Food preservation includes food processing practices which prevent the growth of microorganisms, such as yeasts (although some methods work by introducing benign bacteria or fungi to the food), and slow the oxidation of fats that cause rancidity. Food preservation may also include processes that inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut during food preparation. By preserving food, food waste can be reduced, which is an important way to decrease production costs and increase the efficiency of food systems, improve food security and nutrition and contribute towards environmental sustainability.For instance, it can reduce the environmental impact of food production. Many processes designed to preserve food involve more than one food preservation method. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit's moisture content and to kill bacteria, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). Different food preservation methods have different impacts on the quality of the food and food systems. Some traditional methods of preserving food have been shown to have a lower energy input and carbon footprint compared to modern methods.

1. FOOD
PRESERVATION
Name –Vedant Sawant
Roll no.-19FET107
Food microbiology
presentation

2. Food preservation
• Food preservation is the process of treating and
handling food to stop or greatly slow down spoilage
(loss of quality,edibility or nutritive value) caused or
accelerated by microorganisms.
• Food preservation may also include processes that
inhibit visual deterioration, such as the enzymatic
browning.
• Different food preservation methods have different
impacts on the quality of the food and food systems.
• Eg-Some traditional methods of preserving food
have been shown to have a lower energy
input and carbon footprint compared to modern
methods.

3. History

4. Food spoilage

5. Why to preserve food?
1. To add variety to our meals during seasons when
the food items are unavailable.
2. Perishable foods have been made available year-
round .
3. To make food item available in areas where it is not
grown.
4. Makes transportation of food items easier.
5. Reduces food wastage.
6. To preserve colour ,taste and nutritive value of
food.
7. Also, foods in general are being produced in a
cleaner and more sanitary manner than before.

6. Principles of food preservation
1. Prevention or delay of microbial decomposition
a By keeping out microorganisms (asepsis)
b By removal of microorganisms, e.g., by filtration
c By hindering the growth and activity of microorganisms, e.g., by low
temperatures, drying, anaerobic conditions, or chemicals
d By killing the microorganisms, e.g., by
heat or radiation
2. Prevention or delay of self-decomposition of the food
a By destruction or inactivation of food enzymes, e.g., by blanching
b By prevention or delay of purely chemical reactions, e.g., prevention of
oxidation by means of an antioxidant
3. Prevention of damage because of insects, animals, mechanical causes,
etc.

8. Preservation methods classification
• Traditional methods
1. Drying
2. Cooling
3. Freezing
4. Boiling
5. Heating
6. Salting & Sugaring
7. Pickling
8. Lye
9. Canning
10. Jellying
11. Smoking
• Industrial modern methods
1. Pasteurization
2. Vaccum packing
3. Artificial food additives
4. Irradiation
5. Pulsed electric field
electroporation
6. Modified atmosphere
7. Non-thermal plasma
8. High pressure food
preservation
9. Hurdle technology
10. Biopreservation

9. Food preservation methods
• The chief methods of food preservation are as follows:
• 1. Asepsis, or keeping out microorganisms.
• 2. Removal of microorganisms.
• 3. Maintenance of anaerobic conditions, e,g., in a sealed,
evacuated container.
• 4. Use of high temperatures.
• 5. Use of low temperatures.
• 6. Drying; this includes the tying up of water by solutes,
hydrophilic colloids, etc.
• 7. Use of chemical preservatives, either developed by
microorganisms or added.
• 8. Irradiation.

10. • 9. Mechanical destruction of microorganisms, e.g.,
by grinding, high pressures, etc. (not used
industrially).
• 10. Combinations of two or more of above
methods. Only rarely is a single method effective,
and usually several are combined.
• When preservative methods are combined, the
required intensity of each method usually is reduced
to less than that for preservation by one method
alone.
• For eg-
1. When benzoate or sórbate is added to fruit juices,
less heat is required for sterilization of these
products.
2. Foods previously irradiated with gamma rays or
treated with antibiotic tylosin require less heat for
their sterilization than foods not so treated.

