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The current state of the study of different liquid crystalline (LC) systems doped with carbon nanotubes (CNTs) is discussed. An attempt is endeavored to outline the state-of-the-art technology that has emerged after two past decades. Systematization and analysis are presented for the integration of single- and multi-walled carbon nanotubes in thermotropic (nematic, smectic, cholesteric, ferroelectric, etc.) and lyotropic LCs. Special attention is paid to the effects of alignment and supramolecular organization resulting from orientational coupling between CNTs and the LC matrix. The effects of the specific inter-molecular and inter-particle interactions and intriguing microstructural, electromagnetic, percolation, optical, and electro-optical properties are also discussed.

Typically, the carrot tissues have rather high initial moisture content and low porosity. Expression of juice from such tissue may be rather complicated and include different stages. In this work, a simple creep tests with carrot tissue treated by pulsed electric fields (PEF) were performed. The samples were compressed for 15 min in a special jig using a constant load of F = 0.5 kg (initial pressure p0 = 1.89 bar) or 1 kg (initial pressure p0 = 3.78 bar). PEF treatment was done using electric field strength E = 0, 483, 838, and 1037 V/cm and pulse duration of ti = 10 ms to different levels of tissue disintegration Z. Effect of PEF on volumetric shrinkage V* and Poisson ‘s ratio μ of have been evaluated for the first time. Different stages were observed for time behavior of V* and μ. From time evolution of V* presence of the primary (initial) and final (secondary) creep relaxation processes was suggested. It was demonstrated that the damage of cells induced by PEF resulted in redistribution between contributions of primary and secondary stages. The time evolutions of Poisson ratio’s was described by first order kinetic equation. It was shown that PEF treatment decreased the value of Poisson ratio’s. Significant effects of PEF treatment on volumetric shrinkage and Poisson ‘s ratio were not accompanied with large changes in moisture content inside the carrot tissues.

The pulsed electric field (PEF) assisted extraction of bio-compounds (soluble solids concentration, °Brix, and total polyphenol content, TPC) from apple peels was studied. The aqueous suspensions of apple peels were treated by PEF with different intensities, E (480–1200 V/cm), and different treatment times, tPEF (0–2 s). The cell disintegration was analyzed using measurement of electrical conductivity (disintegration index, Zc) and microstructure evaluation by confocal laser scanning microscopy (microscopic cell disintegration index, Zd). The near linear Zc (Zd) dependencies were obtained for PEF treatment protocols with different treatment time, tPEF, and electric field intensity, E. The °Brix and TPC extraction efficiencies were dependent upon applied value of E. For example, at the highest PEF intensity, E = 1200 V/cm, and Zc ≈ 1, the enhancements in values of °Brix and TPC were approximately the same ≈3.15. However, at lower PEF intensities (480, 600 and 800 V/cm) and the fixed value of Zc the extraction of soluble matter was more effective compared to TPC. Therefore, the extraction efficiency of different bio-molecules is not only affected by the level of tissue disintegration (by value of Zc). The other details of PEF protocols (e.g., value of E) may be also important.

Background Nowadays, electron spin resonance (ESR) is widely used as a powerful, non-destructive and very sensitive technique for the detection of free radicals in food systems. It can be applied for the direct identification of highly reactive oxygen species, organic and inorganic paramagnetic species and screening of food for potential toxicity. Its applications cover investigating food oxidative stability and properties of irradiated foods including fruits and vegetables, meats and fishes, spices, cereal grains, and oil seeds. Scope and approach This review aims at providing specialists in food science and industry with the fundamentals of ESR spectroscopy, typical radicals present in foods and their sources, ESR modalities, and detailed account for the use of the technology for evaluation of the physicochemical and nutritional properties of foods. Examples illustrating ESR applications for the evaluation of the effects of innovative and emerging technologies (ionizing radiation, high pressures, pulsed electric fields, cold plasma and ultrasonication) are discussed. Key findings and conclusions ESR can be used for the identification/quantification of free radicals in foods, for spin-label oximetry, estimation of free radical scavenging, food stability, and chelating activity, with particular interest for food processed using innovative technologies, with the main advantages of its high sensitivity, specificity, and low amounts of sample needed and nowadays many types of ESR instruments are commercially available. However, due to the different nature of foods, the development of novel ESR techniques and methods of analysis specially designed to study foods is of great interest in the future.

