Coating with phenolic branched-chain fatty acid reduces Listeria innocua populations on apple fruit.

An antimicrobial coating was produced by mixing phenolic branched-chain fatty acid (PBC-FA) with glycerol and a carboxymethyl cellulose solution (CMC) at pH 7. The resulting PBC-FA-CMC solution formed an emulsion with an average droplet size of 77 nm. The emulsion in the coating solution was stable for at least 30 days at 20 °C. The in vitro antimicrobial activity of the film formed from the PBC-FA emulsion was tested against a mixture of 3 strains of Listeria innocua (7 log CFU/mL). Film with a concentration of 1000 µg/mL of PBC-FA effectively reduced the population of L. innocua below the limit of detection (<1.48 log CFU/mL) in vitro. The effect of the 1000 µg/mL PBC-FA-CMC coating formulation was then evaluated against L. innocua inoculated on "Gala" apples. Results showed that compared with the non-coated control, the coating reduced L. innocua populations by ~2 log CFU/fruit and ~6 log CFU/fruit on the apple when enumerated on tryptic soy agar and selective media (PALCAM), respectively, indicating that PBC-FA applied as a coating on apples resulted in the sub-lethal injury of bacterial cells. When L. innocua was inoculated onto PBC-FA-coated apples, the L. innocua population decreased by ~4 log CFU/fruit during 14 days of shelf-life at 20 °C. The PBC-FA coating lowered the moisture loss but did not affect the color, firmness, or soluble solids content of apples during the 14-day at 20 °C. Overall, this study revealed that there is a potential that PBC-FA can be used as an antimicrobial coating to inactivate Listeria and preserve the quality of apples.

Inactivation of Desiccation-Resistant Salmonella on Apple Slices Following Treatment with ε-Polylysine, Sodium Bisulfate, or Peracetic Acid and Subsequent Dehydration.

Salmonella is capable of surviving dehydration within various foods, such as dried fruit. Dried fruit, including apple slices, have been the subject of product recalls due to contamination with Salmonella. A study was conducted to determine the fate of Salmonella on apple slices, following immersion in three antimicrobial solutions (viz., ε-polylysine [epsilon-polylysine or EP], sodium bisulfate [SBS], or peracetic acid [PAA]), and subsequent hot air dehydration. Gala apples were aseptically cored and sliced into 0.4 cm thick rings, bisected, and inoculated with a five-strain composite of desiccation-resistant Salmonella, to a population of 8.28 log CFU/slice. Slices were then immersed for 2 min in various concentrations of antimicrobial solutions, including EP (0.005, 0.02, 0.05, and 0.1%), SBS (0.05, 0.1, 0.2, and 0.3%), PAA (18 or 42 ppm), or varying concentrations of PAA + EP, and then dehydrated at 60°C for 5 h. Salmonella populations in positive control samples (inoculated apple slices washed in sterile water) declined by 2.64 log after drying. In the present study, the inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.20 log (with 0.1 and 0.3% of the two compounds, respectively). Based on preliminary studies, EP concentrations greater than 0.1% did not result in lower populations of Salmonella. Pretreatment washes with either 18 or 42 ppm of PAA inactivated Salmonella populations by 4.62 and 5.63 log, respectively, following desiccation. Combining PAA with up to 0.1% EP induced no greater population reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, reducing its biocidal efficacy. These results may provide antimicrobial predrying treatment alternatives to promote the reduction of Salmonella during commercial or consumer hot air drying of apple slices.

Transport and Nonreciprocity in Monitored Quantum Devices: An Exact Study.

We study noninteracting fermionic systems undergoing continuous monitoring and driven by biased reservoirs. Averaging over the measurement outcomes, we derive exact formulas for the particle and heat flows in the system. We show that these currents feature competing elastic and inelastic components, which depend nontrivially on the monitoring strength γ. We highlight that monitor-induced inelastic processes lead to nonreciprocal currents, allowing one to extract work from measurements without active feedback control. We illustrate our formalism with two distinct monitoring schemes providing measurement-induced power or cooling. Optimal performances are found for values of the monitoring strength γ, which are hard to address with perturbative approaches.

