Electric Field Processing Research Articles

Microbial safety and shelf‐life of pulsed electric field processed nutritious juices and their potential for commercial production

Pulsed electric field (PEF) processing criteria which could achieve 5 or more log reduction of foodborne pathogens were obtained to get regulatory approval for the commercial production of three unique nutritious juices. Juice samples inoculated with Escherichia coli O157:H7 and Salmonella Typhimurium were processed in a continuous PEF process system. Among 18 tested conditions, three PEF treatments achieved an over 5 log reduction in populations of these pathogens. There was no recovery or regrowth of the pathogens in treated juices during storage at 4, 10, and 22°C. After 24 week-storage, population levels of native microorganisms in treated juices were the same or lower than those of the control samples at Day 0, except for those in apple-honey juice stored at 22°C. PEF processing had no significant effects on °Brix, pH, color, and vitamin C retention. This study provides an important step for the commercialization of PEF application. Novelty impact statement This study was specially designed for the project sponsored by a commercial juice producer. New and unique neutrinos juices were used to establish PEF processing criteria to achieve a 5 log or greater reduction of foodborne pathogens so that all data from this study can be used for regulatory approval and optimum processing conditions obtained from this study will be used for the commercial production of these juice products. This study also provides valuable information to the juice producers with similar nutritious juice products.

Effect of Pulsed Electric Field (PEF) on Bacterial Viability and Whey Protein in the Processing of Raw Milk

There is growing concern regarding the nutritional value of processed food products. Although thermal pasteurization, used in food processing, is a safe method and is widely applied in the food industry, food products lack quality and nutritional value because of the high temperatures used during pasteurization. In this study, the effect of pulsed electric field (PEF) processing on whey protein content and bacterial viability in raw milk was evaluated by changing the PEF strength and number of pulses. For comparison, traditional pasteurization techniques, such as low-temperature long-time (LTLT), ultra-high temperature (UHT), and microfiltration (MF), were also tested for total whey protein content, bacterial activity, and coliforms. We found that, after treatment with PEF, a significant decrease in total bacterial viability of 2.43 log and coliforms of 0.9 log was achieved, although undenatured whey protein content was not affected at 4.98 mg/mL. While traditional pasteurization techniques showed total bacterial inactivation, they were detrimental for whey protein content: β-lactoglobulin was not detected using HPLC in samples treated with UHT. LTLT treatment led to a significant decrease of 75% in β-lactoglobulin concentration; β-lactoglobulin content in milk samples treated with MF was the lowest compared to LTLT and UHT pasteurization, and ~10% and 27% reduction was observed.

A comparative study on physicochemical properties and in vitro bioaccessibility of bioactive compounds in rosehip (Rosa caninaL.) infusions treated by non‐thermal and thermal treatments

The present study aimed to compare the effects of non-thermal techniques with thermal treatment on physicochemical properties, bioaccessibility, and antioxidant capacity of bioactives in rosehip (Rosa canina) infusions. High pressure processing (HPP) at 200, 400, or 600 MPa for 5 and 15 min; pulsed electric field (PEF) with 5, 10, and 15 kJ/kg specific energy intakes at 1 and 3 kV/cm electric field strength; and thermal treatment (TT) at 85°C/10 min were applied. According to the results, processing method had varying effects on the contents of phenolic compounds, antioxidant capacity, and bioaccessibility in rosehip infusions. The highest retention of total phenolics (TPC) and flavonoids (TFC) were achieved by the TT (2278 mg gallic acid equivalents (GAE)/100 g dry weight (dw) and 3728 rutin equivalents (RE)/100 g dw, respectively) and HPP treatment at a pressure of 600 MPa for 15 min (2268 mg GAE/100 g dw and 3695 mg RE/100 g dw, respectively). These findings are in line with the results of antioxidant capacities of the samples. Besides, TT, HPP treatment at 600 MPa/5 min, and PEF treatment at 5 and 15 kJ/kg energy intakes (PEF1 and PEF3) resulted with a higher recovery of TPC, TFC, and antioxidant capacity after gastrointestinal digestion. It can be concluded that HPP and PEF treatments at specific conditions could be used in the processing of infusions and beverages. However, it should be considered that appropriate processing parameters should be selected and optimized for each sample individually, to assure the best nutritional value and quality characteristics. Novelty impact statement Better retention of bioactive compounds after high pressure processing (HPP) treatment at a pressure of 600 MPa for 15 min. A noticeable improvement in the recovery of bioactive content and antioxidant capacity after HPP and pulsed electric field processing. Potential of non-thermal food processing techniques as alternative to conventional thermal treatments in the production of functional foods with enhanced nutritional value.

