High-voltage Pulsed Electric Field Research Articles

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Chipitsyna et al., pp. 276–285 Study after study has confirmed that cigarette smoking is one of the biggest risk factors for developing pancreatic cancer but the molecular connections between the two are still largely unexplored. In this issue, Chipitsyna et al. present evidence that the nicotine in cigarettes increases the expression of osteopontin, a protein known to promote cancer cell survival, proliferation, invasion and metastasis. Osteopontin, a secreted, integrin-binding protein, is found in a variety of body fluids. It was initially discovered as an inducible marker of transformation of epithelial cells and later was shown to be overexpressed in a variety of cancers, including lung, breast, cancer, stomach and pancreatic cancer. The latter prompted the authors to investigate whether osteopontin might play a role in smoking-induced pancreatic cancer. In their experiments, osteopontin mRNA and protein levels went up in pancreatic cancer cell lines when treated with physiologically relevant nicotine levels. Similarly, rats exposed to cigarette smoke showed a dose-dependent increase in pancreatic osteopontin levels that paralleled the rise in pancreatic and plasma nicotine levels. When the researchers compared endogenous levels of osteopontin in human patients they found that the average osteopontin levels in pancreatic ductal adenocarcinoma (PDA) cells were significantly higher than those in nonmalignant or premalignant lesions. Interestingly, only 27% of patients with premalignant lesions were smokers, whereas 64% of malignant lesions came from patients who were smokers, supporting the hypothesis that nicotine may contribute to PDA pathogenesis through upregulation of osteopontin. Photomicrographs of 3 melanomas taken on the day indicated for each column after nsPEF treatment. Rows are grouped in matched pairs with the top image of the pair being the surface view and the bottom image being the transillumination view of the tumor. Näsman et al., pp. 362–366 Tonsillar squamous cell carcinoma (SSC) is the most common oropharyngeal cancer in Sweden. In an earlier study, the authors reported that the incidence of tonsillar cancer as well as the proportion of HPV-positive tonsillar cancer tripled in the county of Stockholm between 1970 and 2002, despite a decline in smoking and smoking-related cancers during the same period. In their latest study, they found that the trend continued unabated during the last decade. Now, almost all patients diagnosed with tonsillar SCC in this area have HPV-positive tumors (93%). To follow up on their initial findings, Näsman et al. obtained 98 pretreatment samples from patients diagnosed with tonsillar SCC between 2003–2007 and tested them for the presence of HPV DNA as well as HPV-16 E6 and E7 RNA. They found HPV DNA in 83 of 98 tonsillar SCC biopsies and 77 of those were HPV-16 positive. In summary, the incidence rate of HPV-positive tumors almost doubled each decade between 1970 and 2007, in parallel with a decline in HPV-negative tumors. The fact that HPV-16 E6 and E7—both known to be necessary for carcinogenesis in cervical carcinoma—were expressed in the majority of the analyzed tumors suggests that HPV-16 plays an important role in the etiology of tonsillar carcinoma. On the upside, the availability of vaccines against HPV types 16 and 18 raises the possibility that vaccination may be able to put a stop to ever-increasing rates of HPV-positive tonsillar cancer. Nuccitelli et al., pp. 438–445 Using electric fields to bust cancer cells is not a new idea. Electrochemotherapy combines conventional chemotherapy with a short high-voltage pulsed electric field to render the membrane of the tumor cells more porous, allowing toxic drugs to slip inside the cells. Hyperthermia therapy uses electric fields, typically in the radio frequency band, to kill tumors by heating them to temperatures above 42°C. Others employ 100-μs pulses of 2.5 kV/cm amplitude to irreversibly permeabilize cells, leading to necrosis. Nuccitelli et al. discovered that ultrashort electrical pulses can be used as a purely electrical cancer therapy that kills tumors without hyperthermia or drugs. When the researchers applied 300 high-voltage (40 kV/cm), ultrashort (300 ns) electrical pulses to murine melanomas in vivo the treatment triggered both necrosis and apoptosis, resulting in complete remission on an average of 47 days. None of the 17 melanomas treated with nanosecond pulsed electric fields (nsPEFs) recurred during a 4-month period after the initial melanoma had disappeared. The pulses reduced the blood flow to the tumor and increased intracellular Ca2+ , both of which are important signals for initiating programmed cell death. Researchers at the University of Southern California have successfully treated a single patient suffering from basal cell carcinoma with nsPEFs. The patient went into complete remission after only one treatment, suggesting that nsPEF, which has proven very effective for mouse melanoma, might be equally as effective for the treatment of human melanoma.

