pulsed electric field
TRANSCRIPT
PULSED ELECTRIC FIELD
BY-Trishala Verma
WHY PROCESS FOODS?1. Extend shelf life2. Maintain sensory properties3. Maintain nutritive properties4. Ensure safety5. Make more convenient. 6. Economic value
FOOD PROCESSING
THERMAL PROCESSING NONTHERMAL PROCESSING
Non thermal processing
• Producing fresh like foods by replacing thermal treatments.
• Produces minimally processed food with fresh quality and higher nutritive value because of color and flavor retention.
• Examples-- ohmic heating - microwave heating- high hydrostatic pressure (HHP)- ultrasonication- PULSED ELECTRIC FIELD
PULSED ELECTRIC FIELD
Pulse:-• A pulse is a single disturbance that
moves through a medium from one point to the next point.
• A disturbance is in some identifiable medium.
• Energy is transmitted from place to place, but the medium does not travel between two places.
What is pulsed electric field?• Pulsed electric field (PEF) used short electric
pulses to preserve the food.• Pulsed electric field (PEF) treatment is an
innovative and promising method for non-thermal processing of foodstuff.
• It is one of the most appealing technology due to--short treatment time(typically below 1 second).-reduced heating effect.-energy lost during heating food is minimized.-for fresh-like characteristics of food, along with high sensorial quality and nutrient content.
• It is suitable for preserving liquid and semi-liquid foods removing micro-organisms and producing functional constituents. Examples:- milk, fruit juices, soup, egg etc.
Principle• Basic principle - keeping food below temperatures normally
used in thermal processing. • PEF technology is the application of short pulses of high
electric fields with duration of microseconds micro- to milliseconds and intensity in the order of 10-80 kV/cm.
• The processing time is calculated by multiplying the number of pulses times with effective pulse duration.
• The process is based on pulsed electrical currents delivered to a product placed between a set of electrodes; the distance between electrodes is termed as the treatment gap of the PEF chamber.
• The applied high voltage results in an electric field that causes microbial inactivation.
Working• PEF technology is based on a pulsing power delivered to the
product placed between a set of electrodes confining the treatment gap of the PEF chamber.
• The equipment consists of a high voltage pulse generator and a treatment chamber with a suitable fluid handling system and necessary monitoring and controlling devices.
• Food product is placed in the treatment chamber, either in a static or continuous design, where two electrodes are connected together with a nonconductive material to avoid electrical flow from one to the other.
• Generated high voltage electrical pulses are applied to the electrodes, which then conduct the high intensity electrical pulse to the product placed between the two electrodes.
• The food product experiences a force per unit charge, the so-called electric field, which is responsible for the irreversible cell membrane breakdown in microorganisms.
• This leads to dielectric breakdown of the microbial cell membranes and to interaction with the charged molecules of food.
• Hence, PEF technology has been suggested for the pasteurization of foods such as juices, milk, yogurt, soups, and liquid eggs.
Input requirements of PEF
Microbial inactivation15-40kV/cm
Improvement of mass transfer in plant/animal cell
0.7-3.0kV/cm
In apple juice22-34kV/cm
Sludge disintegration10-20kv/cm
Advantages
• LESS TREATMENT TIME.• LOW TREATMENT TEMPRATURE.• Substitute for conventional heat pasteurization or it can
operate at room temperature to retain quality and heat-sensitive vitamins.
• Increase shelf life and maintain food safety with low processing costs.
• Minimally processed foods of fresh quality, which have higher nutritional value because of color and flavor retention
• PEF inactivates vegetative micro-organisms including yeasts, spoilage micro-organisms and pathogens.
• Reduction in microorganisms: 4-6 log• It can be used to pasteurize fluids such as juices, milk and
soups without using additives.
• PEF causes the formation of large, permanent pores in cellular tissues, which can be used to improve juice yield, increase concentrations of functional components and enhance the characteristics of dried produce.
• It can support or replace conventional processing techniques such as enzymatic maceration and mechanical disintegration.
• Low electric field strength and/ or pulse number causes reversible cell rupture stimulating a stress reaction in plants or cell cultures and allowing enzymes or proteins with potential health benefits to be harvested.
• PEF can be used as batch and continuous process.• Used for pretreatment applications for improvement of metabolite
extraction.
Disadvantages
• High capital cost. • PEF treatment is effective for the inactivation of vegetative
bacteria only. • Micro-organisms are destroyed by PEF but spores, with their
tough protective coats, and dehydrated cells are able to survive.
