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The effects of pulsed electric field (PEF) treatment and preliminary vacuum drying (VD) on freezing assisted processes for the potato tissue were studied. The PEF treatment was done at 600 V/cm using the protocol to insure the high level of potato disintegration. The VD was done at sub-atmospheric pressure of p = 0.30 bar. Such conditions allowed relatively fast dehydration accelerated by PEF treatment at low or moderate temperatures inside sample (

International audience; Lactic acid bacteria (LAB) have a long history of applications in the food industry for fermentation and preservation. This feature is due to their metabolic products that can improve the nutritional and sensory characteristics of foods as well as their antimicrobial compounds that contribute to extend the shelf life of food products. Some emerging technologies including pulsed electric fields (PEF), power ultrasound (US), high-pressure processing (HPP), ultraviolet (UV), and microwave (MW) have attracted great attention for their implementation in the food industry as mild processing technologies. They have the advantage of efficiently inactivating the microorganisms, along with maintaining the fresh attributes of the food products. When applied at a sub-lethal level, these technologies present the potential to enhance several processes, such as improved microbial growth and fermentation conditions, as well as modified metabolic properties of LAB. This review covers the characteristics of LAB and their applications in the food industry. It discusses the impacts of emerging technologies on these microorganisms, with a special focus on microbial inactivation, growth stimulation, and improvement of the beneficial features of LAB by emerging technologies.

In this work, steam explosion (STEX), microwave assisted extraction (MAE) and high voltage electrical discharges (HVED) pretreatments have been evaluated for their impact on the physicochemical characteristics of extracted hemicellulosic polymers and on the resulting hemicellulose-based films. Extraction was carried out on spruce sawdust pre-soaked in water (WPS) or 1 M NaOH solution (SPS). The results have shown that STEX pretreatment gave the highest hemicellulose yields (64 and 66 mg g−1 of dry wood from WPS and SPS respectively) followed by MAE and HVED whilst MAE pretreatment produced the highest molecular mass (Mw~66 kDa of arabinoglucoronoxylans from SPS and 56 kDa for galactoglucomannans from WPS). A relatively high acetylation degree was found for STEX WPS (acetylation degree ≈ 0.35) and a high lignin content for STEX SPS (≈12%). Films have been produced by casting using sorbitol as plasticizer. Low oxygen barrier and light transmittance properties were observed for the films obtained from hemicelluloses extracted from SPS due to their high molecular mass and to intermolecular bonding of hemicelluloses and lignin.

An environmentally friendly approach for the reduction of nitrobenzene to aniline promoted by carbonaceous bio-based materials was successfully achieved under subcritical water conditions. The proposed methodology features a metal-free process, no-hydrogen input as reductor, the use of commercial bio-based carbon materials having low cost and availability, and water as green solvent under subcritical conditions. Using optimized conditions, reduction of nitrobenzene in the presence of commercial NORIT GAC 12-40 or DACARB PC1000 was accomplished at 310 °C for 6 h and quantitatively furnished the target aniline. Treatment of NORIT GAC 12-40 with KOH allowed to decrease charcoal loading (6 g vs 40 g) and increase aniline yields (80% vs 66%).

The effects of pulsed electric energy (PEE) on sucrose nucleation in supersaturated aqueous solutions are studied. The supersaturation degree ( S = 1.32) and temperature ( T = 25 °C) were fixed. Pulsed electric field (PEF) treatment without discharge was performed in the chamber with plane-to-plane electrodes geometry using exponential pulses and electric field strength of E = 20–80 kV/cm. High voltage electrical discharge (HVED) treatment was applied in the chamber with rod-to-plane electrodes geometry at E = 20–80 kV/cm. Different number of PEE pulses was applied, n = 1–20. An insignificant reduction of the induction period of nucleation was observed for the PEF treated sample ( n = 10), t ind ≈ 100 min. However, after the HVED treatment ( n = 10) the induction period was only t ind ≈ 55 min. For the HVED assisted nucleation, the time of effective crystallization decreased and a maximum rate of crystallization increased with increasing of E and n . The obtained data evidence promising perspectives for enhancing sucrose crystallization by the HVED treatment.

The aim of this work was to study the effect of steam explosion conditions (severity factor, pH of pre-soaking medium) on the extraction of high molecular weight hemicelluloses from spruce sawdust. The highest yields were obtained at severity factor of 3.65 (47 and 44 mg/g or dry wood in neutral and basic mediums respectively). Treatment at high severity gave lower yield with lower molecular mass. A high extraction selectivity of high molecular weight hemicelluloses was observed as a function of the medium of the impregnation step: after a basic impregnation, ∼90% of extracted hemicelluloses are arabinoglucuronoxylans (∼70 kDa) whereas after a water impregnation ∼85% of galactoglucomannans (∼28 kDa) were recovered. FTIR, HSQC 2D and acetyl content analysis show that the GGM isolated are highly acetylated, with an acetylation rate very closed to the values reported for native AcGGM.

