Antioxidant activity and emulsion-stabilizing effect of pectic enzyme treated pectin in soy protein isolate-stabilized oil/water emulsion

The effect of α-tocopherol incorporated into different carriers on the oxidative stability of oil in water (O/W) emulsions

The effect of the antioxidant activity of α-tocopherol incorporated into different carriers on the oxidative stability of oil in water emulsion was investigated. The antioxidant activity of free and encapsulated α-tocopherol was measured in a 2,2-diphenyl-1-picrylhydrazyl reaction. Apart from α-tocopherol micelles, the samples showed similar antioxidant activity. The number of primary oxidation products in the emulsion with tocopherol liposomes and niosomes was lower than in the emulsion with micelles. During storage, the lipid peroxides gradually increased, whereas in emulsion with no α-tocopherol carriers added they remained constant. The content of the conjugated dienes first increased, and after 14 days at the end of testing time it remained stable in both types of emulsions. Our results might suggest that α-tocopherol when encapsulated into carriers exhibits lower antioxidant activity. The results obtained could be due to the better solubility of α-tocopherol in lipid droplets and thus the lower availability for the interfacial region, which is thought to be the place of the most pronounced lipid oxidation.

Investigation of the optimal production conditions for egg white hydrolysates and physicochemical characteristics

This study aimed to investigate the potential of egg white protein hydrolysate (EWH) as a functional food by identifying the optimum production conditions for EWH with response surface methodology (the results of the sensory evaluation were considered as an essential quality indicator). At the same time, its physicochemical and biological activity was also evaluated. The optimal economic production conditions were selected: substrate concentration of 12.5%, enzyme content of 7.5%, and hydrolysis time at 100 min. The degree of hydrolysis (DH %) was 13.51%. In addition, to the better acceptance of the evaluation, it also helps to reduce the production cost of the protein hydrolysate, which is beneficial to future processing and applications. The antioxidant capacity experiments showed that EWH has good antioxidant activity, which presents a dose-dependent relationship. Hence, this study provides a theoretical basis for future research and application of EWH for processing applications, including dietary supplementation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05708-0.

Prophylactic effect of pectic oligosaccharides against poly I: C- induced virus-like infection in BALB/c mice

Pectin oligosaccharides (POS) are pectin-derived prebiotics that exerts anti-inflammatory effects on the host and stimulates an innate immune response. The role of POS in protective immunity against viral infections is not very obvious. Therefore, the prophylactic effect of POS in the mouse model induced by Poly I: C mimicking viral infection was examined. Mice fed POS showed a significant (p ≤ .05) increase in IgG, sIgA, IgA, IL-12, and a significant (p ≤ .05) decrease in the concentration of pro-inflammatory cytokines IL-5, IL-6, IL-13 and IL-17 in lung and blood serum after Poly I: C stimulation. However, the control group could not inhibit pro-inflammatory cytokines. POS also promoted the growth of the Lactobacillus, Prevotella, Rilenellaceae, and Lachanospiraceae groups. Therefore, this study demonstrate that POS has the potiential to protect against viral inflammation by altering gut microbiota and activating mucosal immunity. PRACTICAL APPLICATIONS: POS is 2-10 mer oligomers of pectin. The human gastrointestinal tract lacks the enzyme to break down POS. They are fermented by gut bacteria in the colon and stimulate the proliferation of specific gut bacteria that are positively correlated with the production of anti-inflammatory cytokines and SCFA. POS also stimulates the secretion of IgA, which inhibits bacterial and viral adhesion and protects the host. Therefore, POS can be used as a functional food ingredient in food to stimulate a specific group of gut bacteria and enhance preventive immunity.

