Hydrostatic pressure processing involves the use of high water pressure in a special pressure vessel to kill the bacteria but preserve texture, nutrients, and color of food.
You can read more about pasteurization here https://agritimps.com/milk-pasteurization-101
Irradiation is the process of exposing fresh food to low amount of x-rays to sterilize and prolong its life. Irradiation can kill microorganisms, insects and parasites and this is a fundamental reason for applying the technology to improve the safety and quality of many food and food products. Food suppliers say that irradiated food is safe and does not make foods radioactive. More than 100 years of research that have gone into accepting of the safe and successful use of irradiation as a food safety method is more than any technology used in the industry today.
A non thermal processing, which primarily used for homogenisation of fat particles in liquid foods. Now emerged as a promising techniques having applications in food processing. This document will deliver the basics and applications of ultrasound in food
Hydrostatic pressure processing involves the use of high water pressure in a special pressure vessel to kill the bacteria but preserve texture, nutrients, and color of food.
You can read more about pasteurization here https://agritimps.com/milk-pasteurization-101
Irradiation is the process of exposing fresh food to low amount of x-rays to sterilize and prolong its life. Irradiation can kill microorganisms, insects and parasites and this is a fundamental reason for applying the technology to improve the safety and quality of many food and food products. Food suppliers say that irradiated food is safe and does not make foods radioactive. More than 100 years of research that have gone into accepting of the safe and successful use of irradiation as a food safety method is more than any technology used in the industry today.
A non thermal processing, which primarily used for homogenisation of fat particles in liquid foods. Now emerged as a promising techniques having applications in food processing. This document will deliver the basics and applications of ultrasound in food
Microwaves are produced inside the oven by an electron tube called a magnetron. The microwaves are reflected within the metal interior of the oven where they are absorbed by food. Microwaves cause water molecules in food to vibrate, producing heat that cooks the food.MW are electromagnetic waves generated by magnetrons and klystrons.
Frequency 300MHz and 300GHz
Wavelength from 1mm to 1m
industrial heating purposes the available frequencies are 915 and 2450MHz
MW giving up their energy to the material, with a consequential rise in temperature
Two imp mechanisms are:
Ionic polarization: conversion of kinetic energy of the moving ions into thermal energy
Dipole rotation: rotation of polar molecules leads friction with surrounding medium and heat is generated
ENERGY EFFICIENCY:
During microwave heating, electrical energy is first converted into microwave energy
The microwave then interacts with foods and is converted into heat
TWO EFFICIENCIES:
Microwave generation efficiency
Microwave absorption efficiency
ENERGY CONSUMPTION
Specific energy consumption was defined as the total energy supplied divided by the amount of water removed during drying
Overheating could increase the energy consumption due to high moisture loss from the overheated region
CONVERSION OF MICROWAVE ENERGY INTO HEAT
MW Heating is a consequence of the interactions between microwave energy and a dielectric material
PD= 55.61 X 10-14 f’ E2 ἐ tanᵹ
where,
PD Power dissipation W/cm3
f ‘ frequency in Hz
E electric field in v/cm (V/m)
ἐ relative dielectric constant
tanᵹ: loss tangent
MICROWAVE OVEN GENERALLY CONSISTS OF THE FOLLOWING BASIC COMPONENTS
(i) power supply and control: it controls the power to be fed to the magnetron as well as the cooking time
(ii) magnetron: it is a vacuum tube in which electrical energy is converted to an oscillating electromagnetic field. Frequency of 2450 MHz has been set aside for microwave oven for home use
Conti…..
(iii) waveguide: it is a rectangular metal tube which directs the microwaves generated from the magnetron to the cooking cavity
(iv) stirrer: it is commonly used to distribute microwaves from the waveguide and allow more uniform heating of food
(v) cooking cavity: it is a space inside which the food is heated when exposed to microwaves
Conti….
