Concept: Preservation of Food
The process by which food is prevented from spoiling or rotting due to the growth of microbes like bacteria and
fungi is called food preservation.
The objectives of food preservation are—
- Increasing the shelf-life of food.
- Keeping the nutritional value of food intact.
- Enabling the storage and supply of stored food for a longer period.
Bacteria and fungi are the main groups of decomposers that are responsible for the spoilage of food.
These microbes require warmth and moisture for multiplication. Hence, food preservation methods have been adopted, keeping these factors in mind.
Depending on the nature of food to be preserved, there are different methods of food preservation—
- Adding sugar
- Adding salt
- Adding preservatives
- Freezing is the method of storing food at extremely low temperatures, which prohibits the bacteria and fungi from multiplying.
- The food items that are preserved by freezing are— Meat, fish, fruits, vegetables, packaged food.
- Canning is the method of sealing food in air-tight containers. Oxygen in air leads to rotting of food.
In canning, the absence of air does not allow the growth of microbes.
- The food items that are preserved by canning are—Chopped fruits and vegetables, fish, meat, poultry, seafood, and dairy products.
- The ingredients used while making pickles prevent the growth of microbes. The common ingredients used are oil, vinegar, salt, and spices.
- Vinegar in pickles is too acidic and hence, not suitable for microbial growth.
- Oil prevents air from reaching the pickle, which prevents the growth of microbes.
- Pickles are made of the following food items—Raw mango, radish, carrot, beetroot, ginger, garlic, lemon, meat, fish, etc.
After removing water from the fruits, huge amounts of sugar are added to make jams, marmalades, and jellies.
Adding sugar checks the growth of microbes and preserves the flavour and colour of fruits.
- Salt absorbs water from foods, making the food too dry to support the growth of harmful moulds or bacteria.
- The food items that are preserved by adding salt—Fish, meat, poultry, raw fruits like mango, etc.
- Some food items are dried in the sun or passed through hot air.Drying removes moisture and thereby prevents microbial growth.
- The food items that are preserved by drying—Cereals, pulses, chips, fish, vegetables like beans, etc.
- Preservatives are chemical substances that are used to increase the shelf-life and prohibit the spoilage of
different food items.
Generally, all canned or packed foods contain chemical preservatives. These preservatives are carefully monitored and are used in specific amounts.
- Some common food preservatives used are—Sorbates (calcium and sodium sorbate), Benzoates, and Nitrites.
- They all prevent the growth of microbes and maintain the quality of food.
This method is used to preserve milk, and includes the following steps:
- Boiling milk at high temperature so that unwanted microbes get killed.
- Chilling the milk quickly for package and storage.
Decomposer: The organisms that break down the remains of dead organisms into simpler products
are called decomposers, like bacteria and fungi.
These also attack different types of foods.
Shelf-life: The duration for storing a food item without becoming unfit for use or consumption.
Did You Know?
- Food can be preserved by freezing for almost 3-12 months.
- Salt, sugar, vinegar, and castor oil are natural preservatives used to preserve food for long durations.
- Preservation of food by adding salt is the oldest method known for food preservation.