Ultraviolet and Pulsed Electric Field Treatments Have Additive Effect on Inactivation of E. coli in Apple Juice

Apple juice inoculated with Escherichia coli ATCC 23472 was processed continuously using either ultraviolet (UV), high-voltage pulsed electric field (PEF), or a combination of the PEF and UV treatment systems. Apple juice was pumped through either of the systems at 3 flow rates (8, 14, and 20 mL/min). E. coli was reduced by 3.46 log CFU/mL when exposed in a 50 cm length of UV treatment chamber at 8 mL/min (2.94 s treatment time with a product temperature increase of 13 degrees C). E. coli inactivation of 4.87 log CFU/mL was achieved with a peak electric field strength of 60 kV/cm and 11.3 pulses (average pulse width of 3.5 mus, product temperature increased to 52 degrees C). E. coli reductions resulting from a combination treatment of UV and PEF applied sequentially were evaluated. A maximum E. coli reduction of 5.35 log CFU/mL was achieved using PEF (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) and UV treatments (length of 50 cm, treatment time of 2.94 s, and flow rate of 8 mL/min). An additive effect was observed for the combination treatments (PEF and UV), regardless of the order of treatment (P > 0.05). E. coli reductions of 5.35 and 5.30 log CFU/mL with PEF treatment (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) followed by UV (length of 30 cm, treatment time of 1.8 s, and flow rate of 8 mL/min) and UV treatment followed by PEF (same treatment conditions), respectively. No synergistic effect was observed.

고전압 전기장을 이용한 하수처리장 방류수 중의 대장균군 소독에 관한 연구

Using high voltage electric fields induced by high voltage AC (10-12 kV/cm, 20 kHz) and pulsed (20-30 kV/cm, 40 Hz) electric field generator as a semipermanent and environment-friendly disinfecting apparatus, the disinfection effect of coliform group in the effluent of sewage plant was investigated. The effects of electric field strength, treatment time, discharge area of a discharge tube, water quality factors (electric conductivity, pH and SS) on its death rate were examined. The death rate of coliform group was increased with increasing electric field strength and treatment time. For AC and pulsed electric field generator, the critical electric field strength was 6 kV/cm and 2 kV/cm, respectively, and the critical treatment time was 5 min and 2 min, respectively, regardless of electric field strength. Comparing the death rate of coliform group by AC and pulsed electric fields used in this study, its death rate was higher for the latter than the former, but did not increase linearly with increasing electric field strength. The results obtained for the effects of discharge area, electric conductivity, pH and SS on the death rate of coliform group using AC electric field (12 kV/cm, 20 kHz) were as follows: its death rate showed the trend to increase linearly with increasing discharge area; for the effect of electric conductivity, its death rate was increased with increasing electric conductivity, regardless of ionic species, increased with increasing cationic valency, but was similar between the same cationic valency; the pH <TEX>$5{\sim}9$</TEX> used in this study did not affect its death rate; its death rate was decreased with increasing SS concentration.

Investigation of erythrocyte membrane damage under the action of γ radiation in a wide dose range using electroporation

Human erythrocyte membrane damage under the impact of γ radiation on blood suspension is studied in a wide dose range (2–1000 Gy, irradiation dose rate 2.75 Gy/min). It is shown that the irradiation in the absorbed dose range from 600 Gy and higher results in hemolysis of erythrocytes immediately (or within several hours) after irradiation, and the value of the hemolysis rate constant increases with increasing absorbed dose. For finding hidden membrane damage occurring several hours after irradiation with smaller doses, the suspension was affected by a high voltage pulsed electric field (PEF). It is shown that, for an absorbed dose range from 2 to ∼350 Gy, no noticeable increase in the erythrocyte hemolysis rate was observed after the action of PEF on the suspension, as compared to the nonirradiated suspension. This testifies that, in this dose range, the degree of membrane damage is small and practically independent of absorbed dose value. For doses from 400 to ∼550 Gy, a noticeable increase in the hemolysis rate after the action of PEF growing with increasing absorbed dose was observed.