• Refrigeration is required to extend shelf-life.• Treatment does not inactivate enzymes• PEF treatment has considerable added value for specific
product ranges.• PEF is a continuous processing method, which is not suitable
for solid food products that are not pump able.• PEF processing is restricted to food products with no air
bubbles and with low electrical conductivity.
ApplicationsMicrobial Inactivation by PEF
• The applicability of PEF for microbial inactivation of liquid food has been proven by a high number of studies investigating the impact of PEF on vegetative organisms in model as well as real food material.
Juice processing• When PEF treatment is introduced,
juice of exceptional sensorial quality is obtained that closely resembles the juice of freshly squeezed fruits but which is safe from a microbial point of view.
• An additional advantage for producers is the extension of the shelf life that is obtained.
• The shelf life of fresh orange juices is extended by PEF treatment from a few days to a few weeks.
• This extension considerably simplifies the distribution of this kind of juice and results in less waste of juice that otherwise would have expired
Milk Processing
To Obtain Safe and Healthy Shelf-Stable Liquid Foods
• Ensuring safety and maintaining the physico-chemical quality of liquid food products without substantially impacting the content and composition of thermo labile compounds.
• This is especially relevant in the case of plant-based foods, because some of the features, such as aroma or bioactive potential, are related to this heat-sensible fraction.
• Specifically, fruit juices and vegetable-based beverages exhibit a remarkable content in phytochemicals with health-promoting benefits, some of them with a significant antioxidant potential.
• PEF technology has recently been used in drying enhancement, enzyme activity modification, preservation of solid and semisolid food products, and waste water treatment, besides.
• The ability of PEF to increase permeabilization means it can be successfully used to enhance mass and heat transfer to assist drying of plant tissues. Studies conducted on different plant tissues such as potato tissue, coconut,carrots, mango and apple slices.
PEF TREATMENT OF MICROALGAE, SEAWEED, AND
OTHER AQUATIC SPECIES• Different varieties of macro- and microalgae are
sources of vitamins, pigments, proteins as well as antixodative and bioactive substances.
• Algae extracts applying PEF treatment could provide a potential toward a gentler downstream processing.
• There is an increasing in the yield after PEF treatment, mainly in the case of extractablity of growth hormones.
Plant Oil Extraction
Sitzmann and Munch (1988) reported an enhanced separation of tankage emulsions when extracting protein and fat from animal tissue.
A similar effect can be expected after PEF treatment of oil seeds prior to recovery.
Yield and quality of oils has been studied and high oil yield was developed.
Oil recovery from olives was improved by 7.4% after a PEF treatment at 1.3 kV/cm in comparison to the control sample.
In soybean oil an increase in iso-flavonoid content was reported.
Meat & Fish Treatment
• Disintegration of animal cellular tissue is used to enhance the curing of fish or meat products.
• In case of raw ham a long-term curing and air drying is applied. During such procedures a PEF treatment can be applied to improve mass transfer processes and to accelerate curing, reducing the time requirements.
• An increase in mass transfer rates, resulting in faster water transport to the product surface and therefore drying time can be reduced.
• This will lead to drastic saving of energy and better utilization of production capacities during convective air drying.
Sugar Processing
• In Conventional procedures for production of sugar from beets, disintegration and destruction of cell membranes a thermal treatment at temperatures in the range from 70 to 78°C is applied.
• The membrane de-naturation results in an acceleration of sugar release into the extraction media, but also cell wall components such as pectin may become soluble and can diminish juice purity and quality.
• A PEF treatment of sugar beets could increase mass transfer rates and could allow to reduce extraction temperatures and better quality of sugar can be obtained.
References for PEF
http://www.novelq.orghttp://altered-states.net/barry/rife/pulsedelectricflds.htmhttp://www.foodtech-international.com/papers/PulsedElectricField.htmhttp://www.youtube.com/watch?v=uSK-7dqaVLohttp://www.hollandinnovations.es/cool-wave-processing/http://www.slideshare.net/steffin101/applications-of-pulse-electric-fieldhttp://www.sciencedirect.com/science/article/pii/S1466856411000701http://www.smartmilk.eu/http://www.power.uwaterloo.ca/HVEL/research.htmhttp://link.springer.com/article/10.1007%2Fs12393-009-9011-7http://link.springer.com/article/10.1007%2Fs11947-011-0731-3http://link.springer.com/chapter/10.1007/978-94-007-1100-6_12http://link.springer.com/chapter/10.1007/978-0-387-31122-7_4http://link.springer.com/chapter/10.1007%2F978-0-387-31122-7_1http://www.docstoc.com/docs/76279678/Pulsed-Electric-Field-Processing-(PDF)