Salmonella enterica serovar Typhimurium melibiose permease (MelBSt) is a prototype of the major facilitator superfamily (MFS) transporters, which play important roles in human health and diseases. ...MelBSt catalyzed the symport of galactosides with Na+, Li+, or H+ but prefers the coupling with Na+. Previously, we determined the structures of the inward- and outward-facing conformation of MelBSt and the molecular recognition for galactoside and Na+. However, the molecular mechanisms for H+- and Na+-coupled symport remain poorly understood. In this study, we solved two x-ray crystal structures of MelBSt, the cation-binding site mutants D59C at an unliganded apo-state and D55C at a ligand-bound state, and both structures display the outward-facing conformations virtually identical as published. We determined the energetic contributions of three major Na+-binding residues for the selection of Na+ and H+ by free energy simulations. Transport assays showed that the D55C mutant converted MelBSt to a solely H+-coupled symporter, and together with the free-energy perturbation calculation, Asp59 is affirmed to be the sole protonation site of MelBSt. Unexpectedly, the H+-coupled melibiose transport exhibited poor activities at greater bulky ΔpH and better activities at reversal ΔpH, supporting the novel theory of transmembrane-electrostatically localized protons and the associated membrane potential as the primary driving force for the H+-coupled symport mediated by MelBSt. This integrated study of crystal structure, bioenergetics, and free energy simulations, demonstrated the distinct roles of the major binding residues in the cation-binding pocket of MelBSt.
In this study, the combined effect of ultrasound (US) and pulsed electric field (PEF) techniques was analyzed for the quality improvement and microbial safety of spinach juice. The spinach juice was ...treated with US at frequency of 40 kHz, radiating power of 200 W below 30 ± 2 °C temperature for 21 min in ultrasonic bath cleaner, and PEF treatment (pulse frequency: 1 kHz, flow rate: 60 mL/min, temperature: 30 ± 2 °C, time: 335 µs, electric field strength 9 kV/cm) was done. In results, the combined (US‐PEF) treatment attained the highest value of minerals and total free amino acids as compared to US or PEF treatment alone. US‐PEF treatment significantly reduced the total plate count (3.83 to 1.97 log CFU/mL), E. coli/Coliform (1.90 to 0.75 log CFU/mL) and yeast and mold (4.23 to 2.22 log CFU/mL). Fourier‐transform infrared spectroscopy (FT‐IR) spectra showed that all nonthermal treatments led to a higher concentration of carbonyl compounds rather generate new carbonyl compounds. US‐PEF treatment significantly reduced the particle size. The rheology of spinach juice was drastically changed by all nonthermal techniques, indicating non‐Newtonian modal accompanied by a decrease of consistency index (K), apparent viscosity (η), and increase of flow behavior (n). Overall, the improved quality of spinach juice shows the suitability of both technologies for industrial applications despite the variations in rheological properties.
Practical Application
Nowadays, nonthermal technologies like US and PEF are being used to enhance the nutritional quality and stability of different fruits and vegetable juices. The current research shows that US‐PEF application can enhance the free amino acids and mineral contents while significantly decrease microbial activities and particle size. The rheology of spinach juice can be dramatically changed, through the reduction of consistency index (K), apparent viscosity (η) and elevation of flow behavior (n). The results of this research proposed that US‐PEF treatment can be a more suitable nonthermal application to enhance the quality of spinach juice at an industrial scale.
The study conducted research aimed at assessing the influence of physical activity on peak expiratory flow (PEF) and the 6-minute walk test (6MTW). The research was carried out at the Department of ...Systemic Rehabilitation - Post Covid at the Pj-Med Rehabilitation Hospital in Popielówek from June 2021 to April 2022.
The inclusion criteria for the studies was a positive PCR test performed up to one year after the end of treatment. Exclusion criteria - active inflammation (CRP <5 or increasing CRP level), acute pulmonary embolism, heart failure with impaired left ventricular ejection fraction (LVEF <35%) without cardioverter-defibrillator protection, unstable disease outside the circulatory system, unstable coronary artery disease, uncontrolled arrhythmias.
The entire rehabilitation program lasted 6 weeks. The beginning of rehabilitation services was on average 4 months after the positive PCR result (min. 1 month and max. 11 months).
A statistically significant difference was observed in the PEF parameter and in the 6MTW test before and after rehabilitation.
Drying as an effective food preservation method, extends the shelf-life of the food and reduces storage, packaging, and transportation costs. Each of the common drying methods imposes limitations on ...the end products' quality and energy efficiency. Novel approaches such as electro-based drying methods have recently emerged to improve the drying process. They can be defined as a drying process in which electrical energy is employed during the pretreatment or during the drying treatment, namely electrohydrodynamic (EHD), pulsed electric field (PEF), ultrasound-assisted, and dielectric drying (microwave and radiofrequency). This review aims to provide an overview regarding the promising common electro-based drying methods used for food and agriculture products. Besides, the mechanism of action and potential applications of electro-based drying methods are discussed. Existing literature data demonstrates that electro-based water removal technologies can enhance drying kinetics without any negative impact on food quality.
