PULSED ELECTRIC FIELD TREATMENT OF LIQUID WHOLE EGG INOCULATED WITH SALMONELLA ENTERITIDIS

The effects of pulsed electric fields (PEF) on the inactivation of Salmonella Enteritidis inoculated into liquid whole egg (LWE) and on the physical properties and the shelf-life of LWE were studied. PEF processing conditions were 1.2 mL/s flow rate, 200 pps frequency, 2.12 μs pulse duration, 25 kV/cm electric field strength, and 250 μs total treatment time. The PEF processing caused up to 1 log₁₀ cfu/mL reduction in S. Enteritidis population in LWE. The PEF-treated samples were subjected to heat at 55C for 3.5 min to inactivate the remaining bacteria without denaturing the LWE. The combination of PEF and heat treatments led to a 4.3 log₁₀ cfu/mL reduction in S. Enteritidis population (P < 0.05 ) and caused no significant change in viscosity, electrical conductivity, color, pH, and Brix, relative to control samples (P > 0.05 ). The PEF + 55C treated LWE samples presented significantly longer shelf-life at 4C compared with the control and heat treated samples (P < 0.05 ).     

Design of a combined process for the inactivation of Salmonella Enteritidis in liquid whole egg at 55°C

This paper is an evaluation of the lethal effectiveness of a successive application of pulsed electric fields (PEFs) and heat treatment in liquid whole egg (LWE) in the presence of different additives on the population of Salmonella serovar Enteritidis. Synergistic reductions of the Salmonella Enteritidis population were observed when LWE samples containing additives were treated with PEF (25 kV/cm; 100 and 200 kJ/kg), heat (55 °C), or PEF followed by heat. The presence of additives, such as 10 mM EDTA or 2% triethyl citrate, increased the PEF lethality 1 log?? cycle and generated around 1.5 log?? cycles of cell damage, resulting in the reduction of undamaged cells of 4.4 and 3.1 log?? cycles, respectively. The application of PEF followed by heat treatment significantly (p < 0.05) reduced D(55 oC) from 3.9 ± 0.2 min in LWE to 1.40 ± 0.06 min or 0.24 ± 0.02 min in the presence of 10 mM EDTA or 2% triethyl citrate, respectively. A PEF treatment of 25 kV/cm and 200 kJ/kg followed by a heat treatment of 55 °C and 2 min reduced more than 8 log?? cycles of the population of Salmonella Enteritidis in LWE combined with 2% triethyl citrate, with a minimal impact on its protein soluble content. The heat sensitizing effect of PEF treatments in the presence of 2% triethyl citrate on the Salmonella population could enable LWE producers to reduce the temperature or processing time of thermal treatments (current standards are 60 °C for 3.5 min in the United States), increasing the level of Salmonella inactivation and retaining the quality of non-treated LWE.     

Modeling the irradiation followed by heat inactivation of Salmonella inoculated in liquid whole egg

ABSTRACT:  This study presents mathematical models that describe the inactivation of Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Senftenberg suspended in liquid whole egg (LWE) by irradiation followed by heat treatments (IR-H treatments). These models also enable prediction of cell injury in Salmonella after exposure to IR-H. Salmonella viability decreased exponentially (primary model) with heat treating time for all the radiation doses (0, 0.1, 0.3, 0.5, 1.0, and 1.5 kGy) and temperatures investigated (55, 57, and 60 °C). Two secondary models that related the D_T values (time required to eliminate 90% of viable cells at a given temperature) with radiation dose, heating temperature, and recovery medium after treatments were also developed. The developed final equations enabled to establish the process criterion (combinations of irradiation doses, temperature, and heat treatment times) required to achieve a given reduction ( performance criterion ) in Salmonella spp. suspended in LWE or the cell damage caused by the treatments. Process criteria to obtain the established performance criteria (a 5-log₁₀ reduction) on any of the investigated Salmonella serovars were determined to be, 57.7 °C/3.5 min following 1.5 kGy when treated cells were recovered in tryptic soy agar and 59.3 °C/3.5 min following 0.5 kGy when cells were recovered in tryptic soy agar amended with 3% NaCl. Based on our results, current industrial LWE heat treatments (60 °C/3.5 min) would inactivate 3 log₁₀ cycles of the Salmonella population. The results of this study can be applied to engineering design and for the evaluation and optimization of the IR-H process as a new technique to obtain Salmonella -free LWE.     

