Changes In Surface Hydrophobicity Research Articles

Physicochemical characterization of changes in pea protein as the result of cold extrusion

Pea protein is a popular plant-based protein for mimicking textures in meat and dairy analogues which are more sustainable than their animal-based counterparts. However, precise mechanisms for generating specific textures through different processing methods are still being evaluated. This work utilizes a novel low-temperature extrusion process to selectively alter the chemical structure of pea protein. Changes in secondary structure, surface hydrophobicity, electrostatic interactions, and disulfide bonding are characterized through FTIR, ANS- probes, zeta potential, and SDS-PAGE. Extrudates are further characterized using texture parameter analysis. It was found that a linear combination of physicochemical data, generated with multiple linear regression modelling, led to reasonable estimates of the specific mechanical energy and textural properties. This work offers a new method of reactive extrusion to selectively modify interactions in pea protein using low temperature extrusion, and applications may include fatty textures, since the extrudates are found to be largely stabilized through hydrophobic interactions evaluated with surface hydrophobicity measurements.

Physicochemical properties of wooden breast-extracted myosin and rheological properties of its heat-induced gel.

It is reported that broilers with 'wooden breast' have poor processing properties, such as low binding and water-holding capacities. However, the reason for the poor functional characteristics has not been clarified. In this study, myosin was extracted from a wooden breast. Its physicochemical properties were investigated to clarify the relationship between the structure and physicochemical properties of the heating gel of myosin obtained from the wooden breast. The turbidity of myosin solution extracted from wooden breast increased with increase in the heat treatment to a higher value than that from the normal breast meat myosin. The solubility of myosin collected from a wooden breast after heating decreased like normal breast muscle myosin. The surface hydrophobicity of myosin removed from wooden breast increased continually above 60 °C, unlike the change in surface hydrophobicity of normal breast myosin. The free thiol group of myosin extracted from the wooden breast was higher than normal breast myosin before and after heating. The apparent elasticity of heat-induced gels and chicken meat sausages was significantly lower in sausages and gel with wooden breast than normal ones (P < 0.05). The microstructure of the heated gel of normal myosin showed a fine network structure. In contrast, the heat-induced gel of wooden breast-extracted myosin showed a structure with loosely connected aggregates and many gaps. The coarseness of the internal gel structure of myosin extracted from wooden breast was shown to affect the apparent elasticity of the gel and sausages made from the chicken meat. © 2023 Society of Chemical Industry.

Abstract 4233: The anti-genotoxic function of Lactobacillus species in the context of bile-mediated DNA damage and inflammation in experimental models of GERD

Abstract Lactobacillus species are commensal organisms with probiotic characteristics found in the human oral cavity and gastrointestinal tract. It has been shown that gram-positive organisms, including lactobacilli, make up the majority of the microbiome in the healthy human esophagus. The general consensus is that the microbiome shifts from gram-positive to gram-negative bacteria during gastroesophageal reflux disease (GERD). In patients suffering from GERD, the esophageal tissue is injured by the low pH and bile acids present in the refluxate, resulting in Barrett’s esophagus if untreated. Interestingly, it has been reported that there is a proportional increase in gram-positive lactobacilli within the esophagus during the progression from GERD to Barrett’s esophagus, and finally esophageal adenocarcinoma. To investigate how lactobacilli are able to colonize and survive in a bile-rich environment of the esophagus during GERD, we first exposed three Lactobacillus species (L. acidophilus, L. plantarum, and L. fermentum) to cholate/deoxycholate bile salts or ox-bile as a more physiological model for human reflux. All three species exhibited bile resistance, in addition to bile adaptation after pre-exposure to sub-lethal concentrations. When assessed for changes in bacterial cell surface hydrophobicity, an indicator for bacterial adhesion to various surfaces, both bile types led to an increase of hydrophobicity in L. plantarum and L. fermentum, while L. acidophilus remained high. This provides mechanistic insight into how Lactobacillus species' attachment and colonization remain during reflux-related diseases. Next, we assessed the host-microbe interactions between lactobacilli and esophageal cells and the role these probiotic organisms may have in disease prevention. Acidic bile salts can induce inflammation and DNA damage to esophageal tissue through ROS during GERD, yet we found that the presence of lactobacilli co-cultured with bile-treated esophageal epithelial cells aids in the repair of bile-induced DNA damage in addition to NFKB reductions. To further investigate the host-microbe interactions, we supplemented epithelial cells with lactobacilli postbiotic metabolites and assessed cell viability during 48 hours of growth. Our current preliminary data show that postbiotic supplementation increases cell viability, providing insight into why lactobacilli are present within the normal and diseased human esophagus. This study demonstrates how the colonization of the esophagus during GERD with lactobacilli is based on their adaptability and survival due to changes in hydrophobicity thereby sustaining attachment. Furthermore, the anti-genotoxic and anti-inflammatory effects these organisms exhibit make them of significant interest in the prevention of Barrett’s esophagus and esophageal adenocarcinoma in patients with GERD. Citation Format: Joshua Bernard, Divya Joshi, Claudia Andl. The anti-genotoxic function of Lactobacillus species in the context of bile-mediated DNA damage and inflammation in experimental models of GERD. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4233.