Microwave-assisted extraction (MAE) at atmospheric pressure has been demonstrated as an efficient technology for the extraction of polymeric hemicelluloses from spruce sawdust. This technology was shown to be more efficient than conventional extraction. MAE leads to a high solubilization of wood and a selective extraction of hemicellulose polymers with high molecular weights. To optimize MAE, different treatment powers (125–573 W) of presoaked spruce sawdust in water and 1 M sodium hydroxide solution for a period of 60 min were tested. The yield of hemicellulose extraction increased with the microwave power in both mediums, but with a clear advantage for presoaked samples in basic medium. The characterization of extracted hemicelluloses has shown high extraction selectivity depending on the medium of impregnation of sawdust before MAE: High-molecular-mass acetylated galactoglucomannans (Mw ∼ 41 kDa) were isolated after presoaking in water and higher molecular mass arabinoglucoronoxylans (Mw ∼ 66 kDa) in basic medium.

The effects of pulsed electric fields (PEF) assisted partial dehydration of apple tissue on freezing-thawing processes and texture characteristics were studied. The apple disks were treated to a high level of tissue disintegration (electrical conductivity disintegration index Z was ≈0.98) and then were subjected to osmotic dehydration (OD) in the apple juice-glycerol solutions using different concentrations of glycerol and time of dehydration. PEF-assisted OD resulted in noticeable acceleration of the freezing/thawing processes as compared with those for untreated samples. The main characteristics of freezing-thawing processes (freezing and thawing time and freezing temperature) and texture of samples in dependence on intrinsic moisture content in the sample were evaluated. The differences in these characteristics were explained by the differences in spatial distributions of soluble solids and water inside the samples. For some optimum parameters of osmotic treatments (e.g., at t = 180 min, C ≈ 20 wt. %), the texture after defrosting was comparable to that of fresh apples.

Impact of apple treatment by pulsed electric field (PEF) on vacuum freeze-drying was studied. Apple discs were PEF treated at an electric field strength of E = 800 V/cm for the different values of disintegration index Z . Then vacuum cooling was applied to decrease the temperature to sub-zero level and freeze-drying experiments were done at a pressure of 10 mbar. Time evolution of temperature and moisture content were compared for the PEF treated and untreated apple samples. Acceleration of cooling and drying processes was observed for the PEF treated samples. The microscopic, macroscopic analysis and data of capillary impregnation test evidenced that the PEF treatment facilitates preservation of the shape of the dried samples, allows avoiding shrinking and results in increase of the tissue pores. The sample rehydration capacity strongly depends on Z. At Z = 0.96 a high level of rehydration capacity (≈ 1.3) was observed. Industrial relevance Different methods of food drying are very popular for food processing and are widely used for food preservation. However, they are very energy intensive processes and can cause undesirable changes of colour, flavour, nutrient and textural properties of foods. Vacuum freeze-drying allows obtaining high-quality food products. On the other hand, this process is power consuming, requires long time and low pressure and can provoke the damage of final dried product. Thus, the development of efficient and optimal methodology for freeze-drying of foodstuff is relevant. Application of PEF as a pretreatment procedure may be useful for improving the efficiency of drying and the quality of dried products.

Over the past years, both food researchers and food industry have shown an increased interest in finding techniques that can estimate modifications in quality, nutritional, and thermophysical properties of food products during processing and/or storage. For instance, differential scanning calorimetry (DSC) has attracted the interest of scientific community because only a small amount of sample is needed for analysis. Moreover, it does not require any specific sample preparation, and is a repeatable and reliable method. In addition, DSC methodology needs a short time for experiments compared with other techniques used for the same purpose. At this stage of investigation, there is a need to evaluate the commonly accepted and new emerging DSC applications to establish the optimum conditions of emerging processing. This paper reviews the current and new insights of DSC technique for the estimation of quality, nutritional, and thermophysical properties of food products during conventional and emerging processing and/or subsequent storage. The estimation of different properties in several food matrices after processing and/or storage is also discussed.

s The objective of this study is to improve aqueous solid/liquid extraction of the polyphenols contained in Norway spruce ( Picea abies (L.) Karst.) bark by the use of pulsed electric field (PEF) treatment. The feasibility of PEF treatment was studied through two different PEF protocols with an intensity of E = 20 kV / cm . These two PEF protocols are applied at different initial humidity of the bark samples (14% and 21%). PEF treatments protocols were compared to untreated samples (simple diffusion without PEF) and to a diffusion from sawdust of Norway spruce bark. The main parameters for the follow-up of the diffusion kinetics and characterization of extracts were studied: moisture content, pH, electrical conductivity, polyphenols concentration and antioxidant activity. The results of this study showed the positive effect of the pulsed electric fields on intracellular compounds extraction. The PEF treatment enhanced extraction of total phenolic content and antioxidant activity. Indeed, the total phenols content has increased of more than 8 times with the use of PEF treatment. The kinetics of pH and electrical conductivity during treatment were studied. The solid fraction was analyzed and the results showed that PEF treatment does not affect the structure of wood and that there are no modifications of the chemical functions by exposing the samples to PEF treatment.