Bio-based phenolic branched-chain fatty acid in wash water reduced populations of Listeria innocua on apple fruit.

Phenolic branched-chain fatty acid (PBC-FA) emulsion was produced by dissolving it in ethanol and mixing with water (pH 7). The resulting monodispersed emulsion droplets were approximately 200 nm in diameter. The stability of the emulsion was evaluated by storing it at 4 and 20 °C for 30 days. The antimicrobial activity of the PBC-FA emulsion was tested against Escherichia coli and Listeria innocua (8 log CFU/mL) by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a microdilution method. The PBC-FA was effective against L. innocua with MIC and MBC of 14.1 µg/mL and caused membrane permeation as determined with SEM and Live/Dead cell assay, but was not effective against E. coli O157:H7 at the tested concentrations (5-250 µg/mL). We also evaluated PBC-FA emulsion's potential to be used as a wash against L. innocua inoculated on apples. The results showed that the 500 µg/mL PBC-FA emulsion with 5 % ethanol had equivalent antimicrobial activity (2-3 logs reductions) against L. innocua as the 20 µg/mL chlorine solution, a commonly used sanitizer. 500 µg/mL PBC-FA emulsion had better antimicrobial efficacy when organic matter (chemical oxygen demand: 9.0 g/L) was present compared to 20 µg/mL of chlorine. The effect of PBC-FA on the quality of the apples, was determined by measuring changes in color, firmness, and soluble solids content over a 14-day storage period at 20 °C. The quality of the apples was not affected by PBC-FA over the 14-day storage period, suggesting that PBC-FA emulsion can be used as a wash for apples without affecting their quality.

Effect of Surface Functionality on the Rheological and Self-Assembly Properties of Chitin and Chitosan Nanocrystals and Use in Biopolymer Films.

Chitin nanocrystals (ChNCs) are unique to all other bio-derived nanomaterials in one aspect: the inherent presence of a nitrogen moiety. By tuning the chemical functionality of this nanomaterial, and thus its charge and hydrogen bonding capacity, one can heavily impact its macroscopic properties such as its rheological and self-assembly characteristics. In this study, two types of ChNCs are made using acid hydrolysis (AH-ChNCs) and oxidative (OX-ChNCs) pathways, unto which deacetylation using a solvent-free procedure is utilized to create chitosan nanocrystals (ChsNCs) of varying degree of deacetylation (DDA). These nanocrystals were then studied for their rheological behavior and liquid crystalline ordering. It was found that with both deacetylation and carboxylation of ChNCs, viscosity continually increased with increasing concentrations from 2 to 8 wt %, contrary to AH-ChNC dispersions in the same range. Interestingly, increasing the amine content of ChNCs was not proportional to the storage modulus, where a peak saturation of amines provided the most stiffness. Conversely, while the introduction of carboxylation increased the elastic modulus of OX-ChNCs by an order of magnitude from that of AH-ChNCs, it was decreased by increasing DDA. Deacetylation and carboxylation both inhibited the formation of a chiral nematic phase. Finally, these series of nanocrystals were incorporated into biodegradable pectin-alginate films as a physical reinforcement, which showed increased tensile strength and Young's modulus values for the films incorporated with ChsNCs. Overall, this study is the first to investigate how surface functionalization of chitin-derived nanocrystals can affect their rheological and liquid crystalline properties and how it augments pectin/alginate films as a physical reinforcement nanofiller.

Comparing interventions for chronic central serous chorioretinopathy: A network meta-analysis.