•Effects of electric fields, ultrasound, and dielectric assisted drying were addressed.•Electrohydrodynamic has been used successfully in drying of food and agricultural products.•Pulsed electric field and ultrasound could increase drying rate and improve the quality of dried food.•Microwave and radio frequency have a positive impact on final products.
The influence of pulsed electric fields (PEF) pre-treatment at different field strength (E = 1–5 kV/cm) and energy input (WT = 5–10 kJ/kg) on the recovery yield of lycopene in either acetone or ethyl ...lactate from industrial tomato peels residues, was investigated. The rate of lycopene extraction in both solvents decreased with time and was predicted rather satisfactorily (R2 = 0.96–0.99) by the Peleg's model. Micrograph of tomato peels showed that PEF induced size reduction and separation between the plant cells likely due to pore formation and leakage of intracellular matter. Coherently, PEF treatment (5 kV/cm, 5 kJ/kg) significantly enhanced the extraction rate (27–37%), the lycopene yields (12–18%) and the antioxidant power (18.0–18.2%) in either acetone and ethyl lactate extracts, as compared with untreated samples. However, acetone gave the highest lycopene yield. HPLC analyses revealed that all-trans lycopene was the main carotenoid extracted and no degradation/isomerization phenomena occurred. The results obtained in this work suggest that the application of PEF prior to solid-liquid extraction with environmentally friendly solvents could represent a sustainable approach for the valorization of industrial tomato peels residues.
Industrial processing of tomatoes generates large amount of by-products, mainly peels, which represent a cheap and abundant source of natural carotenoids, especially lycopene. The recovery lycopene from tomato peels residues is a crucial step for use in a wide range of industrial applications in food, cosmetic and pharmaceutical sectors as natural pigment and antioxidant. PEF pre-treatment allows to intensify the extractability of lycopene from of tomato processing by-products using environmentally friendly solvents, thus adding new value to the tomato processing chain, improving economic performances and decreasing waste problems.
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•Lycopene extraction kinetic is well fitted by Peleg's model.•Acetone allows to extract lycopene more effectively than by ethyl lactate.•PEF induces size reduction and separation between the plant cells.•PEF pre-treatment intensifies the extractability of lycopene from tomato peels.•All-trans lycopene is the most abundant carotenoid in tomato peels extracts.
Sterilization is one of the most effective food preservation methods. Thermal sterilization technologies have been widely employed in food industry since they are well developed and require low ...investment cost. Demands of consumers for higher quality and fresh tasting products are growing rapidly. Recently, non-conventional sterilization technologies have gained significant attention, since they have the potential to provide products with a better quality, fresh-like taste, and may require lower energy to operate. However, none of these technologies have been commercialized yet. This review addresses the efforts, which have been made in the literature to lower sterilization temperature using combination of thermal and one of the non-thermal processing technologies, such as high pressure, UV, pulsed light, ultrasonic, pulsed electric field, irradiation, and cold plasma.
•This review has shown that interest is growing in the use of alternative sterilization technologies.•PEF, HPP, UV, ultrasound and high pressure homogenization could be used in combination with thermal treatment.•The objective of using these combined treatments is to lower sterilization temperature.•Cold plasma could also be used for in-package sterilization.
Moringa leaves (Moringa oleifera) are a "Superfood" food ingredient rich in protein, phenolics, amino acids, and unsaturated fatty acids that benefit human health. Consumption in fresh form is ...prevalent, but the last decade has been plentiful in dry preparations. Pulse Electric Field (PEF) is one of the important preliminary treatments in drying vegetables and fruits. Electroporation on Moringa leaves is applied to determine the effectiveness and efficiency of drying on the leaves. The study aimed to determine the effect of PEF treatment before drying on the kinetics of drying and the microstructure of Moringa leaves. PEF treatment is carried out at voltages of 1000V, 1500V, 2000V and without PEF as a control. The treatment during drying was observed at the level of moisture content and effective diffusivity on each of the PEF and control treatments. Experimental data were entered into seven mathematical models and evaluated through Lewis, Page, Modified Page, Logarithmic, Two-term, Wang and Singh, and Simple exponential models. The results of the evaluation of the drying model were selected as the best drying mathematical model on the Logarithmic model. The highest diffusivity effective value at PEF with a voltage of 2000V of 3.25 × 10−9 m2/s. In the microstructure changes of Moringa leaves, the preliminary PEF treatment was conducted using the scanning electron microscope (SEM) test. Moringa leaves with pretreatment PEF 2000V color analysis was lightness (L*), redness (a*), yellowness (b*), and ∆E values of 41.74±0.34a, -8.64±0.28c, 20.16±0.94a, 7.08±0.53c. The results of moringa leaves extract with pretreatment PEF 2000V were total phenols and IC50 values of 55.60±1.24d mg GAE/gram and 76.79±0.77a ppm. Implementing PEF preliminary treatment on drying is expected to accelerate the drying process and maintain a decrease in the quality of the final product of Moringa leaves.
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•The principles and applications of PEF in food processing are described in detail.•The challenges of PEF in industrial applications are discussed.•PEF can enhance or assist food ...processing.•PEF can be used alone or in combination with other methods to enhance the process.