Effect of pulsed electric field, mild thermal pretreatment and calcium on texture changes of potato (Solanum tuberosum L.) during subsequent cooking

The effect of pulsed electric field (PEF) and/or mild thermal processing at 60 °C (T60) on the cooking behaviour of potato tissue in media with different Ca2+ concentrations (0–0.5%) was investigated. The rate constant for texture degradation during cooking seemed to decrease after the different pretreatments in the order Untreated > T60 > PEF > PEF-T60, but only a significant effect (α = 0.05) could be found in the case of the combination pretreatment in 0.5% Ca2+ medium. These texture changes were linked with changes in pectin degree of methylesterification (DM) and Ca2+ crosslinking obtained after the pretreatments. The mild thermal pretreatment has little effect on the pectin DM but promotes ionic crosslinking. Both the PEF and combination pretreatment reduce the pectin DM and increase ionic crosslinking significantly. An exponential correlation was found between the texture degradation rate constant and the pectin properties studied.

Effects of microsecond pulsed electric field (μsPEF) and modular micro reaction system (MMRS) treatments on whey protein aggregation

Electric field (EF) processing has been suggested to be a promising technology in the valorisation of side-streams, such as whey, by enhancing the functionality of biomacromolecules. Shifting from batch to continuous processes and utilising more industry-relevant matrices are of great interest, yet studies thereof are lacking. A continuous plate–plate microsecond pulsed electric field (μsPEF) setup was optimised and whey protein concentrate (10%, w/w) was treated at 3 kV cm−1, 10 μs, 40–50 Hz. A diffuser inlet/outlet improved the process stability considerably. Average outlet temperatures between 64.1 °C and 73.2 °C were investigated and aggregate formation between 0.04 μm and 2000 μm was quantified. μsPEF-triggered particles were compared with those obtained in thermal treatments, conducted in a modular micro reaction system (MMRS) with similar temperature and residence times. A comparison of the Sauter mean diameter revealed that in the given EF process window, mainly thermal effects were responsible for aggregation shifts.

Effect of pulsed electric field processing on reduction of sulfamethazine residue content in milk.

The whole milk spiked with sulfamethazine was treated under thermal and pulsed electric field processing for maximum reduction. The low-temperature long-time (LTLT, 62.5°C for 30min), high-temperature short time (HTST, 72°C for 15 s) pasteurization and ultra-high temperature processing (UHT, 138°C for 2 s) resulted in the reduction of sulfamethazine 7.3, 5.2 and 4.6% respectively. PEF and combination treatment (thermal + PEF) were found to reduce sulfamethazine content in milk by 67-72% and 73-76% respectively. Combined treatment of milk resulted in a higher percentage of reduction. Similar predicted and actual values proved that they fit the linear regression model and successful application of pulsed electric field technology in reducing antibiotic residues. PEF and mild thermal treatment can be a promising technology to reduce the antibiotic residues with ensuring minimal negative impact on the nutritional quality of food.

