This document provides an overview of various traditional and modern food storage and preservation techniques. It begins by defining food preservation and discussing its importance. Then it describes common traditional methods like drying, pasteurization, freezing, chilling, and thermal sterilization. Modern techniques discussed include irradiation, high pressure processing, pulsed electric field processing, and ohmic heating. For each technique, it provides details on the basic principles, processes involved, effects on microorganisms, advantages and examples of foods preserved. It also includes diagrams of irradiation equipment and the design of an ohmic heating unit developed by the author.

1. WELCOME
Presented
By
Eresh Kumar Kuruba
Teaching Associate
Polytechnic of Agricultural Engineering
Anakaplle, A.P

2. Food Storage Systems

3. Introduction
• Foods are organic substances which are
consumed for nutritional purpose. Food undergo
spoilage due to microbial, chemical or physical
actions.
• Nutritional values, color, texture and edibility of
foods are susceptibility to spoilage. So foods are
required to be preserved to retain their quality
for long period of time.
• Food preservation is defined as the process or
techniques undertaken in order to increase shelf
life, retaining original nutritional values, color,
texture and flavor.

4. • Ancient time – Hunting, direct eating- No
Storage. Storing and preservation is the 1st step
in civilization.
Common Preservation Techniques
Physical methods
Chemical methods
Biological methods

7. Traditional Methods
Drying
• Drying or dehydration is the process of removing
water from a solid or liquid food by means of
evaporation.
• The purpose of drying is to obtain a solid product
with sufficiently low water content. It is one of the
oldest methods of food preservation.
• Drying has numerous advantages. It reduces weight
and volume of foods, facilitates foods storage,
packaging, and transportation, and also provides
different flavors and smells.
• With all these benefits, drying is apparently the
cheapest method of food preservation

8. Pasteurization
• Pasteurization is a physical preservation technique in which food is
heated up to a specific temperature to destroy spoilage causing
microorganisms and eneszym.
• Almost all the pathogenic bacteria, yeasts, and molds are destroyed
by this process. As a result, the shelf life of food increases.
Pasteurization techniques
• The efficiency of pasteurization depends on the temperature–time
combination. This combination is mostly based on the thermal
death-time studies of heat-resisting microorganisms [55]. On the
basis of temperature and heat exposure, pasteurization can be
categorized
• vat –batch Process.
• high temperature short time (HTST) are continuous processes
and ultra-high temperature (UHT)

9. Criteria VAT HTST UHT
Process type Batch Continuous Continuous
Typical temperature–time
combination
65 °C for 30 min 72 °C for 15–30 s 135–150 °C for a few
seconds
Foods preserved Butter milk and sour cream
Milk,
eggnog, frozen dessert
mixes,
fruit juices, etc.
Milk
Shelf life Several days when
refrigerated
2–3 weeks when
refrigerated
6–9 months when
aseptically
Type of microbes destroyed Vegetative pathogens Vegetative pathogens All bacteria and spores
Comparison between different pasteurization techniques

10. Difference between Pasteurization and Sterilization

11. Thermal sterilization
• Thermal sterilization is a heat treatment process that completely
destroys all the viable microorganisms (yeasts, molds, vegetative
bacteria, and spore formers) resulting in a longer period of shelf
life.
• Retorting and aseptic processing are two categories of thermal
sterilization.
Freezing
• Freezing slows down the physiochemical and biochemical
reactions by forming ice from water below freezing temperature
and thus inhibits the growth of deteriorative and pathogenic
microorganisms in foods. It reduces the amount of liquid water
in the food items and diminishes water activity.
• Nucleation and growth are two basic sequential processes of
freezing. Nucleation means the formation of ice crystal, which is
followed by ‘growth’ process that indicates the subsequent
increase in crystal size

12. Chilling
• In chilling process, the temperature of foods is maintained
between −1 and 8 °C. Chilling process reduces the initial
temperature of the products and maintains the final
temperature of products for a prolonged period of time.
• It is used to reduce the rate of biochemical and microbiological
changes and also to extend shelf life of fresh and processed
foods
• In practice, freezing process is often referred to chilling, when
cooling is conducted at <15 °C.
• Chilling can be done by using various equipment's, such as
continuous air cooler, ice bank cooler, plate heat exchanger,
jacketed heat exchanger, ice implementation system, vacuum
attribution system, and cryogenic chamber

14. Irradiation - The Next Level of
Preservation Technology
• Irradiation processing of food involves the controlled
application of energy from ionizing radiations such as
gamma rays, electrons, and X-rays for food
preservation.
• Gamma rays and X-rays are short wavelength
radiations of the electromagnetic spectrum. Gamma
rays are emitted by radioisotopes such as Cobalt- 60
and Caesium-137 while electrons and X-rays are
generated by gaseous discharge using electricity.

15. IRRADIATION EQUIPMENT

16. Process of Irradiation:-
• Gamma rays are a part of the electromagnetic spectrum. They
can penetrate deep into food materials and bring about desired
effects.
• Radiation processing of food is carried out inside an irradiation
chamber shielded by 1.5 to 1.8 meter thick concrete wall.
• Food, either pre-packed or in-bulk, placed in suitable
containers is sent into the irradiation chamber with the help of
an automatic conveyor. The conveyor goes through a concrete
wall labyrinth, which prevents radiation from reaching the
work area and operator room.
• When the facility is not in use the radiation source is stored
under 6 meter deep water. The water shield does not allow
radiation to escape into the irradiation chamber, thus
permitting free access to personnel to carry out plant
maintenance.

