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1.
ChemSusChem ; 15(7): e202102535, 2022 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-35137539

RESUMO

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.


Assuntos
Celulose , Lignina , Biomassa , Celulose/química , Quitina , Lignina/química
2.
Carbohydr Polym ; 273: 118616, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34561014

RESUMO

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.


Assuntos
Antibacterianos/farmacologia , Quitosana/farmacologia , Embalagem de Alimentos , Conservação de Alimentos/instrumentação , Membranas Artificiais , Óleos Voláteis/farmacologia , Antibacterianos/química , Bactérias/efeitos dos fármacos , Quitosana/química , Óleos Voláteis/química
3.
Compr Rev Food Sci Food Saf ; 20(6): 6027-6056, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34435448

RESUMO

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.


Assuntos
Embalagem de Alimentos , Polímeros
4.
Compr Rev Food Sci Food Saf ; 20(5): 5258-5282, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34318596

RESUMO

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.


Assuntos
Embalagem de Alimentos , Conservação de Alimentos , Fazendas , Contaminação de Alimentos/prevenção & controle , Qualidade dos Alimentos
5.
Nanoscale Horiz ; 6(7): 505-542, 2021 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-34017971

RESUMO

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.

6.
J Food Prot ; 84(9): 1528-1538, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-33878157

RESUMO

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.


Assuntos
Anti-Infecciosos , Escherichia coli K12 , Malus , Bebidas/análise , Escherichia coli , Manipulação de Alimentos , Conservação de Alimentos , Sucos de Frutas e Vegetais
7.
Ultrason Sonochem ; 73: 105509, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33684739

RESUMO

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.


Assuntos
Escherichia coli O157 , Ondas Ultrassônicas , Membrana Celular , Permeabilidade da Membrana Celular , Fluidez de Membrana , Potenciais da Membrana , Espectroscopia de Infravermelho com Transformada de Fourier
8.
Int J Food Microbiol ; 337: 108938, 2021 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-33166912

RESUMO

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.


Assuntos
Compostos Clorados/farmacologia , Microbiologia de Alimentos , Armazenamento de Alimentos/métodos , Óxidos/farmacologia , Cloretos/análise , Contagem de Colônia Microbiana , Desinfetantes/farmacologia , Fungos/efeitos dos fármacos , Gases/farmacologia , Percloratos/análise , Sapindaceae/microbiologia
9.
Int J Food Microbiol ; 337: 108936, 2021 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-33161345

RESUMO

Development of novel and effective decontamination technologies to ensure the microbiological safety of fresh produce has gained considerable attention, mainly driven by numerous outbreaks. This work presented the first approach regarding to the application of the previously reported hurdle technologies on the sanitization of artificially contaminated cherry tomatoes. Thyme (Thymus daenensis) essential oil nanoemulsion (TEON, 8.28 nm in diameter with a narrow size distribution) was formulated via ultrasonic nanoemulsification, showing remarkably improved antimicrobial activity against Escherichia coli (E. coli) O157:H7, compared to the coarse emulsion. The antimicrobial effect of ultrasound (US), thyme essential oil nanoemulsion (TEON) and the combination of both treatments was assessed against E. coli O157:H7. The remarkable synergistic effects of the combined treatments were achieved, which decontaminated the E. coli populations by 4.49-6.72 log CFU/g on the surface of cherry tomatoes, and led to a reduction of 4.48-6.94 log CFU/sample of the total inactivation. TEON combined with US were effective in reducing the presence of bacteria in wastewater, which averted the potential detrimental effect of cross-contamination resulted from washing wastewater in fresh produce industry. Moreover, the treatments did not noticeably alter the surface color and firmness of cherry tomatoes. Therefore, ultrasound combined with TEON is a promising and feasible alternative for the reduction of microbiological contaminants, as well as retaining the quality characteristics of cherry tomatoes.


