Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Food Spoilage: The process in which food items deteriorate to the point where they are no longer fit for human consumption, often caused by microorganisms like bacteria and fungi in the presence of (moisture) and warmth.
Traditional Preservation - Dehydration: Removing water () content from food by sun-drying (e.g., grains, papad) to prevent microbial growth.
Traditional Preservation - Pickling: Using salt () and oil to create an environment that inhibits the growth of bacteria.
Modern Preservation - Pasteurization: A process developed by Louis Pasteur where milk is heated to approximately for to seconds and then suddenly chilled to kill harmful microbes.
Modern Preservation - Refrigeration and Freezing: Keeping food at low temperatures (typically to for refrigeration and below for freezing) to slow down the growth of microorganisms.
Canning and Vacuum Packing: Storing food in airtight containers to prevent contact with air (), which is necessary for most spoilage-causing microbes to survive.
📐Formulae
💡Examples
Problem 1:
Why does a slice of bread develop green patches when left in a moist, dark place for several days?
Solution:
The green patches are colonies of fungi (mold). Bread contains and nutrients that, combined with a warm environment, allow fungal spores to germinate.
Explanation:
Microorganisms like bread mold require moisture and warmth to grow. The absence of preservation techniques allows them to decompose the food.
Problem 2:
Explain how salt () acts as a preservative in fish and pickles.
Solution:
Salt draws out the from the food through a process called osmosis and also dehydrates the cells of microbes.
Explanation:
By removing the moisture (), the environment becomes unsuitable for the survival and multiplication of bacteria.
Problem 3:
Calculate the temperature difference if milk is heated from room temperature () to the pasteurization point ().
Solution:
Explanation:
The milk must be raised by to reach the temperature required to kill most pathogens during the pasteurization process.