The aqueous suspensions of Laponite RD (Lap) platelets demonstrate rich phase diagrams. Both poly(ethylene oxide) (PEO) and cetyltrimethylammonium bromide (CTAB) molecules competitively adsorb on the surface of Lap, and strong interactions between PEO and CTAB exist. The stability of ternary systems Lap + PEO + CTAB can be finely regulated by changing the balance of these interactions. The electrokinetic technique was used to study 0.065 and 2% wt Lap suspensions in the presence of different amounts of PEO of various molecular masses

The effects of acid activation of Laponite RD (Lap) on the structure and properties of activated Lap nanoparticles (aLap) and the properties of polyNIPAA

The freshwater microalga Haematococcus pluvialis is well known as the cell factory for natural astaxanthin, which composes up to 4–7% of its total dry weight. The bioaccumulation of astaxanthin in H. pluvialis cysts seems to be a very complex process that depends on different stress conditions during its cultivation. The red cysts of H. pluvialis develop thick and rigid cell walls under stress growing conditions. Thus, the biomolecule extraction requires general cell disruption technologies to reach a high recovery rate. This short review provides an analysis of the different steps in H. pluvialis’s up and downstream processing including cultivation and harvesting of biomass, cell disruption, extraction and purification techniques. Useful information on the structure of H. pluvialis’s cells, biomolecular composition and properties and the bioactivity of astaxanthin is collected. Special emphasis is given to the recent progress in application of different electrotechnologies during the growth stages and for assistance of the recovery of different biomolecules from H. pluvialis.

This work discusses the synthesis and the properties of magnetite modified LAPONITE® RD platelets (Lap). Magnetized Lap (mLap) nanoparticles were synthesized by a co-precipitation method with different weight ratios, X = Fe3O4/Lap (0–2). For characterization of the samples the particle size distributions and sedimentation behavior in an external magnetic field were studied. Temperature sensible hydrogels based on N-isopropylacrylamide cross-linked by mLap were synthesized. An increased aggregation of mLap particles in aqueous suspensions has been revealed, but all the systems demonstrated high sedimentation stability. Significant effects of the value of X on the rate of sedimentation mLap particles in magnetic fields and on the swelling ability of hydrogels have been revealed. For example at X = 2, an increase in swelling by ≈2.7 was observed as compared with the swelling of hydrogels based on pure Lap nanoparticles.

The results of systematic study of the impact of electrolytes (in a wide range of electrolyte concentration, C = 10−5–10−1 M) with alkali metal ions (Li+, Na+, K+, Rb+, Cs+) containing chlorides and sulphate anions on electrosurface properties of aqueous suspensions containing hydrophobic (polystyrene latex with surface sulphate or carboxylic groups) and hydrophilic (aerosil, zirconium dioxide, bentonite, Laponite RD®) particles are presented. The behaviour of zeta potential (ζ-potential) and electrical conductivity was studied. The observed ζ(C) dependencies revealed marked maxima at C = 10−4–10−3 M for hydrophobic and at C = 10−3–10−2 M for hydrophilic particles. This phenomenon was explained accounting for two opposite trends related to the polarization of the electrical double layer (EDL) in the external electric field (increase of ζ-potential at low concentration) and the effect of the EDL compression (decrease of ζ-potential at high concentration). In concentrated solutions (C > 10−3–10−2 M) ζ-potentials always decreased regularly in the direct Hofmeister series from Li+ to Cs+ cations. However, in more diluted solutions, the indirect Hofmeister series for some particles were also observed. Such behaviour can reflect the impact of different properties of the surface including hydrophilic or hydrophobic nature, charge density, and partial dehydration. The sort of anions also influenced the value of ζ-potential. This phenomenon was explained by dehydration effect of sulphate ions, thinning the surface hydrate layer and shift of the shear plane toward the surface.