With the improvement of living standards, growing consumer demand for high-quality and natural foods has led to the development of new mild processes to enhance or replace conventional thermal and chemical methods for food processing. Pulsed electric fields (PEF) is an emerging and promising non-thermal food processing technology, which is ongoing from laboratory and pilot plant level to the industrial level. Chinese researchers have made tremendous advances in the potential applications of PEF for processing a wide range of food commodities over the last few years, which contributes to the current understanding and development of PEF technology. The objective of this paper is to conduct a systematic review on the achievements of PEF technology used for food processing in China and the corresponding processing principles. Research on the applicability of PEF in food processing suggests that PEF can be used alone or in combination with other methods, not only to inactivate microorganisms and extract active constituents, but also to modify biomacromolecules, enhance chemical reactions and accelerate the aging of fermented foods, which are mainly related to permeabilization of biomembranes, occurrence of electrochemical and electrolytic reactions, polarization and realignment of molecules, and reduction of activation energy of chemical reactions induced by PEF treatments. In addition, some of the most important challenges for the successful implementation of large-scale industrial applications of PEF technology in the food industry are discussed. The results bring out the benefits of both researchers and the industry.
A series of poly(ethylene-co-1,4-cyclohexanedimethylene 2,5-furandicarboxylate)s (PECFs) with different compositions were synthesized from 2,5-Furandicarboxylic acid (FDCA), ...1,4-cyclohexanedimethylene (CHDM) and ethylene glycol (EG). Their chemical structures, composition and sequence distribution were determined by FT-IR, 1H NMR and 13C NMR. The composition of the resulted polyesters could be controlled by the feed mole ratio of CHDM to dimethyl furan-2,5-dicarboxylate (DMFD). And for all the copolyesters, the degree of randomness (R) was close to 1, indicating their randomness. Their thermal and mechanical properties were investigated by Differential Scanning Calorimeter (DSC) and tensile testing, results showed that the crystallizability, tensile modulus and strength of PECFs were decreased with the increasing content of CHDM at first (0–59%), and with the introduction of more CHDM (76–100%) units, they were increased accordingly. However the elongation at break was changed contrarily. The barrier properties study demonstrated that although the O2 and CO2 permeability of PEF was increased by the introduction of CHDM, PECF-32 and PECF-76 still showed excellent barrier properties, which were better or comparable to those of PEN and PEI.
A serials of bio-based polyesters (PECFs) in full composition range were synthesized from CHDM, EG and FDCA. Considering the crystallization ability and toughness as well as O2/CO2 permeability of PECFs, the copolyesters PECF-76 might be the promising substitute for PET in packaging industry. Display omitted
•The composition of copolyesters determined by the feed molar ratio of CHDM to DMFD.•The toughness of PEF could be efficiently improved by the introduction of CHDM units.•The oxygen and carbon dioxide barrier properties of the copolymers were much higher than PET homopolymers.•An expectable method is provided to improve the toughness of PEF without sacrificing its Tg and barrier properties.
Different position isomers of furandicarboxylic acid (FDCA) can be obtained from the biomass by a Henkel disproportionation reaction. 2,5- and 2,4-FDCA are obtained in amounts that are large enough ...to be used for the synthesis of polyethylene furanoate (PEF). The homopolyesters obtained with ethylene glycol (EG) and either 2,5- or 2,4-FDCA have a completely different crystallization behavior, for 2,5-PEF can crystallize whereas 2,4-PEF cannot, even after very long annealing times. The synthesis of random copolyesters with EG and different ratios of 2,5/2,4-FDCA may therefore allow to tune PEF crystallization ability. The partial replacement of 2,5-FDCA by its position isomer could help disrupting crystallinity analogously to what happens when EG is partially replaced by cyclohexane dimethanol (CHDM) in glycol-modified polyethylene terephthalate (PETg). This work investigates the thermal behavior of the homopolyester 2,5-PEF and the microstructural consequences of copolymerization (replacement of small amounts of 2,5-FDCA with 2,4-FDCA). Crystallization is performed in isothermal conditions after cooling down from the molten state, and investigated with both conventional DSC and Fast Scanning Calorimetry (FSC). When the amount of 2,4-FDCA-based repeating units is low (10 and 15 mol %), crystallization still occurs but with an increased induction time. Neither the crystalline nor the rigid amorphous fractions are significantly affected by copolymerization. Due to multiple and complex microstructural reorganizations observed at relatively slow heating rates, conventional DSC is inaccurate and does not provide a reliable microstructural depiction of these polyesters. The use of FSC is recommended, for it allows to obtain a better characterization of the quality and thermal stability of the formed crystals.
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•The presence of 2,4-FDCA in 2,5-FDCA-based copolyesters tunes their crystallization.•Up to 10–15 mol% 2,4-FDCA, crystallization occurs with an increased induction time.•Neither the crystalline nor the rigid amorphous fractions are significantly affected.•FSC is recommended to characterize the quality and thermal stability of the crystals.•Only small values of XRAF were observed, with little (if any) correlation with XC.
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