11. Asepsis
• Natural protection-outer layer of animal and plant tissue protects the
inner layer free from microorganisms. This protective covering will
delay/prevent microbial decomposition eg. Shells of nuts, skin of fruits
and vegetables,etc.
• Packaging of foods- such as wrapping, hermetically sealed containers.
This methods will prevent primarily contamination during handling.
• Sanitary methods of handling and processing foods-eg. In dairy industry,
contamination with microorganisms is avoided as much as possible in
the production and handling of market milk.
Removal of microorganisms
1. Filtration
2. Centrifugation/Sedimentation
3. Washing
4. Trimming

12. Anaerobic conditions
• A preservative factor in sealed, packaged foods may be the
anaerobic conditions in the container.
• A complete fill, evacuation of the unfilled space (the head
space in a can), or replacement of the air by carbon dioxide
or by an inert gas such as nitrogen will bring about anaerobic
conditions.
• Spores of some of the aerobic sporeformers are especially
resistant to heat and may survive in canned food but be
unable to germinate or grow in the absence of oxygen.
• Production of carbon dioxide during fermentation and
accumulation at the surface will serve to make conditions
anaerobic there and prevent the growth of aerobes.

13. Preservation using high temperatures
1. Pasteurization
• Pasteurization is a heat treatment that kills part but not all of the
microorganisms present and usually involves the application of
temperatures below 100 C.
• The heating may be by means of steam, hot water, dry heat, or electric
currents, and the products are cooled promptly after the heat
treatment.
• Pasteurization is used
1. when more rigorous heat treatments might harm the quality of the
product, as with market milk,
2. when one aim is to kill pathogens, as with market milk,
3. when the main spoilage organisms are not very heat resistant,
such as the yeasts in fruit juices,
4. when any surviving spoilage organisms will be taken care of by
additional preservative methods to be employed, as in the chilling
of market milk,
5. when competing organisms are to be killed, allowing a desired
fermentation, usually by added starter organisms, as in cheese
making.

14. 2. Heating at about 100 C
• Formerly, home canners processed all foods for varying lengths of time
at 100 C or less.
• Now, most home canners use pressure cookers for the less acid foods.
• Methods-
1. Baking
2. Simmering
3. Roasting
4. Frying
5. Cooking
6. Warming up
3. Heating above 100 C
• Temperatures above 100 C usually are obtained by means of steam
under pressure in steam pressure sterilizers or retorts.
• Thus with no pressure the temperature at sea level is 100 C; with 5 lb of
pressure, 109 C; with 10 lb, 115.5 C; and with 15 lb, 121.5 C.
• When liquid foods are to be sterilized before their introduction into
sterile cans, high steam pressures are used to apply a high temperature
for a few seconds.

15. 4. Canning
• Canning is defined as the preservation of foods in sealed
containers and usually implies heat treatment as the principal
factor in the prevention of spoilage.
• Spallanzani in 1765 preserved food by heating it in a sealed
container
• Nicolas Appert “father of canning” gave exact directions for the
preservation of a wide variety of foods in cork-stoppered, wide-
mouthed glass bottles, which he heated for hours in boiling water.
• Appert’s original container, the cork-stoppered, wide-mouthed
glass jar, was used in much of the early canning.
• Most modern cans are made of steel plate coated with tin. The
trend is toward a thinner and more even coating of tin. Enamels
are coated onto flat sheets of plate before the manufacture of cans
to prevent or slow discoloration or corrosion.

16. Preservation using low temperatures
1. Freezing
■ Sharp freezing usually refers to freezing in air with only natural air
circulation or at best with electric fans. The temperature is usually
−23.3 C or lower but may vary from −15 to −29 C, and freezing
may take from 3 to 72 hr.
■ Quick freezing, in which the food is frozen in a relatively short
time. Quick freezing is variously defined but in general implies a
freezing time of 30 min or less and usually the freezing of small
packages or units of food.
■ Quick freezing is accomplished by one of three general methods:
– direct immersion of the food or the packaged food in a refrigerant
– indirect contact with the refrigerant
– air-blast freezing

17. • Quick Freezing
•small ice crystals formed
• blocks or suppresses metabolism
• brief exposure to concentration of
adverse constituents
• no adaptation to low temperatures
• thermal shock (too brutal a
transition)
• no protective effect
• avoid internal metabolic imbalance
• Slow Freezing
• large ice crystals formed
• breakdown of metabolic
rapport
• longer exposure to adverse or
injurious factors
• gradual adaptation
• no shock effect
• accumulation of concentrated
solutes with beneficial effects
2. Chilling
• Storage is at temperatures not far above freezing and usually involves cooling
by ice or by mechanical refrigeration.
• Enzymatic and microbial changes in the foods are not prevented but are
slowed considerably.
• It may be used as the main preservative method for foods or for temporary
preservation until some other preservative process is applied.