Inactivation of E. coli 8739 in Enriched Soymilk Using Pulsed Electric Fields

ABSTRACT: Soymilk enriched with dairy proteins was subjected to pulsed electric fields (PEF) to evaluate the inactivation of Escherichia coli 8739 and the extension of microbial shelf-life. The maximum thermal exposure level of sample was 60 °C for 1.6 s during a PEF treatment. A 5.7-log reduction was achieved using PEF at 41.1 kV/cm for 54 μs. PEF inactivation of E. coli 8739 followed a 1st-order kinetic model. D-values of E. coli 8739 were 31.9,18.6, and 11.0 μs at 30,35, and 40 kV/cm, respectively. PEF treatment at 41.1 kV/cm for 54 μs significantly extended the microbial shelf-life at 4 °C ( P < 0.05). No significant change in brightness and viscosity of PEF-treated samples was observed during a 30-d storage at 4 °C. PEF was found effective in inactivation of E. coli in and extension of microbial shelf-life of enriched soymilk.     

Inactivation of natural microorganisms in litchi juice by high-pressure carbon dioxide combined with mild heat and nisin

The individual and combined effects of high-pressure carbon dioxide (HPCD), mild heat (MH) and nisin (200 ppm) on the inactivation of natural microorganisms, including aerobic bacteria (AB), yeasts and molds (Y&;M), in litchi juice were evaluated. The samples were treated at a pressure of 10 MPa and temperatures of 32, 42 or 52 °C for 5, 10, 15, 20, 25 or 30 min. Temperature played a prominent role in the inactivation of both AB and Y&;M when combined with HPCD, particularly for AB at 52 °C and Y&;M at temperatures ≥42 °C. Nisin increased the susceptibility of AB to the combined treatment of HPCD and MH (HPCD + MH). A reduction of 4.19 log cycles was achieved by HPCD + MH at 52 °C for 15 min, and complete inactivation of AB was obtained by combination of HPCD, MH and nisin (HPCD + MH + nisin). No significant effect of nisin was found on the inactivation of Y&;M.     

Evaluation of pulsed electric fields technology for liquid whole egg pasteurization

This investigation evaluated the lethal efficiency of pulsed electric fields (PEFs) to pasteurize liquid whole egg (LWE). To achieve this aim, we describe the inactivation of Salmonella Enteritidis and the heat resistant Salmonella Senftenberg 775 W in terms of treatment time and specific energy at electric field strengths ranging from 20 to 45 kV/cm. Based on our results, the target microorganism for this technology in LWE varied with intensity of the PEF treatment. For electric field strengths greater than 25 kV/cm, Salmonella Enteritidis was the most PEF-resistant strain. For this Salmonella serovar the level of inactivation depended only on the specific energy applied: i.e., 106, 272, and 472 kJ/kg for 1, 2, and 3 Log₁₀ reductions, respectively. The developed mathematical equations based on the Weibull distribution permit estimations of maximum inactivation level of 1.9 Log₁₀ cycles of the target Salmonella serovar in the best-case scenario: 250 kJ/kg and 25 kV/cm. This level of inactivation indicates that PEF technology by itself cannot guarantee the security of LWE based on USDA and European regulations. The occurrence of cell damage due to PEF in the Salmonella population opens the possibility of designing combined processes enabling increased microbial lethality in LWE.     

Salmonella Inactivation in Liquid Whole Egg by Thermoradiation

Salmonella enteritidis in liquid whole egg (LWE) was inactivated using heat, radiation and thermoradiation (combined heat and radiation). Rates of Salmonella inactivation were determined as a function of radiation dose, temperature, initial cell number and pH. Thermoradiation caused a greater reduction in viable cell number than either heat or radiation alone. This effect was more pronounced at pH 6.5 than at pH 7.0, and more so at 60°C than at 50°C. The lower the initial cell number, the faster the rate of Salmonella inactivation. Physical denaturation of LWE was not apparent after thermoradiation below 60°C, and endogenous egg white lysozyme was not affected by thermoradiation (19.5 krad, 60°C) treatment.     