Inulin constitutes an important food ingredient, widely used for its fiber content, and its ability to substitute fat and sugar ingredients. Traditionally, industrial inulin production from chicory roots requires high extraction temperature (70–80 °C) and long extraction time (1–2 h). This conventional extraction is generally accompanied with the presence of a large amount of impurities in the extracted juice, mainly due to the application of high temperature, requiring thus further purification steps. To overcome these issues, developing novel extraction technologies, consuming less energy, faster, and providing high yield and purity, is of paramount importance to meet the requirements of a green extraction concept. In this review, the feasibility of using conventional and new promising technologies (enzyme assisted extraction, ultrasounds, microwaves, supercritical fluid extraction, and pulsed electric fields) to recover inulin from plant food materials and by-products from an environmental and economical point of view will be discussed. Industrial relevance Inulin is widely used in food industries mainly due to its ability to substitute fat and sugar ingredients. However, the current industrial recovery process of this molecule is mainly carried out by diffusion in hot water (70–80 °C), followed by a relatively complex purification process, due to the presence of a large amount of impurities generated by the application of high temperatures. The need for obtaining greener, sustainable, and viable processes has led food scientists to develop new processes in full correspondence with the green extraction concept based on the use of non-conventional technologies (i.e. pulsed electric fields, ultrasounds, microwaves, etc). The submitted review discusses the potential of some of these new promising technologies to allow the industrial sustainability and green recovery of inulin, which have as benefits: energy- and time-saving along with higher yields and milder temperatures, reducing thus the subsequent purification steps.

The impact of apple pretreatment by pulsed electric field (PEF) on juice extraction using the freezing-assisted pressing was studied. Apple discs were PEF pretreated at electric field strength of E = 800 V/cm and then air blast frozen inside the freezer (− 40 °C). Then, pressing experiments in a laboratory-pressing chamber (2–5 bars) were started at sub-zero temperature (− 5 °C). Time evolution of juice yield and its nutritional qualities were compared for PEF and untreated apple samples. High improvements of juice yield were obtained for freeze-thawed (FT) and PEF + FT samples. The combination of PEF + pressing (5 bar) at sub-zero temperature gave optimum results for juice extraction with high levels of carbohydrates, and antioxidant bioactive compounds. At fixed value of extraction yield, Y , PEF pretreatment improved nutritional parameters. E.g., at Y = 0.6, an increase in °Brix (by ≈ 1.27), carbohydrates (by ≈ 1.42), total phenolic compounds (by ≈ 1.16), flavonoids (by ≈ 1.09) and antioxidant capacity (by ≈ 1.29) was observed after PEF pretreatment. Industrial relevance Pressing constitutes one of the most commonly used technologies at industrial scale to obtain fruit juices. However, during the pressing some undesirable chemical, physical and biological changes may occur in juices, thus reducing their nutritional and sensorial properties. For instance, the use of freezing-assisted pressing is a promising technique for the production of juice concentrates rich in sugars and other solids as the low temperature operation prevents undesirable modifications. But this method is rather expensive and requires strong control of the quality of “ice” juices, their sensory and compositional profiles. Thus, there is an increased search for obtaining new efficient methodologies for producing high quality juices. In this line, PEF-assisted pressing has been shown as a useful technology to increase juice yield. Therefore, the combination of PEF-assisted “ice” juice extraction by pressing of fruits at subzero temperatures may be a useful tool to improve the extraction yield of juices, thus improving their nutritional, physicochemical and sensorial properties. Keywords: “Ice” juice, Apple, Pulsed electric fields, Freezing-assisted pressing

This work aimed to separate proteins and polyphenols from rapeseed stem extracts. The results showed that coagulation with 40% w/w ethanol and ultra-filtration with 10 kDa membrane were two efficient methods for polyphenols purification. The purity of polyphenols increased from 80.3% to 97.0% after separation. The combination of ethanol coagulation with ultrafiltration permitted decreased the ethanol consumption from 40% to 10% w/w while maintaining high polyphenols purity. Significant protein loss at room temperature was observed during the stability test, which emphasizes the importance of elaborating a fast and effective separation method for rapeseed stem extracts.

This work presents a new efficient process for sugar beet sucrose extraction by tuning experimental conditions. Sliced beets were first treated by PEF at E = 600 V cm −1 and t PEF = 10 ms. Electroporated slices were then pressed and the obtained press cake was finally introduced in a pilot diffuser (10 kg/h) to extract the residual sucrose. Results showed that cold PEF treatment followed by rapid pressing permitted expression 50% of undiluted juice (Brix ≈ 21.2%). Sucrose extraction from pressed slices with reduced draft (80–100%) allowed substantial water and energy savings for the extraction step. Experiments revealed that slices were better exhausted by the new extraction process which permitted to reduce the sucrose loss in pulp from 1.2% to 0.8%. Moreover, the obtained juice was more concentrated in sucrose, less colored (7000 vs. 10,000 IU) and purer (92.8% vs. 91.8%) than that conventionally extracted by diffusion.