Improving the separation efficiency of DNA biosamples in capillary electrophoresis microchips using high-voltage pulsed DC electric fields

This paper proposes a simple method for enhancing the separation efficiency of DNA biosamples in a capillary electrophoresis (CE) microchip by using high-voltage pulsed DC electric fields. A high-voltage amplifier is used to establish electric fields of up to 1 kHz to carry out CE separation; electrophoresis and electroosmotic effects are then pulsely induced. The experimental and numerical investigations commence by separating a mixed sample comprising two fluoresceins with virtually identical physical properties, namely Rhodamine B and Rhodamine 6G. It is found that the level of separation is approximately 2.1 times higher than that achieved using a conventional DC electric field of the same intensity. The performance of the proposed method is further evaluated by separating a DNA sample of HaeIII digested ΦX-174 ladder. The experimental results indicate that the separation level of the neighboring peaks 5a and 5b in the DNA marker is approximately 1.2, which is significantly higher than the value of 0.8 obtained using a CE scheme with a conventional DC electric field. The improved separation performance of the proposed pulsed DC electric field approach is attributed to a lower Joule heating effect as a result of a lower average power input and the opportunity for heat dissipation during the zero-voltage stage of the pulse cycle. Overall, the results demonstrate that the method proposed in this study provides a simple, low-cost technique for achieving a high separation performance in CE microchips.

Comparison of Thermal Processing and Pulsed Electric Fields Treatment in Pasteurization of Apple Juice

Apple juice is a popular beverage worldwide, which is perceived as a wholesome and nutritious product. Overall quality of apple juice is an important factor to consider in processing, since some attributes, such as aroma, colour and flavour, are well appreciated by the final consumer, and are associated with freshness and authenticity. Non-thermal processing was tested in apple juice pasteurization in order to verify its feasibility in microbial inactivation, as well as its possibility of rendering a product impaired in terms of some sensory attributes. The non-thermal technique of high voltage pulsed electric fields (PEF) treatment, was compared with conventional high temperature-short time (HTST) pasteurization. Effects of process variables, such as voltage intensity and frequency for the PEF treatment, as well as temperature and time for the HTST pasteurization were investigated over inactivation of Escherichia coli and changes of pH and colour. Both techniques achieved more than five log reductions in microbial inactivation, normally considered the standard for fruit juices pasteurization. Apparently, PEF preserved better the pH than HTST as the thermal treatment showed an increase in this physicochemical property. Some variability was observed in terms of colour for all the treatments.

Influence of pulsed electric field on various enzyme activities

Effects of high-voltage pulsed electric field (PEF) on native or thermal denatured enzyme activities were studied. When PEF was applied to various native enzymes, 105–120% of initial enzyme activities were observed after PEF treatment. It was suggested that an activation of enzyme would be possible by PEF treatment. We attempted a refolding of thermal denatured enzyme by using PEF. When PEF was applied to denatured peroxidase, enzyme refolding was accelerated in PEF and 60% of initial activity was observed after 12 kV/cm and 30 s of PEF treatment although spontaneous refolding of this enzyme resulted in 40% of initial activity. On the other hand, when PEF was applied to thermal denatured lactate dehydrogenase (LDH), further PEF-induced inactivation was observed. It was suggested that the influence of PEF is dependent on the type of enzyme.

Extracellular production of α-amylase during fed-batch cultivation of recombinant Escherichia coli using pulsed electric field

In this study, extracellular release of recombinant α-amylase from Escherichia coli HB101/pHI301A by high-voltage pulsed electric field (PEF) was demonstrated during fed-batch cultivation. A continuous PEF treatment from the beginning of cultivation caused a decrease in cell growth rate and productivity of α-amylase, although a small quantity of extracellular α-amylase was detected in the culture supernatant. On the other hand, when PEF (12 kV, 3 Hz) was applied intermittently (each for 30 min with an interval of 30 min) from the beginning of stationary phase, the amount of α-amylase released was about 30% of the total amount of α-amylase that was produced in the cells. The release ratio and the total amount of α-amylase released were higher than that of batch cultivation. Suitable PEF treatment can be useful for easy and effective extracellular release of periplasmic proteins by fed-batch cultivation of recombinant E. coli.