(vi) turntable: it rotates the food products through the fixed hot and cold spots inside the cooking cavity and allows the food products to be evenly exposed to microwaves
(vii) door and choke: it allows the food to the cooking cavity. they prevent microwaves from leaking through the gap between the door and the cooking cavity
FACTORS AFFECTING MICROWAVE HEATING
Dielectric properties
Temperature and frequency
Shape and size of food items
DIELECTRIC PROPERTIES
Penetration of microwave energy inside a material is a function of its dielectric properties.
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Introduction to convection
The dimensionless number and its physical significance
Similarity parameters from the differential equation
Dimensional analysis approach and its application
Numerical on Dimensional analysis approach
Review of Navier-Stokes equation
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Food Processing and Preservation Presentation.pptxdengejnr13
The presentation covers key areas on food processing and preservation highlighting the traditional methods and the current, modern methods applicable worldwide for both small and large scale.
2. Content
1. Introduction to Microwave
2.Working of Microwave oven
3. Established Applications in Food
Processing
2
3. 3
Microwaves
(very short wave)
Electromagnetic waves whose frequencies range
from about 300 MHz – 300 GHz or wavelengths
in air ranging from 100 cm –1 mm.
The shortest wavelength region of the radio
spectrum and a part of the electromagnetic
spectrum.
5. 5
History
• The first continuous magnetron was invented
by Randall and Boot, who worked on
producing a radar source to power radar sets
for the British military during World War II.
• A patent was issued in 1950 for “a method of
treating foodstuffs” in which a closed
microwave oven was described for the first
time.
6. •The first major applications:
1. Drying of potato chips
2. Pre-cooking of poultry and bacon
3. Tempering of frozen food and
4. Drying of pasta (Decareau, 1985).
6
• While the first patent describing an industrial
conveyor belt microwave heating system was
issued in 1952 (Spencer, 1952)
Cont..
9. A microwave oven is a kitchen appliance
that cooks or heat food by dielectric
heating.
It is accomplished by using microwave
radiation to heat water and other
polarized molecules in the food.
9
MICROWAVE
OVEN
10. BASIC STRUCTURE OF MICROWAVE OVEN
Stirrer
Waveguide
Magnetron
Power
supply
Cooking
Cavity
Turntable
Door and choke
WORKING
10
12. MAGNETRON OSCILLATOR
12
Have low efficiency and are useful only at low
frequencies (< 500 MHz).
Negative
resistance
Magnetrons
Useful only for frequencies greater than 100 MHz
Cyclotron
frequency
Magnetrons
Provide oscillations of very high peak power and
useful in radar applications
Cavity
Magnetrons
13. MICROWAVE HEATING DEPENDS UPON
13
MOISTURE
CONTENT
• High moisture content generally
translate into greater microwave
absorption and decreased penetration
depth.
• Moisture content is high, product will
heat more efficiently due to larger
dielectric loss factor
• Products of lower moisture content
may also heat well due to lower
specific heat capacity
14. 14
FREQUENCY
• The frequency of microwave greatly
influences the depth of penetration.
• Frequency increases and depth of
penetration decreases.
• The surface heating effect is more
prominent in 2450MHz whereas center
heating effect in more prominent in
915MHz.
15. 15
PRODUCT
PARAMETER
• A direct relationship exists between the
mass and the amount of absorbed
microwave power.
• Density affects microwave heating;
direct relationship exists between
density and dielectric constant.
• It affects the depth of microwave
penetration, and the heating rate and
uniformity
16. 16
TEMPERATURE
• As temperature increases,
evaporation will serve to decrease
the moisture content.
• Temperature effects the dielectric
property.
• Ohlsson (1983) observed that
temperature increased, less
microwave energy was absorbed
18. Microwave heating Conventional heating
Heating process Heated by
surrounding hot air.
Heated by alternating
magnetic field
Organoleptic
property of food
Induce browning or
crisping of food.
Cannot make food
brown and crispy.
Efficiency Heat is lost therefore
less efficient.
