Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Food spoilage is caused by the growth of microorganisms like bacteria and fungi, which require moisture (), warmth, and air to survive.
Food preservation is the process of treating and handling food to stop or slow down spoilage while maintaining nutritional value.
Refrigeration and Freezing: Storing food at low temperatures (around to ) slows down the growth of germs.
Boiling: Heating liquids like milk to their boiling point () kills most of the harmful bacteria present in them.
Dehydration (Drying): Removing water () from food items like grains, pulses, and dry fruits prevents the growth of microbes since they cannot survive without moisture.
Salting and Pickling: Adding common salt () or oil to food helps preserve it. Salt draws out moisture from the food and the cells of microorganisms.
Sweetening: Adding high amounts of sugar () to make jams and jellies acts as a preservative by reducing the available water content.
Canning and Bottling: Storing food in airtight containers prevents exposure to air and microbes from the environment.
📐Formulae
💡Examples
Problem 1:
Why do we keep milk in the refrigerator even after boiling it?
Solution:
Boiling kills existing germs at , while refrigeration at low temperatures (approx. ) prevents new germs from growing.
Explanation:
Boiling is a method of sterilization, but if milk is left at room temperature, bacteria can re-enter and multiply. Low temperatures in the fridge slow down microbial activity.
Problem 2:
Explain how drying helps in preserving grapes to make raisins.
Solution:
Drying removes the content from the grapes.
Explanation:
Microorganisms like mold and bacteria need moisture () to grow. By removing the water through dehydration, the food becomes safe from spoilage for a longer duration.
Problem 3:
Identify the preservative used in making mango pickles.
Solution:
Salt () and Oil.
Explanation:
Salt acts by removing moisture from the fruit pieces, and the layer of oil acts as a barrier that prevents air and moisture from reaching the food, thus stopping the growth of aerobic bacteria.