Novel-Thermal Technologies in Food Processing and Preservation

1. Novel Thermal Technologies in Food Processing and
Preservation

2. Introduction to Food Processing
Food processing is the transformation
of agricultural products into food, or of
one form of food into other forms
The transformation is induced by
physical, chemical or biological means
Food processing combines raw food
ingredients to produce marketable food
products that can be easily prepared
and served to the consumer
Why
Processing ?
Improves
the taste of
the food
Increases
shelf life
Add
convenience
in eating
Suits life
style & can
add extra
nutrients
Enables easy
transportation
Pathogens/
toxin
removal

3. Thermal food processing
Thermal processing is defined as the aggregate of temperature and time
required to remove a specific number of microorganisms from a food
product
Purpose
The basic purpose for the thermal processing of foods is to
reduce or destroy microbial activity, enzymes activity and to
produce physical or chemical changes to make the food meet a
certain quality standard for consumption
E.g., gelatinization of starch & denaturation of proteins to
produce edible food

4. Thermal Technologies
Conventional Thermal
Technologies
Blanching
Pasteurization/
Sterilization
Others (Retorting, Frying, steaming,
baking, drying, smoking etc.)
Novel Thermal Technologies
Microwave processing
Radio frequency processing
Ohmic Heating
Infrared Heating
High Pressure Processing

5. Overview of Conventional Thermal Technologies
Blanching
It is a unit operation prior to freezing, canning,
or drying in which fruits or vegetables are
heated below 100ºC for the purpose of:
Inactivating natural/endogenous enzymes
Modifying texture
Preserving color, flavor, and nutritional value
Lower microbial load (about 90%)
Removing trapped air
Fig. Fruit and Vegetable Blancher

6. Pasteurization
It is a relatively mild heat treatment, in which food is heated to below
100ºC
Partial destruction of microorganisms
• In low acid foods (pH>4.5, for example milk) it is used to minimize
pathogenic micro-organisms and to extend the shelf life for several
days
• In acidic foods (pH< 4.5, for example bottled fruit) it is used to
extend the shelf life for several months by destruction of pathogenic
micro organism and enzyme inactivation
In this method, minimal changes are caused to sensory characteristics or
nutritive value

7. Types of Pasteurization
• 62.8ºC for 30 min
Low-temperature long time (LTLT):
• 71.8ºC for at least 15 sec
High-temperature short-time (HTST):
• 138ºC for at least 2 seconds
• Kills all microorganisms
• Keeping milk in a closed, sterile container at room temperature
Ultrahigh-temperature (UHT):

8. Purpose of pasteurization w.r.t. different foods
Source: (Barbieri et al., 2015)

9. Sterilization
A thermal process causing
complete destruction of micro
organism from food and uses
temperature above 100°C
Types of sterilized Products:
• Retorted
• Aseptically packaged
*Retort
 Retort is a closed chamber that can
withstand high temperature and pressure
 Retort is a processing method that uses
heat and pressure to sterilize food
 Sterilization is carried out in retort at
121°C for 7 mins (Retorting)
Industrial level Retort machine

10. Other Conventional Thermal Processes
Drying or dehydration
Evaporation
Smoking
 Frying
 Roasting
Baking

11. Disadvantages of Conventional Thermal Processing
Loss of color, flavor, freshness, and some nutritional aspects
Increased costs of facilities and labor
More power requirement and high capital costs
Potential difficulties in uniformity of heating
Formation of toxins on high temperature application e.g., :
Furans in tea
HMF (Hydroxymethylfurfural ) in honey
Limited In-package processing scope
Not suitable for heat sensitive materials
More time consuming processes

12. Why Novel Thermal Technologies ?
Contrary to conventional technologies minimal loss of heat-sensitive
nutrients present in the food
Good preservation effect induced by
• Killing of microorganisms
• Arrest of enzymatic activities
Suitable for In-package processing
Processing of food at low temperature or in less time, so there is no
damage to:
• Bioactive compounds
• Nutrients
• Flavors
“The need for novel thermal processing
technologies in the food industry is a
direct result of consumer demand for
fresh, high quality and healthy products
that are free from chemical preservatives
and yet are safe.’’

