Chilling injury, anthracnose and uneven ripening in a mango consignment

Grey-brown discolouration and pitting - chilling injury. Nine degrees Celsius is below the chilling threshold for mango, which is generally around 12–13 °C depending on cultivar and maturity. The discolouration and pitting are classic chilling symptoms, and they also explain part of the uneven ripening, because chilling-damaged tissue ripens abnormally or not at all. Cause: storage temperature set too low for the crop, not a disease.

Black sunken lesions with pink spore masses - anthracnose. Infection by Colletotrichum begins in the field, often at flowering, and stays latent until the fruit ripens. The pink spore masses are diagnostic. Two decisions are responsible for the severity: no pre-harvest or post-harvest anthracnose control, and 30 hours at 32–35 °C in an open lorry, which lets latent infections develop rapidly and spreads inoculum between fruit. Uneven ripening in the box also allows disease to advance on the riper fruit.

Uneven ripening - harvest maturity plus temperature management. Fruit picked at 6.8 °Brix is at the very bottom of the acceptable range, and a consignment like this is never uniform, so a proportion will ripen late or not at all. Thirty hours at 32–35 °C before cooling accelerates ripening on the exposed fruit while shaded fruit stays green, and chilling damage then locks some fruit hard. No ethylene application was used to ripen the load evenly.

Fermented off-flavour and breakdown around the seed - chilling-related internal breakdown. Prolonged storage below the safe temperature damages the pulp and seed tissues; secondary fungi and fermentation complete the breakdown.

Sap burn is a harvesting-technique fault: fruit cut with a long stalk, or handled so that latex from the stem end contacts the skin.

Summary judgement: only the sap burn is purely a harvest fault; the rest is a chain of avoidable decisions - immature harvesting, no field disease control, no cooling and no pre-cooling, a store temperature set too low, and ripening left to chance.

1. Harvest at the right maturity. Target 8–10 °Brix or about 110–125 days from flowering for the local cultivar, and harvest in the cooler part of the day. Immature fruit cannot ripen evenly and is more prone to chilling injury. Leave a 5–10 mm stalk.

2. De-sap and wash immediately. Place fruit stalk-down on racks for 20–30 minutes to drain latex, then wash in clean water. This prevents sap burn and removes field dirt and spores.

3. Hot water treatment. Immerse fruit at 52 °C for 5 minutes (with careful temperature control) to reduce anthracnose and stem-end rot. This is the single most cost-effective post-harvest disease control available to a small operation; the water must be maintained at temperature and the tank changed regularly.

4. Pre-cool and transport cold. Cool to 12–13 °C within 6 hours of harvest and move in a refrigerated or well-ventilated insulated vehicle. Thirty hours at 32–35 °C is where much of the present loss was generated. Keep the relative humidity around 85–90%.

5. Store at 12–13 °C, never 9 °C. This is above the chilling threshold while still slowing ripening and disease. Storage life at this temperature should be 2–3 weeks, which is enough to plan marketing rather than dumping the crop.

6. Ripen deliberately. Use 100–150 ppm ethylene at 20–22 °C and 90–95% relative humidity for 24–48 hours in a ventilated room, then hold at 20 °C until the fruit reaches the target colour and firmness. Ventilation matters: carbon dioxide above roughly 1% inhibits ripening and produces off-flavours.

7. Sort and grade. Remove diseased, damaged and over-ripe fruit before storage, not after. Infected fruit in the box is the main source of spread.

8. Keep records. Record pulp temperature at harvest, time to cooling, store temperature and duration for each lot; these records are what turn a loss into a diagnosis next season.

Processor, whole lot, collected in 48 h 3,000 kg × Rs 95 = Rs 285,000, certain and immediate, with no freight, no rejection risk and no further storage.

Premium sea shipment, seven days at 12 °C The fruit has already been commercially damaged: 25% chilling injury, 30% anthracnose, 5% internal breakdown. Optimistically, perhaps half the fruit looks sound, giving about 1,500 kg × Rs 420 = Rs 630,000, less Rs 60,000 freight = Rs 570,000. But the buyer rejects the whole consignment at more than 5% defects, and even fruit that looks sound carries latent anthracnose that will express during seven days of transit. A rejection returns nothing and the Rs 60,000 freight is still payable.

Break-even probability: the shipment is worth attempting only if p × 570,000 ≥ 285,000, that is p ≥ 0.50. Given established chilling injury, visible anthracnose on 30% of the lot and latent infection in the remainder, the probability of arriving with under 5% defects is far below 50%. The expected value of the shipment is clearly negative.

Recommendation

1. Take the processor offer for the bulk of the consignment. It converts a deteriorating asset into certain cash within 48 hours and stops storage and disease losses from growing.
2. If local market prices justify it, hand-sort first: sell only fruit that is sound, firm and without lesions on the local wholesale market, and send the remainder to the processor. Do not put any of this consignment into the sea shipment; the defects are already present and cannot be reversed by cold treatment.
3. This consignment's real lesson is contractual. With this buyer, use a pre-shipment inspection and a mutually agreed sample before the container is sealed, and only commit fruit that has been through hot water treatment, cooling and storage at 12–13 °C. The premium route should be built on next season's crop, not salvaged from this one.