Effect of Thermal Treatment on the Physicochemical, Ultrastructural, and Antioxidant Characteristics of Euryale ferox Seeds and Flour

Euryale ferox seeds (EFS) were less gelatinized, preventing the release of nutrients and functional compounds, resulting in limited applications in meals and the food industry. Nutraceutical importance of EFS includes starch, protein, lipids, 20 amino acids, minerals, and vitamins (C, E, and beta carotene). This study aimed to evaluate the effect of three different thermal treatments on EFS’s physicochemical and nutritional properties and expected to improve its applicability. The results showed that the bulk density, thousand-grain weight, and hardness of thermal treated EFS were significantly decreased (p < 0.05), whereas the maximum decrease was observed in the industrial infrared heating-assisted fluidized bed (IHFH) treatment. Meanwhile, there were more crevices, fissures, and heightened porous structures in EFS between the pericarp and episperm and the endosperm after heat treatment, which facilitated grinding and water absorption. Notably, EFS’s water and oil absorption capacities increased significantly (p < 0.05) with microwave and IHFH treatments. EFS ground’s solubility into powder was increased significantly with thermal treatment (p < 0.05). Furthermore, the functional properties of TPC, TFC, DPPH radical scavenging activity, and reducing power were significantly increased (p < 0.05). In general, the changes in the physicochemical properties of EFS and increased bioactivity were caused by microwave and IHFH treatments. Hence, it might improve the food value of EFS while providing valuable information to researchers and food manufacturers.

Crude Pectic Oligosaccharide Recovery from Thai Chok Anan Mango Peel Using Pectinolytic Enzyme Hydrolysis

Pectin recovered from mango peel biomass can be used as a potential source for pectic oligosaccharide hydrolysate with excellent probiotic growth-enhancing performance and prebiotic potentials. Consequently, the objectives of the current study were to optimise the enzyme hydrolysis treatment of mango peel pectin (MPP) and to evaluate the pectic oligosaccharide effects of Lactobacillus reuteri DSM 17938 and Bifidobacterium animalis TISTR 2195. Mango of "chok anan" variety was chosen due to its excessive volume of biomass in processing and high pectin content. The optimal treatment for mango peel pectic oligosaccharide (MPOS) valorisation was 24 h of fermentation with 0.3% (v/v) pectinase. This condition provided small oligosaccharides with the molecular weight of 643 Da that demonstrated the highest score of prebiotic activity for both of B. animalis TISTR 2195 (7.76) and L. reuteri DSM 17938 (6.87). The major sugar compositions of the oligosaccharide were fructose (24.41% (w/w)) and glucose (19.52% (w/w)). For the simulation of prebiotic fermentation, B. animalis TISTR 2195 showed higher proliferation in 4% (w/v) of MPOS supplemented (8.92 log CFU/mL) than that of L. reuteri (8.53 CFU/mL) at 72 h of the fermentation time. The main short chain fatty acids (SCFAs) derived from MPOS were acetic acid and propionic acid. The highest value of total SCFA was achieved from the 4% (w/v) MPOS supplementation for both of B. animalis (68.57 mM) and L. reuteri (69.15 mM). The result of this study therefore conclusively advises that MPOS is a novel pectic oligosaccharide resource providing the opportunity for the sustainable development approach through utilising by-products from the fruit industry.

Influence of Hydrolysis on the Bioactive Properties and Stability of Chickpea-Protein-Based O/W Emulsions

This study evaluated the effect of enzymatic hydrolysis on the emulsion microstructure and bioactive properties of oil-in-water emulsions generated using chickpea protein concentrate (CP) and its 10 and 210 min Alcalase CP hydrolysates (CPH₁₀ and CPH₂₁₀, respectively) at three pH values (2.5, 5.0, and 7.5). Chromatographic profiles demonstrated CP protein breakdown following hydrolysis. Increasing the degree of hydrolysis resulted in increased emulsion droplet size and decreased viscoelastic moduli. The antioxidant capacities of the emulsions generated with CPH₁₀ and CPH₂₁₀ increased significantly compared to those generated with CP and were pH-dependent. Both angiotensin-converting enzyme and dipeptidyl peptidase-IV inhibitory activities were significantly increased in emulsions stabilized with CPH₂₁₀; however, these results were also pH-dependent. In vitro gastrointestinal digestion of the emulsions resulted in a significant increase in all bioactivities. These results demonstrate the potential for enzymatic hydrolysis to beneficially modulate the emulsifying and bioactive properties of CP proteins.