Inactivation of Salmonella enteritidis and Salmonella senftenberg in liquid whole egg using generally recognized as safe additives, ionizing radiation, and heat

The effect of combining irradiation and heat (i.e., irradiation followed by heat [IR-H]) on Salmonella Enteritidis and Salmonella Senftenberg inoculated into liquid whole egg (LWE) with added nisin, EDTA, sorbic acid, carvacrol, or combinations of these GRAS (generally recognized as safe) additives was investigated. Synergistic reductions of Salmonella populations were observed when LWE samples containing GRAS additives were treated by gamma radiation (0.3 and 1.0 kGy), heat (57 and 60 degrees C), or IR-H. The presence of additives reduced the initial radiation Dgamma -values (radiation doses required to eliminate 90% of the viable cells) by 1.2- to 1.5-fold, the thermal decimal reduction times (D,-values) by up to 3.5- and 1.8-fold at 57 and 60 degrees C, respectively, and the thermal D,-values after irradiation treatments by up to 3.4- and 1.5-fold at 57 and 60 degrees C, respectively, for both Salmonella serovars. Of all the additives investigated, nisin at a concentration of 100 IU/ml was the most effective at reducing the heat treatment times needed to obtain a 5-log reduction of Salmonella. Thus, while treatments of 21.6 min at 57 degrees C or of 5 min at 60 degrees C should be applied to achieve a 5-log reduction for Salmonella in LWE, only 5.5 min at 57 degrees C or 2.3 min at 60 degrees C after a 0.3-kGy radiation pretreatment was required when nisin at a concentration of 100 IU/ml was used. The synergistic reduction of Salmonella viability by IR-H treatments in the presence of GRAS additives could enable LWE producers to reduce the temperature or processing time of thermal treatments (current standards are 60'C for 3.5 min in the United States) or to increase the level of Salmonella inactivation.     

Instant infusion pasteurisation of bovine milk. I. Effects on bacterial inactivation and physical–chemical properties

Two types of milk, skim milk and non-standardised raw milk, were heat treated using direct heating by instant infusion pasteurisation with treatment temperatures in the range from 72°C to 120°C and with holding times of less than 1 second. Indirect heating by HTST pasteurisation (72°C for 15 seconds) was used for comparison. The inactivation of microorganisms reached at least the same level when using instant infusion pasteurisation compared to HTST pasteurisation. Changes in the physical-chemical properties were observed in the skim milk fractions of instant infusion pasteurised non-standardised milk, whereas for instant infusion pasteurised skim milk less influence from the treatments was observed.     

Inactivation of Listeria innocua in liquid whole egg by pulsed electric fields and nisin

Consumer demand for fresh-like products with little or no degradation of nutritional and organoleptic properties has led to the study of new technologies in food preservation. Pulsed electric fields (PEF) is a nonthermal preservation method used to inactivate microorganisms mainly in liquid foods. Microorganisms in the presence of PEF suffer cell membrane damage. Nisin is a natural antimicrobial known to disrupt cell membrane integrity. Thus the combination of PEF and nisin represents a hurdle for the survival of Listeria innocua in liquid whole egg (LWE). L. innocua suspended in LWE was subjected to two different treatments: PEF and PEF followed by exposure to nisin. The selected frequency and pulse duration for PEF was 3.5 Hz and 2 micros, respectively. Electric field intensities of 30, 40 and 50 kV/cm were used. The number of pulses applied to the LWE was 10.6, 21.3 and 32. The highest extent of microbial inactivation with PEF was 3.5 log cycles (U) for an electric field intensity of 50 kV/cm and 32 pulses. Treatment of LWE by PEF was conducted at low temperatures, 36 degrees C being the highest. Exposure of L. innocua to nisin following the PEF treatment exhibited an additive effect on the inactivation of the microorganism. Moreover, a synergistic effect was observed as the electric field intensity, number of pulses and nisin concentration increased. L. innocua exposed to 10 IU nisin/ml after PEF exhibited a decrease in population of 4.1 U for an electric field intensity of 50 kV/cm and 32 pulses. Exposure of L. innocua to 100 IU nisin/ml following PEF resulted in 5.5 U for an electric field intensity of 50 kV/cm and 32 pulses. The model developed for the inactivation of L. innocua by PEF and followed by exposure to nisin proved to be accurate (p = 0.05) when used to model the inactivation of the microorganism by PEF in LWE with 1.2 or 37 IU nisin/ml. The presence of 37 IU nisin/ml in LWE during the PEF treatment for an electric field intensity of 50 kV/cm and 32 pulses resulted in a decrease in the population of L. innocua of 4.4 U.     

