanism.

BACKGROUND: Carbon dots (CDs) are widely used in cell imaging due to their excellent optical properties, biocompatibility and low toxicity. At present, most of the research on CDs focuses on biomedical application, while there are few studies on the application of microbial imaging. RESULTS: In this study, B- and N-doped carbon dots (BN-CDs) were prepared from citric acid, ethylenediamine, and boric acid by microwave hydrothermal method. Based on BN-CDs labeling yeast, the dead or living of yeast cell could be quickly identified, and their growth status could also be clearly observed. In order to further observe the morphology of yeast cell under different lethal methods, six methods were used to kill the cells and then used BN-CDs to label the cells for imaging. More remarkably, imaging of yeast cell with ultrasound and antibiotics was significantly different from other imaging due to the overflow of cell contents. In addition, the endocytosis mechanism of BN-CDs was investigated. The cellular uptake of BN-CDs is dose, time and partially energy-dependent along with the involvement of passive diffusion. The main mechanism of endocytosis is caveolae-mediated. CONCLUSION: BN-CDs can be used for long-term stable imaging of yeast, and the study provides basic research for applying CDs to microbiol imaging.

Development of Antioxidant and Stable Conjugated Linoleic Acid Pickering Emulsion with Protein Nanofibers by Microwave-Assisted Self-Assembly.

Whey protein isolate nanofibrils (WPNFs) can be used as a novel stabilizer in the Pickering emulsion system to improve the water solubility, stability and bioavailability of lipophilic bioactive ingredients. In this study, conjugated linoleic acid (CLA) and WPNFs were used to prepare a stable Pickering emulsion. We used a transmission electron microscope, low-temperature scanning electron micrographs and other methods to evaluate the micromorphology, surface hydrophobicity and structural units of the obtained WPNFs. Compared with whey protein isolate/CLA Pickering emulsion, the WPNFs/CLA Pickering emulsion has greater ability to remove 2,2-Diphenyl-1-picrylhydrazyl and 2,2'-amino-di(2-ethyl-benzothiazoline sulphonic acid-6) ammonium salt free radicals. Furthermore, the WPNFs/CLA Pickering emulsion has a more stable effect in terms of droplet size and zeta potential over a wider range of ionic strength and temperature conditions. These findings indicate that Pickering emulsion stabilized by WPNFs is more suitable as a carrier of CLA, as it increases the solubility of CLA and has better active applications in biology and food.

Direct separation and purification of α-lactalbumin from cow milk whey by aqueous two-phase flotation of thermo-sensitive polymer/phosphate.

BACKGROUND: α-lactalbumin (α-La) is of great interest to the industry as a result of its excellent functional properties and nutritional value. Aqueous two-phase flotation (ATPF) of thermo-sensitive polymer poly (ethylene glycol-ran-propylene glycol) monobutyl ether (UCON) and KH2 PO4 was applied to directly separate and purify α-La from milk whey, which was purposed to simplify the production process and reduced cost of production. RESULTS: The effect of ATPF composition and operating parameters on the flotation efficiency (E) and purity of α-La were investigated. The optimal conditions included 2 min of premixing time, 30 mL min-1 flow velocity and 20 min of flotation time, whereas the composition conditions comprised 35.0 mL 0.18 g mL-1 phosphate solution (containing 10% (cow milk whey/salt solution, v/v) cow milk whey, 50 ppm defoamer and 2 g NaCl) and 5.0 mL of 40% (w/w) UCON solution. Under the optimal conditions, E of α-La was 95.67 ± 1.04% and purity of α-La was 98.78 ± 1.19%. UCON was recovered by a thermally-induced phase separation and reused in next ATPF process without reducing E of α-La. Purified α-La was characterized by several key technologies. The results indicated that α-La in cow milk whey could be directly separated and purified by the ATPF and the purity was satisfactory. Moreover, it was suggested there was no obvious structure difference between the α-La separated by ATPF and the α-La standard. CONCLUSION: The present study enabled the recycling of UCON, providing an effective, economically viable and environmentally friendly approach for the separation and purification of protein. © 2021 Society of Chemical Industry.

Effective separation of prolyl endopeptidase from Aspergillus Niger by aqueous two phase system and its characterization and application.