Inactivation of E. coli in Cranberry Juice by a High Voltage Pulsed Electric Field

AbstractThe aim of this work was to study the effect of a high voltage pulsed electric field (PEF) on the inactivation of E. coli in cranberry juice to achieve the regulatory requirement of a 5‐log reduction in the microbial count. PEF processing involved the application of high voltage pulses to liquid or semi‐solid materials, placed between two electrodes at ambient, sub‐ambient, or supra‐ambient temperature. In this work, cranberry juice, inoculated with E. coli was subjected to 60 pulses in the voltage range of 5 to 40 kV/cm. The experiments were carried out at 20 °C. The temperature rise was less than 2 °C at the average treatment time of 80 s. PEF is an emerging non‐thermal technology for food preservation that retains the natural taste of food. It has mainly been applied to improve the shelf life of such foods as milk, liquid eggs and fruit juices.

Inactivation of E. coli K12 in apple juice by high voltage pulsed electric field

Pulsed Electric Field (PEF) technology is an emerging non-thermal food preservation technique that has mainly been applied to improve the shelf life of such foods as bread, milk, orange juice, apple juice and liquid eggs. It involves the application of pulses of high voltage to liquid or semi-solid materials, placed between two electrodes at ambient, sub-ambient, or slightly above ambient temperature. The voltage is typically in the range 20–80 kV/cm, and may be applied in the form of exponentially decaying, square wave, oscillatory, or in some cases, bipolar (instant-charge-reversal) pulses. In the present work, the effect number of pulses on the inactivation of E. coli K12 in apple juice was studied at two different voltages, namely 20 and 40 kV/cm and the number of pulses was varied from 0 to 100. The results indicate that the regulatory requirement of 5-log reduction in microbial count for food safety purposes could only be achieved with 40 kV/cm applied voltage and 100 pulses. The experiments were carried out at 20 °C and the maximum temperature rise was 2 °C.

Effect of culture temperature on high-voltage pulse sterilization of Escherichia coli

The effect of culture temperature of Escherichia coli on pulsed electric field (PEF) sterilization has been studied. PEF sterilization, which is a method of inactivation of cells by a high-voltage pulsed electric field, was used. The E. coli cells cultivated at 20°C, 30°C, 37°C, and 42°C, respectively, were collected and homogenous PEF of 16 kV/cm and 50 Hz was applied at various temperatures. When the E. coli cells were cultivated at 20°C or 42°C, the cells were more easily sterilized by PEF sterilization than the E. coli cells cultivated at 37°C, which is the optimal culture temperature of E. coli. The survival ratio after a dose of 100 J/ml of PEF at 50°C was about 10 −2 and 10 −3 as the E. coli cells were cultivated at 30°C or 37°C and 20°C or 42°C, respectively. These results indicate that the sterilization efficiency is dependent on the culture temperature even if the same bacteria are used. The death rates of the E. coli cells under various conditions were shown in a form of an Arrhenius plot. It was revealed that the efficiency of PEF sterilization is influenced by the PEF treatment temperature and this dependence changes between 30°C and 40°C of PEF treatment temperature. Moreover, the death rate of bacteria was found to be considerably influenced by the culture temperature of the E. coli cells. The E. coli cells cultivated at 37°C were practically resistant against PEF sterilization, while the cells cultivated at 20°C or 42°C were easily killed. Our results suggested that it is important to check the culture temperature of treated bacteria if PEF sterilization is applied in the industry.

Microbial inactivation by pulsed electric fields in a batch treatment chamber: effects of some electrical parameters and food constituents

The inactivation of Escherichia coli by high voltage pulsed electric fields in a batch treatment chamber was studied in liquid, solid and semisolid foods or model systems. Treatment heterogeneity was demonstrated and found to be due to the presence of an air bubble trapped inside the chamber. Agitation of the inoculated liquid samples (16 mM sodium phosphate buffer, pH 7, ρ=460 Ωcm) during pulse processing resulted in efficient microbial inactivation (five log cycles at 33 kV/cm and ∼25°C after 261 μs of cumulated pulses). A slower inactivation rate was observed in inoculated solid agar gels of the same pH and resistivity, under the same pulse processing conditions. The inactivation of E. coli in inoculated dairy cream (33% fat, pH 6.8, ρ=370 Ωcm), ovalbumin solution (10% protein w/v, pH 6.7, ρ=370 Ωcm) or fish egg suspension (pH 6.8, ρ=400 Ωcm) was almost identical to that in 16 mM phosphate buffer, pH 7. Thus emulsified lipids, soluble proteins or conductive food particulates do not appear to protect against microbial inactivation by electric pulses.

