Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Microorganisms like bacteria and fungi spoil food by producing toxic substances, making it unfit for consumption.
Chemical Method: Common preservatives include salts and edible oils. Chemicals like Sodium benzoate () and Sodium metabisulphite () are used to check the growth of microbes in jams and squashes.
Preservation by Common Salt: Salt () is used to preserve meat and fish for ages. Salting prevents bacterial growth by causing dehydration through osmosis.
Preservation by Sugar: Sugar reduces the moisture content in food items like jams, jellies, and squashes, which inhibits the growth of bacteria that spoil food.
Preservation by Oil and Vinegar: Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment.
Pasteurization: A process discovered by Louis Pasteur where milk is heated to about for to seconds and then suddenly chilled and stored to prevent the growth of microbes.
Storage and Packing: Dry fruits and vegetables are sold in sealed airtight packets to prevent the attack of microbes.
📐Formulae
💡Examples
Problem 1:
Explain how the process of Pasteurization helps in preserving milk.
Solution:
Milk is heated to approximately for to seconds and then suddenly cooled down.
Explanation:
Heating kills most of the microorganisms present in the milk. The sudden chilling prevents the remaining bacteria from growing. This allows the milk to be consumed without boiling as it is 'pasteurized'.
Problem 2:
Why are salt and oil added to pickles?
Solution:
Salt and oil act as preservatives that create an environment where spoilage-causing microbes cannot survive.
Explanation:
Salt removes moisture via osmosis, and oil creates a barrier against air and moisture. Bacteria cannot thrive in these conditions, thus preserving the pickle for a longer duration.