Effect Of Pulsed Electric Field Treatment Research Articles

Corn processing by pulsed electric fields with respect to microbial inactivation and improvement of seed vigour

Pulsed electric field (PEF) treatment of corn grains to improve seed vigour and inactivation of endogenous microflora by energies ranging from 1.20 to 28.8 J were applied to determine effectiveness of applied energies on germination rate (GR), normal seedling rate (NSR), electrical conductivity (EC), ability to germinate under salt (100- and 200 mM salt) and cold (at 10 °C for 7 days and at 25 °C for 5 days) stresses. Moreover, the effect of PEF treatments was further investigated for the inactivation of total aerobic mesophilic bacteria (TAMB), total mold and yeast (TMY), and inactivation rate (%) of Aspergillus parasiticus. Increased energy provided 11.10 % increase in GR, 21.22 % increase in NSR, 95.50 % increase in germination at 10 °C for 7 days. Germination under stress conditions revealed 32.53 %, 68.35 %, and 76 % increase in germination at 25 °C for 5 days, under 100 mM- and 200 mM NaCI salt stresses. Inactivation on the mean initial TAMB and TMY were approximately 9.25 and 7.93 log, respectively, with 63.33 ± 0.22 % reduction in A. parasiticus culture. PEF treated corn seedlings had stronger and taller body formation with stronger roots. The most optimal processing parameters were detected as 300 Hz, 28.80 J, and 19.78 sec. PEF treatment carries a high potential to improve corn vigour with inactivation of surface microflora.

Effect of pulsed electric field treatment on beef cuts properties: Tenderness, colour, drip loss, pH, electrical conductivity, water activity, cooking losses, drying

The effect of pulsed electric field (PEF) treatment on beef cuts was performed based on two consecutive experiments. In the first experiment, the effect of PEF treatment (100 pulses, 5 μs, 100 Hz) of different voltage intensities (0.5; 0.75; 1.0; 1.5; 2.0; and 4 kV∙cm−1) was evaluated in M. psoas major (PM). A significant effect of treatment on meat colour, texture, drip loss, and electrical conductivity was confirmed (P < 0.01), but no effect on pH value, and water activity. The electrical voltage of 0.75 kV affected the beef cuts most significantly, due to this finding the second experiment was designed. Colour, texture, cooking loss, and drying were evaluated to assess the number of pulses of PEF treatment on M. longissimus thoracis (LT), M. psoas major (PM), M. semitendinosus (ST), and M. brachiocephalicus (BC). In addition to significant effect on colour and cooking loss, PEF has accelerated the drying process of LT cuts (P < 0.01).

Effect of pulsed electric field on soybean isoflavone glycosides hydrolysis by β-glucosidase: Investigation on enzyme characteristics and assisted reaction

This work aimed to investigate how pulsed electric field (PEF) technology as an alternative to enhance the enzymatic hydrolysis of soybean isoflavone glycosides (SIG). To achieve it, the effect of PEF treatment on the activity, kinetics, thermodynamics and structure of β-glucosidase (β-GLU) were evaluated. The parameters for PEF-assisted hydrolysis of soybean isoflavone glycosides were optimized by response surface methodology. The results showed that PEF treatment increased the relative activity and catalytic efficiency of β-GLU with moderate electric field intensity. Furthermore, PEF treatment induced the secondary and tertiary structural change of β-GLU, the α-helix content increased by 4.23% and the β-fold content decreased by 3.70%. The optimum conditions for PEF treatment were established as the highest yield of isoflavone aglycones achieved 94.58%. Therefore, these results indicated that PEF treatment could be used as an efficient process to improve the β-GLU properties, converting soybean isoflavone glycoside to their aglycones form.

Pulsed electric field treatment of Lacticaseibacillus rhamnosus and Lacticaseibacillus paracasei, bacteria with probiotic potential

Lactic acid bacteria play an important role in functional food and fermentation products for human and animal nutrition, as probiotics, paraprobiotics, postbiotics or high-lactic acid-producing strains in biorefineries. Pulsed electric field (PEF) treatment is gaining recognition in the food industry, but little is known about the effects of PEF treatment on the probiotic characteristics of lactic acid (LA) bacteria or its application for the production of paraprobiotics and postbiotics. Thus, we studied the inactivation kinetics and permeabilization of Lacticaseibacillus rhamnosus and Lacticaseibacillus paracasei as high LA-producing strains with probiotic characteristics by batch and continuous PEF treatment.Significant linear correlations between the logN reduction and permeabilization of the studied bacteria and specific energy input and current were observed during PEF treatment. Sublethal PEF treatment (5 kV/cm, 8 × 1 ms, 1 Hz) induced 10% higher LA production in L. rhamnosus, as well as the release of proteins from both bacteria. Sublethal PEF treatment did not change the susceptibility to specific antibiotics in L. rhamnosus, while L. paracasei showed some decrease in susceptibility to antibiotics. The results obtained are valuable for PEF treatment of functional food with probiotics and the production of paraprobiotics and postbiotics to improve food safety and functionality.