The objective of this study was to investigate the effects of pulsed electric field (PEF) pretreatment on the valorization of extractives (proteins and polyphenols) from rapeseed green biomass (stems) by pressing. The effect of pressure, electric field strength and pulse number on the juice expression yield, total polyphenols and total proteins content in the expressed juices were studied. Experiments conducted under optimal conditions (E = 8 kV/cm, tPEF = 2 ms, P = 10 bar) permitted to increase the juice expressed yield from 34% to 81%. Significant increases in total polyphenols content (0.48 vs. 0.10 g GAE/100g DM), in total proteins content (0.14 vs. 0.07 g BSA/100g DM) and in consolidation coefficient (9.0 × 10(-8) vs. 2.2 × 10(-8)m(2)/s) were also observed after PEF pretreatment. The recovered press cake was well dehydrated with an increase of dry matter content from 8.8% to 53.0%.

Box–Behnken response surface methodology was used to investigate and optimize microwave assisted extraction (MAE) (treatment power and time) of antioxidant compounds, especially polyphenols, from bark extracts. Moreover, the effects of solvent composition (methanol and ethanol) particle size, and pH conditions were evaluated and optimized. In addition, the effects of MAE were compared to conventional solvent extraction at room temperature and reflux extraction (at 100 °C). The results indicated that all process variables had a significant effect on polyphenol and antioxidant recovery, except for methanol (p > 0.05). For instance, TPC and antioxidant activity were increased when higher power and longer treatment time were used. Optimum MAE conditions were obtained with a particle size 0.5 × 1 × 0.3 cm3, energy (power 45 W and irradiation time 60 min), pH 10.75, 33% of ethanol and 0.38% of methanol. Verification of predictive model showed that the model was suitable for the optimization of phenolic compounds from bark. Under optimized conditions, extraction efficiencies were increased by 3 times and 2 times respectively for total phenolic content and antioxidant recoveries, as compared to conventional methods that use the same parameters but without MAE. Moreover, the determination of phenolic profile was performed by LC–MS. The LC analysis results showed that MAE increased the content of (+)-catechin, (−)-epicatechin, (−)-epigallocatechin, syringic acid, p-coumaric acid, sinapic acid and naringenin compared to control extraction sample at the equivalent diffusion time conditions and temperature.

Rotating disk module (RDM)-assisted cross-flow ultrafiltration of sugar beet juice, obtained by cold pulsed electric field-assisted pressing, was studied in full recycling and concentration modes. Results of trans-membrane pressure (TMP) stepping tests with 10- and 50-kDa membranes showed that filtration flux increased with rotation speed and TMP until 1000 rpm and 4 bar. A slight variation of filtration purity was observed for a rotation speed range of 0–2500 rpm. A TMP increase resulted in purity reduction due to the formation of thicker fouling layer. A full recycling test study with a 10-kDa membrane confirmed the influence of TMP and rotation speed on filtration flux. A rotation speed of 1000 rpm and a TMP of 4 bar were selected for sugar beet juice purification, by concentrating juice from 13 to 1 L. The results of concentration mode tests revealed that, with a 10-kDa membrane, the filtrate purity could reach 95.6 ± 0.5 %, which was comparable to the purity of sugar beet juice purified by conventional liming-carbonation method. The flux decline in cross-flow filtration was still important, justifying more effective anti-fouling technologies investigation.

This work aims at investigating the effects of pulsed electric field (PEF) on the extraction of polyphenols and proteins from rapeseed ( Brassica napus L.) stems and leaves. The PEF (0.2–20 kV/cm) was applied on fresh rapeseed stems (diameter, d = 6 mm; thickness, h = 10 mm) and leaves (surface, S = 10 × 10 mm 2 ). The PEF-induced cell membrane damage ( Z ) of rapeseed tissue was studied. The PEF (5–20 kV/cm) increased the extraction of total polyphenols from rapeseed stems and leaves. Treatment at 5 kV/cm resulted in the highest polyphenols purity. In addition, the data evidence that the polyphenols content in rapeseed stems and leaves decreased (≈74%) as plant maturity advanced while the change for protein content is more gentle (≈35.6% decrease). Results of the maturation effect may be useful to determine the optimum harvest time for the rapeseed by-products valorization.

The effects of pulsed electric fields (PEF) and osmotic impregnation in glycerol solution on the amount of unfreezable water in apple were determined by means of low-temperature differential scanning calorimetry (DSC). The obtained data were compared with behaviour of pure water–glycerol solutions (sample WG). PEF treatment was applied using a near-rectangular monopolar generator with pulse duration of 100 μs at electric field strength of 800 V/cm. The osmotic impregnation of PEF-treated apple discs was done using water–glycerol (sample AWG) and apple juice–glycerol (sample AJG) osmotic solutions at different concentration of water or juice in glycerol, W = 30–100 wt%. The data evidenced that for the PEF-treated samples the glycerol was able to penetrate successfully inside apple tissue. The state diagrams for WG, AWG and AJG samples were rather similar. It was observed that free water existed only for moisture content above some minimum value. The unfreezable water content was the largest in AJG, followed by WG and AWG. The juice concentration in glycerol W ≈ 80 wt% was found to be optimal for preservation of the texture of PEF-treated samples.