Probing the biotoxicity of starch nanoparticles in vivo and their mechanism to desensitize β-lactoglobulin

Starch nanoparticles (SNPs) were synthesized and characterized in vivo for their subacute biotoxicity. Animal experiments revealed that SNPs would not induce changes in inflammatory cytokines and gut microbiota, avoiding damage to mice's organs. Moreover, SNPs were rapidly excreted from the body after 6 h without any accumulation, demonstrating their biosafety. Based on these findings, SNPs were used for β-lactoglobulin (βLg) desensitization by formation of a protein corona. The thermodynamics and time evolution of βLg's secondary structure were investigated to address the desensitization mechanism. The results showed ∼1600 βLg molecules onto a single SNP coupled with significant changes in secondary structure formed a stable SNPs-βLg corona with binding affinity (Ka) of 8.4 ± 0.5 × 10 5 M −1 . Functionally, the decrease of β-sheet destroyed the conformation of immunoglobulin E (IgE) epitopes and inhibited IgE combining capacity, achieving SNPs' desensitization to βLg. Additionally, it takes ∼2 h to complete changes in βLg's surface hydrophobicity and immunoglobulin E (IgE) combining capacity after incubation with SNPs, consistent with the time evolution of structure changes, indicating protein corona is response for the desensitization. SNPs-βLg corona changed βLg structure, inhibiting the combing with IgE. • Starch nanoparticles (SNPs) were characterized the subacute biotoxicity in vivo and showed biosafety to the mice. • It takes about 2 h to complete secondary structure changes, forming a stable SNPs-βLg corona with about1000 βLg molecules adsorbed. • The time evolution of surface hydrophobicity and IgE combining capacity is corresponding to the changes of secondary structure induce by protein corona.

Proteolysis modification targeting protein corona affects ultrasound-induced membrane homeostasis of saccharomyces cerevisiae: Analysis of lipid relative contributions on membrane properties.