Aspergillus niger prolyl endopeptidase (An-PEP) has become a research focus because of its advantages in specifically cleaving the C-terminal peptide bond of proline residues, especially it was an industrial food-grade acidic PEP. Aqueous two-phase system (ATPS) was first applied for separating An-PEP from fermentation broth. Via response surface method (RSM) experiment, an effectively separation of An-PEP was achieved by ATPS containing27% (w/w) ethanol and 14.5% (w/w) (NH4)2SO4 at pH 6.0 with the recovery of 90.29 ± 0.23% and purification coefficient of 15.35 ± 0.30. The purified An-PEP was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), fourier transform infrared (FTIR) and fluorescence spectrometry. The optimum temperature and pH of An-PEP were 40 °C and 4.5-5.0, respectively. An-PEP was activated and stabilized by Ca2+ but inhibited by Fe3+. The enzymatic application of purified An-PEP was evaluated by hydrolyzing egg white protein (EWP) to prepare bioactive peptides. The obtained hydrolysates had good scavenging ability of OH and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, angiotensin converting enzyme (ACE) inhibitory activity and anti-gout activity. This research realized a low-cost, high-efficiency and simple separation technology of An-PEP and provided a broader idea for the preparation of bioactive peptides and the application of An-PEP.

Carbon Dots Derived from the Maillard Reaction for pH Sensors and Cr (VI) Detection.

The Maillard reaction involves a series of complex reactions; fluorescent compounds have been considered as vital intermediate products of the reaction. In this article, carbon dots (CDs) based on the Maillard reaction (MR-CDs) were prepared with L-tryptophan and D-glucose, and they had excellent photoluminescence stability. MR-CDs showed stable pH-dependence behavior and exhibited an excellent linear response to pH in the range of 4.0-7.5 and 7.5-13.0, respectively. Under the masking effect of sodium fluoride for Fe(III), MR-CDs showed excellent selectivity and sensitivity for Cr (VI). The linear range of Cr(VI) was 0.2-50 µM and the limit of detection was 20 nM. (S/N ≥ 3). Furthermore, MR-CDs were used to detect Cr(VI) in tap water samples. The recoveries were between 95.8% and 98.94%, and RSDs were less than 3.17%.

Efficient Imaging of Saccharomyces cerevisiae Based on B- and N-Doped Carbon Dots.

The estimation of yeast viability with B- and N-doped carbon dots (BN-CDs) was investigated in this paper. BN-CDs with a fluorescent quantum yield of 65.47% were prepared by a one-step hydrothermal method. The size distribution of BN-CDs was relatively narrow, with the majority falling within 7.5-8.5 nm, and they were mainly composed of carbon, oxygen, nitrogen, and boron. BN-CDs were shown to have strong and stable fluorescence. They exhibited excitation-independent photoluminescence property, which could avoid the autofluorescence and limitation of the excitation source. Dead and live yeast cells were distinguished well by BN-CD staining in a short time, and there was no strict requirement for light protection. The application of BN-CDs in beer brewing can solve the problem of estimation of yeast viability.

Targeting Delivery System for Lactobacillus Plantarum Based on Functionalized Electrospun Nanofibers.

With the increased interest in information on gut microbes, people are realizing the benefits of probiotics to health, and new technologies to improve the viability of probiotics are still explored. However, most probiotics have poor resistance to adverse environments. In order to improve the viability of lactic acid bacteria, polylactic acid (PLA) nanofibers were prepared by coaxial electrospinning. The electrospinning voltage was 16 kV, and the distance between spinneret and collector was 15 cm. The feed rates of the shell and core solutions were 1.0 and 0.25 mL/h, respectively. The lactic acid bacteria were encapsulated in the coaxial electrospun nanofibers with PLA and fructooligosaccharides (FOS) as the shell materials. Scanning electron microscopy, transmission electron microscopy, and laser scanning confocal microscopy showed that lactic acid bacteria were encapsulated in the coaxial electrospun nanofibers successfully. The water contact angle test indicated that coaxial electrospun nanofiber films had good hydrophobicity. An in vitro simulated digestion test exhibited that the survival rate of lactic acid bacteria encapsulated in coaxial electrospun nanofiber films was more than 72%. This study proved that the viability of probiotics can be improved through encapsulation within coaxial electrospun PLA nanofibers and provided a novel approach for encapsulating bioactive substances.