This work discusses the effects of pulsed electric field (PEF) and preheating on the lime purification of raw sugar beet expressed juices. The PEF pre-treatment was applied to sugar beet cossettes before their pressing at 20 °C with the PEF strength and duration of respectively E = 600 V/cm and t PEF = 10 ms. Alternatively, cossettes were preheated at 80 °C for 10 min before pressing to produce the thermal juice. A lime-carbonation process was applied for the purification of raw expressed juices. The influences of lime quantity (varied from 0 to 15 kg/m 3 ) on the filterability and the quality of juices were investigated. It was shown that the filtration kinetics of cold PEF juice is faster than that of thermal juice leading to lower values of filtration coefficient F k and specific filter cake resistance α . Analysis showed that thin juices obtained after purification of PEF juices presents better qualitative characteristics than those obtained from thermal expressed juices. For instance, at the optimal lime quantity (10 kg/m 3 ), the purified PEF juice was less coloured (540 vs. 1360 IU), less turbid and had less proteins and colloids leading to a higher juice purity (0.961 vs. 0.945) comparatively to the purified thermal juice.

This work discusses the effects of pulsed electric field (PEF), ohmic heating (OH), and osmotic (O) treatments on the structure of apple tissue and its freezing/thawing behaviour. Apple discs were treated at electric field strength E = 800 V/cm (PEF, isothermal regime) and E = 40 V/cm (OH, non-isothermal regime) to a high level of tissue disintegration (conductivity disintegration index Z was ≈ 0.98) and then were subjected to osmotic (O) treatment in the aqueous solution of glycerol (20 wt.%). The distribution of osmotic solution was practically homogeneous inside the disc of PEF-treated tissue and highly inhomogeneous in untreated and OH-treated samples. The freezing–thawing (FT) experiments (+ 20 °C → − 40 °C → + 20 °C) were done in order to reveal the effects of combined modes of treatment on the structure of apple tissue. The most pronounced reducing of both freezing and thawing times and strengthening of the apple texture were observed for PEF treatment. Industrial relevance Freezing-assisted preservation of plant materials in the most natural-looking state with near-original texture and colours requires thorough optimization of freezing operation. In this study, the research of the impact of pulsed electrotechnologies combined with osmotic pre-treatment on the structure of apple tissue, its freezing/thawing behaviour and texture quality, is provided.

Damage of chicory tissue by combined electroporation and ohmic heating is studied for better solute extraction. Moderate (400–1000 V/cm) and high (10,000 V/cm) PEF treatments were applied varying pause duration between the trains of individual pulses. Ohmic heating was induced with increase of the number of trains N . Temperature dependence of tissue damage degree Z is evaluated for the different PEF intensities. With higher ohmic heating, chicory tissue is faster and better damaged. Electric field strengths of 600–800 V/cm combined with ohmic heating permit to enhance noticeably the solute extraction from chicory tissue. The solute diffusivity D for the different PEF treatments, is nearly the same for same values of Z . Chicory tissue treated to the same damage degree ( Z = 0.8–1.0) using different PEF conditions (800, 1000 and 10,000 V/cm) has nearly the same diffusivity. Combined electroporation/ohmic heating pretreatment by moderate PEF (400–1000 V/cm) presents an interesting alterative for the treatment of high product throughputs (e.g. in the case of inulin production from chicory).

Membrane dead-end ultrafiltration of sugar beet juice (obtained from pulsed electric field assisted nonthermal pressing) was studied as an alternative method to the conventional liming-carbonation purification. A dead-end filtration module, Amicon 8200, was first used to investigate the purification efficiency of ultrafiltration with various polyethersulfone membranes (10 kDa, 50 kDa, and 150 kDa). The purity of sugar beet juice was increased from 93.6 ± 0.5 to 96.4 ± 0.8 % with a 10-kDa membrane. In order to improve the filtration flux, which declined tremendously during dead-end filtration due to membrane fouling, a rotating disk module (RDM) was then applied, and the investigation of the dynamic filtration behavior and filtrate quality of sugar beet juice was carried out. Compared with Amicon stirred module, the RDM had a much higher permeate flux and filtrate purity. The effect of rotating speed and molecular weight cutoff (MWCO) of membranes were studied. The permeate flux increased with rotating speed and pore size of membrane. The permeate flux increased significantly when the rotating speed was raised from 500 to 1,000 rpm, while it slightly increased at higher rotating speed (2,000 rpm). The purification efficiency of dynamic RDM filtration was about twice than that of filtration performed with Amicon stirring module.

This work discusses efficiency of pulsed electric field (PEF) treatment of cellular material with time-variable electric field strength, E. The potato was selected as a model tissue. Computer model, based on electroporation theory, was developed to simulate different strategies of E value changes. In the experimental part of this work, the PEF treatment was applied to disk-shaped and sliced samples using a laboratory compression chamber, equipped with a PEF-treatment system. The experiments were done using PEF generator that provided pulses of near-rectangular shape, the pulse duration was ti = 1000 μs, the value of E was varied within 200 and 800 V/cm, and the total time of PEF treatment, tPEF, was varied within 0 and 0.1 s. The electrical conductivity disintegration index, Z, was used for characterization of the PEF-induced damage of potato tissue. Both theory and experiment predicted the minimum power consumption Wo at the optimal value of Eo ≈ 400 V/cm. The computer simulation predicted that application of protocols with time-variable electric fields would allow optimization of PEF treatment with initial electric field Ei deviating from the optimal value Eo. PEF experiments revealed that exponential increase of E values can be useful at small initial electric field strengths, E < Eo, as far as it allows significant improvement of PEF-treatment efficiency. The PEF experiments with pressing of potato slices have shown that PEF treatment before pressing was more efficient than treatment during the pressing, and the specific energy consumption for the both samples was approximately the same (W ≈ 7.5 kJ/kg).

