Basic Principle and technique of food preservation

Subject -Basic Food Science & Preservation
Stream - M.sc (Food Science & Nutrition)
Paper Code - MSUFSN-104
Class Assessment – 3
▶ Lalhruaitluangi
▶ Sarnali Paul
▶ Sanjana Pal
▶ Ishika Maji
▶ Krittika Mondal
▶ Sukanya Ghosh
Presented By -

1. Introduction
2. Principle of food preservation
3. Shelf Life
4. Food Based on Perishability
5. Food Based on Acidity
6. Relation between pH and Shelf Life
7. Techniques of preservation
8. Canning
9. Pasteurization and types
10. Freezing and types
11. Difference between pasteurization and sterilization
12. Drying and classification
13. Blanching
14. Principle & equipments
15. Effects on food
16. Conclusion

 Food Preservation is a process of prevention of spoilage or decay of food
 Allowing food to be stored in a fit condition for future use

 By keeping out micro-organisms (asepsis)
 By removal of micro-organisms, e.g. by filtration
2. Prevention or delay of self- decomposition of food
 By destruction or inactivation of food enzymes, e.g. by blanching
 By delay of chemical reactions, e.g. by prevention of oxidation by
means of an antioxidant
3. Prevention of damage caused by insects and animals
1. Prevention or delay of microbial decomposition

▶ Add variety to the food
▶ Increases food supply
▶ Increases shelf life
▶ Decrease wastage of food
▶ Decrease dietary inadequacies

 Shelf-life is the length of time a food can be kept
under stated storage conditions while maintaining
its optimum safety and quality.
 Shelf life of a food begins from the time the food is
manufactured and is dependent on many factors
such as its manufacturing process, type of
packaging, storage conditions and ingredients.

1. Perishable foods:
It can be kept at room temperature for only few hours or 1 or 2 days before spoiling. For example- milk and milk
products, meat, fish, poultry, fruits, leafy vegetables and cooked food.
These foods keep well under refrigeration at household as well as commercial level. In general, the most
perishable foods contain a high level of protein or have moisture and carbohydrates in them.
2. Semi -perishable foods:
It can be stored for a couple of weeks or even a month or two without any detectable signs of spoilage.
Temperature and humidity of the environment again affects the shelf stability of such foods. Proper handling and
storage can result in fairly long storage without spoilage.
Examples are all cereal and pulse products like wheat flour, and some fruits and vegetables like citrus fruits,
apples, pumpkin etc.
3. Non- perishable foods:
It will keep for months or years without spoiling unless handled and stored carelessly.
Examples of such foods are all preserved food products (canned, dried, pickled etc.), whole cereal, pulse, fats and
oils, honey, sugar, jaggery, salt, some spices etc.

1.High Acidic Foods: Certain dairy products, including cheese
fish and seafood, high-sodium processed foods, fresh meats and
processed meats, brown rice, oat flakes, carbonated beverages, such
as soda, high protein foods and supplements with animal protein etc.
2.Low Acidic Food: Miso, soy beans, tofu, yogurt and milk
most fresh vegetables, including potatoes, most fruits herbs and
spices, excluding salt, mustard, and nutmeg, beans and lentils
some whole grains, fats like olive oil, avocados, nuts, and seeds etc.

 The pH of foods is a major factor affecting their appearance, texture, flavor, nutritional value,
and safety. The pH values in food range from 2 to 7 and alkaline foods are rare. The reason for
such values of pH is that the acids and bases naturally present in food tend to be weak.
 A pH value of 2,5 to 5.5 tends to prolong the shelf life of fresh fruit and inhibit the multiplication
of micro-organisms. Likewise for vegetables with a more neutral pH in the 4.6 to
6.4 range.
 Shelf life of acidic foods are 12 to 18 months & low acid canned food’s shelf life is 2 to 5
years(meat, vegetables),

 High Temperature – Pasteurization, canning
 Low Temperature - Freezing

 Canning involves the application of temperature of food that are high enough to destroy essentially
all microbes presence plus airtight sealing in sterilized container to prevent recontamination.
 The degree of heat & the length of times of heating vary with the type of food & the kinds of
microbes that are likely to occur in it.
 Most canning is done in fin coated steel or zinc or in glass container.
 The raw product is inspected and all undesirable material is removed.
 After blanching the food is placed in the container mechanically or by hand.
 A brine is added to the vegetable & a syrup solution to the fruits either at the time of sealing
immediately after sealing.
 When the product is arranged in the can & covered with the liquid, the can is ready for exhausting.
 After exhausting process the filled canes are permanently sealed.
 The permanently sealed container is subjected to temperature designed to destroy the heat
resistance organisms likely to be present.
 After heating & before storing the processed canned by are cooled water & the temperature is
reduced to about 38°C.