Protein corona (PCN) adsorbed on the surface of nanoparticles has brought new research perspectives for the interaction between nanoparticles and microorganisms. In this study, the responses of saccharomyces cerevisiae' membrane lipid composition, the average length of the fatty acyl chains and the average number of unsaturation of fatty acids to ultrasound combined with nano-Fe3O4@PCN with time-limited proteolysis (nano-Fe3O4@TLP-PCN) was investigated. Lipidomic data was obtained using Ultra-high performance liquid chromatography coupled with a Q-Exactive plus mass spectrometer. The membrane potential, proton motive force assay and the membrane lipid oxidation were measured using Di-BAC4(3), DISC3(5) and C11-BODIPY581/591 as the probes. Combined with the approach of feasible virtual samples generation, the back propagation artificial neural network (BP-ANN) model was adopted to establish the mapping relationship between lipids and membrane properties. The time-limited proteolysis targeting wheat PCN-coated Fe3O4 nanoparticles resulted in regular changes of hydrodynamic diameters, ζ-potentials, and surface hydrophobicity. In addition, with the prolongation of PCN proteolysis time, disturbances of 3 S.cerevisiae membrane characteristics, and membrane lipidomic remodeling in response to ultrasound+ nano-Fe3O4@PCN were observed. The analysis of relative importance which followed revealed that ergosterol, phosphatidylserine, and phosphatidylinositol phosphate had the greatest influence on membrane potential. For membrane lipid oxidation, ceramide, phosphatidylethanolamine, and sitosterol ester contribute 16.2, 14.9, and 13.1%, respectively. The relative contributions of six lysolecithins to the dissipation of proton motive force remained limited. An adaptation mechanism of cell membrane to proteolyzed PCN, wherein lipidome remodeling could preserved functional membrane phenotypes was revealed. Furthermore, it is highlighted that the relative importances of SiE, Cer, PE and PIP in determining membrane potential, PMF dissipation and membrane lipid oxidation by establishing FVSG-BP-ANN model.

Proteolysis Degree of Protein Corona Affect Ultrasound-Induced Sublethal Effects on Saccharomyces cerevisiae: Transcriptomics Analysis and Adaptive Regulation of Membrane Homeostasis.

Protein corona (PC) adsorbed on the surface of nanoparticles brings new research perspectives on the interaction between nanoparticles and fermentative microorganisms. Herein, the proteolysis of wheat PC adsorbed on a nano-Se surface using cell-free protease extract from S. cerevisiae was conducted. The proteolysis caused monotonic changes of ζ-potentials and surface hydrophobicity of PC. Notably, the innermost PC layer was difficult to be proteolyzed. Furthermore, when S. cerevisiae was stimulated by ultrasound + 0.1 mg/mL nano-Se@PC, the proportion of lethal and sublethal injured cells increased as a function of the proteolysis time of PC. The transcriptomics analysis revealed that 34 differentially expressed genes which varied monotonically were related to the plasma membrane, fatty acid metabolism, glycerolipid metabolism, etc. Significant declines in the membrane potential and proton motive force disruption of membrane were found with the prolonged proteolysis time; meanwhile, higher membrane permeability, membrane oxidative stress levels, membrane lipid fluidity, and micro-viscosity were triggered.

Surface engineering of Ni2P/CoP nanosheet heterojunctions by the formation of F-doped carbon layers for boosting urea-rich water electrolysis

It's highly desirable but still challenging to design bifunctional non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) with high activity and boosted mass transport, especially under large-current densities. Hence, a novel 3D reticular heterostructure nanosheet arrays are fabricated (Ni2P/CoP/P,F–C) through coupling the F-doped carbon to realize urea-rich water electrolysis. The interface of carbon doping F can effectively enhance the conductivity and stability of Ni2P/CoP heterojunctions along with possible changes in surface hydrophobicity to accelerate release of generated bubbles under large-current densities. Benefiting from tailored d-band center of CoP nanosheet arrays and well-designed hydrophilic-superaerophobic feature, the elaborated Ni2P/CoP/P,F–C electrode shows brilliant electrocatalytic HER (198 mV) and UOR (251 mV) performance at 100 mA cm−2 current density. Meanwhile, the assembled alkaline urea-rich water electrolyzer with Ni2P/CoP/P,F–C as both the cathode and anode present ultralow cell voltages of 1.57 V to achieve 100 mA cm−2 with long-time stability. This work will promote research interest in material design for energy conversion technologies and urea-assisted hydrogen production.