Continuously pulsed electric field treatment chamber modelling and design

The perspectives of pulsed electric field (PEF) application for rheological changes in plant materials and treatment chamber design are considered in current paper. By using some mathematical tools and experiments data, viscosity of transporting plant materials confirms proposed Bingham rheological model assumption. Experimental studies have shown the presence of structure formation in material supplied to the treatment chamber channel. An effect of PEF treatment, with changes of material structure and increasing of material plastic viscosity from 0.117 to 0.159 Pa·s for samples after treatment by a field strength of E = 8 kV/cm and the number of pulses n = 300 was found. Obtained results of pulsed electric fields application in continuously material flow can be used in pulsed electric fields technologies, equipment design and help to determine cost efficiency of treatment in industrial application.

Quality and Safety Considerations of Incorporating Post-PEF Ageing into the Pulsed Electric Fields and Sous Vide Processing Chain

The effect of pulsed electric fields (0.7 and 1.5 kV/cm, specific energy 90–100 kJ/kg) processing followed by post–pulsed electric field (PEF) ageing ( 0, 3, 7, 14 days) on the safety and quality attributes of sous vide–processed (60 °C/12 or 24 h) beef briskets was assessed. Ageing did not significantly reduce the hardness of sous vide–processed meat except for those PEF treated either at 0.7 kV/cm followed by sous vide processing for 12 h or at 1.5 kV/cm followed by sous vide processing for 24 h. Post-PEF ageing time had no effect on the collagen solubility of sous vide–processed meat. The effect of PEF treatment on hardness was much greater than the effect of ageing time, and sous vide processing time. Sous vide processing (12 or 24 h) for all treatments reduced both aerobic and lactic acid bacteria numbers to below the detection limit. Initial peptide concentrations during in vitro peptic digestibility were significantly (P 0.05) differences were observed in digestion rates between any treatment. Ageing of PEF-treated meat for a few days prior to sous vide processing may improve tenderness; however, these gains in quality may be offset by a greater total water loss and an increase in lipid oxidation.

Effect of Pulsed Electric Field on Collapse Phenomenon of Apple Tissue in Vacuum Freeze Drying

The effects of pulsed electric field (PEF) on drying characteristics and collapse phenomenon during vacuum freeze drying of apple were investigated. The effects of PEF treatment on drying time, specific energy consumption and rehydration ratio were studied separately with different temperature. Results showed that the board temperature should below the collapse temperature of apple to increase the drying rate without destroying the quality during sublimation processing, and the collapse temperature of the apple after PEF treatment was 75°C, the board temperature should be as high as possible at the maximum allowable temperature of 85-95°C during the desorption processing according to the drying experiment and microstructure analysis. Moreover, the influence mechanism of PEF treatment on collapse phenomenon was discussed from the perspective of moisture migration and mechanics. Therefore, PEF treatment can improve the diffusion rate, and increase the collapse temperature.

Effect of pulsed electric fields (PEFs) on the pigments extracted from spinach ( Spinacia oleracea L.)

Abstract In order to investigate the effect of PEF on the pigments of spinach, pigments were extracted and were treated by different electric field strength at different temperatures (20, 35 and 45 °C). Results showed that with the increasing temperature, the degradation of chlorophyll content was appeared for pigments without PEF treatment. However, the concentrations of chlorophyll a, b and carotenoids were increased by the PEF treatment, especially for the higher electric field strength. Moreover, the structure of spinach pigments treated by PEF also was determined by UV–Vis, FT-IR and XRD. From the structural information, it was indicated that the effect of PEF treatment mainly focused on the hydrogen bonds and the pyrrole ring of chlorophyll, as well as the crystal structure of the compound was modified. In addition, the PEF treatment also significantly increased the antioxidation activity of pigments over the series of temperatures. Industrial relevance This study provide evidences that the PEF treatment can inhibit the degradation of chlorophyll and carotenoids, and can increase the antioxidation activity of extraction solution compared to the thermal treatment. From the structural information, it was indicated that PEF can promote the crosslink reaction with other chlorophyll moleculars, and formed the chlorophyll-aggregated structures, such as dimers and oligomers chlorophyll. Therefore, the PEF treatment is an efficient food processing method, especially foods rich in pigment.