The behavior of a system of two-dimensional elongated particles (discorectangles) packed into a slit between two parallel walls was analyzed using a simulation approach. The packings were produced using the random sequential adsorption model with continuous positional and orientational degrees of freedom. The aspect ratio (length-to-width ratio, $\varepsilon=l/d$) of the particles was varied within the range $\varepsilon \in [1;32]$ while the distance between the walls was varied within the range $h/d\in [1;80]$. The properties of the deposits when in the jammed state (the coverage, the order parameter, and the long-range (percolation) connectivity between particles) were studied numerically. The values of $\varepsilon$ and $h$ significantly affected the structure of the packings and the percolation connectivity. In particular, the observed nontrivial dependencies of the jamming coverage $\varphi(\varepsilon)$ or $\varphi(h)$ were explained by the interplay of the different geometrical factors related to confinement, particle orientation degrees of freedom and excluded volume effects., Comment: 8 pages, 7 figures, 52 refs

Connectedness percolation phenomena in two-dimensional packings of elongated particles (discorectangles) were studied numerically. The packings were produced using random sequential adsorption (RSA) off-lattice model with preferential orientations of particles along a given direction. The partial ordering was characterized by order parameter $S$, with $S=0$ for completely disordered films (random orientation of particles) and $S=1$ for completely aligned particles along the horizontal direction $x$. The aspect ratio (length-to-width ratio) for the particles was varied within the range $\varepsilon \in [1;100]$. Analysis of connectivity was performed assuming a core-shell structure of particles. The value of $S$ affected the structure of packings, formation of long-range connectivity and electrical conductivity behavior. The effects were explained accounting for the competition between the particles' orientational degrees of freedom and the excluded volume effects. For aligned deposition, the anisotropy in electrical conductivity was observed and the values along alignment direction, $\sigma_x$, were larger than the values in perpendicular direction, $\sigma_y$. The anisotropy in localization of percolation threshold was also observed in finite sized packings, but it disappeared in the limit of infinitely large systems., Comment: 13 pages, 14 figures, 75 references

The nematic (5CB) and cholesteric (the mixture of 5CB with chiral M5) liquid crystals (LC) doped with organo-modified inorganic platelets Laponite® (LO) were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), microscopic image analysis, and optical density measurements. Cetyl-trimethylammonium-bromide (CTAB) was used as an organo-modifier and “cold” and “hot” methods were applied for obtaining of LOc and LOh samples, respectively. The data of DSC and XRD for nematic 5CB + LO compositions evidenced the presence of strong interactions between 5CB molecules and LO platelets and the better exfoliation for LOc as compared with LOh platelets. Microscopic structure, optical density and selective reflection for cholesteric compositions evidenced the strong integration of LOc platelets inside LC medium. The observed optical behavior reflects combination of initial perturbation of cholesteric matrix by LOc particles and initiation of formation of topological defects at small concentration of LOc, C

Ultrasound-assisted aqueous extraction (UAE) of soluble matter (°Brix), catechin and total phenolic contents (TPC) from flesh and peel of apple tissues were studied. The commercial green (Granny Smith) and red (Red delicious) apples were used in the investigation. All extractions were done at fixed temperature, T = 50 °C, and protocols with different specific energy inputs, S1 (W = 0 kJ/kg), S2(W ≈ 6.5 kJ/kg), S3(W ≈ 10.6 kJ/kg), S4(W ≈ 21.3 kJ/kg), and S5(W ≈ 26.8 kJ/kg) during the initial period of extraction (first 300–350 s). The total aqueous extraction time was up to 3 h. The kinetics of extractions, and correlations oBrix and concentration of catechin, C, were compared for flesh and peel tissues. The increase of energy resulted in increase of oBrix and C values. For both green and red apples, the values of °Brix and C were noticeably higher for peel as compared to flesh. The distinct correlations between saturation levels of Cm and TPCm at the long extraction time (≈3 h) were observed. However, the relative content of catechin in TPC (i.e., ratio Cm/TPCm) evidenced the presence of selectivity in extraction of catechin. This selectivity depends from the type of tissue (flesh or skin), apple variety (green or red) and applied treatment protocols.