Preparation and Characterization of Coating Based on Protein Nanofibers and Polyphenol and Application for Salted Duck Egg Yolks.

Salted duck egg yolk (SDEY) is one of the traditional pickled egg products in Asian countries, which suffers from the weight loss and deterioration of texture characteristics during storage. To better maintain the texture of SDEY, an edible coating based on whey protein isolate nanofibers (WPNFs) with glycerol (Gly) as a plasticizer and incorporating carvacrol (CA) as an antimicrobial agent was developed. Whey protein isolate (WPI, 5%) was used to self-assemble into WPNFs at 80 °C for 10 h. The particle size, zeta-potential and microstructure of WPNFs-CA emulsion were investigated to evaluate the distribution. Results proved that WPNFs-CA emulsion had smaller particle size and better distribution than WPI-CA emulsion. WPNFs-CA/Gly edible coating was then prepared based on WPNFs-CA emulsion. The WPNFs-CA/Gly edible coating exhibited higher antibacterial activity while the WPNFs-CA/Gly film had smooth and continuous surfaces and better transmittance compared with other samples. Furthermore, weight losses and textural properties changes of SDEYs with WPNFs-CA/Gly coating were evaluated. Results proved that salted duck egg yolks with WPNFs-CA/Gly coating exhibited lower weight losses. Textural properties were significantly improved by the WPNFs-CA/Gly coating on SDEYs than those uncoated samples. It was noted that the egg yolks coated with the WPNFs-CA/Gly coating had the lowest hardness increase rate (18.22%). Hence, WPNF-based coatings may have a good development prospect in the food industry.

Fabrication and Characterization of a Microemulsion Stabilized by Integrated Phosvitin and Gallic Acid.

The purpose of this work was to conjugate phosvitin (Pv) with gallic acid (GA) to explore a new emulsifier that had both good emulsifying properties and antioxidant activity. The Pv-GA complex was prepared at a GA concentration of 1.5 mg/mL with pH 9.0. The Pv-GA complex obtained was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and characterized with infrared, ultraviolet, and fluorescence spectra. The emulsifying activity and stability of the Pv-GA complex were slightly improved, and antioxidant activities was significantly enhanced. Furthermore, the Pv-GA complex was used to load conjugated linoleic acid (CLA) for microemulsion preparation. Results showed that the Pv-GA complex could increase the viscosity and lipid antioxidant capacity of Pv-GA/CLA microemulsion. The Pv-GA/CLA microemulsion had remarkable emulsifying activity, emulsifying stability, pH, and thermal stability and poor salt stability.

Study on the Preparation and Conjugation Mechanism of the Phosvitin-Gallic Acid Complex with an Antioxidant and Emulsifying Capability.

To develop a novel emulsifier with an antioxidant capacity, a phosvitin-gallic acid (Pv-GA) complex was prepared via a free-radical method. This emulsifier characterizes some key technologies. Changes in the molecular weight of the Pv-GA complex were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and the matrix-assisted laser desorption/ionization time of light mass spectrometry (MALDI-TOF-MS). Fourier transform infrared spectroscopy (FTIR) indicated that C=O, C-N and N-H groups were also likely to be involved in the formation of the complex. A redshift was obtained in the fluorescence spectrogram, thereby proving that the covalent combination of Pv and GA was a free radical-forming complex. The results indicated that Pv and GA were successfully conjugated. Meanwhile, the secondary structure of Pv showed significant changes after conjugation with GA. The antioxidant activity and emulsifying properties of the Pv-GA complex were studied. The antioxidant activity of the Pv-GA complex proved to be much higher than that of the Pv, via assays of the scavenging activities of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and because of their ability to reduce power. The emulsification activity of the Pv-GA complex was also slightly higher than that of Pv. To function with the most demanding antioxidant and emulsification activities, the optimum conjugation condition was Pv (5 mg/mL) conjugated 1.5 mg/mL GA. Furthermore, the mechanism of Pv-GA conjugation was studied. This study indicated that GA could quench the inner fluorescence of Pv, and this quenching was static. There was a strong interaction between GA and Pv, which was not obviously affected by the temperature. Furthermore, several binding sites were close to 1, indicating that there was an independent class of binding sites on Pv for GA at different temperatures. The conjugation reaction was a spontaneous reaction, and the interaction forces of GA and Pv were hydrogen bonds and van der Waals force.