17. • For treating food, the source is brought to the irradiation
position above the water level after activation of all safety
devices.
• The goods in aluminium carriers or tote boxes are
mechanically positioned around the source rack and are turned
round their own axis, so that contents are irradiated on both the
sides.
• Absorbed dose is checked by placing dosimeters at various
positions in a tote box or carrier.
• The process consists of exposing food product like potatoes or
onions to gamma rays in a shielded room for a specified
duration
• After exposing the food product to certain duration they are
removed from the conveyor and loaded into the truck for
transportation or stored for certain duration

18. PARTS OF IRRADATION:-
 Radiation source
 Radiation shield
 Radiation room
 Conveyor
 Food material
 Control unit
 Storage pool
MEASUREMENT UNITS :-
• The quantity of dose is measured in terms of unit, called Gray,
abbreviated as Gy. It is the unit of absorbed radiation energy.

19. HPP
• Food subjected to very high pressure up to 1,20,000 pounds per
square inch to kill bacteria present in food.
• This process also inactivates spoilage of foods, delays the onset of
chemical and enzymatic deteriorative processes, and retains the
important physical and physiochemical characteristics of foods.
• Freshness and improved taste with high nutritional value are the
peerless characteristics of HPP technology.
• This process is also environmental friendly, since energy
consumption is very low and minimal effluents are required to
discharge.
• The major drawback of this technology is the high capital cost.
• HPP High pressure processing for food products.mp4

20. Principle
Le Chatelier’s: Any phenomenon accompaind by decrease in volume
is enhanced by pressure. Accordingly pressure shifts that of lower
volume.
Isotactic Pressure: Food Products are accompanied by uniform
pressure from every direction and return to their original shape when
the pressure is released.

21. Functioning of HPP
 Pre packed in vacuum packs (or) flexible packing
materials (plastic bottles).
 Selected packing must be able to withstand the high
pressure used, without loosing seal integrity.
 Here foods are placed into a special designed pressure
chamber which is sealed and completely filled wit
portable.
 A pump connected to pressure chamber pressurizes
the water, ie, hydrostatic pressure.
 Pressure acts instantaneously and is equally
distributed, there is no obvious crushing effect on
food material.

22.  Pressure is applied for a set time period typically for a
few seconds to 20 min.
 On completion of time period, the chamber
depressurizes and food can be removed.
 Processing operations is carried out b/t 400 to 600
Mpa ar room temperature.
 Due to effect of pressure, the temperature of the
product in pressure chamber can be raised by 3-6⁰C
for every 100 Mpa raise in pressure, depending iup on
the composition of the food.

23. Effect of HPP on Microorganism
1. Inactivates certain microorganisms.
2. Reduces no of most vegetative bacteria.
3. Spores of both bacteria and moulds are largely
inactivation by HPP.
4. The effectiveness of HPP treatments will
depend on pressure applied, holding time,
temperature and type of food material matrix
and target organism.

25. Pulsed Electric Field
• Pulsed electric field is one of the emerging techniques
to preserve the foods especially the liquid ones, such as
milk, yoghurt, juices, soups, rice pudding, eggs but not
suitable for solid foods.
• It has the potential to produce foods with excellent
sensory and nutritional quality besides extends shelf
life.
• PHE uses short electric pulses to preserve foods.
• High intensity PEF Processing involves the application
of pulses of high voltage typically 20-80 kv/cm to
foods placed in between two electrodes.
• It good alternative to heat pasteurization which
preserves the nutritional quality of foods and is energy
efficient.

26. Principle
• The processing time is calculated by multiplying
the number of pulse times with effective pulse
duration.
• The process is based on pulsed electric carriers
delivered to the product placed b/t set of
electrodes.
• Food is capable of transferring electricity
because of the presence of several ions.
• When an electrical field is applied, electric
current flows into the liquid and transferred to
each point in the liquid because of the presence
of charged molecules.

27. DESIGN OF CONTINUOUS INFRARED RICE BRAN
STABILIZER

28. Ohmic Heating
• Ohmic heating is also known as joule
heating, direct electric heating, electro
heating and electro conductive
heating.
• It is a process in which A.C is passed
through food material to heat them.
• Electric current is passed through
food, resulting in a temperature rise in
the product due to the conversion of
electric energy into heat.
• Electrical energy is dissipate into
heat, which results in rapid and
uniform heating with minimal thermal
degradation.

29. Working Procedure
• The ohmic heating unit comprised of three sections – (i) Storage
tank (ii) Ohmic heat pipe (iii) Support frame. Each section has
been designed separately considering the various laws and then
the three sections were fabricated and assembled to form a
single unit i.e. Ohmic heating unit.
• Fabrication work of designed prototype of ohmic heating unit
for liquid foods was completed. A prototype of continuous type
ohmic heating unit was designed and fabricated for
volumetric/processing capacity of 15±5 litres/hour and which
could be able to elevate the temperature up to 25±50C.

30. The designed and fabricated ohmic heating
unit was first tested for its performance in
batch mode so as to confirm the theoretical
concept on which the unit was developed for
heating liquid food.
The ohmic heating unit was tested for three
liquid foods i.e. sugarcane juice, milk, and
watermelon juice at very low voltages of 20,
25, 30, 35, and 40 V and temperature increase
was measured at every three minutes interval
at 3, 6 and 9 minutes using the
thermocouples.