Effects of pulsed electric fields (PEF) and preliminary convective air (CA) drying on the water loss and oil uptake during frying of potato disks have been investigated. The PEF treatment was done using a monopolar generator with electric field strength of 600 V/cm and pulsed protocol that allows obtaining the high level of electroporation. The different protocols of drying (for td = 500, 1000 and 2000 s, at T = 50 °C) and frying (for tf = 0–600 s at T = 130 °C) were tested. The frying kinetics was described using extended exponential function. A mean frying time τf decreased with increasing of time of preliminary drying td. The PEF treatment also resulted in decreasing of td. For example, with preliminary CA drying during td ≥ 500 s, the oil uptake after frying (tf = 600 s) was significantly smaller in the PEF treated potato (≈0.30 g/g DM) than in untreated potatoes (≈0.47 g/g DM). Combined preliminary PEF-treatments and CA-assisted dehydration significantly affected the frying time, the oil uptake and texture of samples. They can lead to the formation of a denser and less oil penetrable skin on the potato surface during the frying. Industrial relevance Application of PEF allows acceleration of CA drying of potato. The CA drying has positive effect on characteristics of fried products. Combined preliminary PEF-treatments and CA-assisted dehydration have favorable impacts on oil uptake and texture changes. Such processing could decrease process time, improve qualitative characteristics and safety of fried potato.

The extraction of polyphenols from apple pomace was studied using ultrasound, ethanol/water mixtures and moderate temperatures, 20–37 °C. The extraction kinetics and extraction yields of catechin and total phenolic content (TPC) were evaluated at different times of ultrasound treatment (tᵤ) and concentrations of ethanol (Cₑ). The highest extraction efficiency of TPC was observed at tᵤ = 30 min, Cₑ = 50% and total extraction time of tₑ = 60 min. The high selectivity of catechin extraction was demonstrated by analysing the relative content of catechin (R = Cc/TPC) in dependence of applied extraction protocol. The initial portions of extracts at small levels of TPC (≤50 mg per 100 DM) were richer in catechin content (R ≈ 15%–31%), whereas the last portions of extracts with high level of TPS were more exhausted in catechin (R ≈ 2%).

Stabilization of aqueous suspensions of carbon nanotubes (CNTs) is an acute task for a number of technological processes. The effects of cationic surfactant (cetyltrimethyl-ammonium bromide, CTAB) and clay platelets (Laponite RD® (Lap)) on the electrokinetic potential and aggregation stability/size distribution of CNTs have been studied. The studies were performed at constant pH (4.5 ± 0.1), and at different values of the added amount of the reagent, mass ratio between Lap/CNTs, aging time as well as duration of the suspension ultrasonic treatment. In a CTAB concentration interval of Cs = 3.64.10−5 − 1.82.10-2 wt.% a narrow monomodal size distribution was found. The median size of aggregates was 21–24 μm that is two times larger than the length of individual CNTs (5–10 μm). At higher CTAB concentrations (above critical micelle concentrations (CMC)), formation of aggregates with median size of 140–150 μm takes place, with preserving the monomodal size distribution. Aggregation of CNTs in this case probably occurs by deposition of individual CNT on the surface of primary aggregates. Addition of Lap platelets in the range from X = 0 to 0.4 (where X is the mass ratio of Lap/CNTs) causes a monotonic decrease of the ζ-potential of the CNTs from −40 mV to −30 mV with reaching its plateau value at X = 0.4–1.0. This evidences the high surface coverage of CNTs by Lap platelets at which the CNT + Lap complex acquires the ζ-potential value of Lap. In mixed CNT + Lap suspensions (X = 1.0), a bimodal particle size distribution was registered, with appearance of big aggregates (≈150–300 μm), both in dilute (Cs = 3.64.10−5 – 3.64.10-3 wt.%) and concentrated (Cs > CsCMC) solutions. These big hybrid CNT + Lap aggregates were loose, rather unstable, and they could be easily destroyed by ultrasonic treatment.