13. Microwaves
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
Microwave Heating
Source: (Lentz et al., 2020)

14. 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
While the first patent describing an
industrial conveyor belt microwave
heating system was issued in 1952
(Spencer, 1952)
The first major applications:
1. Drying of potato chips
2. Pre-cooking of poultry and bacon
3. Tempering of frozen food
4. Drying of pasta (Decareau, 1985)

15. The basic structure of microwave heating device consists of:
1) Power Supply and Control
2) Waveguide
3) Magnetron
4) Stirrer
5) Oven cavity
6) Turntable
7) Door and Choke
Structure of Microwave heating device

16. Power supply & control- It controls the power to be fed to the
magnetron as well as the cooking time
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
Structural Component of Microwave heating device
Magnetron and its parts
Source: (Verma et al.,2020)

17. Waveguide: It is a rectangular metal tube which directs the
microwaves generated from the magnetron to the cooking cavity. It
helps prevent direct exposure of the magnetron to any spattered food
which would interfere with function of the magnetron
Structural Component of Microwave heating device
Source: (Verma et al.,2020)
Types of Waveguide

18. Cooking cavity: It is a space inside which the food is heated when
exposed to microwaves
Door and Choke: It allows the access of food to the cooking cavity. The
door and choke are specially engineered that they prevent microwaves
from leaking through the gap between the door and the cooking cavity
Stirrer: It is commonly used to distribute microwaves from the
waveguide and allow more uniform heating of food
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
Structural Component of Microwave heating device Contd…

19. Working Mechanism of MW heating
• Dipolar interaction: Polar molecules such as
water molecules (dipole) inside the food will
rotate according to the alternating
electromagnetic field. The rotation of water
molecules would generate heat for cooking
• Ionic interaction: Ionic compounds (i.e.
dissolved salts) in food can also be accelerated
by the electromagnetic field which in turn
colloid with one another or other molecules to
produce heat.
Water molecules trying
to align themselves in
the direction of magnetic
field, generating heat

20. Working Mechanism of MW Heating
• The Heating through Microwaves depends
upon:
Major factors
affecting MW
Heating
Moisture of food
Density of product
Initial food
Temperature
Frequency of MW
Source: Zhang et. al (2020)

21. ADVANTAGES
Significant reduction
in thermal processing
time (1/4 to 1/10 of
conventional
processing time)
Greatly improved
product visual
and sensory
appeal
Capable of adaptation to
continuous-type
sequential processing
system design
Shelf-stable end-products
eliminate refrigeration
requirements for
processing, warehousing,
transportation, retail sales
storage/presentation
Another applications includes
Tempering of Fish, Meat,
and Poultry
Precooking of Bacon
Cooking Sausage, Puffing
and Foaming
Microwave assisted
extraction of polyphenols
and oleoresins from
different plant and animal
sources
Advantages of Microwave Food Processing

22. 1. Moisture Content
High moisture content generally translate
into greater microwave absorption and
decreased penetration depth
High moisture will cause more
efficient heat generation due to larger
dielectric loss factor
The higher the moisture, there is an
increase in dielectric constant and loss
factor
Factors Affecting MW Heating
However, in some cases, the loss factor
reduces when moisture is increased at
some frequency ranges
Feng et al. reported the increase in the
dielectric constant of apple with an
increase in temperature over the
frequency range (915–1800 MHz) when
moisture is below 70% but decreases
when moisture is greater than 70%
Source: (Verma et al.,2020)

23. 2. Frequency
The frequency of microwave greatly
influences the depth of penetration as:
dp = Depth of penetration (m); λ0 =
Electromagnetic wavelength in free
space (m) = c0 /f; c0 = Light speed in
free space (2.9979×108 m/s);
Factors Affecting MW Heating
f = Field frequency (Hz); 𝝴’ = Dielectric
constant (or) relative electrical
permittivity; 𝝴” = Dielectric loss factor
Frequency increases and depth of
penetration decreases :

24. 3. Product Parameters
 The highly porous food material has
low dielectric properties due to the
extremely low dielectric
properties of air
 The dielectric constant of air is 1
while the loss factor is 0
 Mass of product ∝ amount of
absorbed microwaves power
Density affects microwave heating;
density ∝ dielectric constant
* There is a higher effect of porosity on
the dielectric properties compared to
moisture content
Factors Affecting MW Heating Contd…
Source: (Verma et al., 2020)