Reduction in Levels of Escherichia coli O157:H7 in Apple Cider by Pulsed Electric Fields

Many studies have demonstrated that high voltage pulsed electric field (PEF) treatment has lethal effects on microorganisms including Escherichia coli O157:H7; however, the survival of this pathogen through the PEF treatment is not fully understood. Fresh apple cider samples inoculated with E. coli O157:H7 strain EC920026 were treated with 10, 20, and 30 instant charge reversal pulses at electric field strengths of 60, 70, and 80 kV/cm, at 20, 30, and 42°C. To accurately evaluate the lethality of apple cider processing steps, counts were determined on tryptic soy agar (TSA) and sorbitol MacConkey agar (SMA) to estimate the number of injured and uninjured E. coli O157:H7 cells after PEF treatment. Cell death increased significantly with increased temperatures and electric field strengths. A maximum of 5.35-log10 CFU/ml (P < 0.05) reduction in cell population was achieved in samples treated with 30 pulses and 80 kV/cm at 42°C. Cell injury measured by the difference between TSA and SMA counts was found to be insignificant (P > 0.05). Under extreme conditions, a 5.91-log10 CFU/ml reduction in cell population was accomplished when treating samples with 10 pulses and 90 kV/cm at 42°C. PEF treatment, when combined with the addition of cinnamon or nisin, triggered cell death, resulting in a reduction in E. coli O157:H7 count of 6 to 8 log10 CFU/ml. Overall, the combination of PEF and heat treatment was demonstrated to be an effective pasteurization technique by sufficiently reducing the number of viable E. coli O157:H7 cells in fresh apple cider to meet U.S. Federal Drug Administration recommendations.

QUALITY CHANGES IN APPLE JUICE AS RELATED TO NONTHERMAL PROCESSING

ABSTRACTFresh apple juice was preserved using ultrafiltration and high voltage pulsed electric fields as nonthermal preservation techniques. Changes in quality attributes such as soluble solids, pH, acidity and color were verified for both processes. Changes were tested in terms of membrane pore, transmembrane pressure and recovery percentage for the ultrafiltration treatments, as well as in terms of electric field strength and number of pulses for the pulsed electric fields experiments. Among the quality attributes investigated, soluble solids, pH and acid content did not show significant differences, while color was significantly different for both nonthermal techniques. For the ultrafilteredjuice, a browning trend was observed, whereas for the pulsed electric treated juice an opposite, lightening, tendency was present.

Combined Effect of Nisin and Pulsed Electric Fields on the Inactivation of Escherichia coli

The Doehlert design was applied in order to investigate the combined effect of nisin and high voltage pulsed electric fields (PEF) on the inactivation of Escherichia coli in simulated milk ultrafiltrate media. Nisin alone was totally inactivated by PEF, but in the presence of bacterial cells a protective effect was observed. However, the effectiveness of nisin was still decreased when bacterial cells were subjected to the combined treatment. In spite of this phenomenon, an almost additive response emerged as a consequence of the combined treatment. A 4-log cycle reduction may be accomplished with around 1,000 IU/ml (7.15 μM) of nisin and three pulses of 11.25 kV/cm or 500 IU/ml for five pulses of the same intensity. The observed efficacy arising from the combination of both treatments suggests the possibility of using PEF for improving the action spectrum of natural antimicrobials.

Quality Aspects of Cheddar Cheese Obtained with Milk Pasteurized by Pulsed Electric Fields

High voltage pulsed electric fields were used to pasteurize milk to obtain cheddar cheese. Two thermal pasteurization methods were also employed, and compared with the non-thermal treatment, in terms of some quality attributes of the derived cheeses. A cheese obtained from raw milk was used as the control. Some texture and sensory attributes were determined in order to verify whether the pulsed electric field treatment would produce a product of higher quality. Adhesiveness, cohesiveness, hardness and springiness, measured by a texture analyser, were the texture attributes compared. Hardness and springiness increased in cheese obtained using milk pasteurized by pulsed electric fields, while adhesiveness and cohesiveness were not significantly different ( p

Releasing profiles of gene products from recombinant Escherichia coli in a high-voltage pulsed electric field