The impact of pulsed electric field (PEF) treatment on orange, pomelo, and lemon in aqueous media was studied. Whole fruits and stack of peels were PEF treated at electric field strength of 3 kV/cm and 10 kV/cm, respectively. The PEF induced damage of the whole fruit was evaluated by different disintegration indexes. The PEF treatment increased the yield of juice obtained after pressing by 25% for orange, 37% for pomelo, and 59% for lemon. The effect of PEF on different parts of each fruit was studied. Flavedo and albedo were separated from the untreated fruit or PEF treated fruit and solvent extraction (1/1 ethanol/water solution) of polyphenols was conducted. The quantification and characterization of polyphenols in each part was compared for untreated and PEF treated fruit. The application of high electric field strength on orange peels enhanced the extraction of polyphenols up to 22 mg GAE/g DM. Industrial relevance Citrus fruits are valuable sources of bioactive compounds (vitamins, antioxidants, carotenoids and flavonoids) and their processing represents an industrial importance. An application of PEF to whole fruits may be useful for improving the efficiency of juice extraction from different citrus fruits. The concentration of polyphenols in the extracted juice could be significantly enhanced by the treatment of citrus peels with PEF at high electric field strength.

The combined effect of cationic surfactant (cetyltrimethylammonium bromide, CTAB) and laponite platelets (laponite RD) on the stability of aqueous suspension of carbon nanotubes (NTs) has been investigated. The experimental methods include measurements of electrokinetic potential, radius of particles and aggregation stability. In individual suspensions the concentration of NTs was C n = 0.003% and concentration of laponite was C l = 0.5% and 2%. In hybrid NT + laponite suspensions the concentration of NTs was C n = 0.003% and 0.01% and the laponite/NT mass ratio, X = m l / m n , was varied within the range of X = 0–1. For individual NTs and laponite species the increase of the CTAB concentration, C s , changed the electrokinetic potential from negative to positive. However, the different effects of CTAB on stability of this species were observed: addition of CTAB stabilized the individual NTs and enhanced aggregation of laponite. The CTAB-induced overcharging was also typical for hybrid NT + laponite suspensions. Surprisingly, the minimum of a position of an isoelectric point C s (IEP) (≈ 3·10 − 6 M) at X ≈ 0.1–0.3 was observed. This behavior can reflect the impact of CTAB on adhesion interactions between NTs and laponite platelets and adsorption of CTAB on individual NT and laponite species and their hybrids.

Development of the concept of electroporation opened new perspectives for promising applications in food technology. Treatment of foods with pulsed electric fields (PEFs) allows facilitation of different food transformation operations (extraction, expression, osmotic treatment, drying, and freezing) with minimal energy consumptions and better retention of flavor, color, and preservation of nutritional properties of foods. This work shortly reviews the effects of PEF on the biological cells and food products and gives the examples of PEF-assisted techniques. The PEF protocol, power consumption, and existing small- and large-scale electroporation systems are presented. Some examples of PEF-assisted processing of meat, fish, and fat frying are discussed. The main principles of PEF-assisted cooking and kitchen operations are also discussed. The variants of PEF-assisted non-thermal cooker and PEF/ohmic thermal cooker are presented. It is speculated that PEF allows more homogeneous treatment of foods as compared to the conventional methods of thermal cooking. The PEF-assisted cooking can be faster and more effective for nutrient retention and sensory qualities of foods. Moreover, the PEF treatment can be used for producing the types of the products of fresh/natural quality and new tastes. The recent examples of PEF-assisted processing of meat and fish, assistance of frying, and commercial-scale processing are also presented and discussed.