25. At particular frequencies (like 915
MHz and 2450 MHz) with increase
in temperature :
Dielectric loss factor due to
ionic conductivity increases
(due to ionic dissociations)
Loss factor due to dipole
rotation of free H2O reduces
4. Temperature
Increased temperature raises the
water mobility resulting in
dielectric properties
As temperature increases,
evaporation will serve to decrease
the moisture content
Factors Affecting MW Heating Contd…
Source: (Verma et al.,2020)

26. Applications of MW in Food Processing
1. Cooking and Baking
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
through convection method

27. Microwave assisted baking
The major task of the microwaves is to accelerate the baking, leading to an
enhanced throughput with negligible additional space required for
microwave power generators
Often combined with conventional or infrared surface baking, microwave
use avoids the remedy of lack of crust formation and surface browning
With the fast combined process, different flour can also be used with high
α-amylase and low protein content (for example- from European soft
wheat)
Applications of MW in Food Processing

28. In contrast to conventional baking, the microwave heating
inactivates this enzyme fast enough (due to a fast and uniform
temperature rise in the whole product) to prevent the starch from
extensive breakdown, and develops sufficient CO2 and steam to
produce a high porous good product
Fig. Microwave assisted
commercial bakery oven
Applications of MW in Food Processing

29. 2. Tempering
Microwave tempering Conventional tempering
Microwave tempering can be performed
in few minutes for a large amount of
frozen meat blocks (5–10 min for 20–40
kg)
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
Lower temperature gradients
Tempering process takes a long time
(several days) with considerable drip
loss especially resulting in loss of
protein, which represents an economic
loss
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
Results in large temperature gradients
Source: (Verma et al.,2020)

30. Effects of block types, weights of frozen meat and initial meat temperature
on final meat temperature and condition of meat blocks tempered in a
batch microwave unit:
(Swain and James, 2005)

31. 3. Drying
MW assisted air drying
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
MW Drying
MW assisted Freeze Drying
MW assisted Vacuum Drying
MW assisted Hot air Drying
Methods
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
Nair et. al (2010)
Applications of MW in Food Processing

32. MW assisted Freeze Drying (MFD)
 A freeze drying with additional
capability of allowing microwaves to
be applied in the drying chamber
(Duan et al, 2008) to cause
sublimation MW assisted Vacuum Drying
 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)
Advantage
Heat generation is within the product itself
allowing instantaneous sublimation
throughout the product volume rather than
layer by layer drying as in case of
conventional methods
Advantage
Prevents oxidation due to the absence of
air, and thereby maintains the color,
texture and flavor of the dried products
Applications of MW in Food Processing

33. MW assisted freeze drying MW assisted vacuum drying
Source: (Kalantari, 2018)
Applications of MW in Food Processing

34. 4. 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
No effluent production
Food stuff Procedure Parameter 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

35. 5. MW assisted thermal sterilization
Microwave-assisted Thermal Sterilization
(MATS) process utilizes a combination of
pressurized hot water and long-wavelength
microwave energy to sterilize food products
 It induces dielectric heating within the food,
resulting in a much shorter heating step and less
damage to sensitive nutritional components
Microwave sterilized products are (128°C and 3
min processing time) superior than conventionally
processed products of canning (120°C retort
temperature and 45 min processing time)
(Dhawan et al., 2014)

36. Radio Frequency Heating
• Radio frequency (RF) or high
frequency dielectric heating refer to the
heating of dielectric material (water)
with electromagnetic energy at
frequency between 1 to 300 MHz
• Radio frequency have Higher
penetration power than Microwaves
• Prime goal of this technology is food
preservation by ensuring its safety and
quality
History
•It was first used in 1895 as a medical
treatment method
•In food processing, it was first explored for
blanching and then for cooking and
dehydrating
•In the 1960s, many attempts were made to
use RF to thaw frozen foods
•In those studies, different frozen food
materials were tested using lab-scale and
even industrial-scale (25 kW) RF systems