Assuntos
Descontaminação/métodos , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/efeitos da radiação , Microbiologia de Alimentos/métodos , Óleos Voláteis/farmacologia , Ondas Ultrassônicas , Contagem de Colônia Microbiana , Lycopersicon esculentum/microbiologia
10.
Beilstein J Org Chem ; 16: 2477-2483, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33093927

RESUMO

In this report, chitin and chitosan nanocrystals were used as biomass-based supports for Pd nanoparticles (NPs) used as a heterogeneous catalyst for the Heck coupling reaction. By using a one-pot fabrication method, a Pd salt precursor was directly reduced and deposited onto these nanocrystal catalysts. Characterization of these nanocomposites showed disperse Pd NPs on the surfaces of the chitinous nanocrystals. Heck coupling model reactions revealed full product yield in relatively benign conditions, outcompeting the use of other catalysts supported on biomass-based nanomaterials, including cellulose nanocrystals. These initial results show the potential for using chitinous nanomaterials as effective catalyst supports in cross-coupling reactions.

11.
Phys Rev Lett ; 125(4): 040603, 2020 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-32794778

RESUMO

We introduce the asymmetric extension of the quantum symmetric simple exclusion process which is a stochastic model of fermions on a lattice hopping with random amplitudes. In this setting, we analytically show that the time-integrated current of fermions defines a height field that exhibits quantum nonlinear stochastic Kardar-Parisi-Zhang dynamics. Similarly to classical simple exclusion processes, we further introduce the discrete Cole-Hopf (or Gärtner) transform of the height field that satisfies a quantum version of the stochastic heat equation. Finally, we investigate the limit of the height field theory in the continuum under the celebrated Kardar-Parisi-Zhang scaling and the regime of almost-commuting quantum noise.

12.
J Agric Food Chem ; 68(46): 12769-12772, 2020 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-32433871

RESUMO

This special issue of the Journal of Agricultural and Food Chemistry (JAFC) is a highlight of the Agricultural and Food Chemistry Division (AGFD) technical program at the 258th National Meeting of the American Chemical Society (ACS) in San Diego, CA, U.S.A., on August 25-29, 2019. At the conference, AGFD had 44 oral sessions at 19 symposia and 100 poster presentations with more than 400 abstract submissions. The technical program covered a broad range of current research and development topics in agricultural and food chemistry, including bioactive food components, diet and human nutrition, utilization of agricultural materials in food systems, food packaging, nanotechnology, and food safety, as well as several special award symposia. This is the first JAFC special issue that highlights an ACS national meeting program with joint efforts from AGFD.


Assuntos
Química Agrícola , Análise de Alimentos , Agricultura , Dieta , Manipulação de Alimentos , Humanos , Valor Nutritivo
13.
Biomacromolecules ; 21(6): 2236-2245, 2020 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-32223230

RESUMO

In this study, we demonstrate for the first time the fabrication of carboxylated chitosan nanocrystals (ChsNC) with high degree of deacetylation (DDA) at >80% and narrow size distribution. We also studied its application as a sustainable support material for metal-based catalysts. Carboxylated chitin nanocrystals (ChNCs) were initially prepared through partial cleavage of glycosidic bonds in chitin by ammonium persulfate, with concurrent oxidation of chitin C6 primary alcohols to produce carboxylate groups on the surface of the ChNCs. ChsNCs were subsequently prepared using an alkaline deacetylation procedure in the presence of NaBH4 to preserve the nanorod structure of the biomaterial. The resulting nanocrystals feature both carboxyl and amino functional groups. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used to determine the morphology and composition of these carboxylated ChNCs and ChsNCs. Subsequently, we tested the ability of the as-made ChsNCs as a biomass-based catalyst support for Au nanoparticles (NPs) using the 4-nitrophenol reduction and the aldehyde-amine-alkyne (A3) coupling reactions to demonstrate its capabilities in regard to the ones of cellulose nanocrystals (CNCs). In particular, Au NPs over ChsNCs featured the highest turnover frequency (TOF) value for the 4-nitrophenol reduction reported for all Au-based catalysts supported on carbon-based systems. Spectroscopic and imaging techniques confirmed the importance of precisely controlling the redox state of Au as it is being deposited to afford a highly disperse active site on the bionano-support.