Spatial Distribution and Solvent Polarity-Triggered Release of a Polypeptide Incorporated into Invertible Micellar Assemblies

Extracting, stabilizing, or delivering biomacromolecules such as proteins and peptides in organic phases have potential applications in biocatalysis, protein extraction, and food antioxidation. However, most current delivery/stabilization platforms face various limitations such as protein/peptide molecular size, platform stability/reusability, and/or potential damage to the cargos. A potential solution to these problems is micellar self-assemblies from amphiphilic invertible polymers, which have recently been demonstrated to be powerful as molecular hosts to deliver both small molecular drugs and functional polypeptides in the aqueous phase. To better understand the function of biomacromolecules and predict the usefulness of the formed invertible micellar assemblies (IMAs) as biomacromolecular hosts in organic phases, it is critical to characterize the spatial distribution, structure, and dynamics of biomacromolecules in the IMA including those upon release. However, the background signals of the IMAs limit the application of most peptide characterization approaches. In this work, we overcome the technical barriers by using site-directed spin labeling electron paramagnetic resonance to probe the spatial arrangement and release of a model, the hemagglutinin (HA) peptide, in the IMAs formed from two different amphiphilic invertible polymers. By site-specifically probing three residues along the peptide chain, for the first time, we depict the possible spatial distribution of HA within the IMAs. By triggering the disassembly of the IMAs with a thermodynamically good solvent (in this study, acetone), we detailed the stability of IMAs in toluene and the peptide release conditions once the polarity of the medium changes. Our findings are important for the application of peptides/proteins at the polar-nonpolar interface or using this interface to extract or deliver biomacromolecules. Our work also demonstrates the power of SDSL-EPR on probing peptide or micelle dynamics, which can be generalized to understand proteins or other biomacromolecules in micellar polymer assemblies in varied applications.

Improving Stability and Accessibility of Quercetin in Olive Oil-in-Soy Protein Isolate/Pectin Stabilized O/W Emulsion

Herein we report a soy protein isolate/pectin binary complex particle to stabilize emulsion (olive oil served as dispersed phase) containing quercetin. FTIR was conducted to confirm successful preparation of emulsion before and after embedding quercetin. CLSM was used to determine the microstructure and zeta-potential, rheological behavior, storage stability and freeze-thaw stability were analyzed and were correlated with pH condition. Olive oil-soy protein isolate/pectin emulsion at pH 3.0 can remain stable after 30 days’ storage and exhibited greatest freeze-thaw stability after 3 cycles. Quercetin availability was evaluated by in vitro gastrointestinal digestion experiments and it reached 15.94% at pH 7.0.

Formation of soy protein isolate (SPI)-citrus pectin (CP) electrostatic complexes under a high-intensity ultrasonic field: Linking the enhanced emulsifying properties to physicochemical and structural properties

In this study, a high-intensity ultrasonic field was applied to the electrostatic interactions between soy protein isolate (SPI) and citrus pectin (CP). The emulsifying properties of SPI-CP soluble complexes formed under different ultrasound powers and durations were investigated and peaked at 630 W for 10 min. Micrographs of emulsions revealed that ultrasound-treated complexes generated a more homogeneous emulsion with significantly reduced and uniformly-distributed droplet sizes. To better understand the mechanism for the improved emulsifying properties, the physicochemical and structural properties of the SPI-CP complexes at pH 3.5 with and without ultrasound treatment were investigated. It was revealed that ultrasound increased the absolute values of the zeta potential and surface hydrophobicity of complexes, but significantly decreased their particle sizes, fluorescence intensity and turbidity. Results indicated that cavitation effects resulted in structural modifications in both biomacromolecules, as well as enhanced the electrostatic interactions between SPI and CP, which in combination contributed to the more desirable emulsifying properties of the complex.

Characterisation of the bioactive properties and microstructure of chickpea protein-based oil in water emulsions