37. Principle of RF Heating
• Molecular reorientation and friction occurs due to continuous
realignment (action of changing different position or state) of the
molecules
• Ionic movement towards oppositely charge electrode
• Rapid change in polarity causes heat generation
General radio frequency heating process :

38. Radio Frequency Heating Process
Figure:- Space charge and dipolar polarization in an alternating electric field at radio
frequencies (Orsat and Raghavan, 2005)

39. Conventional Heating vs. RF Heating
• Conventional heating (i.e. conduction, convection, radiation) has a heat source on
the outside
• Heat is transferred to the surface of the material and then conducted to the middle of
the material
• Radio Frequency heating however heats at the molecular level from within
• It heats the middle and surface simultaneously

40. Radio Frequency Heating Microwave Heating
Lower frequency (1-300 MHz) and
high penetration depth
Higher frequency (300 MHz-30 GHz)
and low penetration
One Directional heating Multi-directional heating
Generally 10-15 MHz frequency range
used in industry for food heating
Generally 915-2450 MHz frequency
range used in industry for food heating
RF Penetration depths At 27.12 MHz-
20cm
MW Penetration depths At 915MHz- 8
to 22cm At 2450MHz- 3-8 cm
Radio Frequency Heating Vs. Microwave Heating
Advantages of RF
Faster heating and reduces drying
times
More uniform heating and drying
High efficiency
Selective heating
Energy efficiency
Contactless heating
Deep penetration heating
Avoiding overheating on the surface
of the product

41. Applications of RF in Food based on research work
Meat and fish product
1. RF heating at 27.12 MHz and application of
alternating current of 6kW proved successful to
process meat and fish at industrial level in large
polymeric containers (295 x 253 x 42 mm3) with
better quality retention than conventional heating.
RF
Pasteurization
Sterilization
Thawing
Meat
processing
Blanching
Reheating of
food
Baking
Drying
Wang et al., (2012)

42. 2. RF causes more uniform and deep penetration resulting in rapid and
homogeneous heating, providing nearly 99.999% reduction in infection levels of
Salmonella sp., and Escherichia coli
3. Bulk defrosting of meats and fish
- Because layers, make it difficult to
heat the inner parts. But using RF
there is uniform drying throughout
the product, which improves product
quality.
Iftikhar et. al (2020)
4. Feasible thawing of meat blocks
within a target temperature range of
-1 to +5⁰C
Applications of RF in Food based on research work

43. Thawing of fruits and vegetable
Using RF energy for thawing frozen products such as frozen fruits, vegetables within
2 to 15 min at 14–17 MHz
The use of this technology resulted in better quality due to minimal discoloration
(color loss) and loss of flavor when compared with traditional thawing
Beverages
Orange, apple juice and milk
 For microbial inactivation of orange and apple juice was provided with 27.12 MHz
and product temperature maximum of 65˚C at the outlet
Microbial inactivation in orange ,apple juice and milk was achieved successfully
Applications of RF in Food based on research work

44. RF successfully inactivated E.Coli K12 in apple and orange juice
Application of 2 kW electric power and 27.12 MHz RF demonstrated
optimum conditions to inactivate Listeria and E. coli cells ( Awuah et al.,
2005)
Agriculture produce (drying and
disinfection)
Reduced drying times
Drying and disinfection of high value
commodities like walnut & almonds without
nutritional losses
Control of Mexican fruit fly larvae with
RF treatment used at 48–52˚C with holding
times of 0.5–18 min causing no significant
effect on firmness, soluble solids content and
titratable acidity
Better color retention in fruits
Fig. Reduced drying times

45. Postbaking RF drying
The introduction of RF postbaking into the crackers or biscuits production reduces
checking* from approximately 50% to almost 0% (Holland 2016)
Meanwhile, RF heating increases the
throughput by up to 40% because the RF
energy penetrates the insulating outer crust
of the product to remove water from the
high-moisture center zones.
*Checking
Phenomenon describing cracks on baked
products due to the varying stresses at different
locations caused by uneven removal of moisture
and consequent shrinkage
(Jojo and Mahendran, 2013)
Applications of RF in Food based on research work