18. Preservation using drying
1. Solar drying
• Solar drying is limited to climates with a hot sun and a dry
atmosphere and to certain fruits, such as raisins, prunes, figs,
apricots, nectarines, pears, and peaches. The fruits are spread out
on trays and may be turned during drying.
• Fish, rice, and other grains may also be sun-dried.
2. Freeze drying
• Sublimation of water from a frozen food by means of a vacuum
plus heat applied at the drying shelf, is being used for a number
of foods, including meats, poultry, seafood, fruits, and
vegetables.
• Frozen thin layers of foods of low sugar content may be dried
without vacuum by sublimation of moisture during passage of dry
carrier gas.

19. 3. Drying by Mechanical Dryers
• Most methods of artificial drying involve the passage of
heated air with controlled relative humidity over the food to
be dried or the passage of the food through such air.
• A number of devices are used for controlled air circulation
and for the reuse of air in some processes.
• The simplest dryer is the evaporator or kiln, sometimes
used in the farm home, where the natural draft from the
rising of heated air brings about the drying of the food.
• An alternative method is to move the food on conveyor belts
or on trays in carts through the heated air.

20. 4. Smoking
• Most of the preservative effect of the smoking of foods is due to
the drying of the food during the process.
• Drying is the main preservative factor, especially drying at the
surface of the food.
• Smoking can be done in four ways: cold smoking, warm smoking,
hot smoking, and through the employment of "liquid smoke".
5. Other methods
1. Electronic heating
2. Foam-mat drying, in which liquid food is whipped to a foam,
dried with warm air, and crushed to a powder.
3. Tower drying in dehumidified air at 30 C or lower has been
successful with tomato concentrate, milk, and potatoes.

21. Preservation using modified atmospheres
1. MAP (Modified Atmosphere Packaging).
• (MAP) is a packaging system that involves changing the
gaseous atmosphere surrounding a food product inside a pack,
and employing packaging materials and formats with an
appropriate level of gas barrier to maintain the
changed atmosphere at an acceptable level for preservation of
the food.
• Gas flush consists of an inert gas such as nitrogen, carbon
dioxide, or exotic gases such as argon or helium which is injected
and frequently removed multiple times to eliminate oxygen from
the package.
• By decreasing or controlling the amount of oxygen present in a
package, the food product remains fresher longer, extending its
shelf life and ensuring it remains attractive to consumers.

22. 2. Vaccum packaging
• Refers to the technique of removing air from a pack prior to
sealing and it predates the use of gases as a means of food
preservation.
• Its principal purpose is to remove oxygen by pulling the
packaging material into intimate contact with the product.
• Hand and semi-automatically operated vacuum packaging
chamber machines are available, offering a relatively low cost
option (vs. MAP gas packaging).
• Main objective is to prevent oxidation reactions such as lipid
oxidation, loss of certain vitamins, oxidative browning, loss of
pigments, etc.

23. Preservation using radiation
1. UV Radiation
• Radiation with wavelengths near 260 nm is absorbed strongly by
purines and pyrimidines and is therefore the most germicidal.
• Ultraviolet radiation around 200 nm is strongly absorbed by
oxygen, may result in the production of ozone, and is ineffective
against microorganisms.
• Source of UV radiation -quartz-mercury vapor lamps or low-
pressure mercury lamps, which emit radiation at 254 nm.
• Factors Influencing Effectiveness- only direct rays are effective
unless they come from special reflectors, and even then their
effectiveness is reduced.
1. Time
2. Intensity
3. Penetration

