Inactivation of Salmonella Typhimurium and Staphylococcus aureus by pulsed electric fields in liquid whole egg (original) (raw)
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Food Science and Technology
In this study we demonstrated the inactivation of E. coli, C. difficile, meshophilic bacteria and Salmonella spp. through Pulsed Electric Field (PEF) technology. First, a simulation using Finite Element Method Magnetics Mathematical Modeling was used to obtain the electric field values to be used in the electro-pasteurization tunnel. Then, practical tests were carried out by using an industrial scale apparatus set with the following parameters: pulse 20 s-40 s, 40, 80 and 450 kV, radio frequency of 350 kHz and treadmill speed at 10 m/min. The results from practical tests shows a complete elimination of all microrganisms, thus proving that PEF technology significantly contributes to food safety and can be used on an industrial scale.
2004, Ottawa, Canada August 1 - 4, 2004, 2004
The effects of temperature, treatment time and electric field strength on inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in liquid egg yolk by pulsed electric field (PEF) processing were examined using the reaction kinetics approach. Egg yolk, inoculated with 108CFUmLAˋ1ofE.coliO157:H7orS.enteritidis,wastreatedinacontinuousflowprocessat20,30and40°Cincombinationwithpulsedelectricfieldintensitiesof20and30kVcmAˋ1.AbiphasicinstantreversalPEFwaveformwitha2lspulsewidthwasusedandamaximumof105pulseswereapplied.Increasingtheappliedelectricfieldintensity,treatmenttimeandprocesstemperatureresultedinincreasedbacterialinactivation.At30kVcmAˋ1and40°C,thepopulationsofE.coliO157:H7andS.enteritidiswerereducedby10 8 CFU mL À1 of E. coli O157:H7 or S. enteritidis, was treated in a continuous flow process at 20, 30 and 40°C in combination with pulsed electric field intensities of 20 and 30 kV cm À1 . A biphasic instant reversal PEF waveform with a 2 ls pulse width was used and a maximum of 105 pulses were applied. Increasing the applied electric field intensity, treatment time and process temperature resulted in increased bacterial inactivation. At 30 kV cm À1 and 40°C, the populations of E. coli O157:H7 and S. enteritidis were reduced by 108CFUmLAˋ1ofE.coliO157:H7orS.enteritidis,wastreatedinacontinuousflowprocessat20,30and40°Cincombinationwithpulsedelectricfieldintensitiesof20and30kVcmAˋ1.AbiphasicinstantreversalPEFwaveformwitha2lspulsewidthwasusedandamaximumof105pulseswereapplied.Increasingtheappliedelectricfieldintensity,treatmenttimeandprocesstemperatureresultedinincreasedbacterialinactivation.At30kVcmAˋ1and40°C,thepopulationsofE.coliO157:H7andS.enteritidiswerereducedby5 logs. The inactivation rate constants increased from 0.004 to 0.098 l s À1 for S. enteritidis whereas for E. coli O157:H7 the constants increased from 0.009 to 0.039 ls À1 as processing temperature increased from 20 to 40°C. S. enteritidis was more resistant to PEF inactivation than E. coli O157:H7 at lower processing temperatures.
Journal of Food Engineering, 2007
The effects of temperature, treatment time and electric field strength on inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in liquid egg yolk by pulsed electric field (PEF) processing were examined using the reaction kinetics approach. Egg yolk, inoculated with 108CFUmLAˋ1ofE.coliO157:H7orS.enteritidis,wastreatedinacontinuousflowprocessat20,30and40°Cincombinationwithpulsedelectricfieldintensitiesof20and30kVcmAˋ1.AbiphasicinstantreversalPEFwaveformwitha2lspulsewidthwasusedandamaximumof105pulseswereapplied.Increasingtheappliedelectricfieldintensity,treatmenttimeandprocesstemperatureresultedinincreasedbacterialinactivation.At30kVcmAˋ1and40°C,thepopulationsofE.coliO157:H7andS.enteritidiswerereducedby10 8 CFU mL À1 of E. coli O157:H7 or S. enteritidis, was treated in a continuous flow process at 20, 30 and 40°C in combination with pulsed electric field intensities of 20 and 30 kV cm À1 . A biphasic instant reversal PEF waveform with a 2 ls pulse width was used and a maximum of 105 pulses were applied. Increasing the applied electric field intensity, treatment time and process temperature resulted in increased bacterial inactivation. At 30 kV cm À1 and 40°C, the populations of E. coli O157:H7 and S. enteritidis were reduced by 108CFUmLAˋ1ofE.coliO157:H7orS.enteritidis,wastreatedinacontinuousflowprocessat20,30and40°Cincombinationwithpulsedelectricfieldintensitiesof20and30kVcmAˋ1.AbiphasicinstantreversalPEFwaveformwitha2lspulsewidthwasusedandamaximumof105pulseswereapplied.Increasingtheappliedelectricfieldintensity,treatmenttimeandprocesstemperatureresultedinincreasedbacterialinactivation.At30kVcmAˋ1and40°C,thepopulationsofE.coliO157:H7andS.enteritidiswerereducedby5 logs. The inactivation rate constants increased from 0.004 to 0.098 l s À1 for S. enteritidis whereas for E. coli O157:H7 the constants increased from 0.009 to 0.039 ls À1 as processing temperature increased from 20 to 40°C. S. enteritidis was more resistant to PEF inactivation than E. coli O157:H7 at lower processing temperatures.