Heat is produced and
less energy loss.
(20% energy save)
Comparison Between Microwave And
Conventional Heating
21. BAKING AND COOKING
Case study
MICROWAVE
COOKING
• Microwave cooking with sealed vessels
enabled a drastic reduction in cooking time,
from 110 to 11 min for chickpeas and from
55 to 9 min for common beans, compared
with conventional cooking.
MICROWAVE
BAKING
• Microwave baked cake was found to possess
high springiness, moisture content and the
low firmness as texture attributes compared
with the cake that baked in convection
method.
22. THAWING AND TEMPERING
22
Microwave tempering Conventional tempering
Microwave tempering can be
performed in few minutes for a
large amount of frozen products
(5–10 min for 20–40 kg)
Tempering process takes a long
time (several days) with
considerable drip loss especially
resulting in loss of protein,
which represents an economic
loss.
The lower frequency (915 MHz
band) has an advantage for
tempering of thick products
because of its deeper
penetration and longer
wavelength compared to the
higher frequency (2450 MHz)
microwave.
Done with water or air, subject
the outer surfaces of the product
bulk to warmer temperatures for
long periods, for the heat to
penetrate to the center. This
results in large temperature
gradients.
23. CONTINUOUS MICROWAVE MEAT TEMPERING
SYSTEM
It contains multi-feed processor for meat tempering at 896MHz
23
25. 25
Microwave
assisted air
drying
(MD)
• Microwave assisted air drying is one of the methods
where hot air drying is combined with microwave
heating in order to enhance the drying rate.
• Suitable for drying of high moisture foods in which
reduction in moisture content is time consuming in
final stage as compared to hot air drying process; since
the diffusion process is very slow.
26. 26
Microwave
assisted
freezing
drying
(MFD)
• Freeze drying accompanied concurrently with the help
of microwave
• Microwave drying applied after freeze drying (Duan,
Zhang, Mujumdar,& Wang, 2010a)
Microwave
assisted
vacuum
drying
(MVD)
• In the absence of convection, either conduction or
radiation or microwaves can be combined with vacuum
drying to improve its thermal efficiency (Zhang et al.,
2006).
• Prevents oxidation due to the absence of air, and
thereby maintains the color, texture and flavor of the
dried products
27. Comparison of energy consumption of
different drying methods
Pumpkin
slices
Air oven drying (50 and 75 °C for 45-
90 min)
0.61- 0.78
Microwave drying (with 160 and 350
W for 125-195 min )
0.24 – 0.26
Combined microwave- air drying for
31-51 min (160 W – 50°C, 160 W –
75°C and 350 W- 75°C )
0.33-0.40
Puligundla et al (2013) Potentials of Microwave Heating Technology for Select
Food Processing Applications - a Brief Overview and Update. J Food Process
Technol 4: 278. doi:10.4172/2157-7110.1000278
28. Microwave Blanching
• The first microwave blanching was reported by Proctor and Goldblith
using 3000 MHz for green vegetables, and it was found to retain maximum
amounts of vitamin C.
• Microwave blanching requires little or no water for efficient heat
transfer in food, therefore reduction in the amount of nutrients lost by
leaching.
Foodstuff Procedure Parameters Quantities
Broccoli Traditional
process (92°C
for 0.5-4 min)
Protein (%) 42.62 ±4.88
Vitamin C (mg /100 g dry
sample)
459.77 ± 0.77
Microwave
( 2450 MHz
with 950 W
for 3 min
Protein (%) 44.34 ±1.92
Vitamin C (mg /100 g dry
sample)
565.56 ± 1.49
29. Microwave Pasteurization and Sterilization:
•Firstly, use of microwave systems for pasteurization of
milk was studied by Hamid et al (1969)
•More uniform heating of foods (pasteurization) was
achieved using 915 MHz microwave radiation, and it
could be due to greater penetration depths of 915 MHz
microwaves.