Effect of combination processing on aflatoxin reduction: process optimization by response surface methodology

The food processing techniques have been established to provide nutritionally rich and safe products by reducing the toxin content both from the plant and microbial origin. In this study, the thermal processing method has been optimized, individually and in combination with pulsed electric field (PEF) by using response surface methodology, for its ability to reduce artificially spiked aflatoxin in potato dextrose agar. The thermal process was optimized, with factors pH (4–10), temperature (110–119 °C) and time (10–20 min) of treatment for the reduction percentage of aflatoxin B1 and total aflatoxin, wherein it followed a quadratic type model for both responses. But the effect of PEF treatment on reduction of aflatoxin B1 and total aflatoxin fitted in 2FI and quadratic models respectively. The combination (PEF + thermal) processing was performed using the optimized parameters; which resulted in a marginal increase in percentage of reduction when compared to the treatments performed individually. Practical applications Aflatoxin is a potential threat to human health. The toxin known for its thermal stability has created a need for newer processing technologies to reduce content without compromising the quality and safety of the product. The application of Pulsed Electric Field, a non-thermal process, in combination with thermal processing has been studied in this paper, for its successful application for the reduction in toxin in food products such as fruit juices, milk, peanut butter, and so forth.

Effect of pulsed electric field (PEF) on structures and antioxidant activity of soybean source peptides-SHCMN

Recently, high-intensity pulsed electric field (PEF) has successfully used in improvement of antioxidant activity. Ser-His-Cys-Met-Asn (SHCMN) obtained from soybean protein was chosen to investigate the phenomenon of antioxidant activity improvement. Effects of PEF treatment on antioxidant activity of SHCMN were evaluated by DPPH radical inhibition. Nuclear magnetic resonance (NMR), mid-infrared (MIR), circular dichroism (CD) were used to analyze structures of SHCMN. Two-factor-at-a-time results show that DPPH radical inhibition of SHCMN is significantly (P<0.05) increased to 94.35±0.03% at conditions of electric field intensity of 5kV/cm, pulse frequency of 2400Hz, and retention time of 2h. In addition, MIR and NMR spectra show that the basic structure of peptides SHCMN is stable by PEF treatment. But the secondary structures (α-helix, β-turn, and random coil) can be affected and zeta potential of PEF-treated SHCNM was reduced to 0.59±0.03mV. The antioxidant activity improvement of SHCMN might result from the changes of secondary structures and zeta potential.

Effects of Pulsed Electric Field (PEF) Treatment on Enhancing Activity and Conformation of α-Amylase

To explore an efficient, safe, and speedy application of pulsed electric field (PEF) technology for enzymatic modification, effects of PEF treatment on the enzymatic activity, property and kinetic parameters of α-amylase were investigated. Conformational transitions were also studied with the aid of circular dichroism (CD) and fluorescence spectra. The maximum enzymatic activity of α-amylase was obtained under 15 kV/cm electric field intensity and 100 mL/min flow velocity PEF treatment, in which the enzymatic activity increased by 22.13 ± 1.14% compared with control. The activation effect could last for 18 h at 4 °C. PEF treatment could widen the range of optimum temperature for α-amylase, however, it barely exerted any effect on the optimum pH. On the other hand, α-amylase treated by PEF showed an increase of Vmax, t1/2 and ΔG, whereas a decrease of Km and k were observed. Furthermore, it can be observed from fluorescence and CD spectra that PEF treatment had increased the number of amino acid residues, especially that of tryptophan, on α-amylase surface with enhanced α-helices by 34.76% and decreased random coil by 12.04% on α-amylase when compared with that of untreated. These changes in structure had positive effect on enhancing α-amylase activity and property.