Assuntos
Quitosana , Nanopartículas Metálicas , Catálise , Celulose , Ouro , Espectroscopia de Infravermelho com Transformada de Fourier
14.
Food Res Int ; 132: 109067, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32331688

RESUMO

Chlorine dioxide (ClO2) is an effective disinfectant used in the sanitization of fresh produce. Glucono delta-lactone (GDL), widely used as an acidifier during food processing, can be partially hydrolyzed to become a weak acid-gluconic acid under chemical equilibrium upon dissolution in water. This study focused on the development of a novel polylactic acid (PLA) film which incorporated with sodium chlorite (NaClO2) and GDL for ClO2(g) generation. The effects of PLA amount, NaClO2 + GDL/PLA ratio, NaClO2/GDL ratio, temperature and relative humidity on the release profiles of ClO2(g) were elucidated. The storage test indicated that film efficacy was well maintained after 4 weeks of storage under ambient conditions. The microbial inactivation results revealed that ClO2(g) generated from the films reduced populations of surface-inoculated Salmonella and Escherichia coli O157:H7 from ca. 5 log CFU/tomato to undetectable level (<1 log CFU/tomato) within 2 and 4 h respectively and the complete elimination in populations of both bacterial species was maintained throughout the 14-day storage period at both 10 and 22 °C. The sensory properties of treated tomatoes were evaluated and exhibited no significant difference (p > 0.05) compared to controls except for appearance on day 14 under 22 °C storage.


Assuntos
Cloretos/química , Microbiologia de Alimentos , Embalagem de Alimentos/métodos , Gluconatos/química , Lactonas/química , Lycopersicon esculentum/microbiologia , Cloretos/farmacologia , Compostos Clorados/farmacologia , Contagem de Colônia Microbiana , Desinfetantes/farmacologia , Filmes Comestíveis , Escherichia coli O157/efeitos dos fármacos , Contaminação de Alimentos/prevenção & controle , Inocuidade dos Alimentos , Gluconatos/farmacologia , Lactonas/farmacologia , Viabilidade Microbiana/efeitos dos fármacos , Óxidos/farmacologia , Poliésteres , Paladar , Temperatura
15.
J Food Prot ; 83(5): 902-909, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32032418

RESUMO

ABSTRACT: Dehydrated fruits, including dried coconut (Cocos nucifera) and dried apple (Malus sp.) slices, have been the subject of manufacturer recalls due to contamination with Salmonella. A study was conducted to determine the survival of Salmonella on apple slices of six apple cultivars after dehydration and also following treatment with antimicrobial solutions (0.5%, w/w) and dehydration. Samples of six apple cultivars (Envy, Gala, Red Delicious, Fuji, Pink Lady, Granny Smith) were cored and sliced into 0.4-cm rings, halved, inoculated with a five-strain composite of desiccation-resistant Salmonella, and dehydrated at 60°C for 5 h. Subsequently, Gala apple slices were treated in 0.5% solutions of one of eight antimicrobial rinses for 2 min and then dehydrated at 60°C for 5 h. Antimicrobial solutions used were potassium sorbate, sodium benzoate, ascorbic acid, propionic acid, lactic acid, citric acid, fumaric acid, and sodium bisulfate. Reduction of Salmonella populations varied according to apple cultivar. Salmonella survival on Envy, Gala, Red Delicious, Fuji, Pink Lady, and Granny Smith was 5.92, 5.58, 4.83, 4.68, 4.45, and 3.84 log CFU, respectively. There was significantly greater (P < 0.05) Salmonella inactivation on Granny Smith, Pink Lady, and Fuji apples than on Gala and Envy. Survival of Salmonella on Gala apple slices following dehydration was 5.58 log CFU for the untreated control and 4.76, 3.90, 3.29, 3.13, 2.89, 2.83, 2.64, and 0.0 log CFU for those treated with potassium sorbate, sodium benzoate, ascorbic acid, propionic acid, lactic acid, citric acid, fumaric acid, and sodium bisulfate, respectively. Pretreatment of apple slices with either fumaric acid or sodium bisulfate before dehydration led to lower Salmonella survival than pretreatment with all other antimicrobial treatments. Lower apple pH was statistically correlated (P < 0.05) with decreasing survival of Salmonella following dehydration. These results may provide methodology applicable to the food industry for increasing the inactivation of Salmonella during the dehydration of apple slices.