46. Disinfection of spices
Black and Red pepper spices
RF heating can control food borne pathogens in spices
In black pepper RF heating at 27.12MHz RF for 50 second resulted in 2.80 to 4.29 log
CFU/g reductions of S. Typhimurium and E. coli O157:H7
In red pepper RF heating at 27.12 MHz RF heating for 40 second reduced pathogens by
3.38 log CFU/g to more than 5 log CFU/g without affecting the color
Effect of RF
disinfestation on quality
parameters of cereals
and cereal products
(↔): no change
(↑): increase/improvement
(↓): decrease
(Radhakrishnan, 2013)

47. Ohmic Heating
• Ohmic heating is an advanced terminal processing method wherein the food material
which serves as an electrical resistor, is heated by passing electricity through resulting
in rapid & uniform heating
*Also known as electrical resistance
heating or joule heating or electro-heating

48. • The electrical energy is dissipated into heat, which results in rapid
and uniform heating. The heating occurs in the form of internal energy
generation within the material.
• Ohmic heating is also known as:
Ohmic
Heating
Joule heating
Electrical
resistance heating
Electro heating
Direct electrical
resistance
heating
Electro conductive
heating

49. The interaction between the local field strength and local electrical conductivity
will govern the local heat generation according to :
Where, Q is heat generation rate per unit volume (W/m³); E is the electric field strength
(V/cm)
k is the electrical conductivity (S/m); λ is the resistivity (ohm-meter); J is the current
density (A/m²)
Q = E²k = λJ²
The actual heating rate for the substance can then be calculated from the equation:
Where,
T is temperature in degree Celsius; t is the time in second; ρ is the density (kg/m³)
C is the specific heat capacity (kJ/kg- C)
ρC is the volumetric heat capacity
dT /dt = Q/ ρC
Ohmic Heating

50. Major parts of Ohmic Heating System
Contains mainly 3 parts:
1. Power supply
2. Heater assembly
3. Control panel
Figure- Ohmic heating process diagram
(Source: Lee et al., 2017)

51. Mechanism of Microbial Inactivation
Thermal inactivation
1) Damage to outer membrane:
loss of lipopolysaccharide
2) Damage to cytoplasmic
membrane: lipoprotein
denatures, membrane lipid melts
3) Ribosome, RNA and DNA
degradation: degradation of ribosomal
subunit , oxidation of DNA
4) Protein denaturation
Electroporation - Formation of holes in a cell membrane due to individual ion
pressure, which cause change in permeability of cell membrane
- Low frequency used in ohmic heating (50-60Hz) allows cell wall to build up
charges and form pores

52. Mechanism contd…
Raj et. al (2020)
Possible
induced
mechanism

53. Factors affecting Ohmic heating
In food with non cellular
structure (e.g., mixture of
water/maltodextrin/agar or
gels) heating rate increase
with increase in frequency
For food with cellular
structure, initial rise in
temperature was obtained with
low frequency
 Rate of heating ∝ to electrical
conductivity of food material
 It increase with increase in ionic
content and moisture mobility.
 Conductivity of food increase by
2-3 times over a temperature rise
of 120ºC
2. Frequency
1. Electrical conductivity

54. Factors affecting Ohmic heating
4. Starch gelatinization
 It cause decrease in EC
and hence slow down
the heating rate
3. Voltage and Electric field
 Rate of heat generation
is ∝ to square of applied
voltage
 Heating time decrease
approx. 78% with increase
in voltage gradient by
2V/cm
5. Fouling effect on electrodes
As temperature increases, protein undergoes
denaturation. These denatured protein
adhere to the electrode and hence fouling
occurs. This cause power to drop and
electrode temperature increase rapidly

55. Applications of Ohmic Heating in Food Industry
Meat processing
The Cooking time of brine cured meat was reduced by great extent
(>0.5Kg/min)
Quicker and uniform thawing with good sensory properties can be obtain
by ohmic thawing of meat (Wang et al., 2002)
Milk product processing
 HTST ohmic pasteurization on quality of goat milk is comparable with
conventional pasteurization
The physical and chemical properties of milk is not affected by ohmic heating
when compared with conventional heating