Succinylated whey protein isolate-chitosan core–shell composite particles as a novel carrier: Self-assembly mechanism and stability studies

Single protein [whey protein isolate (WPI) or succinylated whey protein isolate (SWPI)] and composite particles of proteins with chitosan (CS) were tested for their ability to encapsulate and protect curcumin (CUR). Combining protein and CS resulted in changes in zeta-potential and surface hydrophobicity, particularly in the SWPI-H (high degree of succinylation, 90 %) and CS composite particle (H-CS). Furthermore, the secondary and tertiary structures were dramatically altered using Fourier transform infrared (FTIR), circular dichroism (CD), and X-ray diffraction (XRD). Scanning electron microscopy (SEM) and atomic force microscope (AFM) analyses revealed that H-CS exhibited a soft core-rigid shell morphology due to electrostatic interactions, hydrophobic interactions, and H-bond interactions. Fluorescence quenching results demonstrated that H-CS had a higher binding constant (K, 1.69 ×104 M−1) and encapsulation effectiveness (EE, 88.3 %) of CUR. Because of increased binding sites and steric hindrance, CUR was stabilized more effectively in H-CS in photostability and thermostability tests,. These results show that SWPI-CS composite particles can be utilized to build a protection system for water-insoluble nutritional supplements.

Study on functional improvement of freeze-thaw egg yolk pellet by enzymatic hydrolysis.

Freeze-thaw egg yolk pellet (FYP) could be produced as a by-product in the process of egg yolk immunoglobulin (IgY) extraction. The FYP contained many superior nutritional components like fresh egg yolk, but it has poor functionalities because of protein denaturation resulted from freezing treatment during IgY extraction. For the purpose of comprehensive utilization of egg yolk resources, FYP was subjected to enzymatic hydrolysis with alcalase to produce FYP hydrolysates (FYPh) with four enzyme concentrations of 250, 500, 1000 and 2000U/g for improved functional properties. And then FYPh was spray dried to obtain hydrolyzed egg yolk pellet powder (HYP). Solubility, emulsifying property and surface hydrophobicity of HYP were investigated. The results showed that enzymatic hydrolysis could lead to noticeable changes in surface hydrophobicity, microstructure, solubility and emulsifying properties of HYP compared with the control group without enzymatic hydrolysis treatment. Solubility and emulsification stability index generally increased from 19g/100g, 12.33 to 87g/100g, 76.63 with increasing degree of hydrolyze, respectively. This study demonstrated that the functional properties of FYP could be effectively improved when the enzyme addition amount reached 1000U/g. HYP prepared under this condition owes desirable solubility and emulsification, and has the potential of application in food industry.

Magnetic Mesoporous Silica Nanoparticles for Drug Delivery Systems: Synthesis, Characterization and Application as Norfloxacin Carrier

Mesoporous silica nanoparticles, with and without the inclusion of a magnetic core, were hydrothermally synthesized and employed as carrier of the antibiotic norfloxacin (NFX). The antibiotic-loaded materials were prepared by wet impregnation. Differences in drug content (and in further release profile) were directly related to changes in surface area, particle aggregation and hydrophobicity of the solids. The kinetics of NFX release has been studied in batch experiments. In all cases, more than 55% of the antibiotic was quickly desorbed during the first 5 min due to the localization of NFX on the external surface of the nanoparticles. The rest of the drug (situated inside the mesopores) was released through a diffusion-controlled transport and the rate was strongly dependent of the pH, reaching its minimum value at neutral pH. The calculated activation energy confirmed that the release was controlled by a diffusion process. Breaking of H-bonds and electrostatic and hydrophobic interactions appear to be responsible for NFX desorption from the solid surface. Such interactions increase, however, the thermal stability of the drug when the NFX and the carriers are combined. The antimicrobial activities of the drug loaded nanoparticles and the free antibiotic were compared and discussed.