International Journal of Food Science and Technology, 2009
Pulsed electric field (PEF) exposes a fluid or semi-fluid product to short pulses of high-energy electricity, which can inactivate microorganisms. The efficacy of PEF treatment for pasteurisation of liquid eggs may be a function of processing temperature. In this study, effects of PEF, temperature, pH and PEF with mild heat (PEF + heat) on the inactivation of Salmonella typhimurium DT104 cells in liquid whole egg (LWE) were investigated. Cells of S. typhimurium were inoculated into LWE pH adjusted to 6.6, 7.2 or 8.2 at 15, 25, 30 and 40 °C. The PEF field strength, pulse duration and total treatment time were 25 kV cm−1, 2.1 μs and 250 μs respectively. Cells of S. typhimurium in LWE at pH 7.2 were reduced by 2.1 logs at 40 °C and 1.8 logs at 30 °C. The PEF inactivation of S. typhimurium cells at 15 or 25 °C was pH dependent. Heat treatment at 55 °C for 3.5 min or PEF treatment at 20 °C resulted in c. 1-log reduction of S. typhimurium cells. Combination of PEF + 55 °C achieved 3-log reduction of S. typhimurium cells and was comparable to the inactivation by the heat treatment at 60 °C for 3.5 min. With further development, PEF + heat treatment may have an advantage over high-temperature treatment for pasteurisation of liquid eggs.
Critical Reviews in Food Science and Nutrition, 2008
Pathogenic microorganisms such as Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni have been implicated in foodborne diseases and outbreaks worldwide. These bacteria have been associated with the consumption of fresh fruit juices, milk, and dairy products, which are foodstuff, highly demanded by consumers in retails and supermarkets. Nowadays, consumers require high quality, fresh-like, and safe foods. Pulsed electric field (PEF) is a non-thermal preservation method, able to inactivate pathogenic microorganisms without significant loss of the organoleptic and nutritional properties of food. The PEF treatment effectiveness to destroy bacteria such as Listeria innocua, E. coli, Salmonella Typhimurium, E. coli O157:H7 and E. coli 8739 at pasteurization levels (≥ 5.0 log10 cycles) in some fluid foods was reported. However, data on the inactivation of some microorganisms such as Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni in fluid foods by PEF processing is very limited. Therefore, future works should be focused toward the inactivation of these pathogenic bacteria in real foods.
Food Research International, 1995
Inactivation of microorganisms exposed to high-voltage pulsed electric fields is a promising non-thermal food preservation technology. This paper demonstrates and validates the inactivation of Escherichia coli, a Gram-negative bacterium and Staphylococcus aureus, a Gram-positive bacterium, subjected to high-voltage electric field pulses. A four-log cycle reduction in microbial population is achieved in model foods such as simulated milk ultrafiltrate (SMUF) with a peak electric field strength of 16 kV/cm and 60 pulses with a pulse width ranging between 200 and 300 μs. The temperature of the cell suspension was kept below the lethal temperature, demonstrating that inactivation is not due to thermal effects induced by the pulses of high-voltage electricity. Thermal food preservation causes undesirable changes in the physical character, quality and nutrient content of foods. Non-thermal preservation techniques minimize the undesirable changes in foods. A comparison between the inactivation of microorganisms by high-voltage pulsed electric fields and thermal methods of food preservation is also discussed.
INACTIVATION of E. COLI FOR FOOD PASTEURIZATION BY HIGH-STRENGTH PULSED ELECTRIC FIELDS
Journal of Food Processing and Preservation, 1995
Pulsed electric fields of very high field strength and short duration are effective in the inactivation of E. coli. Nine log reduction in E. coli viabiliry was achieved using a stepwise pulsed electric field treatment where E. coli suspensions were treated repeatedly in batches. It was demonstrated that high-strength pulsed electric field treatment is adequate for pasteurization of liquid foods. A 40,000 volt pulse generator was constructed to supply high voltage electric pulses to a treatment chamber with two parallel plate stainless steel electrodes where fluid food was contained. The gap between electrodes was 0.51 em and the chamber volume was 14 ml. Pulse electric field strength ranged from 35 to 70 kV/cm. Pulse width was selected at 2 ps. Number of pulses per treatment varied from 1 to 80. E. coli were suspended in a simulated milk ultra-filtrate (SMUF) and treated with pulsed electric fields in a batch mode. The suspension fluid was maintained at constant temperatures of 7, 20, or 33C. Maximum temperature change occurring during each pulse was 0.3C measured by a fiber optics temperature probe. E. coli viability before and after treatment were assayed by counting colony forming units (@).