We compare efficacy of treatments for chronic central serous chorioretinopathy (CSCR) > 3 months. Four treatment classes were considered: photodynamic therapy (PDT), subthreshold laser therapies (SLT), mineralocorticoid receptor antagonists (MRA) and antivascular endothelial growth factor (anti-VEGF) agents. Pairwise and network meta-analyses (NMA) of the primary outcomes (complete resolution of subretinal fluid (SRF), mean change in best corrected visual acuity (BCVA as logMAR) and mean change in SRF) and secondary outcomes (mean change in central retinal thickness, and central choroidal thickness (µm), recurrence of SRF, and adverse events) at 3, 6, and 12 months were compared. Confidence in Network Meta-Analysis (CINeMA) informed the certainty of NMA evidence. Eleven RCTs of 458 eyes (450 patients) were included. NMA at 3 months showed that both PDT and SLT were superior to control for resolution of SRF (OR 4.83; 95% CI 1.72-13.55 and 2.27; 1.14-4.49, respectively) and SLT was superior to control for improving BCVA (MD -0.10; -0.17 to -0.04). PDT was superior to SLT for improving CRT (MD -42.88; -75.27 to -10.50). On probability ranking, PDT and SLT were consistently the best-ranked treatments for each outcome at 3 months, but low confidence of evidence and paucity of studies preclude definitive conclusions.

Mechanism of Synergistic Photoinactivation Utilizing Curcumin and Lauric Arginate Ethyl Ester against Escherichia coli and Listeria innocua.

This study investigated the mechanism of how lauric arginate ethyl ester (LAE) improves the photoinactivation of bacteria by curcumin after diluting the 100 µmol/L stock curcumin-LAE micelle solution to the concentration used during the treatment based on the curcumin concentration. The photoinactivation of bacteria was conducted by irradiating the 1 µmol/L curcumin-LAE solution containing cocktails of Escherichia coli and Listeria innocua strains (7 log CFU/mL) for 5 min with UV-A light (λ = 365 nm). The changes in solution turbidity, curcumin stability, and bacterial morphology, viability, and recovery were observed using SEM, TEM, and live/dead cell assays. The study found that LAE enhances the photoinactivation of bacteria by increasing the permeability of cell membranes which could promote the interaction of reactive oxygen species produced by photosensitized curcumin with the cell components. The combination of curcumin and LAE was demonstrated to be more effective in inhibiting bacterial recovery at pH 3.5 for E. coli, while LAE alone was more effective at pH 7.0 for L. innocua.

Application of yellow mustard mucilage and starch in nanoencapsulation of thymol and carvacrol by emulsion electrospray.

Starch/water soluble yellow mustard mucilage nanocapsules loaded with thymol and carvacrol (TC) were developed using electrospray atomization. Emulsions were electrosprayed, aiming to generate nanocapsules with a controlled release behavior of TC for antimicrobial packaging applications. To understand the effect of water soluble yellow mustard mucilage (WSM) on the nanocapsules, the emulsion viscosity, morphology, encapsulation efficiency, molecular interactions, and release kinetics were evaluated. Surface and internal morphological analysis revealed that nanocapsules were non-porous with minimal surface shrinkages and had inner multicore spheres within a solid wall layer. Encapsulation efficiency ranged from 61.17 to 84.10 %, increasing at higher TC contents. Fourier transform spectroscopy confirmed the molecular interaction between wall materials. The release kinetics of encapsulated TC (30 % w/w) followed a Fickian diffusion mechanism and a controlled release pattern up to 120 h. Results indicated that the addition of WSM can modulate the release kinetics of bioactives and achieve a controlled release pattern.

High-Humidity Shaker Aging to Access Chitin and Cellulose Nanocrystals.

To unlock nature's potential for functional biomaterials, many efforts have been devoted to isolating the nanocrystalline domains within the supramolecular structure of polysaccharides. Yet, low reactivity and yield in aqueous systems along with excessive solvent usage hinders its development. In this report, the first solvent-free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high-humidity shaker aging (HHSA). The method involves a mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high-humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp.

Antimicrobial coating with organic acids and essential oil for the enhancement of safety and shelf life of grape tomatoes.