Effects of high pressure treatment on the quality and storage of kimchi

The effects of high pressure treatment on the microflora and storage of kimchi were investigated. In a bacterial suspension, numbers of Lactobacillus plantarum were reduced by 6 logs by 500 MPa, at 25 °C for 10 min. Kimchi juice did not alter the rate of inactivation of lactic acid bacteria by high pressure treatment. There was no change in the texture of kimchi subjected to a pressure of 400 MPa, but an increase in cutting force was observed at 600 MPa. When kimchi was pressurized at 400 MPa for 10 min at 25 °C and subsequently stored at 20 °C for 4 weeks, the total number of viable cells stayed at 10³ CFU mL⁻¹. High pressure treatment above 400 MPa prevented excessive acidification that typically occurs during the extended storage of kimchi. The inflation of pouches as a result of accumulated carbon dioxide was also prevented by high pressure treatment. Although colour changes were accelerated by high pressure treatment, this study demonstrates that high pressure treatment can be used to control overripening during the distribution and storage of kimchi products.     

High Intensity Ultrasound for Salmonella Enteritidis Inactivation in Culture and Liquid Whole Eggs

High intensity ultrasound (HIU) continues to be researched as a nonthermal inactivation technology of appeal to food manufacturers. The advantages of HIU include maintenance of product quality, freshness, product homogenization, along with simultaneous inactivation of pathogens. Besides, it is simple, relatively inexpensive, and easily adaptable to most processing environments. This study investigated the effect of HIU for Salmonella Enteritidis inactivation in culture and liquid whole eggs (LWEs) to decrease egg‐associated outbreaks. Overnight S. Enteritidis cultures and spiked LWE (both at 8 log CFU/mL) were treated with 20‐kHz HIU for 0, 1, 5, 10, and 30 min (n = 6) in a temperature‐controlled system, not to exceed 20 °C, and replicated thrice. At each time point, samples were enumerated on XLT4 agar and morphologically analyzed using scanning electron microscopy, with measurements of color and rheological properties. Our results revealed significant reduction of healthy S. Enteritidis cells up to 3.6 log CFU/mL and 2.3 log CFU/25 mL after HIU treatment of merely 10 min of overnight culture and 30 min in LWE, respectively (P < 0.05). After 5 and 10‐min HIU treatment, significant reduction of 1.4‐log CFU/25 mL healthy S. Enteritidis in LWE was obtained (P < 0.05). Even at 1‐min exposure time, HIU showed significant 1.9 log CFU/mL reduction of cultures (P < 0.05); however, no log‐reduction was observed in LWE after 1 min. Scanning electron micrographs showed increased cell structural damage using longer HIU exposure. For product color changes, lower redness and yellowness of LWE were observed visually and instrumentally after 5‐min HIU treatment (P < 0.05). The rheological properties of LWE measured at 0 to 200 s^?1 shear rate, showed that shear stress of HIU‐treated LWEs decreased after 5‐min HIU exposure, but increased after 30‐min treatment. This study demonstrated that HIU shows promise for rapid Salmonella control in LWE and other liquid foods, as an alternative inactivation method for use in hurdle approaches.     

Inactivation of Salmonella spp. in liquid whole egg using pulsed electric fields, heat, and additives

This paper evaluates the lethal effectiveness on 7 different Salmonella serovars of the application, in static and continuous conditions, of pulsed electric fields (PEF) followed by heat treatments in liquid whole egg (LWE) with additives (EDTA or triethyl citrate-TC-). Compared to heat treatments, the PEF (25 kV/cm and 75-100 kJ/kg) followed by heat (52°C/3.5', 55°C/2', or 60°C/1') in LWE with 2% TC permitted the reduction of heat treatment time from 92 fold at 52°C to 3.4 fold at 60°C, and 4.8 fold at 52°C in LWE with EDTA for a 9-Log(10) reduction of the population of Salmonella Enteritidis. The new designed treatments inactivated more than 5 Log(10) cycles of Salmonella serovars Dublin, Enteritidis 4300, Enteritidis 4396, Typhimurium, Typhi, Senftenberg, and Virchow, both in static and continuous conditions. Conversely, current heat pasteurization treatments of 60°C/3.5' and 64°C/2.5' reduced 5 Log(10) cycles of various serovars of Salmonella but only 2 and 3-4 Log(10) cycles of Salmonella Senftenberg and Salmonella Enteritidis 4396, respectively. Soluble protein content (SPC) decreased 1.8%, 1.3%, and 5.0% after the successive application of PEF followed by heat at 52, 55, and 60°C in the presence of 2% TC, respectively, whereas 1.6% and 9.4% of SPC were reduced after heat pasteurization at 60 and 64°C, respectively. Results indicate that designed treatments could be an alternative to current heat pasteurization of LWE as showed higher lethal effectiveness against Salmonella serovars with a similar or even lower decrement of the soluble protein content.     

