medium importancemedium difficulty4 min

Rancidity

Rancidity is the bad smell and bad taste that develop in fats and oils when they oxidize.

In one line: No air, less rancid smell.

Understand it

Food items with oil or fat can turn unpleasant when exposed to air for too long. Heat and light can make the process faster. That is why packed snacks are stored carefully.

Example

Open chips left for many days may smell stale because their oil becomes rancid.

Rule to remember

Rancidity is oxidation of fats and oils; it is slowed by airtight packing, nitrogen, antioxidants, and refrigeration.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

An open packet of chips becomes stale after many days because the oil oxidizes and develops rancid smell.

Method you can reuse

1Look for fats or oils in the food.
2Check whether air, heat, or light exposure is mentioned.
3If yes, link it to rancidity.

Sketch it in your answer

Show a sealed snack packet with nitrogen inside and oxygen kept away from the oil.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why are fried snacks often packed in nitrogen-filled pouches?

Think first, then show answer

They are packed in nitrogen to reduce contact with oxygen and slow down rancidity.

Common wrong answer

Saying the food becomes dirty or turns into a metal.

Why it loses marks: Rancidity is an oxidation change in fats and oils.

Don't mix this up

Students often confuse rancidity with spoilage by germs only. Rancidity is mainly due to oxidation of oils and fats.

Exam tip

If the question mentions stale smell, bad taste, or oily food kept open, think rancidity.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Questions may ask causes of rancidity or methods used to prevent it in food items.

1
Enough for 1 mark
Rancidity is the bad smell and bad taste that develop in fats and oils when they oxidize.
2
Add for 2 marks
Example: Open chips left for many days may smell stale because their oil becomes rancid.
3
Add for 3 marks
Food items with oil or fat can turn unpleasant when exposed to air for too long.

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