UPPSC 2021 Prelims GS Paper-I · Question 70 of 150

Correct — C, Rate of respiration is decreased. Harvested fruits are still living tissue that continue to respire, using up stored sugars and giving off heat, carbon dioxide and water while they ripen and age. Respiration is a temperature-dependent, enzyme-driven process, so lowering the temperature in a cold chamber slows it down. A reduced respiration rate delays ripening, senescence and microbial spoilage — which is exactly why cold-stored fruits keep for much longer.

• (a)Exposure to sunlight is prevented — Cold rooms are dark, but keeping fruit out of sunlight is not why it lasts longer. Fruit spoils chiefly through its own respiration and ripening, not through light exposure; a dark room at warm temperature would still spoil quickly.
• (b)Concentration of CO2 in environment is increased — Raising CO2 is the principle of controlled-atmosphere (CA) storage, a separate technique. An ordinary cold chamber works by lowering temperature, not by deliberately increasing CO2; here the operative mechanism is reduced respiration due to cold.
• (d)There is an increase in humidity — Cold stores do maintain humidity to stop fruit from shrivelling, but higher humidity only prevents moisture loss — it does not extend storage life the way slowing respiration does. Excess humidity can even encourage mould.

After harvest, fruits remain metabolically active: they respire, converting stored carbohydrates into energy while releasing CO2, heat and water, and this drives ripening and eventual decay. Because respiration and the associated enzyme activity speed up with temperature, refrigerated (cold-storage) conditions slow them down. Lower respiration means slower ripening, less water and sugar loss, and reduced growth of spoilage microbes — the basis of cold-chain preservation.

The question offers four plausible-sounding effects of a cold room, so isolate the primary mechanism. Fruit is alive and ages by respiring; cold slows that respiration. Sunlight, CO2 and humidity are side conditions — darkness and humidity are incidental, and raising CO2 belongs to controlled-atmosphere storage — but the core reason a cold chamber prolongs shelf-life is the decreased rate of respiration.

• Harvested fruit is living tissue and continues to respire, which drives ripening and spoilage.
• Respiration is temperature-dependent; cold storage lowers its rate.
• Slower respiration delays ripening, senescence and microbial decay — extending storage life.
• Controlled-atmosphere (CA) storage adds high CO2 / low O2, but a plain cold chamber works by cooling.

• Choosing 'increased CO2' — that is controlled-atmosphere storage, not an ordinary cold chamber
• Thinking humidity or darkness is the main reason, rather than slowed respiration

UPPSC and UPSC ask why cold storage prolongs shelf-life (answer: respiration slows) or test related ideas — ethylene and ripening, or controlled-atmosphere storage.

• practice — not a real PYQ

  The plant hormone chiefly responsible for the ripening of fruits is:

  • (a)Auxin
  • (b)Ethylene
  • (c)Cytokinin
  • (d)Gibberellin

  Answer(b) Ethylene — it is the gaseous ripening hormone; cold storage is often combined with ethylene control to delay ripening.

• practice — not a real PYQ

  Controlled-atmosphere storage extends the life of fruits mainly by:

  • (a)Increasing oxygen and decreasing carbon dioxide
  • (b)Lowering oxygen and raising carbon dioxide to slow respiration
  • (c)Adding ethylene to speed ripening
  • (d)Raising temperature to sterilise the produce

  Answer(b) Lowering oxygen and raising carbon dioxide, which suppresses respiration and delays ripening.