Twenty-Two Percent Never Reaches the Buyer
A vegetable cooperative's collection centre in Kavre handles about 3 t of tomato a day in the main season. Members harvest in the morning, fill 40 kg jute sacks, and truck them 180 km to Kathmandu overnight. Fruit is picked at the pink stage because members believe pink tomatoes 'look better and fetch more'. Last year's arrival records show 22% of consignments unmarketable: cracked fruit, water-soaked collapse with a sour smell, and grey-white cottony growth with black pinheads on the stem scar. Ripe fruit sharing a sack with firmer fruit were worst affected. The cooperative's accountant puts the value of these losses at NPR 2.6 million. A new buyer has now asked for fruit that will still be saleable seven days after it reaches the market. The centre has a forced-air cooler of 3 t capacity running at half load, plastic crates available on hire, and no ripening chamber.
1. Diagnose the post-harvest problems from the symptoms and the handling described, ranking the causes in order of importance.
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Symptom-to-cause mapping
- Grey-white cottony growth with black pinheads on the stem scar = Rhizopus soft rot, a wound pathogen that enters through harvest and compression injuries and spreads between fruit in a closed sack.
- Water-soaked collapse with a sour smell = Geotrichum sour rot (or a bacterial soft rot), typical of over-mature fruit, free moisture and warm holding.
- Cracking = irregular moisture and calcium nutrition in the field, worsened by picking at pink and by rough handling.
- Ripe fruit in the same sack were worst = ethylene from ripe fruit accelerates ripening and softening of neighbours, and the ripe ones leak juice that inoculates the rest.
Ranked causes
- Harvesting at pink for a 180 km journey. Pink fruit has little shelf life left; it softens, respires and produces ethylene all the way to market. This is the single largest driver.
- 40 kg jute sacks. Compression bruising at the bottom of a 40 kg sack creates the wounds that rots need, and jute does not protect from impact.
- No pre-cooling and overnight ambient transport. Field heat drives respiration, water loss and pathogen growth; a truck bed in the terai is not a cool chain.
- No sorting or grading at the centre. Diseased fruit travel with healthy fruit and inoculate the whole load.
- Mixing ripeness stages and no sanitation of containers.
Cracking and field calcium are real but secondary; fixing harvest maturity, packaging and cooling will remove most of the 22%.
2. Advise on harvest maturity, sorting, packaging and cooling to meet the seven-day requirement. Support the plan with the loss figures given.
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Harvest maturity
- For a 180 km journey plus seven saleable days at the market, pick at mature green: full-sized fruit, shiny skin, gel visible in the locules when cut, and a greenish-white star at the blossom end.
- Reserve breaker/pink harvest for the local market only. Pink fruit for Kathmandu is the direct cause of the soft-rot losses.
- Harvest in the early morning, keep filled crates in shade, and move to the centre within two hours.
Sorting and packaging
- Sort at the centre on a shaded table: remove cracked, diseased, over-ripe and undersized fruit; grade into two or three sizes.
- Replace 40 kg sacks with 10–20 kg ventilated plastic crates. This alone removes most compression bruising and improves airflow.
- Never mix maturity stages in one crate; ethylene from ripe fruit softens the green ones.
- Sanitize crates between trips and never reuse sacks contaminated by rotten fruit.
Cooling and ripening
- Pre-cool to 12–13 °C within about four hours of harvest at 85–90% RH. Do not go below 10 °C for mature green fruit; chilling injury causes pitting and uneven ripening.
- The 3 t cooler at half load can handle the daily 3 t if loads are batched and the door discipline is enforced.
- Ripen at the destination, not at the farm: 100–150 ppm ethylene at 18–20 °C for 24–48 hours, then ventilate.
Numbers The NPR 2.6 million loss corresponds to 22% of about NPR 11.8 million of consignment value. Cutting losses to 8% would save roughly 14 percentage points, about NPR 1.65 million per season - far more than the crate hire and cooling cost.
3. What simple records and measurements should the cooperative keep to prove that the changes are working?
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Keep it to a one-page daily sheet that a centre supervisor can complete in ten minutes; anything more elaborate will not be filled in.
At intake
- Grower code, number of crates, net weight, harvest date and time, maturity stage at receipt (mature green / breaker / pink).
- Field temperature at harvest if a simple thermometer is available.
At dispatch
- Pulp temperature at loading, cooler set point, time out of the cooler, vehicle and departure time.
At arrival
- Arrival temperature, and a simple condition score per crate: 1 = sound, 2 = slight defect, 3 = unsaleable.
- Percentage culled, classified by cause: crack, Rhizopus, sour rot, bruising, over-ripe, other.
- Days from harvest to sale, and price realised per kg by grade.
Analysis
- Plot per-crate loss against maturity stage at harvest and against pulp temperature - this shows within one season which change is paying.
- Compare loss percentage before and after the crate and cooling change using the same cause categories.
- Track cost per kg handled (crate hire, cooling, labour) against the value of loss avoided.
- Review monthly with members and feed results back to growers, because harvest maturity is a field decision the centre cannot enforce on its own.