Effects of heat treatment and simulated digestion on the properties and osteogenic activity of bovine lactoferrin

Lactoferrin (LF) is known to stimulate osteoblast proliferation and differentiation, potential to be applied in products improving skeletal health. However, LF is sensitive to thermal processing, and oral administration leads to hydrolysis in gastrointestinal tract, probably influencing the osteogenic activity. To determine the impacts of heat treatment, we explored the changes in secondary structure and surface hydrophobicity underlying aggregation along with surface charge alteration of bovine LF under four conditions commonly used in dairy production and found 72 °C/15 s, bringing the least structural alteration, was optimal to retain effect of LF promoting osteogenesis, while LF was completely deprived of the effect treated at 85 °C/10 min and 95 °C/10 min. In vitro adult and infant digestion models were established to identify the degradation of LF, and, despite impaired effect on osteoblast growth, LF hydrolysates from intestinal digestion stage presented stronger effect of boosting osteoblast differentiation independent of p38 and vitamin D receptor.

Physical and hydraulic properties of bioretention substrate using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite

ABSTRACT This study using hexadecyl trimethyl ammonium bromide (HDTMA) modified zeolite as a component of bioretention substrate, to investigate the effect of HDTMA modification on the basic physical and hydraulic properties of substrate layer. Two different levels of HDTMA modified zeolite (ZHD10 and ZHD50) were mixed with a mixture consists of peat soil, river sand and compost (fixed volumetric proportion at 5:4:1) with varying volumetric percentage (25%, 50%, and 75%) to form substrate media. The modification only changes the physical properties of zeolite and media with zeolite slightly, while significant changes in surface hydrophobicity and hydraulic properties were observed. A distinct decline of saturated hydraulic conductivity () values of zeolite can be observed after the modification, values drop 36.5% for ZHD10 and 55.1% for ZHD50. In contrast, values of substrate media using zeolite increase after the modification at the same volumetric ratio of zeolite. When 50% of zeolite (v/v%) was used in substrate, for natural zeolite, ZHD10 and ZHD50 was 0.024, 0.038 and 0.075 cm/s, respectively. Such alterations in are associated with the changes of surface hydrophobicity after the modification and ion exchange between modified zeolite and other materials after soaking into water. Changes in water retention characteristics (WRC) curves were in good accord with the variations in , and can be interpreted by the changed of tested materials. The orientations of HDTMA molecules loaded on zeolite surface were suggested to play crucial roles in altering the hydraulic properties of zeolite added substrate.

Effects of Ultrasonic Treatment on the Structure, Functional Properties of Chickpea Protein Isolate and Its Digestibility In Vitro

This study evaluated the effects of different levels of ultrasonic power (200, 400, 600 W) and treatment time (0, 10, 15 and 30 min) on the structure, emulsification characteristics, and in vitro digestibility of chickpea protein isolate (CPI). The changes in surface hydrophobicity of CPI indicated that ultrasound treatment exposed more hydrophobic amino acid residues. The analysis of sulfhydryl content and zeta potential showed that ultrasound caused the disulfide bond of CPI to be opened, releasing more negatively charged groups, and the solution was more stable. In addition, Fourier Transform Infrared Spectroscopy (FT-IR) and intrinsic fluorescence spectroscopy showed that ultrasound changes the secondary and tertiary structure of CPI, which is due to molecular expansion and stretching, exposing internal hydrophobic groups. The emulsification and foaming stability of CPI were significantly improved after ultrasonic treatment. Ultrasonic treatment had a minor effect on the solubility, foaming capacity and in vitro digestibility of CPI. All the results revealed that the ultrasound was a promising way to improve the functional properties of CPI.

Does bacterial community succession within the polyethylene mulching film plastisphere drive biodegradation?