Optical transmission and selective reflection data are reported for suspensions of single-walled carbon nanotubes (CNTs) in photoactive nematic material ZhK-440 with a mesogenic chiral dopant M5. At small concentrations of CNTs (C ≈ 0.01–0.05%), the preferential localisation of CNTs at oily sticks (cholesteric topological defects) and suppression of the network of oily streaks by CNTs were observed. At the same time, the optical density D was shown to be essentially non-linear and a minimum at certain concentration of CNTs, C ≈ 0.05–0.08%, was observed. This anomalous behaviour was explained by the presence of the structural transition from the loose (ramified) aggregates with highly anisotropic shape (oriented along the anchoring direction on rubbed polyvinyl alcohol) to the compact aggregates with denser packing. The location of this minimum, as well as the selective reflection maximum (helical pitch), was sensitive to partially reversible UV-induced trans–cis–trans isomerisation effects. The UV...

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.

Potato and carrot are important sources of energy (starch), high-quality proteins, fibers, and vitamins. This chapter considers examples of PEE application for the processing of potato and carrot crops. For potato, the applications of PEF for French fries manufacturing, improving of drying and extraction processes and treatment of peel wastes are presented. For carrot, the PEF assisted process of juice manufacture, inactivation of microorganisms in juice, extraction of valuable compounds, osmotic dehydration and drying are discussed.

The “fruit” means the fleshy seed-associated structures of a plant that are sweet or sour, and edible in the raw state. The systems for classifying of fruits are related to food composition and based on botanic families, colours, and edible parts of plants. This chapter discusses examples of application of the PEE for processing of three types of fruits: apple, tomato, and citrus.

Cell membrane electroporation phenomena depend on the size of cells, their spatial orientation, electro-physical parameters of cells, pH of surrounding media and presence of osmotic agents. This chapter discusses fundamentals of membrane electroporation, various non-pore and pore models (condenser and conductor approximations), stages of electroporation development and simulations of electroporation in planar lipid membranes. Electroporation of single cell, Schwan’s equation for spherical and non-spherical cells are presented. Electroporation of cell ensembles, mixtures of intact and electroporated cells, and biological tissues are also discussed.

The random sequential adsorption (RSA) of identical elongated particles (discorectangles) on a line ("Paris car parking problem") was studied numerically. An off-lattice model with continuous positional and orientational degrees of freedom was considered. The possible orientations of the discorectanles were restricted between $\theta \in [-\theta_\text{m}; \theta_\text{m}]$ while the aspect ratio (length-to-width ratio) for the discorectangles was varied within the range $\varepsilon \in [1;100]$. Additionally, the limiting case $\varepsilon=\infty$ (i.e., widthless sticks) was considered. We observed, that the RSA deposition for the problem under consideration was governed by the formation of rarefied holes (containing particles oriented along a line) surrounded by comparatively dense stacks (filled with almost parallel particles oriented in the vertical direction). The kinetics of the changes of the order parameter, and the packing density are discussed. Partial ordering of the discorectangles significantly affected the packing density at the jamming state, $\varphi_\text{j}$, and shifted the cusps in the $\varphi_\text{j}(\varepsilon)$ dependencies. This can be explained by the effects on the competition between the particles' orientational degrees of freedom and the excluded volume effects., Comment: 10 pages, 12 figures, 32 references

Detection and quantifying of electroporation effects in food and biological materials (food plants, biomass feedstocks and bio-suspensions) is very important for numerous practical applications. Currently, different methods and techniques have been proposed to detect and measure electroporation effects. This chapter presents the current methods to quantify electroporation effects based on the dielectric spectroscopy data (low-frequency, low-high frequency and phase shift methods, electro-kinetic methods), texture analysis (stress–deformation and relaxation tests, and acoustic methods), solute diffusivity data, image analysis (light and electron microscopy), and other methods. Numerous examples of electroporation detection and quantification are presented for different food materials. Benefits and disadvantages of each method are discussed.