Assuntos
Desinfetantes/farmacologia , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Malus , Salmonella/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Dessecação , Humanos , Malus/classificação , Malus/microbiologia
16.
Phys Rev E ; 101(1-1): 012115, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32069547

RESUMO

For a quantum system in a macroscopically large volume V, prepared in a pure state and subject to maximally noisy or ergodic unitary dynamics, the reduced density matrix of any sub-system v≪V is almost surely totally mixed. We show that the fluctuations around this limiting value, evaluated according to the invariant measure of these unitary flows, are captured by the Gaussian unitary ensemble (GUE) of random matrix theory. An extension of this statement, applicable when the unitary transformations conserve the energy but are maximally noisy or ergodic on any energy shell, allows to decipher the fluctuations around canonical typicality. According to typicality, if the large system is prepared in a generic pure state in a given energy shell, the reduced density matrix of the sub-system is almost surely the canonical Gibbs state of that sub-system. We show that the fluctuations around the Gibbs state are encoded in a deformation of the GUE whose covariance is specified by the Gibbs state. Contact with the eigenstate thermalization hypothesis is discussed.

17.
Chem Rev ; 120(2): 986-1041, 2020 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-31725267

RESUMO

Localized surface plasmon resonance (LSPR) is a physical phenomenon exhibited by nanoparticles of metals including coinage metals, alkali metals, aluminum, and some semiconductors which translates into electromagnetic, thermal, and chemical properties. In the past decade, LSPR has been taken advantage of in the context of catalysis. While plasmonic nanoparticles (PNPs) have been successfully applied toward enhancing catalysis of inorganic reactions such as water splitting, they have also demonstrated exciting performance in the catalysis of organic transformations with potential applications in synthesis of molecules from commodity to pharmaceutical compounds. The advantages of this approach include improved selectivity, enhanced reaction rates, and milder reaction conditions. This review provides the basics of LSPR theory, details the mechanisms at play in plasmon-enhanced nanocatalysis, sheds light onto such nanocatalyst design, and finally systematically presents the breadth of organic reactions hence catalyzed.

18.
Phys Rev Lett ; 123(8): 080601, 2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31491217

RESUMO

We present the solution to a model of fermions hopping between neighboring sites on a line with random Brownian amplitudes and open boundary conditions driving the system out of equilibrium. The average dynamics reduces to that of the symmetric simple exclusion process. However, the full distribution encodes for a richer behavior, entailing fluctuating quantum coherences which survive in the steady limit. We determine exactly the steady statistical distribution of the system state. We show that the out-of-equilibrium quantum coherence fluctuations satisfy a large-deviation principle, and we present a method to recursively compute exactly the large-deviation function. As a by-product, our approach gives a solution of the classical symmetric simple exclusion process based on fermion technology. Our results open the route towards the extension of the macroscopic fluctuation theory to many-body quantum systems.

19.
J Food Prot ; 82(6): 988-996, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31121101

RESUMO

There are numerous obstacles to the detection of foodborne pathogens in foods that exhibit a low water activity (aw). These obstacles include the presence of antimicrobial compounds, particulates, PCR inhibitors, and fatty matrices. New approaches should be sought to increase the sensitivity of pathogen testing in low-aw foods and to overcome the effects of various inhibitors and antimicrobials. The U.S. Food and Drug Administration and other laboratories are working toward this goal. This review will address these issues while delineating specific inhibitors and antimicrobials that impede testing of low-aw foods. A review of relevant rapid and conventional testing methodologies for Salmonella in low-aw foods will also be discussed.


Assuntos
Microbiologia de Alimentos , Salmonella , Água , Microbiologia de Alimentos/métodos , Salmonella/isolamento & purificação , Água/química
20.
J Food Prot ; 82(4): 628-644, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30917037

RESUMO

HIGHLIGHTS: Consumers are demanding more natural and organic foods and ingredients. Many additives alone are insufficient to inactivate pathogens or prevent growth. Mild heat combined with antimicrobial agents synergistically inactivate pathogens. Here we review studies using thermally assisted antimicrobial inactivation. Many opportunities exist for the application of this hurdle technology in foods.


Assuntos
Antibacterianos/farmacologia , Contagem de Colônia Microbiana , Escherichia coli O157 , Microbiologia de Alimentos , Temperatura Alta
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