INFRARED HEATING

1. INFRARED HEATING
Submitted by- Arati Yadav
Roll no: 22412FST007
MSc Hnrs– Food Technology

2. INFRARED
RADIATION
 William Herschel discovered infrared
in 1800.
 He did this by using a thermometer
for measuring the temperature of the
spectrum of light passing through a
prism.
 IR radiation is electromagnetic
energy which falls between the
region of visible light (0.38-0.78
μm) and microwaves . (11000
mm)
 Therefore, infrared radiation is
defined as part of an
electromagnetic spectrum whose
wavelength ranges from 0.78 to
1000 µm
 Most of the thermal radiation
emitted by objects near room
temperature is infrared.

3. Infrared
radiation is
divided into
three types
1. Near-IR (NIR) with
wavelength ranging from
0.75 to 1.4 µm.
2. Mid-IR (MIR) with a
wavelength between 1.4 and
3 µm.
3. Far-IR radiation (FIR) with
wavelength between 3 and
1000 µm.

4. MECHANISM
IR heating utilizes radiative and conductive heat transfer mechanisms to generate and transfer heat.
IR radiation penetrates directly into the sample and impinges on the surface of material which has
to be dried.
Electromagnetic waves causes thermal movements of the molecules, rotational movement (rotational
frequencies range from 1011 to 1013 Hz with a wavelength of 30 µm-1mm) and the vibrational (stretching)
movement of internal atomic bonds of the food product.
Absorption of EM waves increases the molecular vibration inside the material and results in heat generation in both inside
and surface of material concurrently
(Sakai and Hanzawa, 1994).
Molecules excited by the vibratory movement continuously lose energy in random directions as a result
of collisions between the molecules, which transfer energy to the surrounding environment in the form of
heat
Uniform heating is achieved

5. Energy balance on a thin layer of rough rice
exposed to IR radiation.

6. Interaction of IR with various food
components
 Absorption of proteins by infrared radiation is
at wavelengths 3–4 and 6–9 µm.
 Fat absorption is at wavelengths 3–4, 6 and
9–10 µm.
 Sugars absorption is at 3 and 7–10 µm.
 The water absorption beams are 3, 4.7, 6,
and 15.3 µm (Sandu, 1986) [42].
 Helps reduce beta-carotene and chlorophyll
degradation in the heating process.
 IR irradiation is more effective for
pasteurization than NIR, killing bacteria and
spores
Food materials can be considered complex
matrices consisting of different biochemical
macromolecules, biological polymers, inorganic
salts, and water. During IR heating, the food
object can absorb radiation at certain
wavelengths, reflect and transmit radiation at
other wavelengths.

7. Electrical Emitters Gaseous Type Emitters
Produce infrared radiation in a range
of 1100–2200 ⁰C
Produce infrared radiation in a range of
343–1100 ⁰C
Operating cost- High Cost- very high
Operating cost- relatively low
Are more widespread because of their
ease of control, fast heating rate, and
clean energy
Have relatively less availability
Conversion efficiency- 78% to 85%, conversion efficiency- 40–46%
Powered electrically
Eg. incandescent lamps, quartz tubes
Powered by propane or natural gas
Eg. Direct-flame IR radiator, ceramic
burner, metal fiber burner,
Classification of Emitters
based on Energy Source
Gas Type
Electrical type

8. Wavelength Short Medium Long
Range 0.7–1.4 μm 1.4–3.0 μm > 3.0 μm
Color of radiation Bright white Bright orange Dull orange
Radiator temperature 1300–2600 K 850–1200 K 500–800 K
Time to maximum temperature or
peak emissive power
Few seconds One minute Five minutes
Power density 300 kW m−2 90 kW m−2 40 kW m−2
Common applications Powder coating, adhesive bonding,
metal castings, preheating
Drying and curing of food products In processes requiring both
convection and IR heating
Source of heating Electric Electric, gas Electric, gas
Dominant mechanism of energy
absorption
Vibration and rotation of atoms and
molecules
Vibration and rotation of atoms and
molecules
Vibration and rotation of atoms and
molecules
Classification of Emmiters based on
wavelength

9. ADVANTAGES
 Less drying time
 Highly energy efficient
 Uniformity in drying
 Homogeneity of heating
◦ High heat transfer rate
◦ Improves the quality of the treated product
◦ Improves the safety of treated food.
◦ High controllability
◦ Reduces the consumption of chemicals and water and also
increases manufacturing efficiency (pan and atungulu,
2010)
◦ Does not produce volatile organic compounds, carobon
monoxide or nitrogen oxides
◦ It does not need heat recycling and does not need an
isolated system (nindo and tang, 2007).
◦ Preserves vitamins and has very little flavor loss, and the
temperature of the surrounding air is not affected
(skjöldebrand, 2001)
LIMITATIONS
Insensitivity to the
reflective properties
of the coating

10. APPLICATIONS
Drying and
Dehydration
Pasteurizatio
n
Infrared
blanching
Infrared
peeling
Infrared
drying
Infrared for
microbial
inactivation
Baking breads
and baked
goods
Browning
meats and
other foods. Roasting
nuts IR radiation could conveniently
be used for decontamination
and disinfection of food and
food-contact surfaces.

11. ◦ Safety- The current research on infrared radiation is that it is not powerful enough to alter the molecular structure of food cooked
using it as a heat source, and its food results are safe for human use and consumption.
Investigation
1. Investigation on heating using infrared radiation at temperatures of 55, 65, 75, and 85 °C, and its effect on
pumpkin drying.
Result- with increasing temperature from 55 to 85 °C, the drying time decreases by about 60%, and the
effective diffusion coefficient has increased by 140%.
2. Investigation on Rice bran which has a high-water content, free fatty acids, vitamin E, and ɣ-oryzanol
content.
Result- Infrared heating affects the water content of rice bran, reducing its shelf life.
Additionally, infrared exposure produced an insecticidal effect in rice bran

12. Contd..
Effect of infrared temperature on total
phenols of orange peel and leaves Changes in peroxide value of roasted almonds with
IR and IR with hot air during storage at 37 °

13. Contd..
Juice
temperatures
change over
time
(a) conventiona
l heating
(a) Infrared
heating

14. (a) IR blanching (b) Hybrid drying system
IR-microwave combination oven. (1)
Upper halogen lamps, (2) lower
halogen lamp, (3) microwaves, (4)
turntable.
Hybrid Infrared Systems

15. Benefits of Hybrid Infrared in Roasting

16. CONCLUSIO
N
 IR heating utilizes radiative and conductive heat transfer mechanisms to generate and transfer heat.
Radiation heating occurs at the surface and conductive heating occurs on the inside of the food
 IR drying is a promising novel method and has attracted a lot of attention for surface heating applications
such as prevention of growth of yeasts and fungi on cheese surfaces, pasteurization of the surface of eggs,
as well as ready-to-eat meats such as hotdogs, arresting fungal spoilage of strawberry during storage as
well as dry pasteurization of raw almonds.
 The development and implementation of IR technologies in the food and agricultural sectors as alternative
and sustainable methods will benefit the environment and reduce energy and water use.
 The need for improved product quality, safety, and energy and processing efficiency are expected to drive
the industrialization of IR technologies for food and agricultural processing.
 IR heating is attractive primarily for surface heating applications. In order to achieve energy optimum and
efficient practical applicability in the food processing industry, combination of IR heating with microwave and
other common conductive and convective modes of heating holds great potential as it heats food quickly and
eliminates the problem of poor quality.
 It is quite likely that the utilization of IR heating in the food processing sector will augment in the near future,
especially in the area of drying and minimal processing.