Recovery of Struvite from Sewage Sludge Using Pulsed Electric Field Technique and Process Optimization

Recovery of Struvite from Sewage Sludge Using Pulsed Electric Field Technique and Process Optimization

Ohmic Heating of Basil-based Sauces: Influence of the Electric Field Strength on the Electrical Conductivity

The Moderate Electric Field (MEF) processing of foods consists in the application of an electric potential gradient (????/??) ranging from 1 to 1000 V/cm on a food item (homogeneous or heterogeneous) placed between two electrodes, its main effect being the food heating due to the dissipation of a part of the electric energy into heat within the food item. The heating performances of such a system depend on several process and system parameters, including the applied ????/??, the food electrical conductivity, and its thermo-physical properties. In this study, the effects due to the salt composition and to the applied ????/?? to a heterogeneous food (constituted by a basil-based sauce, mainly fibers dispersed in a slightly salted water-oil emulsion) treated in a custom MEF system on the food heating rate are investigated. The samples were prepared at different salinities (3.25, 1.63, 0.86 and 0.43% w/w respectively). In the explored range of compositions, the heating rate increased linearly with the square power of applied ????/??. A slight linearity deviation above 55°C was observed for the basil-based sauce at 1.63% and 5.20 V/cm, associated with bubble formation within the ohmic system and the electrolytic reactions occurring at the electrode-solution interface during the MEF heating process.The salt content as well as the ratio between water and oil in the sample formulation played a crucial role in determining the thermo-electrical behavior of the basil-based sauce samples. Samples with salinity of 1.63%, compared to samples at 3.25%, exhibited a higher electrical conductivity, being due to a minor concentration of the non-conductive phase (namely the oil phase as well as the dispersed vegetable fibers into the solution) that exerts a major degree of electrical insulation. As the salinity decreases from 1.63% to 0.43%, samples were characterized by lower electrical conductivities, being due to a reduced ionic mobility when the salt contained into the sample is drastically reduced.

Comparative analysis of ohmic and conventional heat‐treated carrot juice

The study was conducted to optimize the ohmic heating (OH) parameters for carrot juice and to compare the physicochemical characteristics (color, total soluble solid, pH, total carotenoid content, total phenolic content, and ascorbic acid) of optimized ohmic heated juice with thermally treated juice and fresh juice. The experiment was designed using central composite rotatable design (CCRD) with electric field strength (15–25 V/cm) and processing time (40–90 s) as independent parameters and the responses were analyzed using response surface methodology (RSM). The electrical conductivity and rate of heating were varied from 1.57 to 5.46 S/m and from 0.43 to 1.17°C/s, respectively. The optimized OH parameters were found to be electric field strength of 17 V/cm and processing time of 40 s. The optimized OH carrot juice was fit for consumption for 10 days with respect to both sensory and microbial parameters and had better stability than conventional heat-treated carrot juice. Practical applications The underlying motive of this study was to generate sufficient scientific information and foundation for application of ohmic heating (OH) to food products and its utilization by industries. The results of this research could be useful in design and development of OH chamber for industrial purpose. Carrot is a seasonal vegetable and with proper processing, and preservation can be made available throughout the year in the form of juice. Ohmic heating is seen as a potential alternative to conventionally pasteurized products in order to retain higher nutritional value of food products.

Pulsed electric field of goat milk: Impact on Escherichia coli ATCC 8739 and vitamin constituents

AbstractThere is a dire need to produce shelf‐stable and safe goat milk with minimal effects on its nutritive quality. In this study, raw goat milk was processed with a continuous pulsed electric field (PEF) system, at various electric field strength (EFS: 20, 25, 30, 35, and 40 kV/cm) and processing time (5, 7, 10, and 13 μs). The maximum log reduction of Escherichia coli was 3.87 log CFU/ml, achieved at 40 kV/cm for 13 μs. Weibull and Peleg models were better fitted to the inactivation kinetics of E.coli ATCC 8739 as a function of processing time and EFS, respectively. The mean concentration of vitamin A (as β‐carotene) and B‐group vitamins (thiamine, riboflavin, and niacin) were nonsignificantly (p > .05) decreased compared to the unprocessed sample. Since the inactivation level did not reach the minimum log reduction recommended by USFDA, PEF is recommended as a complementary method to mild thermal pasteurization.Practical ApplicationsPEF processing has gained recognition in food processing through halting an adverse issue of thermal processing. Although PEF is drifting toward industrial practice, it is essential to verify the efficiency of PEF in a complex matrix like goat milk to assure PEF can be utilized for industrial use. The results of this study show that the PEF can be recommended as a complementary method to mild thermal pasteurization as a hurdle processing technique to ensure the safety and nutritive qualities of goat milk at the industry level.