56. Fruit and vegetable processing
Loss of solid during processing was reduced by great extent ( 50% in some
case) with ohmic pretreated potato cubes as compared to conventional
pretreatment
Studies found that, ohmic blanching enhance water and sugar transfer, since
ohmic heating cause electroporation of cell membrane
Extraction
Beet dye extraction was enhanced by 40% during ohmic heating and was
proportional to electric field
Ohmically heated apple produce more juice than non-treated apple during
mechanical juice extraction
Applications of Ohmic Heating in Food Industry

57. Thawing
Carcasses can be thawed rapidly from -30 C to 30 C and the time is reduced
by 1/4th to 1/5th times that of conventional one
Cell damage and softening were prevented by ohmic heating which reduce
drip loss
Blanching
The quick process time and no dicing reduce solute losses during blanching
It was also found that ohmic blanching at 50V/cm give shortest critical
inactivation time of 54s with best color quality
Fermentation
Ohmic heating of a fermentation vessel containing L. acidophilus reduced the
lag period of the bacteria
Waste water treatment
The lab scale ohmic heating system possessed good performance to coagulate
protein (60 %) from waste water
Applications of Ohmic Heating in Food Industry

58. Advantages of Ohmic Heating
Better nutrient and vitamins retention
Rapid (1-100 C/s) and uniform heating i.e. the product doesn’t experience
large temperature gradient
High energy efficiency (90% electrical energy is converted into heat)
No theoretical upper temperature limit :Environmentally friendly
No hot surface for heat transfer; less risk of surface fouling and
burning of the product
Reduced maintenance cost because of the lack of moving parts
Process can simply be controlled with switch on and off

59. Infrared Heating
• Discovered by William Herschel
• Infrared: below red (infra: below)
• Red is the color of the longest wavelengths of visible light
• “Wavelength longer than visible light but shorter than those of radio waves
are the infrared waves ”
Types of IR waves :
Near IR waves : 0.76-2 µm (Short waves)
Medium IR waves : 2-4 µm (Medium waves)
Far IR waves : 4-1000 µm (Long waves)

60. Radio frequency (RF) also known as high frequency dielectric
heating refer to the heating of dielectric material(water) with
electromagnetic energy at frequency between 1 to 300 MHz
Radio frequency have Higher penetration power than Microwave
Electromagnetic radiation emitted by hot objects
 When it is absorbed, the radiation gives up its energy to heat
materials
Infrared Heating
Rate of heat transfer depends upon
surface temperatures of heating & receiving
materials
surface properties of the two materials
shapes of the emitting & receiving bodies

61. Amount of heat emitted from a perfect radiator (black body) the Stefan–
Boltzmann eq:
Q (J s-1): rate of heat emission; σ = 5.7x10-8 (J s-1m-2K-4): the Stefan-
Boltzmann constant ; A (m2): surface area ;T (K = ºC + 273): absolute
temperature
Radiant heaters are not perfect radiators & foods are not perfect
absorbers, although they do emit and absorb a constant fraction of the
theoretical maximum.
Infrared Heating
Q = σAT4
W = ε σAT4
Where, ε is emissivity of the grey body
(a number from 0 to 1)

62. Principle of IR heating
The efficiency of converting absorbed energy into heat is great at high
wavelengths in IR radiation
Infrared radiation is absorbed by organic matter at separate frequencies
that correspond to the transport of internal molecules between energy
levels.
Principal food components or the radiation-absorbing molecules, including
water, organic compounds, and biological polymers, absorb IR radiant
energy efficiently in the wavelength range of 2.5 μm to 10 μm through
changes in molecular vibration, chemical bonding, electronic excitation
corresponding to the medium- and far-IR regions to generate heat

63. • Such transition within the range of infrared energy is expressed
regarding the rotational movement and the vibrational (stretching)
movement of internal atomic bonds.
• The infrared absorption bands characteristic of chemical groups
relevant to the heating of food presented in table:
Principle of IR heating Contd…
(Source: Aboud et al., 2019)

64. Advantages and Limitations of IR heating
(Source: Sakare et al.. 2020)

65. Applications in food processing and preservation
IR Drying
Infrared wavelengths range from 2.5 to 200 µm and are mostly used in food
drying processes
Application of hot air–assisted IR drying for high-moisture foods that can be
spread in thin layers is widely employed
IR drying has been studied for drying onions, bananas, apples, pineapples,
potatoes, herbs, blueberries, walnuts, cashews, shrimp, rice, barley, and other
foods
Hot air–assisted
IR drying
(Source: Sakare et al.. 2020)