Freezing at subzero temperatures is widely used to preserve quality of food products and obtain minimal deterioration of original colour, flavour, texture and other organoleptic and nutritional properties of foods. Existing freezing preservation technique goals to avoid formation of large ice crystals inside the foods by control the heat removal. This chapter discusses the physical aspects of water and food materials freezing, regulation of freezing processes, dehydrofreezing as well as different methods to improve freezing, including application of physical treatments, such as ultrasound, microwaves, radiofrequencies, high pressure, electric field, and vacuum cooling. More detailed discussion concerns the effects induced by electric fields (static, AC and PEE) on nucleation and crystallisation, including the results of PEF application to assist freezing, dehydro-freezing, vacuum cooling/freezing, crystallisation, and ice pressing.

Among conventional extraction techniques in food and biorefinery applications, solvent extraction (named leaching, diffusion) and expression (pressing) are the most important. Solid/liquid extraction and expression are widely used for the production of fruit juices, wines, sugar, vegetable oils and starch, as well as for the extraction of different molecules of agricultural origin (carbohydrates or polysaccharides, proteins, aromas, flavours, etc.). This chapter discusses general principles of solid/liquid extraction and expression assisted by pulsed electric energy (PEE). The analysis of solid/liquid extraction includes presentation of Crank’s and more recent physical models of solvent extraction from biological materials treated by pulsed electric fields (PEF). The analysis of solid/liquid expression includes presentation of filtration-consolidation and more recent physical models of pressing from PEF treated biological materials. Examples of laboratory and pilot devices for PEF enhanced solid/liquid expression are also presented. Several examples of PEE assisted solvent extraction and expression of biomolecules from fruits and vegetables, mushrooms, leaves herbaceous plants, and microorganisms are also included.

Farming and production of food are one of the oldest industries in the human history. Among other issues, food processing is an important part in the whole food industry. It includes the methods and techniques used to transform raw material into food for human consumption. Most of these techniques are well known and their principals have not been changed since the first utilization. However, there are some undesirable changes that could occur during food manufacturing. Therefore new technologies, such as pulsed electric field (PEF), are attracting more and more interest of food industry and science. This chapter presents an overview of the existing application of PEF to produce healthier product.

The grapes are cultivated all over the world and used as a fresh fruit and for the production of juice and wine. The grape berries are very rich in bioactive molecules such as carbohydrates, fruit acids, mineral elements, nitrogenous and aroma-producing compounds, vitamins, thiamine, riboflavin, anthocyanins responsible for the colour of red wine, and tannins determining astringency of wine. These substances have important antioxidant and beneficial effects on human health.

Dead-end electro-filtration of polyphenols extracted from apple skin was studied. The influence of membrane pore size (dm = 3.02–50 nm), transmembrane pressure (ΔP = 1–6 bar) and direct current (DC) electric field (U = 5–15 V) on the purification efficiency was investigated. The sieving ratios R of selected membrane UH030 (dm = 4.35 nm) towards the polyphenols, proteins, total solutes, and colour intensity increased with increase of transmembrane pressure. It was demonstrated that utilization of this membrane for the DC electro-filtration allowed more effective rejection of proteins at the anode part of the filter. Such effects can be attributed to the large size of protein molecules and their positive charge. Obtained data evidenced the possibility of selective purification of polyphenols by membrane electro-filtration.

Starting from two-three decades ago pulsed the electric field (PEF) treatment became very popular in a food industry. Many important effects and mechanisms related with impact of PEF on bio-, food or agricultural products have been discovered and elucidated for this period. Concept of electroporation has been fundamentally developed. The positive effects of PEE-assisted processing for inactivation of microorganisms, extraction, pressing, osmotic dehydration, drying, and freezing have been observed. Recent development and success of PEF applications has been also supported by the growing number of commercially available PEF generators with different characteristics, power and particular protocols. In the current paper, research works and applications of electricity and specifically pulsed electric fields in food processing over the period until the middle of the 1990s are summarized. A historical overview is presented in two steps devoted to: (a) the early studies on impact of electricity on growth, vegetation and germination and treatment of food by electricity before the 1940s and (b) the development of concept of selective electroplasmolysis and the first attempts to use the electricity and specifically the PEF treatment in food industry in the period between the 1940s ;and 1990s. Industrial relevance During the long history of testing of electricity and specifically the PEF treatment in industrial relevant processing the serious problems and obstacles were revealed. Many pilot scale constructions were proposed and tested during the period between the 1940s and until the middle of the 1990s by different investigators from West Germany and USSR (Ukraine and Moldova). However, finally that technology was not industrialised due to the technical difficulties, the absence of necessary financial support and the lack of knowledge about basic mechanisms responsible for the impact of PEF. This historical experience can be very instructive for the development of modern applications of PEF technology in food industry.