Influence of different pulsed electric field strengths on the quality of the grapefruit juice

SummaryGrapefruit juice was investigated using pulsed electric fields (PEF) with (electric field strengths: 0, 5, 10, 15, 20 and 25 kV cm−1; flow rate: 80 mL min−1; pulse frequency: 1 kHz at 40 °C for 600 μs). Total phenolics, DPPH, total antioxidant capacity (TAC), total anthocyanins, total carotenoids, sugars and physicochemical properties of grapefruit juice were studied. In addition, the effect of PEF treatment on micro‐organisms was also observed. Results indicated that no significant change was observed in pH, Brix, titratable acidity, sugars, total anthocyanins and colour attributes with the increase in pulsed electric strength as compared to control treatment. However, significant decrease in nonenzymatic browning (NEB) and viscosity while an increase in cloud value, DPPH, TAC, total phenolics and total carotenoids, while reduction in the activity of micro‐organisms, was also observed with the increase in pulsed electric strength as compared to control treatment. This study suggested that PEF at 25 kV cm−1 could improve the quality of grapefruit juice.

Pulsed electric field treatment to improve the phenolic compound extraction from Graciano, Tempranillo and Grenache grape varieties during two vintages

Abstract The aim of this work was to study and compare the effect of pulsed electric field (PEF) treatment on the content of individual anthocyanins, phenolic acids, flavanols, and flavonols of three grape varieties from two vintages. For this purpose, the treatment showing to induce the highest release of phenolic compounds out of four different PEF applications assayed during the 2011 vintage was applied in 2012. The same continuous system was used over three grape varieties: Graciano, Tempranillo, and Grenache. Additionally, the influence of PEF on the physicochemical composition of the grapes was also studied. The effect of PEF treatment in the amount of individual phenolic compounds released and in the values of the physicochemical parameters analysed was qualitatively similar yet quantitatively different between the two years of study. Considering that the initial values of the physicochemical parameters were dependent on the vintage, it was observed that the lower the initial values the higher their increase after PEF treatment. Hence, the lower the initial values the higher the benefit obtained by PEF treatment. Furthermore, the influence of PEF treatment depended on the variety treated. For instance, Tempranillo was the variety showing the most significant differences in the content of individual anthocyanins upon PEF treatment, while Grenache variety showed major differences in the content of gallic acid, catechin, and epicatechin. Graciano variety showed almost no differences in the amount of individual phenolic compounds released after PEF application. For the three varieties, colour intensity, TPI, and total anthocyanins were increased by PEF application during the two assayed vintages, as well as antioxidant activity in 2012. Industrial relevance Pulsed electric field treatment is a suitable technology for the extraction of phenolic compounds. However, its suitability depends on the grape variety treated, and its quantitative effect depends on the initial phenolic composition of the grapes. Consequently, this technology could be used in the food industry to enhance the healthy properties of must and wine.

Effect of different pulsed electric field treatments on the volatile composition of Graciano, Tempranillo and Grenache grape varieties

The aim of this work was to study the influence of pulsed electric field (PEF) treatments on the volatile composition of three grape varieties. In order to do this, grapes were crushed and destemmed, and four PEF treatments were applied. The process was carried out continuously using a semi-industrial equipment. Volatile compounds were analyzed by SPME-GC–MS. The results showed that the effect of PEF treatment was different depending on variety. However, the aromatic profile of the studied varieties was not affected in any case. PEF enhanced the aromatic composition of Grenache, increasing the quantity of monoterpenoids. Moreover, a positive effect was observed in the amount of β-ionone, total esters and benzenoid compounds, and little difference was observed between treatments for C6 compounds. However, the volatile composition of Tempranillo and Graciano was not favored by PEF. In conclusion, from the point of view of the volatile composition and taking into account the treatments used in this study, it can be concluded that PEF is an appropriate technology to improve the aromatic quality of Grenache variety. Pulsed electric field is a non-thermal technology that enhances the volatile content in Grenache. Consequently, this technology could be used in the food industry to improve the aromatic quality of Grenache must and therefore the overall quality of Grenache wine, as this variety is one of the most widely grown in the world.

Modeling of yeast inactivation of PEF-treated Chinese rice wine: Effects of electric field intensity, treatment time and initial temperature