66. Applications in food processing and preservation
IR Blanching
Save energy and water
Fast temperature achievement
Prevent loss of water-soluble nutrients such as ascorbic acid, that are otherwise
lost in water blanching
IR blanching of fruits and vegetables also provides the opportunity to achieve
simultaneous drying
IR Peeling (Dry peeling)
Because of the high heat delivery capability and low penetration depth, IR is a
suitable heating method for loosening skin and peeling of fruits and vegetables
Avoid wastewater generation
Maintains the quality of peeled product

67. Applications in food processing and preservation
Microbial inactivation
IR heating is a nonchemical emerging technology that also has shown potential to be an
effective method for decontamination of pathogens on foods while also preserving high
product quality
Key factors that affecting IR microbial inactivation :
IR power intensity
 Food temperature
 Peak wavelength and bandwidth of IR heating source
Types of microorganisms and their physiological phase
Size and type of food material
Areas of applications
Milk sterilization
Fruit surface
decontamination
Almond
pasteurization
Rice disinfestation
etc.

68. High Pressure Processing
• Also known as “High Hydrostatic Pressure” or “Ultra High Pressure” processing
• It involves the application of high pressures ranging from 100 to 1000 MPa in batch or
semicontinuous manner from a millisecond pulse to over 20 min. at temperatures as low
as 0ºC to above 100 ºC
Intense pressure in the range of 100 – 1000 MPa
with or without heat, allowing most foods to be
preserved with minimal effect on:
-Taste
-Texture
-Nutritional characteristics
Source: Alexandre et. al (2019)

69. HPP+ Heat ?
HPP coupled with heating mechanism is known to impart Synergistics effect.
However the food temperature always increases through the adiabatic heating
i.e., around 3 ºC per 100 MPa at 25 ºC
It broadens the application area
Highly resistant spore-forming microorganisms can be significantly
reduced with a combination of high pressure (exceeding 1000 MPa) and heat
(above 80ºC) to attain significant log reduction
Increase the effect of pressure faced by the food system
Loosens the intermolecular bonding's and making pressure effect more severe
Why ?

70. Working Principle of HPP
• Pascal’s Isostatic Principle : Pressure applied
to a sample is transmitted uniformly and
instantaneously by the entire food sample
whether in direct contact or in a flexible
container, regardless of its shape, volume, size,
or geometry, unlike thermal treatment, which
has slower heating points.
• Le Chatelier’s Principle: Any phenomenon
(phase transition, change in molecular
Configuration, chemical reaction)
accompanied by a decrease in volume is
enhanced by pressure. Accordingly, pressure
shifts the system to that of lowest volume.

71. High Pressure Processing
Source: Huang et al. (2018)

72. Effect of HPP on Microorganism
 Increased pressure causes an increase in
pressure inside microbial cell membrane which
ultimately:
 Ruptures the cell
 Cytoplasmic fluids comes out & cell looses
its integrity
 Interrupts homeostasis and cellular
functions
 Above 300 MPa irreversible cell damage is
achieved breaking the cell membrane integrity
and the flow of internal substances, leading to
cell death
 Bacterial cells are most susceptible
• Higher Pressure 400-600 MPa is required to
kill spores
Source: Srinivas et al. (2018)

73. Application of HPP
Fruit and Vegetables
• Shelf-life extension
• Inactive microorganisms and quality
deteriorating enzymes
Meat and Fish
• Extend shelf-life with no effect on
flavor or nutrients
• No effect on flavor
Dairy Industry
• Increase shelf-life (3 to 10x)
• Better suited for acidic dairy products

74. Milk Processing
HHP treatment at 400–600 MPa can gives raw milk the same quality as
that of pasteurized milk without affecting sensory properties
Application of HPP
(Chawla et al., 2011)