30. 30
• Microwave sterilization process is a high-
temperature-short-time (HTST) type, used not only
to inactivate spoilage microorganisms in foods, but
also to minimize the quality deterioration of foods.
• Microwave sterilization process (128°C and 3 min
processing time) produced products superior to
those from conventional processes of canning
(120°C retort temperature and 45 min processing
time).
Cont..
31. Changes In Viable Counts Of
Microorganisms In Liquid Foods After
Microwave And Conventional Heating
Growth
medium
Treatment Microorganis
m
D value
Foods
Conventional
heating
E. Coli
17.8 min
Microwave
heating
11.6 s
32. 32
Microwave sterilization unit with
external covering
removed(overpressure of 2.5
bar,OMAC, 1992)
Microwave pasteurization line
for prepared meals
(Berstoff, 1992)
33. 33
• Microwave heating has also been used to
concentrate heat-sensitive solutions and slurries at
relatively low temperatures.
• Strawberry concentrate were heated to an internal
temperature of 82–88 °C for 3–4 min resulted in
improved color stability and had a protective effect
on anthocyanin pigment, reactive phenolics, and
ascorbic acid (Wrolstad et al., 1980).
Concentration
34. 34
A Federal standard limits the amount of microwaves that can leak from an
oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per
square centimeter at approximately 2 inches from the oven surface.
35. PENETRATION POWER
RAPID HEAT TRANSFER
MINIMUM FOULING DEPOSITION
HIGH HEATING EFFICIENCY
PERFECT GEOMATRY FOR CIP
SUITABLE FOR HEAT
SENSITIVE, VISCOUS FLUIDS
LOW COST MAINTAINANCE
35
36. Non availability of actual temperature
profiles
Microwave-assisted process not
always results better quality retention
of food products
Leakage of microwaves from the microwave
ovens
Microwave cooking may also increase the
production of carcinogens in foods.
36
37. 37
• Many people believe that microwave ovens are
unsafe.
• Microwaving garlic for 60 seconds depleted allinase,
garlic’s primary cancer-fighting ingredient. (Song &
Milner 2001)
• Microwaves cause a higher degree of “protein
unfolding” than conventional heating. (George DF et
al, 2008)
CONTROVERSIES
38. 38
• Most of the studies are done for short exposure periods at higher
intensities. There is an immense shortage of studies using long
exposure periods with low-level radiation.
• Microwave (MW) Technologies are much more complicated than
conventional methods. Successful development requires
extensive R&D efforts based on good understanding of MW
heating principles and the systems.
• The main obstacles to industrial setup of MW heating processes
are the difficulties in controlling the process and the high energy
costs. Moreover the food industry and the consumer are very
conservative about the use of new technologies.
CONCLUSION
39. REFERENCES
• Microwave (and RF) Heating in Food Processing Applications. Juming Tang, Ph.D.
Professor of Food Engineering Department of Biological Systems Engineering
Washington State University, Pullman WA
• June 2005 Food and Environmental Hygiene Department The Government of the
Hong Kong Special Administrative Region MICROWAVE COOKING AND FOOD
SAFETY Risk Assessment Studies Report No. 19
• A.C. Metaxas Microwave heating IEE (1991). Power Engineering Journal 5(5) in
September
• Venkatesh M.S & Raghavan G.S.V. (2004). An Overview of Microwave Processing
and Dielectric Properties of Agri-food Materials Biosystems Engineering 88 (1), 1–18.
• Kouchakzadeh A& Safari. A. (2015). Studies on microwave energy absorption of
fresh green bell pepper (Capsicum) AgricEngInt: CIGR Journal 17(2): 105.
• YuanY, Xiong S L Q. Jiaqi Zhong Yuzhe Zhang Jiannan L. (2015). Temperature
Control Using Hybrid Control with MRAC and ECS into a MIMO Microwave
Heating Process. Journal of Microwave Power and Electromagnetic Energy, 49 (1):
46-54.
39