The application of pulsed electric field (PEF) technology as an alternative method of spoilage microbiological control for Chinese rice wine was investigated. PEF was applied at the initial temperature of 25–35°C, the electric field strength of 12–21kV/cm, with respective treatment time of 30–180μs to evaluate the efficiency of this technology on the inactivation of spoilage yeast Saccharomyces cerevisiae commonly associated with rice wine. The results from atomic force microscope imaging of yeast cells indicated that PEF treatment induced the destruction of cell membrane structures, which supported by the decrease of yeast number, the blurring of images, and the flattened yeast border. The highest inactivation values, corresponding to approximately 5.5-log cycles, were obtained at 21kV/cm and 180μs with the initial treatment temperatures of 30 and 35°C, respectively. Based on calculations by both log-linear and Weibull models, the decimal reduction times (5-D values) over the range of treatment conditions were 336.53–1804.1μs and 150.17–1127.6μs, respectively. Then the 5-D values were fitted as a function of electric field strength and initial treatment temperature, with R2 of 0.986 and 0.963 for log-linear and Weibull model, respectively. The model validation results showed that the 5-D values calculated from Weibull model (Af=1.169 and Bf=0.996) provided more accuracy than those from log-linear model (Af=1.773 and Bf=1.773), suggesting that the Weibull model was more suitable for calculating the survival ratio of PEF-treated spoilage microorganisms in Chinese rice wine. Finally, the effects of PEF treatment on physicochemical properties (including °Brix, pH, conductivity and color) of rice wine exactly after treatment and during storage at room temperature (22°C) were also investigated. The results indicated that PEF was able to inactivate (to some degree) the yeast in rice wine with minor variations in the physicochemical parameters and affect the quality indices of rice wine positively.

PEF based hurdle strategy to control Pichia fermentans, Listeria innocua and Escherichia coli k12 in orange juice

The combination of pulsed electric fields (PEF) and bacteriocins in a hurdle approach has been reported to enhance microbial inactivation. This study investigates the preservation of orange juice using PEF in combination with nisin (2.5 ppm), natamycin (10 ppm), benzoic acid (BA; 100 ppm), or lactic acid, (LA; 500 ppm). Pichia fermentans, a spoilage yeast frequently isolated from orange juice, Escherichia coli k12 or Listeria innocua were inoculated into sterile orange juice (OJ) with, and without, added preservatives. The antimicrobial activity over time was evaluated relative to an untreated control. The effect of PEF treatment (40 kV/cm, 100 μs; max temperature 56 °C) was assessed on its own, and in combination with each antimicrobial. The acidic environment of OJ inactivated E. coli k12 (1.5 log reduction) and L. innocua (0.7 log reduction) slightly but had no effect on P. fermentans. PEF caused a significant decrease ( P < 0.05) in the viability of P. fermentans, L. innocua and E. coli k12 achieving reductions of 4.8, 3.7 and 6.3 log respectively. Nisin combined with PEF inactivated L. innocua and E. coli k12 in a synergistic manner resulting in a total reduction to 5.6 and 7.9 log respectively. A similar synergy was shown between LA and PEF in the inactivation of L. innocua and P. fermentans (6.1 and 7.8 log reduction), but not E. coli k12. The BA–PEF combination caused an additive inactivation of P. fermentans, whereas the natamycin–PEF combination against P. fermentans was not significantly different to the effect caused by PEF alone. This study shows that combining PEF with the chosen preservatives, at levels lower than those in current use, can provide greater than 5 log reductions of E. coli k12 , L. innocua and P. fermentans in OJ. These PEF–bio–preservative combination hurdles could provide the beverage industry with effective non-thermal alternatives to prevent microbial spoilage, and improve the safety of fruit juice.

Ascorbic acid in orange juice–milk beverage treated by high intensity pulsed electric fields and its stability during storage

The degradation of ascorbic acid was determined in a ready-to-drink orange juice–milk beverage treated by high intensity pulsed electric fields (PEF). The effects of PEF treatment were compared to those of heat pasteurization (90 ºC, 20 s). Four electric field strengths (15, 25, 35, 40 kV/cm) and six treatment times for each field (from 40 µs to 700 µs) were studied. Ascorbic acid degradation was adjusted to an exponential model. The obtained ascorbic acid degradation rate constants (kE) were − 0.11·10− 3 ± 0.03·10− 3 μs− 1, − 0.23·10− 3 ± 0.07·10− 3 μs− 1, − 0.42·10− 3 ± 0.09·10− 3 μs− 1 and − 0.60·10− 3 ± 0.06·10− 3 μs− 1 for field strengths of 15, 25, 35 and 40 kV/cm, respectively. For the shelf-life study a 25 kV/cm at 280 µs treatment was applied and the beverages were stored at 4 and 10 ºC. The ascorbic acid degradation rate during storage was adjusted to zero-order kinetics showing that beverages stored at 4 ºC had better ascorbic acid retention than beverages stored at 10 °C. No significant differences were found between heat pasteurization and PEF treatments during storage. Food beverages are mainly preserved and made available to the consumer by different thermal treatments which involve a destruction of desirable food constituents such as nutrients, bioactive compounds, colour, flavour and texture. The present work demonstrates that the ascorbic acid degradation in an orange juice–milk beverage treated by pulsed electric fields was adjusted to zero-order kinetics and degradation rate during storage was adjusted to first-order kinetics. The shelf life of the orange juice–milk beverages is similar so much for the pasteurized beverages as for the treated by PEF.