75. Sterilization of Juices and beverage
Study:
The stability of cloudy pomegranate
juice treated with HHP at 400 MPa for 5
min and HTST at 110 °C for 8.6s was
compared. The Total aerobic bacteria
(TAB) count was analyzed between
HHP-treated and HTST-treated samples
during storage at 4 °C for 100 days
HHP almost provided comparable
effect to that of HTST
Application of HPP
(Chen et al., 2013)

76. Study
Effect of HPP on storage stability of
sterilized cloudy pomegranate juice:
HPP proved significant in
inactivation of yeast and mold
Yeats and mold was detected
occasionally in HHP-treated sample
during storage
Application of HPP
Sterilization of Juices and beverage
(Chen et al., 2013)

77. Cold-smoked dolphin fish fillets were
processed at (200–400 Ma)
High pressure did not extend the shelf life,
was able to diminish bacterial counts during
early storage (highlighted in the graph)
*HP-High Pressure
No HP- No High Pressure
Application of HPP
Fish Preservation (Go´mez-Estaca al., 2013)
Fig. Aerobic plate counts at 15 C and lactic acid bacterial counts

78. Conclusions
Food processing is important in transforming agricultural products into
food or more convenient food forms ensuring food security
The Novel thermal technologies has the potential to process the foods,
eliminating nutritional and structural losses otherwise encountered in
conventional thermal food processing
Novel thermal technologies are much more complicated than
conventional methods. Successful development and application requires
R&D efforts based on good understanding of these technologies and their
interaction patterns with food system

79. References
Jojo, S., & Mahendran, R. (2013). Radio frequency heating and its application in food
processing: A review. International Journal of Current Agricultural Research, 1(9), 42-46.
Barbieri, J., Colombo, E., Jerome Ndam, M., Riva, F., Berizzi, A., Bovo, C., ... & Caniato,
M. (2015). SET4food guidelines on sustainable energy technologies for food utilization in
humanitarian contexts and informal settlements.
Verma, D. K., Mahanti, N. K., Thakur, M., Chakraborty, S. K., & Srivastav, P. P. (2020).
Microwave heating: Alternative thermal process technology for food application.
In Emerging Thermal and Nonthermal Technologies in Food Processing (pp. 25-67). Apple
Academic Press.
Huang, H. W., Hsu, C. P., & Wang, C. Y. (2020). Healthy expectations of high hydrostatic
pressure treatment in food processing industry. Journal of Food and Drug Analysis, 28(1),
1-13.

80. Swain, M., & James, S. (2005). Thawing and tempering using microwave
processing. The microwave processing of foods, 174-191.
Kalantari, M. (2018). Microwave Technology in Freeze-Drying Process. Emerging
Microwave Technologies in Industrial, Agricultural, Medical and Food Processing.
IntechOpen, 143-157.
Aboud, S. A., Altemimi, A. B., RS Al-HiIphy, A., Yi-Chen, L., & Cacciola, F. (2019). A
comprehensive review on infrared heating applications in food
processing. Molecules, 24(22), 4125.
Lentz, R. R., Tang, J., & Resurreccion Jr, F. P. (2020). Electromagnetic basis of
microwave heating. In Development of Packaging and Products for Use in Microwave
Ovens (pp. 3-71). Woodhead Publishing.
Dhawan, S., Varney, C., Barbosa‐Cánovas, G. V., Tang, J., Selim, F., & Sablani, S. S.
(2014). The impact of microwave‐assisted thermal sterilization on the morphology, free
volume, and gas barrier properties of multilayer polymeric films. Journal of Applied
Polymer Science, 131(12).
References

81. Chawla, R., Patil, G. R., & Singh, A. K. (2011). High hydrostatic pressure technology in
dairy processing: a review. Journal of Food Science and Technology, 48(3), 260-268.
Chen, D., Xi, H., Guo, X., Qin, Z., Pang, X., Hu, X., ... & Wu, J. (2013). Comparative
study of quality of cloudy pomegranate juice treated by high hydrostatic pressure and
high temperature short time. Innovative Food Science & Emerging Technologies, 19, 85-
94.
Gómez-Estaca, J., Gómez-Guillén, M. C., & Montero, P. (2007). High pressure effects
on the quality and preservation of cold-smoked dolphinfish (Coryphaena hippurus)
fillets. Food Chemistry, 102(4), 1250-1259.
References