Transcript Microwave and RF

Microwave and RF
Plasma Microwave
Ohmic Heating
Why nonthermal processing?
• Enhance microbiological safety
• Extend shelf life
• Low temperature exposure to food products– minimal effect on heat sensitive components
• flavor & functional compounds
• Fresh like attributes
• Shelf stable products can be processed by combining with a
moderate heat
treatment.
High
Pressure Processing
Pulsed Electric Field Processing
Ozone Processing
Irradiation
HIGH PRESSURE PROCESSING
Elevated pressures (up to
120,000 psi or approximately
900 MPa) with or without
addition of heat to achieve
microbial inactivation or to
alter the food attributes in
order to achieve desired
qualities.
• Quality Similar to Fresh Products
– Juices, Seafood, Jam, Avocado, Oysters, Purees,
Sauces, Coffee drink
– Pasteurized and shelf stable high acid food
products
– Pasteurized low acid products
– Shelf stable low acid products
• Equipment/processing costs are
comparable to similar processes
– Typically < $.05/lb
Semi-Continuous
BATCH
Concept from Flow International, Kent, WA
Pressure
T
m
Temperature
P2
P1
T2
Ts
Ps
Pf
Tf
ts
t1
Come-Up
t2
Hold ing
tf
Decompression
Packaging
• Flexible packaging is widely used
– At least one interface of the package should
be flexible for pressure transfer
– Minimize headspace
• Air has different compressibility than food
Process and products development
PRODUCT
NEW
Process OLD
related
limitations
PROCESS
Value
added
NEW
OLD
Compete
against
existing
product
MICROBIAL SAFETY
• HPP treatments are effective in
inactivating most of the vegetative
microorganisms, with pressures
between 200 and 600 MPa at ambient
temperatures.
• Gram-positive organisms are more
resistant than Gram negatives.
• There can be variations in pressure
resistances between strains.
Combined effect of pressure and
temperature on C. botulinum spore
inactivation
•
0
-1
Log (N/No)
-2
-3
35oC
40oC
-4
45oC
50oC
•
-5
-6
550
600
650
700
750
800
850
Pressure (MPa)
Reddy et al., 1999
•
Achieved a 5-log
reduction of type E
spores in phosphate
buffer and model food
system such as crab meat
blend
Spores of nonproteolytic
type B strains (17-B and
KAP9-B) in both
phosphate buffer and
crab meat blend offer
higher resistance
Research is in progress to
identify most resistant C.
OSU HPP Facilities
•HPP pilot plant with kitchen
•Custom made equipment
for microbial inactivation,
in-situ property measurement
under pressure
High Pressure Research
Program at OSU
• High pressure processing of low-acid shelf-stable foods
• Control of food pathogens and spoilage organisms in
food products
• Mathematical modeling of high pressure process and
food property measurement under pressure
• Quality of high pressure processed products
• Impact of high pressure processing on packaging
materials
• Consumer acceptance of high pressure processed foods
• High pressure pasteurization of cheese, milk, and meat
products
Pulsed Electric Field Processing
• Application of short burst
of high voltage (approx.
30-50 kV/cm) to foods
placed between two
electrodes
– pulses applied at
ambient or
refrigerated
temperatures for
short treatment
time of seconds or
less
Potential Food
Applications
• Juice
• Milk
• Liquid eggs
• Soups
• Syrups, sauces
• Emulsion
• Flavor ingredients
Simplified PEF Equipment Layout
Power
Supply
Capacitor
Inductor
Provide Energy
Store Energy
Switch
Release Energy
Treatment
chamber
Process Food
Variables in PEF processing
Primary
Secondary
• Electric field strength
• Processing/conditioning
temperature
• Electrical conductivity / ionic
strength
• Growth stage of
microorganisms / adaptation
• pH
• gas liquid mix
– Average peak field U/d
– Uniformity of field
• Total treatment time
– Resident time in PEF
zone
– Flow velocity profile
– Pulse repetition rate
– Number of PEF
chambers
Microbiological Resistance
– Bacteria > Yeasts
– Gram (+) > Gram (-)
– Bacterial spores & Mold ascospores >
Vegetative cells
– Stationary or Lag growth phase > Logarithmic
phase
Mechanism for cell destruction
a
-
Cytoplasm
•
•
•
•
+
b +
+
+
+
Medium
+
+
+
+
+
+
c
d
(a) Cell membrane with a potential V’m,
(b) membrane compression,
(c) pore formation, reversible breakdown,
(d) large pores are formed, irreversible dielectric breakdown (cited
Zimmermann, 1986)
OSU-6 Commercial Scale PEF processing system
Aseptic processing system, 0-60kV output, 75kW, 2-8 chambers, up to 2000L/h
Food products evaluated using PEF at OSU
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Orange juice
Tomato juice
Apple cider
Peach nectar
Yogurt drink
Beer
Apple sauce
Salsa
• Salad dressing
•Wheat grass juice
•Milk
•Chocolate milk
•Soymilk
•Enriched soymilk
•Rice pudding
•Liquid egg
•Liquid egg white
•Liquid egg Yolk
How can we help you?
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Technology evaluation
Lab scale studies
Pilot scale product tests
Product development technology
Evaluation of processing effects
on food attributes
SUMMARY
– Nonthermal processing technologies offer UNIQUE
opportunities and challenges.
– Nonthermal technologies such as high pressure processing
likely to be used commercially before it could be well
understood scientifically to exploit its full potential.
• Refrigerated products are commercially available.
• Shelf-stable low-acid foods require further research and regulatory
approval.
• Identification of suitable products is critical.
…a safer world through food
safety and technology research
Thank you!
High voltage arc discharge
http://www.designer-bg.com/tok-v-gazove/en/images/dygov.gif
Pulsed light
Oscillating magnetic fields
Irradiation