scholarly journals Continuous processing of skim milk by a combination of pulsed electric fields and conventional heat treatments: does a synergetic effect on microbial inactivation exist?

2006 ◽  
Vol 86 (3) ◽  
pp. 203-211 ◽  
Author(s):  
Juliane Floury ◽  
Noël Grosset ◽  
Elodie Lesne ◽  
Romain Jeantet
Keyword(s):  
Electric Fields ◽  
Synergetic Effect ◽  
Skim Milk ◽  
Pulsed Electric Fields ◽  
Heat Treatments ◽  
Microbial Inactivation ◽  
Continuous Processing

Enhancing Inactivation of Staphylococcus aureus in Skim Milk by Combining High-Intensity Pulsed Electric Fields and Nisin

2006 ◽  
Vol 69 (2) ◽  
pp. 345-353 ◽  
Author(s):  
ÁNGEL SOBRINO-LÓPEZ ◽  
OLGA MARTÍN-BELLOSO
Keyword(s):  
Staphylococcus Aureus ◽  
Electric Fields ◽  
High Intensity ◽  
Treatment Time ◽  
Skim Milk ◽  
Pulsed Electric Fields ◽  
Microbial Inactivation ◽  
Preservation Method ◽  
Set Up ◽  
Treatment Design

High-intensity pulsed electric fields (HIPEF) can be used as a nonthermal preservation method that is believed to enhance the effect of nisin on microorganisms such as Staphylococcus aureus. The survival of S. aureus inoculated into skim milk and treated with nisin, with HIPEF, or with a combination of nisin-HIPEF was evaluated. Nisin dose, milk pH, and HIPEF treatment time were the controlled variables that were set up at 20 to 150 ppm, pH 5.0 to 6.8, and 240 to 2,400 μs, respectively. HIPEF strength and pulse width were kept constant at 35 kV/cm and 4 μs, respectively. No reduction in S. aureus concentration was observed in skim milk at its natural pH after treatment with nisin, but 1.1 log units were recovered after 90 min of treatment at pH 5.0 with 150 ppm nisin. A reduction in viable S. aureus counts of 0.3 and 1.0 log unit in skim milk treated with HIPEF at its natural pH was observed at 240 and 2,400 μs, respectively. The nisin-HIPEF treatment design was based on a response surface methodology. The combined effect of nisin and HIPEF was clearly synergistic. However, synergism depended on pH. A maximum microbial inactivation of 6.0 log units was observed at pH 6.8, 20 ppm nisin, and 2,400 μs of HIPEF treatment time, whereas a reduction of over 4.5 log units was achieved when pH, nisin concentration, and HIPEF treatment times were set at 5.0, 150 ppm, and 240 μs, respectively.

Inactivation of Microorganisms in Cloudy Ginkgo (Ginkgo biloba Linn.) Juice by Pulsed Electric Fields

2007 ◽  
Vol 13 (2) ◽  
pp. 83-90 ◽  
Author(s):  
H. Zhang ◽  
Z. Wang ◽  
R.-J. Yang ◽  
S.-Y. Xu
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Treatment Time ◽  
Synergistic Effects ◽  
Pulsed Electric Fields ◽  
Bath Temperature ◽  
Microbial Inactivation ◽  
Plate Counts

Pulsed electric fields (PEF) were applied to neutral ginkgo cloudy juice to study the influence of the electric field strength, the treatment time and temperature on microbial inactivation. The results showed that microbial inactivation increased with the electric field strength, the treatment time and temperature. PEF treatment caused 3.39 and 4.44-log cycles reduction of coliforms and total plate counts, respectively, when pulse duration was 3 μs, the electric field strength 30 kV/cm, the treatment time 520 μs and the water bath temperature 15°C. Under the same conditions, the microbial shelf life of ginkgo cloudy juice was extended to 24 days at 4°C and 18 days at room temperature. A 3.7-log cycles reduction of the total yeast and mould counts was obtained by applying 390 μs of 30 kV/cm at 15°C.Yeast and mould cells were less resistant to PEF process than bacteria cells. The effect of heat generated during the PEF treatment was limited on microbial inactivation. Temperature and the induced heat by PEF had synergistic effects to microbial inactivation in cloudy ginkgo juice.

Combined Effects of Heat and PEF on Microbial Inactivation and Quality of Liquid Egg Whites

2007 ◽  
Vol 3 (4) ◽  
Author(s):  
Wei Zhao ◽  
Ruijin Yang ◽  
Yali Tang ◽  
Rongrong Lu
Keyword(s):  
Electric Fields ◽  
Treatment Time ◽  
Combined Treatment ◽  
Pulsed Electric Fields ◽  
Egg White ◽  
Microbial Inactivation ◽  
Processing Temperature ◽  
Combined Effects ◽  
Egg White Proteins ◽  
Emulsifying Capacity

Combined effects of heat and pulsed electric fields treatment (20 and 40oC, 0-800 µs at 30 kV/cm) on microbial inactivation inoculated in egg whites were studied. Pulsed electric fields treatment time and processing temperature had profound effects on microbial inactivation. Pulsed electric fields treatment with a bipolar pulse (2 µs wide), an intensity of 30 kV/cm, a frequency of 100 Hz, the processing temperature of 40 oC and treatment time for 800 µs, was sufficient to achieve pasteurization conditions using S. enteritidis , E. coli and S. aureus, common spoilage and pathogenic micro-organisms in egg products. This treatment produced a non-significant (p>0.05) increase in foaming capacity and stability and an increase (p<0.05) in emulsifying capacity and stability. Surface free sulfhydryls and hydrophobicity of egg white proteins increased with the increment of the PEF treatment time due to the partial unfolding of egg white proteins. Almost 50 % of trypsin inhibitory activity of ovomucoid in liquid egg white was decreased when the treatment time extended to 800 µs. These results suggested that combined treatment of heat and pulsed electric fields could be applied to process liquid egg whites to get desired products.

MICROBIAL INACTIVATION of FOODS BY PULSED ELECTRIC FIELDS

1993 ◽  
Vol 17 (1) ◽  
pp. 47-73 ◽  
Author(s):  
ARMANDO J. CASTRO ◽  
GUSTAVO V. BARBOSA-CÁNOVAS ◽  
BARRY G. SWANSON
Keyword(s):  
Electric Fields ◽  
Pulsed Electric Fields ◽  
Microbial Inactivation
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