Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Pulsed Electric Fields for Food Processing Technology
MMA. SHAKOORAFSTUSJP
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Name: M.M. Aaysha Shakoora
School attended: KM/ Mahmud Ladies College
Hobbies: Reading, handicraft & travelling
Interested in: Archery, Horseback riding & Swimming
Believes ,
“THE BEST AMONG YOU ARE THOSE WHO HAVE THE BEST MANNERS & CHARACTER”
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
OVERVIEW
INTRODUCTION SYSTEM COMPONENTS PRINCIPLES OF PEF FACTORS AFFECTING THE OUTCOME OF PEF ADVANTAGES & DISADVANTAGES OF PEF REFERENCES
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
PEF is a non-thermal method of physical food preservation that uses short pulses of electricity for microbial inactivation.
Pulse-burst of current/ voltage/ electromagnetic field energy. A pulse may last from a nanoseconds to several seconds.
Offer High-quality foods.
For food quality attributes, PEF technology is considered superior to traditional thermal processing methods because it avoids or greatly reduces detrimental changes in the sensory and physical properties of foods.
INTRODUCTION
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Use of electricity in food preservation already has more than a 100 year history, since investigations in to bactericidal effect of current carried out by Prochowchik & Spaeth. In the 1940s, treatment of apple mash by DC & AC current was used for increasing juice yield.
In the beginning of 1960s, application of pulsed electric fields (PEF) for disruption of cells in food material was patented by Doevenspeck. He also reported achievement of up to 96% inactivation of Salmonella bacteria suspended in marination brine.
HISTORY………..
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
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foods most often treated in PEF: Fruit juices Apple sauce Milk Liquid egg productsYogurt drinks Salad dressingTomato juice Liquid whole egg
The sensory attributes of foods well preserved & retain a fresh-like quality with extended shelf life after processing
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
System components High-voltage power source - a high voltage DC generator, converts (low)voltage from
an utility line (in Sri Lanka230 V) into high voltage AC, then rectifies to a high voltage DC.
capacitor bank - energy storage
Treatment chamber - hold the food during processing and house the discharging electrodes to generate an electric field in the food material
Electrical switch - to discharge energy from the capacitor across the food
An oscilloscope - used to observe the pulse waveform
former - used to charge a capacitor bank
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Flow chart of a PEF food processing system with basic component.
Schematic diagram of a pulsed electric fields operation
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Two electrodes are connected together with a nonconductive material to avoid electrical flow from one to the other.
Apart from those major components, some adjunct parts are also necessary. In case of continuous systems,
Pump - to convey the food through the treatment chamber Chamber cooling system - diminish the ohmic heating effect & control food
temperature during treatment.
High-voltage & high-current probes - measure the voltage & current delivered to the chamber
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
The Principles of Pulsed Electric
Field The process is based on pulsed electrical currents delivered to a product placed between a set of electrodes.
Food is capable of transferring electricity because of the presence of several ions. So, when an electrical field is applied, electrical current flows into the liquid food and is transferred to each point in the liquid because of the charged molecules present.
The food product experiences a force per unit charge, the so-called electric field, which is responsible for the dielectric cell membrane breakdown in MOs & interaction with the charged molecules of food
Application of pulsed electric fields of high intensity and duration from microseconds to milliseconds may cause temporary or permanent permeabilization of cell membranes enables inactivation of vegetative cells of bacteria and yeasts in various foods.
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
A microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs or DNA to be introduced into the cell.
ELECTROPORATION OR ELECTROPERMEABILIZATION
Process of the cell electroporation by PEF :(1) building the transmembrane potential up by the applied external electric field(2) creation of small metastable hydrophilic pores (3) Evolution of the pore population(4) post-treatment stage (leakage of intracellular compounds, pore shrinkage and disappearance, etc.)
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Electroporation can be either: reversible (cell membrane discharge) or irreversible (cell membrane breakdown or lysis)
but this effect can be controlled depending on the application.
