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The Mystery of Food - Food Spoilage and Preservation Methods

Grade 5CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Food Spoilage: Food is said to be spoiled when there is a change in its appearance, color, smell, or taste, making it unfit for consumption. Microorganisms like bacteria and fungi (molds) are the primary cause.

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Conditions for Spoilage: Microbes need three main conditions to grow: moisture, air, and a warm temperature (usually between 25∘C25^{\circ}\text{C} and 40∘C40^{\circ}\text{C}).

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Food Preservation: The process of treating food to stop or slow down spoilage. This helps in increasing the shelf life of food.

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Drying (Dehydration): Removing water from food items like grains, pulses, and papads to prevent microbial growth. Many microbes cannot survive without H2OH_{2}O.

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Refrigeration and Freezing: Keeping food at low temperatures. A refrigerator at 5∘C5^{\circ}\text{C} slows down microbe growth, while a freezer at −18∘C-18^{\circ}\text{C} stops it completely.

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Boiling: Heating liquids like milk to 100∘C100^{\circ}\text{C} kills most harmful bacteria present in them.

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Using Preservatives: Adding substances like salt (for pickles), sugar (for jams and jellies), and oil/vinegar to create an environment where microbes cannot grow.

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Pasteurization: A process primarily for milk where it is heated to about 70∘C70^{\circ}\text{C} for 1515 to 3030 seconds and then quickly cooled to kill germs.

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Canning and Bottling: Storing food in airtight containers to prevent contact with air and moisture.

📐Formulae

Microbial Growth∝Moisture+Warmth\text{Microbial Growth} \propto \text{Moisture} + \text{Warmth}

Boiling Point of Water=100∘C\text{Boiling Point of Water} = 100^{\circ}\text{C}

Freezing Point of Water=0∘C\text{Freezing Point of Water} = 0^{\circ}\text{C}

Pasteurization≈70∘C for 15−30 seconds\text{Pasteurization} \approx 70^{\circ}\text{C} \text{ for } 15-30 \text{ seconds}

💡Examples

Problem 1:

Reema bought a packet of bread on Monday. By Friday, she saw greenish-black furry patches on it. What happened to the bread?

Solution:

The bread has spoiled due to the growth of a fungus called bread mold.

Explanation:

In the presence of moisture and warmth (25∘C25^{\circ}\text{C} to 30∘C30^{\circ}\text{C}), fungal spores from the air settled on the bread and multiplied, causing spoilage.

Problem 2:

Why do we add a lot of salt to mangoes while making pickles?

Solution:

Salt acts as a natural preservative that removes moisture from the mango pieces.

Explanation:

Salt draws out water from the food and the microbial cells through a process called osmosis. Since microbes need H2OH_{2}O to survive, the high salt concentration prevents them from growing.

Problem 3:

Calculate the temperature difference between the boiling point of milk and the freezing point of water in a refrigerator.

Solution:

Difference =100∘C−0∘C=100∘C= 100^{\circ}\text{C} - 0^{\circ}\text{C} = 100^{\circ}\text{C}

Explanation:

Using the vertical subtraction format: 100−0100\begin{array}{r} 100 \\ - 0 \\ \hline 100 \end{array}