Pulsed Electric Fields infood preservation

 

Pulsed Electric Fields

 

Pulsed electric fields PEF is a non-thermal method of food preservation that uses short pulses of electricity for microbial inactivation and causes minimal damaging effect on food qualities. PEF technology aims to offer consumers high-quality foods. High Intensity Pulsed Electric Field (PEF) Processing involves the application of pulses of high voltage (typically 20-80 kV/cm) to foods placed between 2 electrodes. PEF may be applied in the form of exponentially decaying, square wave, bipolar, or oscillatory pulses and at ambient, sub-ambient, or slightly above ambient temperature for less than 1s. Energy loss due to heating of foods is minimized, reducing the detrimental changes of the sensory and physical properties of foods. PEF treatments showed effects on the microbial inactivation in milk, milk products, egg products, juice and other liquid foods

Some important aspects in pulsed electric field technology are the generation of high electric field intensities, the design of chambers that impart uniform treatment to foods with minimum increase in temperature and the design of electrodes that minimize the effect of electrolysis.

Although different laboratory-and pilot-scale treatment chambers have been designed and used for PEF treatment of foods, only 2 industrial-scale PEF systems are available. A PEF system for food processing generally  consists of three basic components : a high voltage pulse generator, a treatment chamber and a control system for monitoring the process parameters (Loeffler, 2006).

Several theories have been proposed to explain microbial inactivation by PEF The most studied are electrical breakdown and electroporation.

Factors that affect the microbial inactivation with PEF are process factors (electric field intensity, pulse width, treatment time and temperature, and pulse wave shapes), microbial entity factors (type, concentration, and growth stage of microorganism) and media factors (pH, antimicrobials and ionic compounds, conductivity, and medium ionic strength. Generally, Gram-positive and Gram-negative bacteria are thought to be more resistant in comparison with yeast cells. Although PEF has potential as a technology for food preservation, existing PEF systems and experimental conditions are diverse, and conclusions about the effects of critical process factors on pathogens of concern and kinetics of inactivation need to be further studied.

Applications :

Application of PEF technology has been extensively used for the pasteurization of various food products like juices, milk & dairy products, soup and liquid eggs. The main limitations are products must be free from air bubbles and must have lower electrical conductivity. Additionally, particle size of food should be less than the gap of the treatment region to ensure appropriate treatment. PEF is generally not suitable for solid foods

PEF in fruit processing

PEF processing has promising applications in fruit processing industry  :-

•       Inactivates microorganisms

•      Prevents of developing off-flavors during the storage

•      Enhances the extraction of intracellular compounds from different fruits.

PEF in dairy industry

•      reduces microbial load from milk without disturbing its quality.

Presence of fat globules and protein molecules protect bacterial cells during treatment. Therefore, it is crucial to validate the worth of PEF treatment to inactivate bacteria with thermal pasteurization. PEF processing of milk was combined with heat treatment up to 55-60°C and a significant reduction was observed in the microbial load.

 PEF and meat  industry

PEF technology  has many positive implications  when employed in meat processing :-

•      such as improves cell permeation to increase tenderness

•      decrease microbial load and increase shelf life

•      maintenance of volatile compounds  in meat during storage.

 

 

 

 

 

 

 

 

 

 


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