Inactivation of Salmonella enteritidis in liquid egg products using pulsed electric field (PEF)
2005
The effects of pulsed electric field (PEF), hydraulic high pressure (HHP) and ultrasound alone and in combinations on inactivating Salmonella enteritidis in liquid whole egg were investigated. The optimum conditions were: PEF-30 pulses of 5Á67 kV/mm (+ve peak) at 55 1C, HHP-2-2-4 min cyclic treatment at 138 MPa and 20 1C, and ultrasound-40 W at 55 1C for 5 min.The PEF was not effective due to high viscosity of the egg. The use of HHP in multiple cycles was better than single treatments of equivalent time. Increasing the exposure time to ultrasound resulted in greater microbial reductions. Increasing the temperature increased the effectiveness of ultrasound. Treatment combinations only exhibited additive effects. No synergy was observed. A combination of high pressure and ultrasound treatments resulted in the greatest microbial reduction of 3Á2 log cycles and, with the addition of mild heat, provides an alternative to thermal processing where high temperature has caused protein coagulation.
Innovative Food Science & Emerging Technologies, 2013
The behavior of the surviving population of Lactobacillus plantarum 564 growing in MRS broth after pulsed electric field (PEF) treatments of different intensities was monitored by isothermal calorimetry, optical density and plate counts. Bacterial cells were treated with monopolar square pulses at varying nominal electric field strengths and number of pulses, corresponding to applied energies of 34.6, 65.8 and 658.1 J/cm 3 . After the PEF treatment, samples were inoculated into the MRS broth and incubated at 37°C. The presented results show that surviving bacterial cells resume growth after a treatment-dependent delay. Both the untreated and treated cultures had similar growth rates, but the latter showed a higher growth rate during the late-growth phase, and the growth rate increased with the intensity of applied electric field. After the PEF treatment, the surviving population of bacteria was less susceptible to killing by further PEF application, showing that this subpopulation was less sensitive to the PEF treatment and could grow again. Industrial relevance: The application of pulsed electric field (PEF) technology as a non-thermal alternative to traditional pasteurization of liquid foods has received considerable attention during the last years. Effective inactivation for most of the spoilage and pathogenic microorganisms has been shown in fruit and vegetable juices and milk with little or no impact on nutritional and sensorial properties of the food. However, very little is known about the growth abilities of the surviving population. Ensuring food safety requires a better understanding of the behavior of the surviving populations of microorganisms which may be recovering from sub lethal injury, such as PEF-induced stress. This paper reveals that the surviving population of the bacteria subjected to the PEF treatment could grow again, showing higher growth rates as the intensity of the PEF treatment increased. Also, the new bacterial population showed higher resistance to further PEF treatment. Therefore, for industrial application of the PEF technology, an in-depth characterization of surviving microorganisms in the treated product is required. Moreover, the evidence of bacterial persistence indicates that the PEF technology, as a non-thermal alternative to traditional pasteurization, could not completely replace thermal treatment, but can be applied as a supplement treatment.
PULSE ELECTRIC FIELD APPLICATION FOR INACTIVATION OF MICROORGANISMS IN LIQUID FOODS: A REVIEW
Journal of Xi’an Shiyou University, Natural Science Edition, 2022
The world's perishable and imperishable food production is rising as a result of agricultural technological advancements, but the production is greatly influenced by the cyclical nature of the world's seasons. As a result, civilised society has adopted food processing and preservation techniques to preserve such seasonal food and supply consumers all year long. Although thermal preservation techniques have been around for a while, they significantly modify the food being preserved, especially its flavour. Demand for alternative food processing processes is rising internationally due to healthy eating trends and desires for high-quality foods. The growing demand for high-quality, fresh-like food items has led to research on non-thermal food processing techniques. An novel method for improving food quality that replaces traditional thermal methods is called pulsed electric field (PEF). PEF technology benefits include shorter processing times, lower process temperatures, and environmental friendliness. The PEF procedure works by exposing a food product to a pulsed electric field in a treatment zone. PEF causes a trans-membrane potential to be produced between cell membranes, which results in cell death when a microbe is exposed to it. The effectiveness of the PEF therapy may be determined using both biological and electrical data, such as cell size and structure, such as voltage amplitude, pulse width, and frequency. Since the PEF technology's parameters are interdependent, it is possible to study the impact of each parameter alone as well as in conjunction with the others. If the electrical energy transmitted to the food product is increased, the bacteria may be greatly inactivated newline.