Effects of Pulsed Electric Fields and Thermal Processing on the Stability of Bovine Immunoglobulin G (IgG) in Enriched Soymilk

ABSTRACT: To investigate influences of pulsed electric field (PEF) on bovine IgG immunoactivity, soymilk enriched with hyperimmunized dairy milk protein concentrate was subjected to PEF and thermal treatments. Thermal treatment at 78.8 °C for 120 s inactivated 5.1 logs in natural flora and resulted in 86% decrease in IgG activity PEF at 41 kV/cm for 54 μS inactivated 5.3 logs of natural flora and resulted in no significant change ( P > 0.05) in bovine IgG activity. Specific antigen-binding activity of bovine IgG against Salmonella enteritidis showed parallel correlation with the measurement of IgG concentration. No further significant change in IgG immunoactivity was observed during a 10-wk storage at 4°C in PEF-, thermally-, or un-treated samples.     

Effects of pH,temperature, and pre-pulsed electric field treatment on pulsed electric field and heat inactivation of Escherichia coli O157:H7

This investigation was undertaken to study the inactivation of Escherichia coli O157:H7 by pulsed electric field (PEF) treatment and heat treatment after exposure to different stresses. E. coli O157:H7 cells exposed to different pHs (3.6, 5.2, and 7.0 for 6 h). different temperatures (4, 35, and 40 degrees C for 6 h), and different pre-PEF treatments (10, 15, and 20 kV/cm) were treated with PEFs (20, 25, and 30 kV/cm) or heat (60 degrees C for 3 min). The results of these experiments demonstrated that a pH of 3.6 and temperatures of 4 and 40 degrees C caused significant decreases in the inactivation of E. coli O157:H7 by PEF treatment and heat treatment (P < 0.05). Pre-PEF treatments, pHs of 5.2 and 7.0, and a temperature of 35 degrees C, on the other hand, did not result in any resistance of E. coli O157:H7 cells to inactivation by PEF treatment and heat treatment (P > 0.05).     

Inactivation of Salmonella Typhimurium and Staphylococcus aureus by pulsed electric fields in liquid whole egg

In this study, the lethal effectiveness of pulsed electric fields (PEF) on the inactivation of Salmonella enterica subs. enterica ser. Typhimurium and Staphylococcus aureus in liquid whole egg (LWE) has been investigated. Maximum inactivation levels of 4 and 3 Log₁₀ cycles of the population of Salmonella Typhimurium and S. aureus were achieved with treatments of 45 kV/cm, 30 μs and 419 kJ/kg, and 40 kV/cm for 15 μs and 166 kJ/kg, respectively. The non-linear kinetics of inactivation observed for both microorganisms at all the investigated electric field strengths were described by mathematical equations based on the Weibull distribution. The developed equations enabled to compare the microbial resistance to PEF and to establish the most suitable treatment conditions to achieve a determined level of microbial inactivation. PEF treatments varying from 30 kV/cm, 67 µs and 393 kJ/kg to 45 kV/cm, 19 µs and 285 kJ/kg allow to reduce 3 Log₁₀ cycles the population of the microorganism of concern in PEF food processing of LWE, Salmonella Typhimurium.Industrial relevanceThe data presented in this investigation in terms of electric field strength, specific energy and treatment time result of relevance to evaluate the possibilities of PEF technology to pasteurize LWE with this technology. The models developed in this study can be applied to engineering design, and for the evaluation and optimization of the PEF technology as a new technique to obtain Salmonella free LWE.Based on our results it is not recommended to apply treatments of energy levels higher than 250 kJ/kg, since PEF lethality hardly increased but markedly augmented the energetic costs. For these energy values, PEF technology by itself is not sufficient (3 Log10 cycles in the best case scenario) to assure the safe security of LWE. Therefore, intelligent combinations of PEF with other preservation technologies have to be developed in order to use pulsed electric fields as an alternative to heat pasteurization of LWE.     

