Theory:

Salt and oil are some of the common items used to check (or) control the growth of microorganisms. Have you ever wondered why pickle have so much oil? This is because pickles will be stored for a longer period of time. And, to protect it from the growth of microorganisms, the higher quantity of oil is used as a preservative method.
  
Sodium benzoate and sodium metabisulfite are commonly used preservatives.
Some preservatives used as ingredients are:
  • Common salt
  • Oil
  • Sugar
  • Vinegar
  
Common salt is added in food products such as pickles, and also fresh meat and fish are covered with dry salt rocks to prevent the growth of bacteria, hence acting as a preservative.
 
Excessive use of oil in pickles can save it from getting spoiled, from fungal or bacterial growth as it is stored for a longer period.
 
In jams and squashes, sugar, a preservative is used as an ingredient, so that it can be stored for a longer time.
 
Vinegar is also used as a preservative in pickles, to ensure that the pickle can be used for a longer period of time.
 
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Pasteurisation
The process of boiling milk to a temperature of around \(70°\)Celsius for about \(15\) to \(30\)  seconds, and then chilled, and stored before consuming is called Pasteurization.
 
Milk packets have pasteurized milk, which every manufacturing company has to ensure so that milk is both fresh and free from microbes.
 
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Ways to avoid the growth of microorganisms
We store vegetables and fruits at a lower temperature (refrigerator) to reduce the growth of microorganisms. Storing it in airtight sealed packets can also reduce the growth of microbes.