 Temperature usually 65⸰C and holding at that point for at least 30 minutes.
 In recent years it is found that some micro organisms are more resistant and required a treatment of
63⸰C for 30 minutes.
 It is the heating of milk to a temperature which destroys organisms responsible for tuberculosis and
fever and nearly all the other micro-organisms present in that product without seriously affecting the
composition on properties of the product.
 Pasteurization treatment have two different primary objects:
• To kill pathogenic microorganisms
• Inactivate Enzymes
Three general methods are in use nowadays

 Raising the temperature of Milk heat 72⸰C for 15 seconds
 The UHTS system results in a complete pasteurization of milk
 Milk is held for 3 seconds at 93.4° C or, 1 second at 149.5°C
 Raw milk contains alkaline phosphatase. This enzyme as a built in indicators by which the adequacy
of pasteurization may be measured.
 Therefore, it alkaline phosphatase activity beyond a certain level in found in pasteurized milk it is
evidence of inadequate processing.
 This enzyme has the ability to liberate phenol from phenol phosphoric acid compound. The liberated
phenol gives a deep blue colour with certain organic compounds. If the milk is incubated, it does not
give blue colour with the indicator it means the pasteurization is complete.

So sensitive is this test that it gives positive in the presence of 0.1 percent raw milk added or if
the pasteurization temperature is less by 1°F.

 Freezing may preserve foods for long periods of time provided the quality of the food is good to begin
with the temperature of storage is far enough below the actual freezing temperature of food for long
preservation.
 Freezing can be done by –
• Slow Freezing Process
• Quick Freezing Process
• Dehydro Freezing
 The foods are placed in refrigerated rooms at the temperature from - 4⸰C to - 29⸰C
 Time may require 3 to 72 hours under such condition
 For fruits and vegetables the temperatures employed are - 15⸰C to - 21⸰C

 The temperatures used -32°C to -40°C
 The fine crystals formed by quick freeing have a lesser effect on breaking up plant and animal cells
than do methods of slow freezing
 In quick freezing large quantity of food can be frozen in a short period of time.
 Dehydro freezing of fruits and vegetables consists of drying the food to about 50 percent of it's
original weight and volume then freezing the food to preserve it

1. Definition Pasteurization is the process of heating
liquid to a specific temperature for a
specific time period to reduce microbial
growth.
Sterilization is the process of
eliminating all bacterial growth from
various different objects.
2. Processing
Temperature
Below 100⸰C Above 100⸰C
3. Different types High Temperature Short Time (HTST) &
Ultra High Temperature Processing ( UHT)
Appling heat, irradiation, chemicals
& applying high pressure.
4. Taste Taste of the food remains the same. Alter the taste of the food
5. Use Liquids, food etc Food, medical cleaning

 Drying is the process of removing excess water from the food particle keeping the nutritive value
same.
 Drying is a process that remove water from material. This can be done in a number of ways
including using oven, microwave, or dehydrator.
There are two types of drying-
 Natural drying
 Artificial drying

 Cost is less
 No needs skilled labour
 No need of any fuel
 This process requires large area
 The process takes long time
 When sun is not available it is not possible
 Natural drying means sun drying.
 Sun Drying: When excess water is removed by sunlight, the process is called sun drying.
Example - Crops drying.

 The method, in which excess water of grain removed artificially, is called artificial drying.
 It used in the industry.
 There are 3 types of artificial drying :
• Mechanical drying
• Dielectric drying
• Chemical drying
 It takes very short time
 It needs a small area
 No risks of loss of grain
 The method is costly
 Needs skill labour
 Needs a large amount of initial investment
 The main purpose of drying is to extend the shelf-life of foods by lowering water activity
 Lowering the water activity will inhibit microbial growth and enzyme activity
 Drying helps to reduce the weight and bulk of dried foods, reducing transportation & storage costs.

 Blanching is a unit operation prior to freezing, canning, or drying in which fruits or vegetables are
heated for the purpose of inactivating enzymes; modifying texture; preserving color, flavor, and
nutritional value; and removing trapped air.
 For a given product, typically mass flow rate is fixed, temperature is measured, and heating media
flow rate is adjusted to ensure that the temperature is kept at the set point.
 Processing conditions are usually set up to inactivate enzymes, but other quality parameters also ,
such as color and texture, are commonly monitored.

 The design of blanching systems depends on the product, the process following it, and the final use of the
product. Blanching is carried out as a pretreatment for freezing, canning, and drying.
 Most vegetables are blanched prior to freezing to inactivate enzymes that cause the development of off flavors
and off-colors during frozen storage.
 Blanching facilitates peeling and dicing, and is also accompanied by microbial load reduction. Fruits are usually
not blanched, or blanched under mild (low temperature)conditions prior to freeze.
 TYPES OF BLANCHERS USED IN FOOD INDUSTRY :
 Water Blanching
 Steam
 Gas
 Microwave

 Flavour
 Texture
 Colour
 Quality indicator
 A micro-organism
 Flavor, texture, and color are quality parameters that are typically assessed for fresh products
 Immediately after blanching and after a given storage time. These studies allow determining
the efficacy of the process in retaining or improving food quality and depend on each process.

 The preservation of food minimizes pathogenic bacteria; keeps food at high quality;
and reduces costs for both home consumers and in commercial industries.
 Food preservation methods include smoking, canning, chemical, and sugar to name a
few. Each food source will have its own unique preservation method used.
 Techniques for food preservation began in ancient times using fermentation, drying,
and more.
 Louis Pasteur used food science to create the technique of pasteurization to make
milk safe to drink. It is still used as a food preservation method to this day.

1. B.srilakshmi; 7th Edn; New Age International Publishers;2018; Food
science
2. www.google.com

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