Impact of pulsed electric field processing on reduction of benzylpenicillin residue in milk.

The presence of residues of veterinary drugs in animal-derived food is one of the major problems for food safety. The consumption of milk containing antibiotic residues can evoke allergic reactions in hypersensitive individuals, disorders of intestinal flora and produces the risk of emerging antibiotic resistance microorganism. In this study, the effect of the thermal treatments and pulsed electric field (PEF) on the reduction of benzylpenicillin (PNG) spiked artificially in milk was evaluated quantitatively by calculating the loss of the concentration using HPLC. Fresh raw milk was subjected to a high-temperature short-time (72°C for 15s, HTST), low-temperature long- time (62.5°C for 30min, LTLT) and ultrahigh-temperature processing (138°C for 2s, UHT). The PEF process factors output voltage (20-65%) and pulse width (10-26μs) were optimized for maximum reduction of PNG by employing the statistical tool response surface methodology (RSM). HTST, LTLT, and UHT have resulted in the reduction of PNG 13.5%, 6.1%, 1.2% respectively. The optimized parameters of the PEF treatment had reduction efficiency in the range of 79-86%. The saddle response surface obtained from RSM showed that the center was neither at maximum point nor at the minimum point. The predicted and experimental values of the response were nearly similar which proved the suitability of the fitted quadratic model. Combined thermal and PEF treatment has a significant synergistic effect in reducing the PNG. PEF induced reduction efficiency achieved was 79-86%. The reduction percentages were observed higher in the combined pasteurization and PEF treatment of milk. The pulsed electric field can be adopted as a unique processing tool for degradation of antibiotic residues whilst retaining nutritional quality parameters.

Pulsed Electric Field (PEF) Processing of Chilled and Frozen-Thawed Lamb Meat Cuts: Relationships between Sensory Characteristics and Chemical Composition of Meat.

The effect of PEF processing and chilled storage on the volatile composition and sensory properties of chilled and frozen lamb cuts was investigated in this study. Results showed that PEF-treated chilled and frozen lamb cuts varied in temporal flavour attributes with storage. Storage for 7 days resulted in oxidized flavour, while PEF treatments for all chilled and frozen cuts were associated with browned and livery flavour attributes. Partial least squares regression (PLSR) was applied to determine the predictive relationships between the volatile composition, fatty acid and amino acid profiles, and sensory responses for PEF treated lamb cuts. The results showed that some volatile compounds (2-nonanone, 2-pentylfuran, pyrrole, methyl pyrazine, 2-ethyl-3-methyl pyrazine, and thiophene) correlated well with the meaty and juicy flavour of PEF treated frozen lamb cuts. In PEF treated chilled lamb cuts, meaty and juicy flavours were associated with the presence of fatty acids (C18:0, SFA, 20:5(n-3), and n-3). In contrast, livery and browned perception of both PEF processed chilled and frozen lamb cuts were associated with the presence of amino acids (threonine, phenylalanine, isoleucine, tyrosine, and methionine), and some volatile compounds (heptanal, 2-ethylfuran, pyridine, dimethyl disulphide, dimethyl trisulphide, and 3,5-diethyl-2-methyl pyrazine). Overall, these results imply that careful consideration of type of meat cuts, PEF pre-treatment, and storage are important when subjecting lamb meat to PEF processing.

A Review based study on Soymilk: Focuses on production technology, Prospects and Progress Scenario in last Decade

Soy food has been consumed for more than a thousand years, but only in the last 15 years they have made way for Western cultures and diets. Soymilk is a cheap, decent protein source that does not contain lactose. It replaces bovine milk as well. Though, soy milk protein is less digestible and more anti-nutrient than milk protein, it resolves the lactose intolerance problem and acts as a vegan milk supply. Soy milk is typically divided into two categories: fermented and unfermented. In comparison with unfermented one, fermented soy milk is less favorable. But there are also some inconveniences, such as low stability, shorter shelf-life and anti-nutritional causes. Different technology should overcome all these disadvantages such as Ultra high temperature, Microwave processing, Ultra-high pressure homogenization, Pulsed electric field and High pressure processing. Besides both of these soy milk, bioactive compounds like isoflavones, genistein, daidzein, and glycitein can also be minimized by thermal processing. A brief description of the importance, production technology, nutritional properties and development concerns over the decade has been discussed in this article.

