What happens when the fat and oil containing food materials are left outside for a long time ?
- A.Fats and oils in the food get oxidized
- B.Fats and oils in the food get reduced
- C.Fats and oils in the food get ice-covered
- D.No reaction takes place
Correct answer
Explanation
The correct answer is A, Fats and oils in the food get oxidized. Oxygen in the air reacts with the fats and oils, and the food turns rancid, with a bad smell and taste.
This change is called rancidity. The oxidation breaks fats into smaller compounds that smell and taste unpleasant. It is slowed by keeping food away from air, light and heat. Chip makers fill packets with nitrogen gas to push out oxygen, and antioxidants are added to fatty foods. Keeping food in airtight containers and in a refrigerator also delays rancidity.
B is wrong because reduction is the removal of oxygen or the addition of hydrogen, which does not happen to food left in air. C is wrong because food at room temperature does not get covered in ice. D is wrong because a clear chemical change, oxidation, does take place.
Exam tip: rancidity is oxidation of fats; nitrogen in chip packets and antioxidants prevent it.
Practice Questions
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- B.100 mm of Hg
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- D.140 mm of Hg
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- D.Thyroxine
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