Moderate and high intensity pulsed electric fields : Effect on microbial inactivation, shelf life and quality of fruit juices

2018 ◽  
Author(s):  
Rian Adriana Hendrika Timmermans
Keyword(s):  
Shelf Life ◽  
Electric Fields ◽  
High Intensity ◽  
Pulsed Electric Fields ◽  
Fruit Juices ◽  
Microbial Inactivation

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.

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