food

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Environmental Health, Class notes ©Phr. Rashmi Adhikari. NPC No. G-992.
Environmental Health, Class notes ©Phr. Rashmi Adhikari. NPC No. G - 992.
2.16 Food preservation: 2 hrs
• Define food preservation and describe importance of food preservation.
• List methods of food preservation.
• Drying, smoking, cooking, pickling, fermentation, pasteurization, parboiling, refrigeration/freezing and
canning/bottling.
Food preservation
Food preservation is the process of treating and handling food to stop or slow down food spoilage, loss of
quality, edibility, or nutritional value and thus allow for longer food storage.
Advantages:
• Food preservation prevents the food from being spoiled by the action of enzymes and
microorganisms.
• It prevents the incidence of food borne disease.
• It prevents the transmission of food borne disease.
• It prevent from intake of toxic substances.
• To prevent the primary exposure of items to dust and allergens.
• The foods can be taken for longer period of time.
• It increases the availability of out of season foodstuffs.
• Food preservation increases the safe storage period of foodstuffs.
• It increases the availability of various foodstuffs even at distant and not easily approachable places.
Methods of food preservation:
1. Traditional methods
a. Drying.
b. Cooling
c. Freezing
d. Boiling
e. Heating
f. Salting
g. Sugaring
h. Smoking
i. Pickling
j. Canning
k. Lye
l. Jellying
m. Jugging
n. Burial.
2. Industrial modern methods
a. Pasteurization.
b. Vacuum packing

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Environmental Health, Class notes ©Phr. Rashmi Adhikari. NPC No. G-992.
c. Artificial food additives
d. Irradiation
e. Hurdle technology
f. Biopreservation
g. High-pressure food preservation
h. Nonthermal plasma.
i. Modified atmosphere.
j. Pulsed electric field electroporation.
Drying:
Drying (dehydrating) food is one of the oldest and easiest methods of food preservation. Dehydration is the
process of removing water or moisture from foods. Dehydrated foods are ideal for bagpacking, hiking, and
camping because they weigh much less than their non-dried counterparts and do not require refrigeration.
Drying food is also a way of preserving seasonal foods for later use.
E.g: cereals, nuts, fruits, vegetables, meat etc.
Smoking:
The process in which meat and fish are salted and exposed to smoke produced from the wood. The preservation
is possible due to the presence of compound called creosote.
For e.g.: Meat and fish.
Cooking:
The raw food materials are preserved by cooking process.
For e.g.: Meat and fish, vegetables etc.
Sugaring:
Sugaring is the process of desiccating a food by first dehydrating it, then packing it with pure sugar. This sugar
can be crystalline in the form of table or raw sugar, or it can be a high sugar density liquid such as honey, syrup
or molasses. The concentrated sugar solution used draws water from the fruits thus preventing the growth of
microorganism.
For e.g.: vegetables and fruits etc.
Salting:
Salting is the preservation of food with dry edible salt .It is related to pickling (preparing food with brine, that
is, salty water) and is one form of curing. Salting is used because most bacteria, fungi and other potentially
pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any
living cell in such an environment will become dehydrated through osmosis and die or become temporarily
inactivated.
Pickling:
It is the process of soaking food in solution containing oil, salt, acid or alcohol and keeping them in jar to
protect from microbial growth. A layer of vegetable oil is put in jar to prevent entry of microorganism. Pickling
is often combined with other method such as fermenting, canning or just refrigerating.

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Environmental Health, Class notes ©Phr. Rashmi Adhikari. NPC No. G-992.
Freezing:
It is the process of chilling food to at least 0ºC or below for about 24 hours. At freezing temperature,
microorganism became inactive, thus food cannot spoil when it is frozen. Mostly the preservation of meat and
fish are done by this method. Similarly, vegetables and fruits can also be preserving maintaining the appropriate
temperature.
Bottling and Canning:
It is the process of applying heat to food and sealed in a jar in order to destroy any microorganisms that can
cause food spoilage. The food is boiled to kill microorganism and then sealed. During the canning process, air is
driven from the jar and a vacuum is created.
Vacuum Packing:
Vaccum packing is a method of packaging that removes air from the package prior to sealing. This method
involves (manually or automatically) placing items in a plastic film package, removing air from inside, and
sealing the package.
Fermenting:
Fermentation is a natural process through which microorganisms like yeast and bacteria convert crabs such as
starch and sugar into alcohol or acids that act as a natural preservative. Fermentation also promotes the growth
of beneficial bacteria, known as probiotics for better digestion, stronger immunity and heart health. The process
is still used to produce foods like wine, cheese, sauerkraut, yogurt, and kombucha.
Parboiling:
The process of partially boiling food materials is known as parboiling. This can be done at about 30-35º C.
For e.g.; Paddy grain before milling.
Pasteurization:
Pasteurization means heating food to a certain temperature for some time followed by rapid cooling. Heating at
such high enough temperature kills most bacteria. However it does not affect taste and nutritional value of food.
For e.g.: fresh milk, yoghurt drink and juices are pasteurized to make them last longer.