Agricultural fields are severely contaminated with polyethylene mulching film (PMF) and this plastic in the natural environment can be colonized by biofilm-forming microorganisms that differ from those in the surrounding environment. In this study, we investigated the succession of the soil microbial communities in the PMF plastisphere using an artificial micro-ecosystem as well as exploring the degradation of PMF by plastisphere communities. The results indicated a significant and gradual decrease in the alpha diversity of the bacterial communities in the plastisphere and surrounding liquid. The community compositions in the plastisphere and surrounding liquid differed significantly from that in agricultural soil. Phyla and genera with the capacity to degrade polyethylene and hydrocarbon were enriched in the plastisphere, and some of these microorganisms were core members of the plastisphere community. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis detected increases in metabolism pathways for PMF plastisphere Xenobiotics Biodegradation and Metabolism, thereby suggesting the possibility of polyethylene degradation in the plastisphere. Observations by scanning electron microscopy (SEM) and confocal laser scanning microscopy demonstrated the formation of biofilms on the incubated PMF. SEM, atomic force microscopy, Fourier transform infrared spectroscopy and water contact angle detected significant changes in the surface microstructure, chemical composition and hydrophobicity change of the films, thereby suggesting that the plastisphere community degraded PMF during incubation. In conclusion, this study provides insights into the changes in agricultural soil microorganisms in the PMF plastisphere and the degradation of PMF.

3D-imprinted superhydrophobic polyvinylidene fluoride membrane contactor incorporated with CaCO3 nanoparticles for carbon capture

Carbon capture using membrane gas absorption was limited by membrane wetting. In this work, superhydrophobic poly(vinylidene fluoride) (PVDF) membrane contactors were developed through 3D-imprinting and nanoparticle incorporation. Membranes were cast on woven support before phase inversion in a water bath to imprint the micro-roughness. The low-cost and biocompatible calcium carbonate (CaCO3) nanoparticles were blended into PVDF dope solution to build the hierarchical structure. The nanoparticles were premodified using stearic acid to reduce surface energy or removed using ethylenediaminetetraacetic acid for achieving nanotemplating. The presence of CaCO3 nanoparticles could be observed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The membrane hydrophobicity, pore size, and porosity were significantly improved due to the addition of CaCO3 and stearic acid-modified CaCO3 (SA-CaCO3). Removing CaCO3 nanoparticles enlarged the pore size greatly but affected the surface hydrophobicity slightly. The PVDF membrane incorporated with SA-CaCO3 achieved a CO2 permeation flux as high as 1.86 ± 0.05 × 10−2 mol m−2 s−1 and only showed slight changes in surface hydrophobicity after being immersed in amine solution for 50 h.

Effect of sodium bicarbonate on solubility, conformation and emulsion properties of pale, soft and exudative meat myofibrillar proteins

To investigate the effects of sodium bicarbonate on aggregation and emulsion properties of pale, soft and exudative (PSE) meat myofibrillar proteins, the changes in pH, turbidity, particle size, free sulfhydryl, surface hydrophobicity, emulsifying ability, and emulsion stability were studied. The pH, solubility, proportion of free sulfhydryl groups, surface hydrophobicity, emulsifying ability, and emulsion stability significantly increased (P < 0.05) with an increase in sodium bicarbonate concentration from 0 g/kg to 6 g/kg. In contrast, zeta potential, turbidity, and particle size significantly decreased (P < 0.05). In summary, the addition of sodium bicarbonate increased the pH of PSE meat myofibrillar proteins and enhanced the electrostatic repulsion between the proteins, causing the absolute value of zeta potential to increase, leading to greater exposure of sulfhydryl and hydrophobic groups and formation of smaller aggregations, enhancing its solubility, emulsifying ability and emulsion stability. Thus, sodium bicarbonate could improve the processing performance of PSE meat.

The interaction of allicin with bovine serum albumin and its influence on the structure of protein

The interaction of allicin with bovine serum albumin (BSA) and the effect of allicin binding on the structure of protein were investigated. The BSA fluorescence displayed decreased fluorescence strength after binding with allicin, which quenched BSA fluorescence in a concentration-dependent manner. The number of binding sites and binding constants were measured by fluorescent quenching method. The result of reverse phase HPLC showed that the peak of BSA shifted to higher retention time, which indicated that allicin had bound to BSA. 88.4 % of total free thiol groups of BSA have bound to allicin at the allicin/BSA molar ratio of 0.1. Allicin could destabilize the secondary and tertiary structure of BSA. At the allicin/BSA ratio of 0.1, the BSA's circular dichroism spectrum showed that allicin caused a decrease of α-helix content and a significant increase of the β-sheet content (p < 0.05). Changes in surface hydrophobicity indicated that more hydrophobic groups were exposed due to the action of allicin. These results provide important insight into the study of prevailing role of protein in drug pharmacokinetics and pharmacodynamics.