Effect of pulsed electric field and mild thermal processing on texture-related pectin properties to better understand carrot (Daucus carota) texture changes during subsequent cooking

Pulsed electric field (PEF) and/or mild thermal (60 °C) processing distinctly affect the texture degradation of carrot tissues during subsequent cooking. The impact of PEF and/or mild thermal processing on texture-related pectin properties was studied in terms of pectin extractability, degree of methylesterification (DM) and Ca2+ crosslinking in carrot cortex and vascular tissue. In the case of cortex tissue, the treatments significantly (α = 0.05) reduced the extractability of pectin in water and alkali; the pectin DM and ionic crosslinking were not affected. In the case of vascular tissue, mainly the PEF and combination treatment reduced the extractability of pectin in water and alkali, reduced the pectin DM (approx. 60 to 50%), and improved its ionic crosslinking. Addition of Ca2+ ions may help preserve the texture of both tissues during subsequent cooking. Further research is necessary to investigate the effect of the treatments on covalent pectin crosslinking, especially in cortex tissue.

Pulse Electric Field Technology for Wastewater and Biomass Residues’ Improved Valorization

Development and adoption of more efficient and robust technologies for reuse of wastewater embedded resources, in particular materials and energy, is becoming an unavoidable necessity. Among many emerging technologies in the sector of wastewater treatment residuals valorization, Pulsed Electric Field (PEF) processes have shown interesting potential, although they have not yet entered the sector’s mainstream as a consolidated commercial technology, as in other industrial applications, such as the food, medical, and bio-based industries. PEF is a non-thermal technology suitable to biological applications, involving gentle cell disintegration and enhanced cell membrane permeability and as such applicable to disinfection, sterilization, and to those processes that benefit from an enhanced extraction of organic compounds from biological matter, such as anaerobic digestion, biological processes for recovery of nutrients, and biorefinery of cell-embedded compounds. PEF technology applications in wastewater/biomass residues management are reported and advantages, drawbacks, and barriers of the technology are discussed in this paper.

Unveiling the synergistic effect of combining low and high frequency electric fields for microbiological safety in liquid food processing

The synergistic effect of combining low and high radio frequency electric fields processing on Escherichia coli (E. coli) inactivation in liquid food was investigated. We show that by processing with low frequency (LF) at 12.5 kV cm−1 and 40 °C, followed by high frequency (HF) at 2.1 kV cm−1 and 65 °C, a synergistic effect on E. coli inactivation in saline water was achieved yielding approx. 5 log reduction and metabolic activity of 8.01 ± 4.34%. When similar treatment was applied to cranberry juice, an inactivation of 5.13 ± 0.21 log10 was achieved. Electron microscopy revealed that when both LF and HF treatments were applied alone, they disrupted the bacterial cell wall ultrastructure, with HF treatment additionally degrading cytoplasmic components. The sequential combination of LF and HF processes led to greater ultrastructural damage of E. coli as indicated by the observed perforation and rupture of the cell walls as well as leakage of cytoplasmic content.

Effects of Pulsed Electric Field Processing and Sous Vide Cooking on Muscle Structure and In Vitro Protein Digestibility of Beef Brisket.

Pulsed electric fields (PEF) in conjunction with sous vide (SV) cooking has been explored for meat tenderisation. The aim of this experiment was to study the effect of PEF–SV treatment on the muscle structure and in vitro protein digestibility of beef brisket. Pulsed electric field treatment (specific energy of 99 ± 5 kJ/kg) was applied to bovine Deep and Superficial pectoral muscles in combination with sous vide (SV) cooking (60 °C for 24 h). A similar micro- and ultrastructure was detected between the control SV-cooked and PEF-treated SV-cooked pectoral muscles. The combined PEF–SV treatment increased the in vitro protein digestibility of the pectoral muscles by approximately 29%, in terms of ninhydrin-reactive free amino nitrogen released at the end of simulated digestion. An increment in proteolysis of the PEF-treated SV-cooked meat proteins (e.g., myosin heavy chains and C-protein) during simulated digestion was also observed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. More damaged muscle micro- and ultrastructure was detected in PEF-treated SV-cooked muscles at the end of in vitro digestion, showing its enhanced digestive proteolysis compared to the control cooked meat.