Pasteurization of Fresh Orange Juice Using Low-Energy Pulsed Electrical Field

ABSTRACT: Using the hurdle approach, temperature, acidity, and number of pulses were varied to maximize microbial inactivation in orange juice. The effect of PEF combined with the addition of nisin, lysozyme, or a combination of both to orange juice was also investigated. Optimal conditions consisting of 20 pulses of an electric field of 80 kV/ cm, at pH 3.5, and a temperature of 44 °C with 100 U nisin/ml resulted in over a 6-log cycle reduction in the microbial population. The process was most influenced by a change in temperature (p < 0.0001). Following treatment, there was a 97.5% retention of vitamin C, along with a 92.7% reduction in pectinmethylesterase activity. The microbial shelf-life of the orange juice was also improved and determined to be at least 28 d when stored at 4 °C without aseptic packaging. Gas chromatography revealed no significant differences in aroma compounds before and after pulsing.     

Inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in Liquid Egg White Using Pulsed Electric Field

ABSTRACT: The effects of temperature and pulsed electric field (PEF) intensity on inactivation of pathogens such as Escherichia coli O157:H7 and Salmonella enteritidis in egg white was investigated. Liquid egg white inoculated with 10⁸ colony-forming units (CFU)/mL of each pathogen was treated with up to 60 pulses (each of 2 JAS width) at electric field intensities of 20 and 30 kV/cm. The processing temperatures were 10°C, 20°C, and 30°C. After treatment, uninjured and total viable cells were enumerated in selective and nonselective agars, respectively. Maximum inactivations of 3.7 and 2.9 log units were obtained for S. enteritidis and E. coli O157:H7, respectively, while injured cells accounted for 0.5 and 0.9 logs for E. coli O157:H7 and S. enteritidis , respectively. For both bacteria, increasing treatment temperature tended to increase the inactivation rate. There was synergy between electric field intensity and processing temperature. The inactivation rate constant k _T values for E. coli O157:H7 on both selective and nonselective agars were 8.2 × 10^-3 and 6.6 × 10^-3/μS, whereas the values for S. enteritidis were 16.2 × 10^-3 and 12.6 × 10^-3/μS, respectively. The results suggest that E. coli O157:H7 was more resistant to heat-PEF treatment compared with S. enteritidis.     

Cross-protective effects of temperature, pH, and osmotic and starvation stresses in Escherichia coli O157:H7 subjected to pulsed electric fields in milk

The effect of exposure of Escherichia coli O157:H7 to prior stress on the effectiveness of pulsed electric field (PEF) treatment of milk was studied. Cells were exposed to a variety of temperatures (7–45 °C), pH (4.0–7.0), osmotic conditions (0–10% NaCl), starvation (100 h at 25 °C), and cold shock (5 °C for 250 h). Stress responses were explained by the Gompertz and Weibull models with similar goodness-of-fit. Using these models, conditions that induced adequate stress were identified and used to pre-condition E. coli O157:H7 cells. The inactivation of the bacterial cells in milk by PEF was characterized by downward concavity with differences in mean time of resistance between cells exposed to temperature, acid or osmotic stress. Application of the Weibullian–Log-Logistic model indicated that, at higher field strengths, inactivation occurred at lower onset temperatures, and this was related to an increase in heat dissipation.     

Effect of heat,nisin and ethylene diamine tetra‐acetate treatments on shelf life extension of liquid whole egg

This study examined the effect of nisin alone or in combination with pasteurisation or ethylene diamine tetra‐acetate (EDTA), on the shelf life of unpasteurised liquid whole egg (LWE) stored at refrigerator temperature for a period of 21 days. The shelf life of samples was determined by counting total mesophilic bacteria, yeast and mould and also pH changes. It was observed that addition of 3 ppm nisin to pasteurised LWE was effective enough to extend the shelf life of this product from about 7 days to at least 21 days. However, for unpasteurised LWE nisin alone had no significant effect on shelf life while treatment of LWE with nisin in combination with EDTA showed a significant antibacterial and antifungal activity leading to extended shelf life of unpasteurised LWE from 1 to 4 days to at least 21 days.