Legumes, such as chickpea, represent a good source of high quality proteins for which there is an increasing global consumer demand. A chickpea protein concentrate (CP) was generated by isoelectric precipitation. Protein determination, electrophoretic and gel permeation chromatographic analysis revealed that the order of CP solubility was pH 7.5 > 2.5 > 5.0. Sunflower oil in water (O/W) emulsions were generated with the CP at pH 2.5, 5.0 and 7.5. Microstructural evaluation of the emulsions using laser light-scattering particle size analysis, optical microscopy and rheological analysis showed that smaller droplet size (3.1 ± 0.2 and 1.1 ± 0.1 μm) and the highest elastic moduli (876.0 ± 3.2 and 563.5 ± 6.5 Pa) were obtained in those emulsions generated with CP at pH 2.5 and 7.5. The ferric reducing (FRAP) and oxygen radical absorbance capacity (ORAC) values of the CP emulsions ranged from 194.5 ± 19.2 to 242.4 ± 8.4 μmol Trolox Eq·g^-1 CP for FRAP at pH 2.5 and 5.0, respectively, and from 313.2 ± 2.6 to 369.0 ± 1.6 μmol Trolox eq·g^-1 CP for ORAC at pH 5.0 and 2.5, respectively. The enzyme inhibitory activity of the emulsions was generally low irrespective of the pH value (c.a. 3 and 30% inhibition for dipeptidyl peptidase IV (DPP-IV) and angiotensin converting enzyme (ACE) activity, respectively). Simulated gastrointestinal digestion (SGID) of the emulsions significantly decreased their FRAP whereas it increased their ORAC values as well as their ACE and DPP-IV inhibitory activities irrespective of the pH value of the CP. These results demonstrate the potential application of reduced fat CP-stabilized emulsions for the provision of antioxidant and enzyme inhibitory activities.

Influence of Pectin Structural Properties on Interactions with Divalent Cations and Its Associated Functionalities

Pectin is an anionic cell wall polysaccharide which is known to interact with divalent cations via its nonmethylesterified galacturonic acid units. Due to its cation-binding capacity, extracted pectin is frequently used for several purposes, such as a gelling agent in food products or as a biosorbent to remove toxic metals from waste water. Pectin can, however, possess a large variability in molecular structure, which influences its cation-binding capacity. Besides the pectin structure, several extrinsic factors, such as cation type or pH, have been shown to define the cation binding of pectin. This review paper focuses on the research progress in the field of pectin-divalent cation interactions and associated functional properties. In addition, it addresses the main research gaps and challenges in order to clearly understand the influence of pectin structural properties on its divalent cation-binding capacity and associated functionalities. This review reveals that many factors, including pectin molecular structure and extrinsic factors, influence pectin-cation interactions and its associated functionalities, which makes it difficult to predict the pectin-cation-binding capacity. Despite the limited information available, determination of the cation-binding capacity of pectins with distinct structural properties using equilibrium adsorption experiments or isothermal titration calorimetry is a promising tool to gain fundamental insights into pectin-cation interactions. These insights can then be used in targeted pectin structural modification, in order to optimize the cation-binding capacity and to promote pectin-cation interactions, for instance for a structure build-up in food products without compromising the mineral nutrition value.

Synergistic Antitumor Effect of Oligogalacturonides and Cisplatin on Human Lung Cancer A549 Cells

Cisplatin (DPP), a clinically potent antineoplastic agent, is limited by its severe adverse effects. The aim of this study was to investigate the effect of oligogalacturonides (OGA) and DDP on human lung cancer A549 cells. The combined use of OGA and DDP had a synergistic effect on the growth inhibition of A549 cells, changed the cell cycle distribution, and enhanced apoptotic response, especially in sequential combination treatment group of DDP 12 h + OGA 12 h. Western blot analyses showed that the combination treatment of OGA and DDP upregulated Bax, p53, and Caspase-3 and downregulated Bcl-2 proteins. More importantly, DDP-induced toxicity was attenuated by OGA and DDP combination treatment in normal HEK293 cells. Our data suggests that the combined use of OGA from natural sources and DDP could be an important new adjuvant therapy for lung cancer as well as offer important insights for reducing kidney toxicity of DDP and delaying the development of DDP resistance.