Changes in the Glutinous Rice Grain and Physicochemical Properties of Its Starch upon Moderate Treatment with Pulsed Electric Field.

Pulsed electric field (PEF) processing is an emerging non-thermal technology that shows potential to improve food quality and to maintain stability. Glutinous rice is composed mainly of amylopectin and has low amylose content. This study investigated the effect of PEF treatment at 3 kV/cm field strength for 50 to 300 pulses on whole, water-soaked glutinous rice grains. Micro-pores were created at the surface of PEF treated rice grains, increasing grain porosity from 7.3% to 9.8%. Peak viscosity of PEF treated rice flour decreased, and breakdown, final and setback viscosities increased as the number of PEF treating pulses increased, indicating that the swelling degree of rice starch was promoted after PEF treatment. Lower values of gelatinization enthalpy and lower crystalline degree of PEF treated glutinous rice flour were also observed. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) studies confirmed the secondary structure changes in rice protein and partial gelatinization of rice starch after PEF treatment.

Combined effect of charges and external electric field on collision-coalescence of microns and nanoscale droplets: A numerical simulation perspective

Corona discharge is gradually attracting attention in catalyzed artificial rainfall due to its high efficiency and simplicity. Considerable researches focus on the macro phenomena, such as the increase of rainfall probability in statistics, and the observation of large particle size generation. However, due to the complexity of solving space charges, electric field and phenomena induced by corona discharge, relevant research on the micro mechanism is deficient, especially for the collision-coalescence of droplets with a diameter from nano-sized to micron-sized under the effect of charges and electric field. In this paper, systematic numerical simulations are conducted to study the coalescence between micron-sized droplets by phase field method, and coalescence time is introduced to characterize the speed of coalescence. In addition, “charged particle tracking” module is used to study the collision and coalescence between micron-sized droplet and nano-sized droplet, and collision efficiency is used as the evaluation index. The evolution of charged droplets under different conditions are discussed in detail in this paper, and results demonstrate the significant combined effect on the collision-coalescence process of charges and external electric field. The research results are conducive to reveal the micro-mechanism of the coagulation of macro droplets induced by corona discharge to some extent, and also provide a guidance for optimizing the water-collecting device by improving the speed and efficiency of droplet coalescence.

Elucidating the pH influence on pulsed electric fields-induced self-assembly of chitosan-zein-poly(vinyl alcohol)-polyethylene glycol nanostructured composites

HypothesisThe high incompatibility of bio-based materials such as protein and polysaccharides require a series of modifications to develop stable microstructures effectively. By modifying the density and charge of surface residues, pulsed electric fields processing can improve inter/intramolecular interactions, compatibility, and microstructure of bio-based nanostructured composites. ExperimentIn this work, the impact of pulsed electric fields at a specific energy of 60–700 kJ/kg (electric field strength = 1.6 kV/cm) on self-assembly of zein-chitosan-poly(vinyl alcohol)-polyethylene glycol composite dispersion was investigated at pH 4.0, 5.7, and 6.8. FindingsSuperior complex coacervated matrices were assembled at pH 4.0 and 5.7 before and after pulsed electric fields treatment at a specific energy of 390–410 kJ/kg. The compact and homogenous behaviour was attributable to pulsed electric fields-induced alteration of functional group interactions in a pH-dependent manner. Irrespective of the pH, very high electric field intensity caused excessive system perturbation leading to severe fragmentation and poor development of coacervates. The crucial insights from this study reveal that the self-assembly behaviour and integration of biopolymer-based systems possessing different local charges can be enhanced by optimising pulsed electric fields processing parameters and the properties of the colloidal systems such as the pH.