2. WHY PROCESS FOODS?
1. Extend shelf life
2. Maintain sensory properties
3. Maintain nutritive properties
4. Ensure safety
5. Make more convenient.
6. Economic value
FOOD PROCESSING
THERMAL PROCESSING NONTHERMAL PROCESSING
3. 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
4. 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.
5. 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.
6. 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.
7. 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.
8. • 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.
9.
10.
11.
12. Microbial
inactivation
15-40kV/cm
Improvement
of mass
Sludge Input transfer in
disintegration requirements plant/animal
10-20kv/cm of PEF cell
0.7-3.0kV/cm
In apple juice
22-34kV/cm
13. 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.
14. • 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.
15. 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.
16. Applications
Microbial 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.
17.
18. 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
21. 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.
22. • 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.
23. 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.
24. 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.
25. 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.
26. 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.