Development of Pickering Emulsions Stabilized by Gliadin/Proanthocyanidins Hybrid Particles (GPHPs) and the Fate of Lipid Oxidation and Digestion

This work attempted to engineer emulsions' interface using the special affinity between proline-rich gliadin and proanthocyanidins (PA), to develop surfactant-free antioxidant Pickering emulsions with digestive-resistant properties. This binding interaction between gliadin and PA benefited the interfacial adsorption of the particles to corn oil droplets. Pickering droplets as building units assembled into an interconnected three-dimensional network structure, giving the emulsions viscoelasticity and ultrastability. Oxidative markers in Pickering emulsions were periodically monitored under thermally accelerated storage. Lipid digestion and oxidation fates were characterized using in vitro gastrointestinal (GI) models. The interfacial membrane constructed by antioxidant particles served as a valid barrier against lipid oxidation and digestion, in a PA dose-dependent manner. Briefly, lipid oxidation under storage and simulated GI tract was retarded. Free fatty acid (FFA) fraction released decreased by 55% from 87.9% (bulk oil) to 39.5% (Pickering emulsion), implying engineering interfacial architecture potentially benefited to fight obesity. This study opens a facile strategy to tune lipid oxidation and digestion profiles through the cooperation of the Pickering principle and the interfacial delivery of antioxidants.

Interfacial Antioxidants: A Review of Natural and Synthetic Emulsifiers and Coemulsifiers That Can Inhibit Lipid Oxidation

There has been strong interest in developing effective strategies to inhibit lipid oxidation in emulsified food products due to the need to incorporate oxidatively labile bioactive lipids, such as ω-3 fatty acids, conjugated linoleic acids, or carotenoids. Emulsifiers or coemulsifiers can be utilized to inhibit lipid oxidation in emulsions. Both of these molecular types can adsorb to droplet surfaces and inhibit lipid oxidation, but emulsifiers can also stabilize droplets against aggregation whereas coemulsifiers cannot. There are a host of existing emulsifiers, covalent conjugates, or physical complexes that have the potential to inhibit lipid oxidation by a variety of mechanisms. Existing emulsifiers with antioxidant potential consist of surfactants, phospholipids, proteins, polysaccharides, and colloidal particles. Conjugates and complexes are typically formed by covalently or physically linking together a surface-active molecule with an antioxidant molecule. This article reviews the molecular and physicochemical basis for the surface and antioxidant activities of emulsifiers and coemulsifiers, highlights the important properties of interfacial layers that can be engineered to control lipid oxidation, and outlines different kinds of existing emulsifiers, conjugates, and complexes that can be used to inhibit oxidation.

Structurally modified pectin for targeted lipid antioxidant capacity in linseed/sunflower oil-in-water emulsions

The present work explored the lipid antioxidant capacity of citrus pectin addition to 5%(w/v) linseed/sunflower oil emulsions stabilized with 0.5%(w/v) Tween 80, as affected by pectin molecular characteristics. The peroxide formation in the emulsions, containing tailored pectin structures, was studied during two weeks of storage at 35°C. Low demethylesterified pectin (≤33%) exhibited a higher antioxidant capacity than high demethylesterified pectin (≥58%), probably due to its higher chelating capacity of pro-oxidative metal ions (Fe²⁺), whereas the distribution pattern of methylesters along the pectin chain only slightly affected the antioxidant capacity. Nevertheless, pectin addition to the emulsions caused emulsion destabilization probably due to depletion or bridging effect, independent of the pectin structural characteristics. These results evidence the potential of structurally modified citrus pectin as a natural antioxidant in emulsions. However, optimal conditions for emulsion stability should be carefully selected.

Enhancement of the solubility and antioxidant capacity of α-linolenic acid using an oil in water microemulsion

The applications of α-linolenic acid (ALA) in the food industry are restricted due to its poor water solubility and antioxidant stability. This study concentrates on developing an ALA-loaded microemulsion (ALA-ME) to enhance its solubility and antioxidant capacity. The formulation of the microemulsion was investigated based on pseudoternary phase diagrams. The ALA-ME was characterized by using electrical conductivity, viscosity and transmission electron microscopy (TEM). The microstructure of the ALA-ME was probed using nuclear magnetic resonance (¹H-NMR). The results proved that ALA-ME consisted of spheroidal droplets with 20-40 nm diameter. A structural transformation from water in oil (W/O) to oil in water (O/W) occurred, as seen from the electrical conductivity determination. The ¹H-NMR results revealed a transition of the ALA position encapsulated from the core area of the microemulsion to the lipophilic layer of the surfactant. Furthermore, two microstructural models of ALA-ME were proposed. The antioxidant evaluation demonstrated that the ALA antioxidant capacity in microemulsions was enhanced to about 80% compared with that of ALA in oil solution.