.Treatment packaged aseptically stored under refrigeration.
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Factors affecting the outcome of pulsed electric fields treatments
The lethality factors contributing to the effectiveness of PEF
technological biological media factors
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
TECHNOLOGICAL FACTORS
• FIELD STRENGTH - Microbial inactivation increases with an increase in the electric field intensity, above a critical trans membrane potential.
Evenly distributed electric field intensity efficient treatment. Electric field intensities of smaller than 4-8 kV/cm usually do not affect microbial inactivation. In general, the electric field intensity required to inactivate MOs in foods, in the range of 12-45 kV/cm.
• TREATMENT TIME• TREATMENT TEMPERATURE• PULSE SHAPE & SIZE - square waveforms may be more lethal, energy efficient than
exponentially decaying pulses. square pulses have longer peak voltage duration compared to exponential pulses.
short pulses - avoid excessive heating or undesirable electrolytic reactions.
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
BIOLOGICAL FACTORS
● Individual characteristics of target MOs ● Physiological characteristics
● Growth states Gram (+) cells more resistant to PEF than Gram(-)negative bacteria Yeasts - higher sensitivity than bacteria Larger cells - Induction of electric fields into cell membranes is greater
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
MEDIA FACTORS
The effects of PEF on the food system : PEF system - conductivity, resistivity, dielectric properties, ionic strength, pH & composition Properties of the food - physical and chemical
These factors most likely influence the recovery of injured microbial cells and their subsequent growth following PEF exposure, since the presence of food components, such as fats and proteins , has reportedly had a preventive effect on MOs against PEF treatment
Each of these parameter influences the PEF treatment either alone or in combination.
● But enzymes and proteins are generally more resistant to electric field intensity & pulses than microorganisms. This requires further investigation, especially on the effects of pH, temperature, resistivity and composition of the enzyme or protein-containing medium or food system. As bacterial spores are resistant to pulsed electric fields, applications of this technology mainly focus on food-borne pathogens and spoilage microorganisms, especially for acidic food products
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Advantages of Pulsed Electric Fields Technology
Preservation of solid, semisolid & liquid food
pasteurization - temperatures below 30-40°C
(juices, milk, yogurt, soups, and liquid eggs) Economically & efficiently improve energy usage
Providing microbiologically safe and minimally processed foods.
Causes minimal detrimental effect on food quality attributes
Enhance extraction of sugars (sugar beet) and other cellular content from plant cells
(Improvement of metabolite extraction)
Enhance mass & heat transfer to assist drying of plant tissues
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
Enzyme activity modification
Reducing the solid volume of wastewater
Biotechnology and genetic engineering (electroporation in cell hybridization)
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
● Restricted to food products with air bubbles & low electrical conductivity. presence of bubbles lead to non-uniform treatment, operational & safety problems. When the applied electric field > dielectric strength of the gas bubbles, partial discharges take place inside the bubbles that can volatize the liquid and therefore increase the volume of the bubbles. The bubbles may become big enough to bridge the gap between the 2 electrodes and may produce a spark. Therefore, air bubbles in the food must be removed, particularly with batch systems. Vacuum degassing or pressurizing the treatment media during processing, using positive back pressure, can minimize the presence of gas.
● Continuous processing – so not suitable for solid food products that are not pumpable.
● The systems need to be scaled up to commercial systems.
● The lack of methods to accurately measure treatment delivery
● Costly
DISADVANTAGES
Emerging Food Technologies Presentation Series - 2016
University of Sri Jayewardanepura
https://www.researchgate.net/publication/226595907_Electroporation_of_Cell_Membranes_The_Fundamental_Effects_of_Pulsed_Electric_Fields_in _Food_Processing
Pulsed Electric Fields for Food Processing Technology http://dx.doi.org/10.5772/48678
https://www.researchgate.net/publication/226595907_Electroporation_of_Cell_Membranes_The_Fundamental_Effects_of_Pulsed_Electric_Fields_in_ Food_Processing
REFERENCES