Release of recombinant proteins from gene-engineered Escherichia coli by applying a pulsed electric field (PEF) to a cell suspension was studied. When E. coli/pNC1, which produces β-glucosidase and accumulates it in cytoplasm, was exposed to PEF, the most effective release of this enzyme was achieved in the cell suspension of 5% glycine and 15% PEG solution under 10 kV/cm and 280 J/ml of a PEF in a needle–plate electrode chamber. However, the amount of released β-glucosidase by PEF treatment was only 26% of that by ultrasonic treatment. On the other hand, α-amylase produced by E. coli/pHI301A and accumulated in the periplasmic space could be easily released by PEF treatment. When this recombinant E. coli was suspended in 0.9% NaCl and 10% PEG solution and exposed to 10 kV/cm and 200 J/ml of a PEF in a plate–plate electrode chamber, 89% of intracellular α-amylase with nine-times higher specific activity compared with that by ultrasonic treatment was released. The release tendency of cellobiohydrolase, produced by E. coli/pNB6 and accumulated in both the cytoplasm and periplasmic space, was intermediate between those of β-glucosidase and α-amylase. In this case, 70% of cellobiohydrolase with 1.9-times higher specific activity compared with that by ultrasonic treatment could be released when E. coli/pNB6 was suspended in 15% PEG and 10 kV/cm and 200 J/ml of a PEF was applied in a needle–plate electrode chamber. These results indicated that PEF treatment could easily disrupt the outer membrane, but it was difficult to disrupt the cytoplasmic membrane simultaneously. Therefore, PEF treatment is useful for easy release of periplasmic protein with selectivity.

PULSED ELECTRIC FIELD INACTIVATION of MICROORGANISMS and PRESERVATION of QUALITY of CRANBERRY JUICE

Cranberry juice was treated either by high voltage pulsed electric field (PEF) at 20 kV/cm and 40 kV/cm for 50 and 150°s, or by thermal treatment at 90C for 90s. Higher field strength and longer treatment time reduced more viable microbial cells. the overall volatile profile of the juice was not affected by PEF treatment but it was affected by thermal treatment. No Significant difference in color was observed between the control and PEF treated samples. the application of 40kV/cm for 150 1ts resulted in no growth of molds and yeasts during storage at 22 and 4C, and no growth of aerobic bacteria during storage at 4C. PEF is an alternative process to thermal pasteurization for cranberry juice.

Inactivation of Escherichia coli O157:H7 and Escherichia coli 8739 in Apple Juice by Pulsed Electric Fields

The effect of high voltage pulsed electric field (PEF) treatment on Escherichia coli O157:H7 and generic E. coli 8739 in apple juice was investigated. Fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 were treated by PEF with selected parameters including electric field strength, treatment time, and treatment temperature. Samples were exposed to bipolar pulses with electric field strengths of 30, 26, 22, and 18 kV/cm and total treatment times of 172, 144, 115, and 86 μs. A 5-log reduction in both cultures was determined by a standard nonselective medium spread plate laboratory procedure. Treatment temperature was kept below 35°C. Results showed no difference in the sensitivities of E. coli O157:H7 and E. coli 8739 against PEF treatment. PEF is a promising technology for the inactivation of E. coli O157:H7 and E. coli 8739 in apple juice.

Apple Juice Pasteurization Using Ultrafiltration and Pulsed Electric Fields

Apple juice was treated by means of non-thermal processing methods as a way of verifying whether a microbial stable and quality-acceptable product could be obtained. Ultrafiltration and high electric voltage pulsed electric fields were the techniques used. For ultrafiltration, the factors under study were membrane pore (10,000 and 50,000 daltons), trans-membrane pressure (103, 120.5, 138 and 155 kPa) and recovery percentage (0, 25, 50 and 75% for the 10,000 daltons membrane, as well as 0, 10, 20, 30, 40, 50 and 60% for the 50,000 daltons membrane). In terms of the pulsed electric fields experiments, electric field strength (50, 58 and 66 kVcm–1) and number of pulses (2, 4, 8 and 16) were the factors investigated. The responses to these factors were evaluated for microbial determinations, namely: aerobic plate count, yeasts and moulds, aciduric bacteria, and quality attributes such as pH, acidity, soluble solids and colour. Appropriate statistical comparisons were made between types of membrane and techniques. Multiple linear regression models were fisstted by means of a stepwise technique. Both membrane treatments and pulsed electric fields technique showed that microbial inactivation is possible and efficient. Except for colour, quality attributes were kept unaltered. Significant relative colour changes were observed for both techniques such as browning for the ultrafiltered juice and fading for pulsed electric field treatment.