The effect of electrolytes with mono-, bi-, and trivalent anions on the surface charge (ζ-potential) of magnetite nanoparticles was investigated. The nanoparticles of magnetite, Fe 3 O 4 , were synthesised using different methods: a) coprecipitation of bivalent and trivalent iron sulphates at temperature T = 25 °C (sample NM 1 ) and b) oxidation of rotating steel disk in distilled water at T = 25 °C (sample NM 2 ) and at T = 50 °C (sample NM 3 ). All samples were characterized using transmission electron microscopy, infra-red spectroscopy, by measurements of electrophoretic mobility and particle size distribution. Transmission electron microscopy data evidenced that primary particles in dried powder samples have quasi-spherical shape with mean diameters of ⿿15 nm (Nп 1 ), ⿿80 nm (Nп 2 ) and ⿿70 nm (Nп 3 ). From other hand data of particle size distribution analysis in aqueous suspensions at pH 6 indicated formation of aggregates of size of ⿿30 nm (Nп 1 ), ⿿1200 nm (Nп 2 ) and ⿿520 nm (Nп 3 ). Infra-red data also evidenced the presence of different functional groups in dependence on the protocol of synthesis. In presence of background electrolyte KCl (1 mM) the isoelectric point for all particles was in the interval ѿп 6.0⿿8.0. Adding of electrolytes with mono- (Cl ⿿ ), bi- (SO 4 2⿿ ), and trivalent (PO 4 3⿿ ) anions resulted in noticeable differences in behaviour of the ζ-potential and position of the isoelectric point for particles Nп 1 , Nп 2 and Nп 3 . An increase of concentration of electrolytes always resulted in overcharging (changing from positive to negative charge) of particles Nп 1 and NM 3 , whereas for particle Nп 2 the overcharging was observed for both bivalent (SO 4 2⿿ ) and trivalent (PO 4 3⿿ ) anions. This behaviour cannot be explained by changes in the structure of electric double layer. The observed shifts of the isoelectric point and changes in the pH values in the presence of electrolytes reflected the impact of specific adsorption of anions on the ζ-potential of magnetite nanoparticles. Differences in pH values at which overcharging of nanoparticles took place can be explained by diverse structure of the surfaces of particles Nп 1 , Nп 2 and Nп 3 .

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.

Background Negative pressure cavitation (NPC) extraction is a novel effective and eco-friendly technology. In this method, cavitation is generated by negative pressure and continuously introduced into the liquid-solid system to enhance the turbulence, collision and mass transfer between the extracting solvent and solid matrix. This technique was found to be efficient for improving the substrate and enzyme mixing, increasing the enzymatic hydrolysis of the plant cell wall components and improving the intracellular contents release into the extraction solvent. Scope and approach So far, several studies evaluated the feasibility of using this system alone or in combination with other extraction methods (e.g. enzyme, homogenization, microwave, ionic liquid solvents and deep eutectic solvents) for extraction of food active compounds (e.g. flavonoids, isoflavonoids, saponins, stilbenes, polyphenols and alkaloids) from plant materials. This review gives an overview of the principle of NPC method and its application alone or in combination with other extraction techniques for extraction of active compounds from plant materials. Key findings and conclusions The outcome of the studies using NPC demonstrated that this technique is a simpler procedure, requiring low cost, and provides high efficiency. It is eco-friendly, and possesses a remarkable potential application in the industrial production compared to other extraction techniques. Moreover, since this method is performed at room temperature, it can reduce or prevent the degradation of thermosensitive compounds.