Inulin was extracted by pulsed electric fields (PEFs) assisted diffusion. Rotating disk module (RDM) assisted dead-end filtration of chicory juice was studied. Filtration behavior, flux decline and fouling coefficient of RDM assisted filtration were investigated and compared with the performance of previously used normal stirred filtration unit. Response surface methodology (RSM), based on a three levels and two variable central composite rotatable design (CCRD), was employed to obtain the best possible combination of trans-membrane pressure (TMP) (X1: 2–6 bar), shear rate (X2: 12,000–102,000 s−1) for maximum average flux and minimum specific energy consumption. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression and were also analyzed by variance analysis (ANOVA). The 3-D response surface and contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimum filtration conditions were: a TMP of 3.34 bars, and a shear rate of 102,000 s−1. Under these conditions, the experimental average flux and specific energy were 154 L/m2 h and 169 kwh/m3, respectively, which were in close agreement with the values predicted by the model. Results of this work may contribute to increase chicory juice filtration for inulin purification.

The aim of this work is to extract hemicelluloses polymers from spruce sawdust using High Voltage Electrical Discharges (HVED) pretreatment. HVED pretreatment was carried out in order to improve deconstruction of the wood matrix and to allow easier release of high molecular mass hemicelluloses. The results revealed the advantage of HVED activation step in the process of extraction. The yield of hemicellulose extraction increased with HVED treatment time. In fact, after 4 ms of HVED treatment time in 1 M NaOH solution, the yield obtained was higher as compared to the untreated sample (19 mg/g of dry matter and 15.8 mg/g of dry matter respectively). The molecular weights of extracted hemicelluloses are very high (55 kDa and 47 kDa for 4 ms of HVED-treatment in 1 M NaOH solution and water respectively). The use of different mediums of extraction with HVED pretreatment have revealed a selective solubilization of spruce hemicelluloses.

Membrane fouling and flux decline are important problems in chicory juice clarification by membrane process for inulin production. In this study, a rotating disk module (RDM) equipped with four micro- and ultra-filtration membranes was used to treat raw chicory root extract, and the permeate flux behavior at high-shear conditions was investigated. Increasing disk rotating speed can reduce concentration polarization and cake fouling, and thus improve permeate flux. However, a moderate rotating speed of 1000 rpm was a good compromise between energy saving and polarization/cake layers control, while a higher disk rotating speed can be used at regular intervals for on-line membrane cleaning. Threshold and limiting fluxes were determined in chicory juice clarification at 1000 rpm and 50 °C by pressure stepping experiments, and they were almost independent of pore size, permeability and fouling extent, with ranges of 130–140 L m−2 h−1 for threshold and 155–168 L m−2 h−1 for limiting flux. Below threshold flux, filtration resistance is independent of flux, while above it, membrane fouling increases with increasing permeate flux. This work confirmed that threshold flux criterion was also applicable to high-shear microfiltration and ultrafiltration, and size-dependent shear-induced and Brownian back diffusions played an important role in such filtration resistance transition. Moreover, both limiting flux and flux fluctuations should be avoided in practical applications because they cause high fouling and flux decline.

Alternative process of sugar beet transformation is investigated by tuning experimental conditions. A three-step process has been set-up: (1) sugar beet cossettes pretreatment by pulsed electric field (PEF) and (or) short preheating to different temperatures; (2) extraction of juice from pre-treated cossettes by pressing; and (3) purification of the expressed juice by ultrafiltration. The PEF treatment was applied to cold (10 °C) and preheated (to 20, 50, 60, 70, and 80 °C) sugar beet cossettes with intensity of E = 600 V cm−1 using rectangular monopolar pulses of 100 μs during tPEF = 5–20 ms. Experiments were performed with cossettes of three sizes. Control experiments were done without PEF treatment using cold (10 °C) and preheated (to 20–80 °C) cossettes. PEF-treated and (or) preheated cossettes were pressed at 5 bars during 15 min. Afterward, expressed juices obtained from the PEF-treated cossettes at 20 °C and from the untreated ones at 80 °C were purified by dead-end ultrafiltration with stirring (500 rpm) at the temperature of 20 °C by using polyethersulfone membrane with MWCO of 30 kDa. Application of PEF (E = 600 V cm−1, tPEF = 10 ms, T = 20 °C) with following pressing of cossettes at 5 bars during 15 min permits to obtain the juice yield Y = 66,5 %, which is equivalent to that obtained from cossettes preheated to 80 °C and untreated electrically (Y = 64 %). The energy consumption of cold PEF treatment (≈2–3 Wh/kg) is very attractive as compared to preheating at high temperatures (≈138–194 Wh/kg). Combination of thermal and electrical pretreatments leads to additional softening of sugar beet tissue and to a slightly higher (on 5–10 %) juice yield, but the electroporation of preheated cossettes is more energetically costly. The raw juice expressed from PEF-treated cossettes at 20 °C has higher purity (93.5 %) than juices expressed at 50 °C (92.9 %) and at 80 °C (92.3 %). The temperature increasing from 20 to 80 °C results in a higher juice coloration (5680 IU at 20 °C and 7820 IU at 80 °C) and leads to a higher (on about 35 %) colloids concentration in the expressed juice. The filtrate obtained from the juice expressed at 20 °C with PEF treatment has a higher purity (96 %) than the filtrate obtained from the juice expressed at 80 °C (95.3 %) and its coloration is considerably lower (330 IU versus 1930 IU). In addition, the quantity of proteins and colloids in the filtrate of juice expressed at 20 °C is lower than that in the filtrate of juice expressed at 80 °C