This study investigated the antimicrobial efficacy of two coatings against populations of nalidixic acid-resistant Salmonella, Listeria monocytogenes and native microorganisms on whole grape tomatoes. Tomatoes were surface-coated in two chitosan-acid coating solutions. Solution 1 (Chitosan) consisted of 1 % chitosan and 2 % acetic, lactic and levulinic acids. Solution 2 (Chitosan+AIT) consisted of Solution 1 plus 2 % allyl isothiocyanate (AIT). After the treatments, tomatoes were placed in PET containers and stored at 10 °C for 21 days. Chitosan and Chitosan+AIT treatments reduced Salmonella populations from 3.65 to 1.28 and <0.70 log CFU/tomato on day 1, respectively. Both treatments reduced Salmonella populations to undetectable levels (<0.70 log CFU/tomato) from Day 2 through Day 21. Similarly, Chitosan+AIT treatments caused a greater reduction in Listeria populations than Chitosan treatment on day 1, but there were no significant differences between the two treatments after day 2. Chitosan and Chitosan+AIT reduced native bacteria populations to an undetectable level after 2 days and reduced the population of native yeasts & molds to an undetectable level after 1 day. The presence of mold was only observed on control sample after 21 days. Quality analyses showed that samples which were subject to coating treatment maintained their texture and color for 21 days at 10 °C with less water loss compared to the controls. This study suggests that chitosan-acid coating is applicable for extending the shelf-life and enhancing the safety of grape tomatoes.

Mechanochemical Transformations of Biomass into Functional Materials.

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Kardar-Parisi-Zhang Physics and Phase Transition in a Classical Single Random Walker under Continuous Measurement.

We introduce and study a new model consisting of a single classical random walker undergoing continuous monitoring at rate γ on a discrete lattice. Although such a continuous measurement cannot affect physical observables, it has a nontrivial effect on the probability distribution of the random walker. At small γ, we show analytically that the time evolution of the latter can be mapped to the stochastic heat equation. In this limit, the width of the log-probability thus follows a Family-Vicsek scaling law, N^{α}f(t/N^{α/ß}), with roughness and growth exponents corresponding to the Kardar-Parisi-Zhang (KPZ) universality class, i.e., α_{KPZ}^{1D}=1/2 and ß_{KPZ}^{1D}=1/3, respectively. When γ is increased outside this regime, we find numerically in 1D a crossover from the KPZ class to a new universality class characterized by exponents α_{M}^{1D}≈1 and ß_{M}^{1D}≈1.4. In 3D, varying γ beyond a critical value γ_{M}^{c} leads to a phase transition from a smooth phase that we identify as the Edwards-Wilkinson class to a new universality class with α_{M}^{3D}≈1.

Emerging chitosan-essential oil films and coatings for food preservation - A review of advances and applications.

With the rising demand for fresh and ready-to-eat foods, antimicrobial packaging has been developed to control or prevent microbial growth as well as maintain food quality and safety. Chitosan is an advanced biomaterial for antimicrobial packaging to meet the growing needs of safe and biodegradable packaging. The application of natural essential oils as antimicrobial agents effectively controls the growth of spoilage and pathogenic microbes. Thus, chitosan edible coatings and films incorporated with essential oils have expanded the general applications of antimicrobial packaging in food products. This review summarized the effect of essential oils on modifying the physicochemical characteristics of chitosan-based films. Notably, the antimicrobial efficacy of the developed composite films or coatings was highlighted. The advances in the preparation methods and application of chitosan films were also discussed. Broadly, this review will promote the potential applications of chitosan-essential oils composite films or coatings in antimicrobial packaging for food preservation.

Electrohydrodynamic processing of natural polymers for active food packaging: A comprehensive review.

The active packaging materials fabricated using natural polymers is increasing in recent years. Electrohydrodynamic processing has drawn attention in active food packaging due to its potential in fabricating materials with advanced structural and functional properties. These materials have the significant capability in enhancing food's quality, safety, and shelf-life. Through electrospinning and electrospray, fibers and particles are encapsulated with bioactive compounds for active packaging applications. Understanding the principle behind electrohydrodynamics provides fundamentals in modulating the material's physicochemical properties based on the operating parameters. This review provides a deep understanding of electrospray and electrospinning, along with their advantages and recent innovations, from food packaging perspectives. The natural polymers suitable for developing active packaging films and coatings through electrohydrodynamics are intensely focused. The critical properties of the packaging system are discussed with characterization techniques. Furthermore, the limitations and prospects for natural polymers and electrohydrodynamic processing in active packaging are summarized.