Evaluation of the prebiotic effects of citrus pectin hydrolysate

Citrus pectin enzyme hydrolysate (PEH) of different hydrolysis time intervals (6 hours, PEH-6; 12 hours, PEH-12; 24 hours, PEH-24; or 48 hours, PEH-48) or concentrations (1%, 2%, and 4%) was tested for its growth stimulation effect on two probiotics, Bifidobacterium bifidum and Lactobacillus acidophilus. Higher monosaccharide concentrations and smaller molecular weights of PEHs were obtained by prolonging the hydrolysis time. In addition, higher PEH concentrations resulted in significantly higher (p < 0.05) probiotic populations, pH reduction, and increase in total titratable acidity than the glucose-free MRS negative control. Furthermore, significantly higher populations in the low pH environment and longer survival time in nonfat milk (p < 0.05) were observed when the two probiotics were incubated in media supplemented with 2% PEH-24, than in glucose and the negative control. In comparison with other prebiotics, addition of 2% PEH-24 resulted in a more significant increase in the probiotic population (p < 0.05) than in the commercial prebiotics. This study demonstrated that PEH derived from citrus pectin could be an effective prebiotic to enhance the growth, fermentation, acid tolerance, and survival in nonfat milk for the tested probiotics.

Adsorption of histones on natural polysaccharides: The potential as agent for multiple organ failure in sepsis

Histones are intracellular proteins that are structural elements of nuclear chromatin and regulate gene transcription. However, the extracellular histones released in response to bacterial challenges have been identified as mediators contributing to endothelial dysfunction, organ failure, and death during sepsis. In the present study, the adsorption of histones as well as plasma proteins (α1-acid glycoprotein (AGP), albumin, and γ-globulin) on alginic acid, pectin, dextran, and chitosan was examined in order to evaluate the potential of natural polysaccharides as therapeutic agents for multiple organ failure in sepsis. Alginic acid and pectin strongly adsorbed histones, whereas the adsorption abilities of dextran and chitosan toward histones were very low or negligible. Among the natural polysaccharides examined, only alginic acid did not adsorb any of the plasma proteins. These results demonstrated that alginic acid strongly adsorbed histones, but not plasma proteins; therefore, it has potential as a candidate drug for the treatment of multiple organ failure in sepsis.

Polypeptide modification: an improved proglycinin design to stabilise oil-in-water emulsions

β-Conglycinin and glycinin are soybean major seed storage proteins. Previous studies have shown that adding the extension region of β-conglycinin α subunit improves the emulsifying properties of proglycinin and confers more favourable characteristics than fusing the extension region of β-conglycinin α' subunit or the hypervariable regions (A4IV) of glycinin A1aB1b subunit. To evaluate the polypeptide properties, we designed mutants of A1aB1b subunits fused with truncated versions of A4IV (A4IVcut), α (αcut) or α' (α'cut) extension regions lacking the C-terminus 25 or 31 residues (A4IVC25, αC25 or α'C31), and also A4IVcut and α'cut with αC25 residues added (A4IVcut-αC25 and α'cut-αC25). All the modified proteins displayed conformations similar to the wild type. With good solubilities, the emulsion properties of the modified proteins were much better at ionic strength μ = 0.08 than at μ = 0.5. The modified A1aB1bαcut and A1aB1bα'cut showed poorer emulsion properties than those of A1aB1bα and A1aB1bα'. Replacing the hydrophobic A4IVC25 region of A1aB1bA4IV with hydrophilic αC25 created A1aB1bA4IVcut-αC25, which had the best emulsion stability among these proglycinin mutants. We found that addition of αC25 improves the emulsifying properties of two C-terminally truncated proglycinin variants, thereby illustrating its potential general utility. Our investigation showed that in order to improve the emulsifying ability and emulsion stability of a globular protein, the introduced polypeptide should (i) be highly hydrophilic, (ii) consist of multiple hydrophobic-strong hydrophilic regions comprising at least two alpha helixes, (iii) harbour a terminal α-helix at the end of the C-terminus and (iv) have properties similar to those of αC25.