Qualitative characteristics and dead-end ultrafiltration behavior of chicory juice obtained at different temperatures from untreated and pulsed electric field (PEF) treated chicory roots are investigated. The chicory juices obtained at lower temperatures (30 and 60 °C) from PEF treated chicories are less colorized, have lower turbidity, lower protein content, and higher purity than conventional juice obtained at 80 °C. The ultrafiltration behavior of the untreated and PEF treated chicory juice was studied in the dead-end filter cell under different pressures (1, 2 and 4 bars) and with stirring at 500 rpm. Three types of polyethersulfone membranes with MWCO of 150, 50 and 5 kDa were used. The membrane with MWCO of 50 kDa produced the most purified filtrate, while the membrane with lower MWCO (5 kDa) produced less purified filtrate probably due to the partial retention of inulin molecules. The increase of TMP from 1 to 2 bars increased the filtration flux and the juice purity. The ultrafiltration behavior of obtained chicory juices was successfully described by the filtration model with intermediate blocking mechanism.

This work discusses the effects of pulsed electric field (PEF) (electric field strength, E , 100–1000 V; pulse duration, t p , 100 μs) on disintegration of potato slices treated between parallel plate electrodes by using a laboratory compression chamber equipped with a PEF-treatment system. The apparent density of slices (bed of particles), ρ , was varied within 0.313 g/cm 3 and 1 g/cm 3 . The electrical conductivity σ ( ρ ) of the packing of slices versus volume fraction of particles ϕ was approximated by the percolation law σ ∝ ( φ − φ c ) t , where ϕ c ≈ 0.290, t = t i ≈ 0.46 and t = t d ≈ 1.39 for the intact and completely damaged tissues, respectively. The impact of electric field strength and apparent density of slices on PEF-induced damage kinetics was studied. The more accelerated kinetics of damage was observed for more dense packing of slices. The approximated relation between the applied, E , and effective, E e , electric field strengths accounting for the σ ( ρ ) dependence was derived. Industrial relevance The practical applications of PEF treatment (e.g., pressing, drying, extraction, etc.) demand operations with slices of food particles. In this study, research towards the electroporation efficiency of PEF applied to the porous packing of sliced food particles is provided.

Clarification is the first step of inulin production from chicory juice, and membrane filtration as an alter- native can greatly simplify this process, increase juice yield, improve product quality, and reduce the cost and waste volume. In this study, a rotating disk module (RDM) was used to investigate the clarification of chicory juice by four micro- and ultrafiltration membranes. Compared with dead end filtration, the RDM had a much higher permeate flux and product quality. High rotating speeds produced high permeate fluxes and reduced flux decline, because of the strong back transport of foulant from fouling layer to feed solution. At high rotating speeds of 1500-2000 rpm, the permeate flux increased with membrane pore size and transmembrane pressure (TMP), while at low rotating speeds (

The expression behaviour of a sugar beet tissue pre-treated thermally (at 50 and 70 °C) and electrically (by pulsed electric fields applied at 20 °C and after preheating at 50 and 70 °C) was studied at constant pressure (5 bar). The filtration–consolidation behaviour of slices’ assemblies (press-cake of sugar beet slices) was studied and compared to that of disk sample. The application of a pulsed electric field (PEF) treatment (600 V cm −1 during 10 ms) induces the electroporation of cell membranes and facilitates the expression process. It was demonstrated that after treatment of sugar beet tissue by heat (at 70 °C), PEF, and combined (heat and PEF) pre-treatments, the solid–liquid expression followed the filtration–consolidation behaviour for both disk sample and slices’. The computational semi-empirical model employed in this paper allows the determination of the consolidation coefficient, which characterizes filtration diffusivity. Adjustment of experimental and model data showed that the filtration–consolidation behaviour of the disk sample was similar to that of slices’ assemblies. Model adjustment showed that experimental data reasonably well coincide with the model, which permits a good prediction of the compression behaviour of thermally and electrically treated tissue and press-cake.

