Nature of the inactivation of Escherichia coli suspended in an orange juice and milk beverage (original) (raw)
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Journal of Food Engineering, 2007
This work studies the effect of electric field strength, treatment time, process temperature, and pulse width on the inactivation of Lactobacillus plantarum inoculated in an orange juice-milk based beverage. For any given quantity of energy applied, the highest degree of inactivation was achieved with high field intensities and short treatment times. The inactivation curve had different slopes, one up to application of 200-285 • 10 3 J L À1 , a second stage up to application of 813-891 • 10 3 J L À1 in which the inactivation did not increase significantly, and a third stage up to application of 1069-1170 • 10 3 J L À1. When the process temperature was raised to 55°C the inactivation increased by 0.5 cycles, achieving an energy saving of up to 60%. No increase in inactivation was achieved when the pulse width was increased from 2.5 • 10 À6 to 4 • 10 À6 s. The inactivation achieved with L. plantarum in this beverage is less than that reported by other authors in foods with a simpler composition.
Journal of Food Protection, 1999
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.
Pulsed electric field for Escherichia coli inactivation in pumpkin juice and nectar
Acta Scientiarum. Technology, 2022
In this study experiments were performed using a batch pulsed electric field (PEF) system at different electric field strengths with a voltage of 35 kV and pulse frequency of 3 Hz, at 20 and 40°C, with pulse width between 0.8 and 1.0 µs, to evaluate the inactivation of Escherichia coli in pumpkin juice and nectar. The performance of the PEF technology can vary as a function of several process parameters and the conditions and procedures applied. The physicochemical characteristics (pH, total soluble solids, electrical conductivity) of the pumpkin juice were also evaluated. The juice showed 5.01 ± 0.01 of pH, 10.70 ± 0.11 (mS cm-1) of electric conductivity and 9.85 ± 0.07 of soluble solids while in nectar, these parameters were changed to 5.11 ± 0.01 of pH, 8.54 ± 0.21 of electric conductivity and 6.40 ± 0.12 of soluble solids. The use of a temperature of 40°C and pumpkin nectar (70:30, juice: distilled water) showed no difference in the bacterial reduction compared to 20°C and usin...
Journal of Innovative Technology Research, 2017
A laboratory-scale pulsed electric field system for inactivating microorganisms in an orange juice was developed and preliminary tested in this study. The developed system consists of a high-voltage power source, an energy storage capacitor bank, a charging current limiting resistor, a switch to discharge energy from the capacitor across the food and a parallel-plate treatment chamber. In this system, the parallelplate treatment chamber was applied with the DC pulsed voltage in order to create the high pulsed electric field strength inside the chamber for inactivating a microorganisms in the liquid food inside the chamber by electroporation process. In this study, the developed system was preliminary tested with an orange juice inoculated with E. coli. and compared with thermal pasteurization. It was shown that both technologies reduced the population of the E. coli. inoculated in orange juice. No viable cells were observed after thermal processing of orange juice whereas PEF treatment achieved 6 logarithmic reductions of the microbial viability at the electric field strength up to 25 kV/cm and the pulse number of about 500 pulses.
Food Microbiology, 2004
Pulsed electric fields (PEF) are an emerging non-thermal treatment valid for liquid foods. This novel technology offers a relevant alternative to traditional thermal methods avoiding thermal damage to the product (loss of flavour and nutritional value). The aim of this work was to evaluate the influence of PEF treatment conditions, inoculum size (initial cell concentration) and substrate conditions after PEF treatment on the inactivation and potential growth of Lactobacillus plantarum and Escherichia coli in orangecarrot juice. Although a maximum inactivation of 1.3 and 2.6 log reductions were achieved for L. plantarum and E. coli, respectively, after PEF treatment, it was effective inducing sub-lethal injury. An increase in the lag-phase duration was evidenced under refrigeration conditions. When sub-lethal damage could be repaired, the subsequent growth rate was not affected. An increased inhibitory effect of PEF, low temperature and low inoculum size on the delay in lag phase was observed. r
Reduction in levels of Escherichia coli O157:H7 in apple cider by pulsed electric fields
Journal of food protection, 2001
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 degrees 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 degrees C. Cell injury measured by the difference ...
Innovative Food Science & Emerging Technologies, 2011
Treatments involving pulsed electric fields (PEF) in combination with high intensity light pulses (HILP) were applied to reconstituted apple juice in a continuous system using a 2 × 4 factorial design, with sequence and energy levels as main factors. Two PEF field strengths (24 kV/cm or 34 kV/cm) were selected (treatment time 89 μs each) corresponding to "high" (H) and a "low" (L) energy inputs (261.9 and 130.5 J/ml, respectively). Juice was also pumped through a HILP system (pulse length 360 μs, frequency 3 Hz) and exposed to energy dosages of 5.1 J/cm 2 (H) or 4.0 J/cm 2 (L) corresponding to 65.4 and 51.5 J/ml, respectively. Microbiological analysis was performed by inoculating juice with Escherichia coli K12 and counting microbial populations preand post-processing. Selected physical and chemical quality attributes were compared with those of unprocessed controls. A sensory evaluation was conducted using 31 untrained panellists and the products compared to thermally processed juice (94°C for 26 s). With the exception of HILP (H) and PEF (L), all combinations achieved the minimum microbial reduction of 5 log units required by the FDA. The results obtained for PEF (L) followed by either HILP (L or H) suggest a synergistic effect on microbial inactivation. In general, the quality attributes were not affected by the chosen treatments and sensory evaluation revealed that the HILP(L)/PEF(L) combination was the most acceptable of the selected non-thermal treatments. Industrial Relevance: Heat remains the dominant microbial/enzyme inactivation technique though its impact on food quality is often at odds with increased consumer demand for minimally processed (MP) products. The reduction in intrinsic preservation in MP products raises new safety and stability risks and a major trend is the combination of inhibitory techniques to effectively preserve without the extreme use of a single technique (i.e. hurdle technology). PEF and HILP are emerging nonthermal/mild-heat technologies which have antimicrobial capabilities when applied alone or in combination with other physicochemical hurdles. Only a limited amount of work has focused on combinations of emerging technologies. As consumers have less reservations about physical (vs. chemical) preservation treatments, the objective of this paper is to assess if novel combinations of these emerging physical hurdles achieves the twin goals of food safety and quality in apple juice. This will involve assessing whether these combinations are effective vs. selected microorganisms un-/mildly heated products. In addition the nutritional/sensory quality of these MP products will be compared to untreated products.
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.
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 (@).
Modelling the inactivation of Escherichia coli ATCC 25922 using pulsed electric field
Innovative Food Science & Emerging Technologies, 2008
Microbial tests were conducted to determine the effect of pulsed electric field treatment on microbial inactivation of gram negative Escherichia coli ATCC 25922 suspended in simulated milk ultra filtrate (SMUF). Kinetic analysis of microbial inactivation due to combined pulsed electric ...