Fabrication and characterization of antioxidant pickering emulsions stabilized by zein/chitosan complex particles (ZCPs)

Lipid peroxidation in oil-in-water (o/w) emulsions leads to rancidity and carcinogen formation. This work attempted to protect lipid droplets of emulsions from peroxidation via manipulation of the emulsions' interface framework using dual-function zein/CH complex particles (ZCPs). ZCP with intermediate wettability was fabricated via a simple antisolvent approach. Pickering emulsions were produced via a simple and inexpensive shear-induced emulsification technique. ZCP was irreversibly anchored at the oil-water interface to form particle-based network architecture therein, producing ultrastable o/w Pickering emulsions (ZCPEs). ZCPE was not labile to lipid oxidation, evidenced by low lipid hydroperoxides and malondialdehyde levels in the emulsions after thermally accelerated storage. The targeted accumulation of curcumin, a model antioxidant, at the interface was achieved using the ZCP as interfacial vehicle, forming antioxidant shells around dispersed droplets. The oxidative stability of ZCPEs was further improved. Interestingly, no detectable hexanal peak appeared in headspace gas chromatography of the Pickering emulsions. The novel interfacial architecture via the combination of steric hindrance from ZCP-based membrane and interfacial cargo of curcumin endowed the emulsions with favorable oxidative stability. This study opens a promising pathway for producing antioxidant emulsions via the combination of Pickering stabilization mechanism and interfacial delivery of antioxidant.

Effect of the biopolymer mixing ratio on the formation of electrostatically coupled whey protein-κ- and ι-carrageenan networks in the presence and absence of oil droplets

The rheological properties of 1.0% (w/w) whey protein isolate (WPI)-κ-/ι-carrageenan (CG) mixtures were investigated during a slow acidification process by glucono-δ-lactone from pH 7.00 to ∼4.20 as a function of biopolymer mixing ratio and in the presence and absence of oil droplets. In all cases, electrostatic coupled biopolymer and emulsion gel networks were formed at pH values corresponding to where attractive interactions between WPI and CG began. Formed WPI-CG complexes were found to be surface active, capable of lowering interfacial tension and forming viscoelastic interfacial films within emulsion-based systems. Both biopolymer and emulsion-based gels increased in strength and elasticity as the CG content increased, regardless of the type of CG present. However, WPI-ι-CG coupled networks were stronger than WPI-κ-CG networks, presumably due to the higher number of sulfate groups attracting the WPI molecules.

Assessment of oligogalacturonide from citrus pectin as a potential antibacterial agent against foodborne pathogens

Foodborne diseases are an important public health problem in the world. The bacterial resistance against presently used antibiotics is becoming a public health issue; hence, the discovery of new antimicrobial agents from natural sources attracts a lot of attention. Antibacterial activities of oligogalacturonide from commercial microbial pectic enzyme (CPE) treated citrus pectin, which exhibits antioxidant and antitumor activities, against 4 foodborne pathogens including Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa was assessed. Pectin hydrolysates from CPE hydrolysis exhibited antibacterial activities. However, no antibacterial activity of pectin was observed. Citrus oligogalacturonide from 24-h hydrolysis exhibited bactericidal effect against all selected foodborne pathogens and displayed minimal inhibitory concentration at 37.5 μg/mL for P. aeruginosa, L. monocytogenes, and S. Typhimurium, and at 150.0 μg/mL for S. aureus.

Physical and antimicrobial properties of peppermint oil nanoemulsions

The mixture of peppermint oil (PO) with medium-chain triacylglycerol was emulsified in water and stabilized with a food-grade biopolymer, modified starch, to form PO nanoemulsions. The effects of emulsifying conditions including homogenization pressure, the number of processing cycles, and oil loading on the mean diameters and viscosities of nanoemulsions were characterized by dynamic light scattering, optical microscopy, and rheological measurements. The formulated PO nanoemulsions with mean diameters normally <200 nm showed high stability over at least 30 days of storage time. Their antimicrobial properties related to those of PO have also been evaluated by two assays, the minimum inhibitory concentration (MIC) and time-kill dynamic processes, against two Gram-positive bacterial strains of Listeria monocytogenes Scott A and Staphylococcus aureus ATCC 25923. Compared with bulk PO, the PO nanoemulsions showed prolonged antibacterial activities. The results suggest that the nanoemulsion technology can provide novel applications of essential oils in extending the shelf life of aqueous food products.