Summary A pilot study for the pulsed electric fields (PEF) assisted countercurrent diffusion of inulin from chicory roots is presented. The influence of PEF parameters (electric field intensity E = 600 V cm−1, treatment duration tPEF = 10–50 ms) and diffusion temperature (varied between 30 and 80 °C) on soluble matter extraction kinetics, inulin content of juice, and pulp exhaustion are investigated. The draft (liquid to solid mass ratio) was fixed at 140%, similar to the industrial conditions. PEF treatment facilitates extraction of inulin at conventional diffusion temperature (70–80 °C), and diffusion temperature can even be reduced by 10–15 °C with comparable juice inulin concentration. Less energy consumption can be achieved by reducing PEF treatment duration to 10 ms, which is observed sufficient for effective extraction.

This study describes experiments on pulsed electric field (PEF)-assisted water extraction of sugar from sugar beet using a pilot countercurrent extractor with 14 extraction sections. Cossettes were prepared from sugar beet by industrial knives and PEF treatment of the cossettes was done with electric field strength E varied between 100 and 600 V/cm. The total time of PEF treatment was t PEF = 50 ms. The effects of the main extraction parameters (temperature of extracting water and draft) on the extraction kinetics, as well as on the juice and cossette (pulp) characteristics, were investigated. The temperature of extraction from PEF-treated cossettes was varied from 30 to 70 °C; the draft was varied from 120 to 90%. The principal possibility of cold (at 30 °C) and moderate thermal (50–60 °C) extraction of sucrose from sugar beet cossettes treated by PEF was confirmed on the pilot countercurrent extractor. The purity of the juice obtained by cold and moderate thermal extraction was not lower than the purity of juice obtained by conventional hot water diffusion at 70 °C. The sugar beet pulp can be well exhausted by cold or mild thermal extraction of cossettes treated by PEF. Decrease of draft to 100–90% permitted increasing of the extracted juice concentration, but the cossettes were worse exhausted. The pulp obtained by cold extraction of PEF-treated cossettes had dryness >30%, which was noticeably higher than dryness of the pulp obtained by conventional hot water extraction technique.

The steam gasification kinetics of wood char is studied. First, the kinetic expression of wood char gasification is derived (kinetically controlled). The modelling, uses the random pore model, has been experimentally validated. The char gasification study is performed in a tubular kiln, at various temperatures (850 °C, 900 °C, 950 °C and 1000 °C) and vapour pressures (0.2 bar, 0.5 bar and 0.7 bar). The steam gasification kinetics parameters (activation energy…), together with the physical properties of the char (porosity, specific surface…) are experimentally determined. By performing experiments with different particle sizes, steam flow rates and initial sample weights, the experimental conditions which permit the minimization of the steam penetration limitation, are found. Secondly, a 1D isothermal and non-equimolar reaction-diffusion model is developed in order to assess the diffusional effects taking place during steam gasification in a fixed bed. The model takes into account local chemical reaction rate and effective transport properties dependant on time and position within the char bed. Inter particle diffusion and structural changes of the char bed during the gasification are taken into account. The model shows a good agreement with the experimental results, obtained at various bed heights, and point out the relevant role played by diffusional effects within a fixed bed reactor. Finally, the kinetic results are used to estimate, in a down draft gasifier, the total carbon yield conversion as a function of both the mass fraction of stagnant zones within the bed char and of the characteristic length of these stagnant zones.

Gasification is an attractive technology for waste thermal treatment. The successful design and modelling of a gasifier requires reliable kinetic data. The purpose of this work is to study the steam gasification kinetics of chars produced by municipal wastes pyrolysis. The municipal solid wastes (MSW) are modelled as a mixture of four organic constituents: paper, wood, plastics, and vegetables. The various char samples are obtained by pyrolysis of each waste constituent, in a fixed bed reactor at 1000°C, in order to minimize their volatile content and thus, to eliminate any subsequent devolatilization of the carbonaceous residues. These chars are used as raw materials in steam gasification experiments. The gasification studies are performed on each char separately, in a tubular kiln at various temperatures (900°C, 950°C and 1000°C) and various vapour pressures (0.2 bar, 0.5 bar and 0.7 bar). The gases produced are analysed by gas chromatography in order to determine the gasification kinetics. The kinetics parameters, with respect to H2O, together with the influence of the char's physical properties are experimentally determined. A kinetic expression for the gasification reaction, based on the random pore model is deduced. It is shown that the char resulting from the pyrolysis of MSW constituents, essentially paper, wood and vegetables have the same gasification kinetics. On the contrary, the plastic char steam gasification kinetic appears to be significantly slower.

The objective of this study was to investigate the effects of ultrasound-enhanced aqueous extraction on the valorization of polyphenols and proteins from rapeseed green biomass. Two types of biomass were studied: mature rapeseed stems collected around the time of seed harvest, and immature rapeseed stems used as a cover crop. Response Surface Methodology (RSM) was employed for obtaining optimal extraction conditions: ultrasound power of 400 W, treatment time of 50 min, sample length of 0.5 cm and agitation speed of 250 rpm. Compared to mature rapeseed stems, immature rapeseed stems require shorter treatment time (30 vs. 50 min), and exhibit higher extraction yield of polyphenols (100 vs. 86%) and proteins (18 vs. 11%) due to their less fibrous structures. These promising findings are opening doors to a potential market for rapeseed stems as a renewable biomass.