Effects of pulsed electric fields (PEF) treatment on physicochemical properties of potato starch

Abstract Potato starch–water suspensions (8.0%, w/w) were subjected to pulsed electric fields (PEF) treatment at 30 kV·cm − 1 , 40 kV·cm − 1 and 50 kV·cm − 1 , respectively. The physicochemical properties of PEF-treated potato starch samples were investigated using scanning electron microscopy (SEM), laser scattering technique, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and the Brabender rheological method, with native potato starch as reference. It has been concluded from SEM analysis that dissociation and damage of PEF-treated potato starch granules appeared. Some granules aggregated with each other and showed gel-like structures. It was revealed from particle size analysis that there was an obvious increase of the granule size after PEF treatment. This has been attributed to the aggregation among granules. It was also demonstrated from other analysis that relative crystallinity, gelatinization temperatures, gelatinization enthalpy, peak viscosity as well as breakdown viscosity of modified samples all decreased with increasing electric field strength. Industrial relevance In this study, the effect of PEF treatment (up to 50 kV·cm − 1 ) on physicochemical properties of potato starch has been investigated. The results from SEM images showed that dissociation, denaturation and damage of potato starch granules had been induced by the PEF treatments. Some of granule fragments showed gel-like structures, and congregated with each other or with other starch granules. Laser scattering measurements of particle size revealed that an obvious increase of granule size under electric field strength of 50 kV·cm − 1 , which was attributed to the aggregation of the starch granules. The X-ray diffraction pattern showed an obvious loss of crystalline structure after the PEF treatment at 50 kV·cm − 1 , which induced a trend of transformation from crystal to non-crystal in potato starch granules. DSC analysis showed a decrease in gelatinization temperatures ( T o and T p ) and gelatinization enthalpy (Δ H gel ) with increasing electric field strength. Brabender rheological method has been used to show that the peak viscosity and breakdown viscosity decrease with increasing electric field strength of PEF treatment. All the results reveal that the PEF treatment can lead to an intragranular molecular rearrangement of potato starch granules, which induces changes of various physicochemical properties of the treated starch thus may endow it some new characteristics and functions. This phenomena may warrant further more detailed study.

An investigation on pulsed electric fields technology using new treatment chamber design

A pulsed electric field (PEF) system was designed and constructed using modern IGBT technology. The main focus of this work was to design a new PEF treatment chamber that operate at high electric field intensities with limited increase in liquid temperature and limited fouling of electrodes. Four multi-pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% w/w was investigated. Treatments with the same electrical input power but with higher electric field strengths provided larger degree of killing. The effect of PEF treatment using suspensions at different flow rates and different pulse frequencies was also investigated. In general, the inactivation rate of E. coli increased with increasing electric field strength, treatment time and processing temperature. More than 6 log reductions in E. coli suspended in SMUF was achieved using electric field intensity in the range of (37.2–49.6 kV/cm) with a treatment temperature not exceeding 38 °C.

Pulsed Electric Field Processing of Beer: Microbial, Sensory, and Quality Analyses

ABSTRACT: In this study, pulsed electric field (PEF) treatment of beer, effectiveness of PEF treatment on microbial inactivation, effects of PEF treatment on sensory properties, and detection of electrode material migration were explored. Beer samples were treated by PEF for the inactivation of natural flora and inoculated cultures of Saccaromyces uvarum, Rhodotorula rubra, Lactobacillus plantarum, Pediococcus damnosus, and Bacillus subtilis. Inactivation induced by the PEF treatment was 0.5, 4.1, 4.3, 4.7, 5.8, and 4.8 log10 colony‐forming units/mL in the above microorganisms, respectively (P &lt; 0.05). There was a significant increase in the amount of Cr, Zn, Fe, and Mn ions in the beer samples after PEF treatment (P &lt; 0.05) leading to a statistically significant degradation in flavor and mouth feel. Further studies are needed to optimize electrode materials and PEF treatment to minimize or eliminate this degradation.