Heat-induced changes in lupin seed γ-conglutin structure promote its interaction with model phospholipid membranes

A number of scientific data indicate that γ-conglutin can be internalised by different human cells and undergoes secretion from the seed in response to high temperature. In both of these cases, the protein must interact in some manner with biological membranes, however, the mechanisms underlying this phenomenon remain unknown. Herein, we found that the remarkable change of total surface hydrophobicity after appropriate heat treatment of γ-conglutin monomer led to its interaction with model membranes (liposomes). Before the interaction, the protein undergoes an intriguing thermal unfolding pattern which was studied based on a spectroscopic approach. Insight into the interaction mechanism with liposomes was possible thanks to applying two molecular probes that were differentially localised in the lipid bilayer. The results show that the thermal rearranged γ-coglutin monomer affects hydrocarbon chains in model membranes leading to their morphology change and disruption. The main driving force of this phenomenon is based on hydrophobic interaction.

Antimicrobial and antibiofilm effects of total flavonoids from Potentilla kleiniana Wight et Arn on Pseudomonas aeruginosa and its potential application to stainless steel surfaces

Pseudomonas aeruginosa (P. aeruginosa) contamination poses challenges to the food industry. Total flavonoids of Potentilla Kleiniana Wight et Arn (TFP) are poorly understood for their antibiofilm effects against P. aeruginosa. Therefore, the inhibitory effects of TFP against planktonic cells were determined by agar diffusion, microtiter plate and time-kill curve assays. The mechanism of inhibition is evaluated by changes in membrane (potential, permeability and damage), cell motility and virulence factors production. Morphological changes were verified by transmission electron microscopy (TEM). A modified microtiter-plate assay determined its inhibitory effects against biofilm cells. The inhibitory mechanism was studied by changes in extracellular polymeric substances (EPS) and cell surface hydrophobicity. These inhibition effects were verified by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Finally, TFP was applied to stainless steel surfaces to evaluate its potential application in food production. TFP damaged P. aeruginosa cell membrane integrity, inhibited bacterial motility, virulence factors, surface hydrophobicity and colony counting on stainless steel. These results provide evidence for the utilization of TFP as a novel natural bioactive preservative in food processing.

Formation of whey protein aggregates by partial hydrolysis and reduced thermal treatment

Thermal treatment to form functional, soluble whey protein aggregates often generates undesired off-flavours. The aim of the present study was to generate soluble aggregates of whey protein isolates (WPI) at lower temperature than traditionally used by introducing partial hydrolysis of WPI prior to thermal treatment. WPI was partially hydrolyzed either by Bacillus licheniformis protease (BLP) or by a trypsin type protease (TP) at pH 7.0 and 65 °C for 1–10 min prior to thermal treatment at 80 °C for 5–10 min to generate soluble protein aggregates. Partial hydrolysis by BLP and TP induced structural changes and exposure of free thiol groups, but no change of surface hydrophobicity of WPI. After incubation with BLP or TP and thermal treatment, the yield of protein aggregates was 36–48%, which was similar to the reference sample obtained by thermal treatment at 90 °C for 10 min. In addition to non-covalent interactions, disulfide bonds also contributed to the association of protein aggregates. The soluble protein aggregates obtained by BLP partial hydrolysis and thermal treatment, had particle size range of 10–100 nm in radius which was in the same range as observed for the reference sample; and samples obtained by TP treatment had a particle size range of 7–50 nm in radius. However, aggregates obtained by BLP or TP and thermal treatment were not UHT (140 °C/5 s) stable.