Mixed Cold Storage of Guava, Banana and Okra
A cold store near Varanasi has one room maintained at 4°C and 90% relative humidity. In June, the operator accepts three consignments: 2 tonnes of mature-green guava, 1 tonne of ripe banana, and 1 tonne of okra. All are stacked together with no air gap between pallets. The cooling coils are near the ceiling and the fan runs continuously. No ethylene absorber is used and the door is opened frequently. After 4 days, guava shows brown sunken spots and fails to ripen evenly; banana peel is black and the fruit is soft; okra has brown streaks. The operator claims the store is 'working' because the thermometer reads 4°C and there is no rotting smell. Buyers reject the guava and okra; the banana is sold quickly at a low price. The operator plans to lower the temperature to 2°C next time.
1. Explain the defects in guava, banana and okra. Are they primarily chilling injury, ethylene damage, or microbial spoilage? Support your answer with the temperature and storage details.
Read the worked answer
- Guava: brown sunken spots and uneven ripening at 4°C are typical chilling injury. Guava is chilling-sensitive below about 10°C.
- Banana: black peel and soft fruit at 4°C are also chilling injury. In addition, the ripe banana releases ethylene, which accelerates softening and ripening of guava and okra.
- Okra: brown streaks at 4°C are consistent with chilling injury.
The absence of a rotting smell does not mean the store is working: these are physiological disorders, not necessarily microbial rot. Mixed stacking with no air gaps, continuous high-velocity fan operation and no ethylene absorber can worsen uneven cooling and ethylene accumulation.
2. Critically assess the plan to lower the room to 2°C. What storage and handling changes would you recommend instead?
Read the worked answer
Lowering to 2°C would worsen chilling injury in all three crops. Recommended changes:
- Do not store these three together in one 4°C room.
- Temperature and RH: guava 10–12°C, banana 13–15°C (ripe fruit often 14–16°C), okra 10–12°C; RH 85–95%.
- Segregate ethylene sources: keep ripe banana away from guava and okra; use an ethylene absorber or controlled ventilation.
- Air distribution: leave gaps between pallets and avoid a continuous high-velocity fan directed at the produce.
- If only one room is available: hold at 10–12°C and market banana quickly; never use 2°C.
A thermometer reading alone is not proof that the store is suitable; compatibility and air circulation matter equally.