24. 2. Ionizing Radiations
1. X-rays -are penetrating electromagnetic waves which are
produced by bombardment of a heavy-metal target with
cathode rays within an evacuated tube. They are not currently
considered economical for use in the food industry.
2. Gamma rays- are like x-rays but are emitted from by-products of
atomic fission or from imitations of such by-products. Cobalt 60
and cesium 137 have been used as sources of these rays in most
experimental work thus far, with cobalt 60 being the most
promising for commercial applications.
3. Beta rays -are streams of electrons (beta particles) emitted from
radioactive material. Electrons are small, negatively charged
particles of uniform mass that form part of the atom.
• They are deflected by magnetic and electric fields. Their
penetration depends on the speed with which they hit the target.
The higher the charge of the electron, the deeper its penetration.
4. Cathode rays- are streams of electrons (beta particles) from the
cathode of an evacuated tube.
• In practice, these electrons are accelerated by artificial means.

25. 3. Microwave
• Microwaves are electromagnetic waves between infrared
and radio waves.
• The energy or heat produced by microwaves as they pass
through a food is a result of the extremely rapid oscillation
of the food molecules in an attempt to align themselves with
the electromagnetic field being produced.
• This rapid oscillation, or intermolecule friction, generates
heat.
• The microwaves themselves do not result in any inactivation
of foodborne microorganisms; rather, it is the heat produced
by the excitation of food molecules that actually results in
microbial destruction.

26. Preservation using food additives
• A food additive is a substance or mixture of substances, other than
the basic food stuff, which is present in food as a result of any aspect
of production, processing, storage or packaging.
• Those food additives which are specifically added to prevent the
deterioration or decomposition of a food have been referred to as
chemical preservatives.
• Factors that influence the effectiveness of chemical preservatives-
• (1)concentration of the chemical,(2)kind, number, age, and previous
history of the organism (3) temperature (4) time and (5) the chemical
and physical characteristics of the substrate in which the organism is
found (moisture content, pH, kinds and amounts of solutes,etc).
• Principal preservatives-
• Sodium Chloride, Sugar , Sulfur dioxide ,Nitrate and Nitrite, Sorbic
Acid , Acetic Acid, Propionic acid ,Benzoic acid ,Parabens ,Epoxides,
Antibiotics ,Diethyl pyrocabonate.

27. Groups Examples
Preservatives Chemical preservatives
Colors Natural, Synthetic
Flavors Nature identical extracts
Sweeteners Saccharin, Aspartame, Polyols
Emulsifiers and Stabilizers Lecithin
Antioxidants Vitamin E, BHA, BHT
Flour improvers Vitamin C, Cysteine, Chlorine
Humecants and Anticaking
agents
Polyhydroxy alcohols, Calcium silicate
Leavening agents Baking soda, Ammonium carbonate
Chelating agents Polycarboxylic acids
Curing agents Sodium nitrite, Polyphosphates
Nutrient supplements Thiamine, Nicotinic acid, Iron, Calcium
Processing aids Acids, Acidity regulators, Gelling agents, Antifoaming
agents

28. Other food preservation methods
1. Pulsed electric fields
• non-thermal method of food preservation that uses short
pulses of electricity for microbial inactivation and causes
minimal detrimental effect on food quality attributes.
• The process is based on pulsed electrical currents delivered to a
product placed between two elctrodes.
2. Mano-thermo-sonication
• a food preservation technology that efficiently combines the
effects of pressure, heat and ultrasonic waves at an optimal
level to reach the desired levels of food stability and safety while
ensuring minimum negative effects on quality of food material.
• It is a developing technique proved for its antimicrobial action
and enzyme inactivation preventing food spoilage without
altering sensory properties of foods.

29. 3. High pressure processing
• A “non thermal” food preservation technique that inactivates
harmful pathogens and vegetative spoilage microorganisms using
pressure.
• Also known as Pascalization, high hydrostatic
pressure (HHP) processing, ultra high pressure (UHP) processing.
4. Aseptic packaging
• Also a type of thermal sterilization.
• It is process in which commercially sterilized food item is placed
in a sterilized package followed by sealing under aseptic
environment.
• The process by which microorganisms are prevented from
entering a package during and after packaging.

30. References
1) Food microbiology by WC Frazier
2) Modern Food Microbiology 6th edition - James M. Jay
3) www.sciencedirect.com