Cold Storage for Lemons and Citrus in Bangladesh: Chilling Injury, Humidity and Decay

Lemons and limes look like the easiest crop to store: hard skin, no visible bruising, and a reputation for lasting on a kitchen counter. Commercial handlers know the opposite. Citrus fruit loses weight, shrivels, moulds and, if it is chilled wrongly, develops skin damage that only shows after it leaves the cold room. In Bangladesh, where lemon supply peaks in a short season and prices swing hard, a well-run cold store can move the sale date without destroying quality — but only if the operator understands what citrus actually needs.

This guide explains how citrus behaves after harvest, why temperature and humidity settings matter, what handling problems cause the worst losses, and how to plan a small cold room for lemons. It contains no fixed set-point tables: recommended temperatures differ between species, varieties, maturity and intended storage time, so get the set-point for your specific fruit from a horticultural adviser or your supplier and verify it with a trial lot.

How citrus differs from ripening fruit

Fruits divide broadly into those that continue to ripen after harvest, such as mango and banana, and those that do not. Citrus belongs to the second group: it does not become sweeter or juicier once picked, so storage is about holding quality, not developing it. This changes the goal. You are trying to slow water loss, respiration and decay, not to manage a ripening curve. It also means that fruit picked too early stays sour and fruit picked too late is already declining, so harvest maturity matters as much as the room.

Chilling injury: the trap for the over-cold room

Many tropical and subtropical fruits suffer chilling injury if held below a threshold temperature for long enough, even though they are not frozen. Lemons and limes are among the citrus fruits generally regarded as chilling-sensitive. Symptoms include pitting or sunken patches on the peel, brown staining and increased decay, and they often appear only after the fruit is moved back into warm shop conditions, when the operator can no longer connect them to the cold room. This is why an instinct that colder is safer can cost you. The same principle affects other produce; see our guide to tomatoes and chilling injury for a parallel example. Set the room at the recommended temperature for your fruit and check it with an independent thermometer, since a badly calibrated controller can run colder than displayed.

Humidity: enough to prevent shrivel, not enough to breed mould

Citrus peel is a thin barrier holding a lot of water. In dry air the fruit loses moisture, becomes lighter, softer and wrinkled, and sells for less. In very wet conditions, or when surfaces are dripping, mould spreads faster. The practical aim is a high but not saturated humidity and gentle, even air movement. Avoid direct blasts of cold air on the fruit, which dry the peel and cause local chilling. Read humidity control in mini cold storage for the mechanisms and for practical ways to raise or lower humidity in a small room, and airflow, stacking and clearance for layout.

Ethylene and degreening

Green lemons turn yellow as chlorophyll breaks down, and the process speeds up in the presence of ethylene, the ripening gas released by many fruits. Some citrus is deliberately degreened with controlled ethylene to give a uniform colour before sale. If you want to keep fruit green and firm, avoid storing it alongside ethylene-producing produce such as ripe bananas, mangoes and tomatoes. Ethylene can also trigger calyx (button) drop and accelerate decay. If you handle mixed produce, separate the rooms or at least separate the fruit types; see ethylene ripening chambers for how deliberate ripening rooms are run, and why crops need separate conditions for another example of incompatible storage needs.

Decay: where most losses begin

The dominant storage losses in citrus come from mould, particularly green and blue moulds that enter through cuts, punctures and abrasions in the peel and then spread from fruit to fruit. A single damaged lemon can contaminate its neighbours. Prevention starts before the cold room: harvest with clippers rather than pulling, avoid dropping fruit, sort out cut or bruised specimens, keep bins clean and pick when fruit is dry. Chemical treatments are used commercially in some markets, but permitted products, doses and residue limits are a regulated matter; ask an agricultural extension officer or your buyer what is allowed for your market rather than copying a foreign recipe. Regular inspection and removal of rotting fruit is cheap and effective.

Packing and stacking

Use ventilated crates or cartons that allow air to circulate through the load, and do not overfill so that the weight crushes the bottom layer. Sacks and closed bags trap heat and moisture and encourage decay. Stack with gaps so that cold air reaches every crate, and keep them off the floor and away from evaporator coils. Label each lot with harvest date and origin so that the oldest stock is sold first; the discipline in FIFO versus FEFO picking applies directly. For transport, insulated packing and gel packs help small consignments; see cold chain packaging.

Pre-cooling and the first hours

Fruit picked in the heat carries field warmth. If it goes straight into a room designed only to hold temperature, the room struggles, the fruit cools slowly and condensation forms. Shade the harvested fruit, move it to the store quickly and, where possible, allow a period of gradual cooling. Pre-cooling methods for fresh produce describes the options. When taking cold fruit out, let it warm gradually in its packaging where possible; moving chilled fruit into humid air causes condensation, which encourages mould on the surface.

Is a mini cold room worth it for lemons?

It depends on your volumes, your local price swings and your alternative. A small cold room can let a wholesaler or grower hold fruit for a period rather than dump it at glut prices, and it can protect quality on the way to market. It cannot rescue poor fruit, and it adds electricity, labour and equipment cost. Work out your own numbers with your electricity tariff, your expected holding time and your realistic price difference. Do not rely on a generic return figure; ask us for a quote and a sizing based on your crop quantity, and use our heat load and sizing guide and project report guide to build the case. For wider produce planning, read reducing post-harvest loss and pack houses for fruit and vegetables.

A trial-lot routine before you commit

• Buy or harvest one representative lot and record its condition on day one.
• Store it at the recommended set-point with a data logger next to the fruit.
• Inspect at regular intervals, noting weight loss, colour, firmness and decay.
• Move a sample to normal shop conditions and watch for skin damage after removal.
• Adjust temperature, humidity or packaging and repeat before scaling up.

That trial costs little and answers the only question that matters: how long can your fruit, in your room, keep saleable quality.

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