Informative and corrective responsive packaging: Advances in farm-to-fork monitoring and remediation of food quality and safety.

Microbial growth and fluctuations in environmental conditions have been shown to cause microbial contamination and deterioration of food. Thus, it is paramount to develop reliable strategies to effectively prevent the sale and consumption of contaminated or spoiled food. Responsive packaging systems are designed to react to specific stimuli in the food or environment, such as microorganisms or temperature, then implement an informational or corrective response. Informative responsive packaging is aimed at continuously monitoring the changes in food or environmental conditions and conveys this information to the users in real time. Meanwhile, packaging systems with the capacity to control contamination or deterioration are also of great interest. Encouragingly, corrective responsive packaging attempting to mitigate the adverse effects of condition fluctuations on food has been investigated. This packaging exerts its effects through the triggered release of active agents by environmental stimuli. In this review, informative and corrective responsive packaging is conceptualized clearly and concisely. The mechanism and characteristics of each type of packaging are discussed in depth. This review also summarized the latest research progress of responsive packaging and objectively appraised their advantages. Evidently, the mechanism through which packaging systems respond to microbial contamination and associated environmental factors was also highlighted. Moreover, risk concerns, related legislation, and consumer perspective in the application of responsive packaging are discussed as well. Broadly, this comprehensive review covering the latest information on responsive packaging aims to provide a timely reference for scientific research and offer guidance for presenting their applications in food industry.

Chitin and chitosan on the nanoscale.

In a matter of decades, nanomaterials from biomass, exemplified by nanocellulose, have rapidly transitioned from once being a subject of curiosity to an area of fervent research and development, now reaching the stages of commercialization and industrial relevance. Nanoscale chitin and chitosan, on the other hand, have only recently begun to raise interest. Attractive features such as excellent biocompatibility, antibacterial activity, immunogenicity, as well as the tuneable handles of their acetylamide (chitin) or primary amino (chitosan) functionalities indeed display promise in areas such as biomedical devices, catalysis, therapeutics, and more. Herein, we review recent progress in the fabrication and development of these bio-nanomaterials, describe in detail their properties, and discuss the initial successes in their applications. Comparisons are made to the dominant nanocelluose to highlight some of the inherent advantages that nanochitin and nanochitosan may possess in similar application.

Apple Juice Preservation Using Combined Nonthermal Processing and Antimicrobial Packaging.

ABSTRACT: This study was conducted to investigate the effectiveness of pulsed electric fields (PEFs), pulsed UV light (PL), and antimicrobial packaging (AP), either individually or combined, for inactivating bacteria and maintaining the quality of fruit juices. Apple juice samples were inoculated with Escherichia coli K-12 or native molds and yeasts (M&Y), treated with bench-scale PEF and/or PL processing systems, and stored in glass jars with antimicrobial caps containing 10 µL of carvacrol. The reductions in microbial populations and the physicochemical properties of juice samples were determined after treatments and during storage at 10°C. The treatments were PL (5 to 50 s at 1.04 J/cm2/s), PEF (19, 23, and 30 kV/cm), PEF followed by PL (PEF+PL), PL followed by PEF (PL+PEF), and PEF+PL+AP. PEF treatments at 19 to 30 kV/cm (PEF19, PEF23, and PEF30) resulted in 2.0-, 2.6-, and 4.0-log reductions of E. coli, respectively, and PL treatments for 10 to 50 s (PL10, PL20, PL30, PL40, and PL50) resulted in 0.45-, 0.67-, 0.76-, 2.3-, and 4.0-log reductions, respectively. No significant differences (P > 0.05) were found between the combined PL20+PEF19 and PEF19+PL20 treatments; both treatments reduced E. coli K-12 populations to nondetectable levels (>5-log reductions) after 7 days. Both PEF+PL and PEF+PL+AP treatments achieved >5-log reductions of M&Y; however, juice samples subjected to PEF+PL+AP treatment had lower M&Y counts (2.9 log units) than did samples subjected to PEF+PL treatment (3.9 log units) after 7 days. No significant differences (P > 0.05) in pH, acidity, and total soluble solids were found among all samples after treatments. Increased PL treatment times reduced color a* and b* values, total phenolics, and carotenoids. This study provides information valuable to juice processors for consideration and design of nonthermal pasteurization of juice products.