Ultrasonic Thermal-Assisted Extraction of Phosvitin from Egg Yolk and Evaluation of Its Properties.

Phosvitin (Pv) is the principal phosphoprotein in chicken egg yolk and the most highly phosphorylated protein in nature. Pv is a good natural food antioxidant and emulsifier. However, the current extraction methods present disadvantages of complicated operation and are time-consuming. In this paper, Pv was extracted from the egg yolk by ultrasonic thermal-assisted extraction (UTAE). The effects of heating time, ultrasonic power and ultrasonic time on the extraction of Pv were investigated by a single factor. The purity of Pv, ratio of nitrogen to phosphorus (N/P), and activity were used as evaluation indexes. An efficient extraction of Pv was achieved when the sample was heated for 15 min at 80 °C and then processed for 10 min of ultrasonic treatment with an ultrasonic power of 600 W. Under optimal conditions, the purity and activity of Pv were 80% and 98%, respectively, whereas the ratio of N/P was 3.1. The obtained Pv was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fluorescence analyses, fourier-transform infrared (FT-IR), and liquid chromatography-nanoelectrospray ionization mass spectrometry (Nano LC-ESI-MS/MS) analysis. The results showed there is no significant difference in the properties of Pv obtained by UTAE and Pv standard. The developed extraction approach is a simple, industrial compatible method without the use of any organic solvents.

Reutilization of Food Waste: One-Step Extration, Purification and Characterization of Ovalbumin from Salted Egg White by Aqueous Two-Phase Flotation.

For the purpose of reducing pollution and the reutilization of salted egg whites, which are byproducts of the manufacturing process of salted egg yolks and normally treated as waste, an aqueous two-phase flotation (ATPF) composed of polyethylene glycols (PEG 1000) and (NH4)2SO4 was applied to develop a simple, inexpensive and efficient process for the separation of ovalbumin (OVA) from salted egg whites. The effects of the concentration of PEG, the concentration of (NH4)2SO4, the flow rate and the flotation time on the flotation efficiency (Y) and purity (P) of OVA were investigated. A response surface method (RSM) experiment was carried out on the basis of a single-factor experiment. An efficient separation was achieved using ATPF containing 5 mL of 80% PEG 1000 (w/w), 28 mL of 28% (NH4)2SO4 (w/w), 35 mL/min of the flow rate and 30 min of the flotation time, while 2 mL of the salted egg white solution (salted eggs white (v): water (v) = 1:4) was loaded. Under the optimal conditions, Y and P of OVA could reach 82.15 ± 0.24% and 92.98 ± 0.68%, respectively. The purified OVA was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), reverse phase high-performance liquid chromatography (RP-HPLC), liquid chromatography-nano electrospray ionisation mass spectrometry (Nano LC-ESI-MS/MS), ultraviolet spectrum (UV), fluorescence spectrum (FL) and fourier transform infrared spectroscopy (FT-IR). The results indicated that the purity of OVA obtained by ATPF was satisfactory and there was no obvious difference in the structure of the OVA separated by ATPF and the standard. The results of the functional properties revealed no significant differences between OVA obtained by ATPF and the standard in oil binding capacity, viscosity, emulsibility and foam capacity.

Structure and Functional Properties of Antioxidant Nanoemulsions Prepared with Tea Polyphenols and Soybean Protein Isolate.

In this study, tea polyphenols (TP) was added to a soy protein isolate (SPI) to prepare nanoemulsions by ultra-high pressure homogenization (UHPH). The nanoemulsions were characterized by a confocal laser scanning electron microscopy, infrared spectroscopy, dynamic rheometer and size-potential analyzer. The effects of TP on the hydrophobicity, emulsifiability, particle size, potential and antioxidant capacity of the prepared nanoemulsions were investigated. The properties of the nanoemulsions with different concentrations of TP were analyzed. The results indicated that ultra-high pressure homogenization treatment contributed to the formation of the SPI-TP complex that showed higher antioxidant activity. The nanoemulsions with good emulsifying properties and high DPPH scavenging ability at the concentration of TP ranged from 0.15-0.20g / mL. Furthermore, nanoemulsions prepared in this way also had a uniform particle size. Therefore, this nanoemulsions exhibited a good potential to act as an efficient emulsifier.