Antibacterial mechanism of ultrasound against Escherichia coli: Alterations in membrane microstructures and properties.

This study was aimed at providing new insights on the response of bacterial cell membranes to ultrasound exposure. Escherichia coli (E. coli) O157:H7 cells were exposed to different ultrasound treatments (power intensities of 64, 191, 372, and 573 W/cm2, frequency of 20 kHz, pulsed mode of 2 sec: 2 sec) and the dynamic changes in cell viability within 27 min were assessed. With an increase in ultrasonic intensity and prolonged duration, a 0.76-3.52 log CFU/mL reduction in E. coli populations was attained. The alterations in the sensitivity of ultrasound-treated cells to antimicrobial compounds were evaluated by exposure to thyme essential oil nanoemulsion (TEON). The treatment reduced the E. coli population by 2.16-7.10 log CFU/mL, indicating the effects of ultrasonic field on facilitating the antibacterial efficacy of TEON. Ultrasonic-treated E. coli cells also displayed remarkable morphological and ultrastructural damages with destroyed membrane integrity and misshaped cell structures, which was observed by electron microscopy analysis. Significant increase in outer and inner membrane permeability, along with the cytoplasmic leakage and membrane depolarization were assessed utilizing spectrophotometry. For the first time, significant reduction in the membrane fluidity in response to ultrasound exposure were investigated. Additional efforts in exploring the effect of ultrasonic field on some bacterial membrane compositions were performed with infrared spectroscopy. In this study, multiple lines of evidence effectively served to elucidate the alterations on cellular membrane structure and property during exposure to sonication that could extend our understanding of the antimicrobial molecular mechanisms of ultrasound.

Extension of shelf life of semi-dry longan pulp with gaseous chlorine dioxide generating film.

A packaging system using gaseous chlorine dioxide generating film (CDGF) in a sealed container was developed to extend the shelf life of semi-dry longan pulp (moisture content 38.8 wt%; aw0.8). The antimicrobial properties, formation of chloroxyanion residues and effects of CDGF on the quality of semi-dry longan pulp were investigated. CDGF was triggered by the moisture vapor from semi-dry longan pulp in the sealed container and released gaseous ClO2 into the headspace of the container. The antifungal test showed that CDGF significantly inactivated artificially inoculated molds in semi-dry longan pulp and achieved reductions of over 3 log CFU/g after 28 days storage at room temperature (25 °C). CDGF reduced total aerobic bacterial populations by over 6.4 log CFU/g and maintained these population levels at around 2.0 log CFU/g throughout the 180-day storage period at room temperature. The residual concentrations of chloride, chlorate and perchlorate in longan pulp increased and then decreased during the 180-day storage. Residual chloride levels were maintained at 1.5 mg/g after Day 120 and residual chlorate and perchlorate levels were not detected after Day 120 and Day 180, respectively, in CDGF-treated samples. CDGF treatments reduced total polyphenol content but didn't have any significant impact on the levels of polysaccharides in samples. There were no significant differences between CDGF-treated and control samples in color changes during storage. The content of 5-hydroymethylfurfural (5-HMF) in both samples increased during storage, suggesting that the Maillard reaction occurred. This study demonstrated an effective approach to develop a new antimicrobial packaging system for semi-dry longan pulp.