Ethylene Management in Postharvest Handling: A Practical Guide

Ethylene is invisible, nearly odourless, and almost never measured in commercial handling. That combination is why it does so much damage — the losses show up in the consumer’s kitchen, days after the produce has left your control, and rarely get traced back to the cold room where they started.

This is a practical guide to managing it: which crops produce it, which crops suffer from it, where it comes from in a packing shed, and what actually works to reduce it.

The two classes of produce

Every crop falls into one of two groups. Climacteric produce releases a burst of ethylene as it ripens, alongside a rise in respiration — these are the fruits that continue ripening after harvest, softening, changing colour and sweetening. Non-climacteric produce does not. It will soften slightly, lose green colour and eventually develop rots, but it never improves in eating quality after picking.

The practical test is simple: does it ripen after harvest? If yes, it is climacteric, and it is a source of ethylene. If no, it is non-climacteric, and it is a victim of it.

Climacteric — produces ethylene	Non-climacteric — damaged by it
Apple, pear, quince	Cherry, blackberry, strawberry
Apricot, nectarine, peach	Eggplant, cucumber, pepper
Mango, avocado, banana	Lemon, orange, mandarin
Tomato, sapodilla	Watermelon, honeydew melon
Rockmelon, passionfruit	Grape, lychee, loquat

Classification after Kader (1992), Postharvest Technology of Horticultural Crops, p. 16.

Where the ethylene in your shed comes from

There are two sources, and only one of them is obvious.

The produce itself. Any climacteric fruit in the room is generating ethylene continuously. Over-ripe and rotting fruit generate more.

Combustion engines. Ethylene is a component of petrol engine exhaust. A gas-powered forklift working inside a cold room, or a truck left idling during loading, is actively dosing your produce.

A Sydney-region survey of wholesale markets, distribution centres and retail stores found ethylene concentrations in the range of 0.017 to 0.06 ppm during normal marketing — enough, on the research available, to cost a meaningful share of remaining shelf life.

The effect accumulates. Produce may spend only a short time in any one location, but each moderate exposure adds to the last. A chain of individually unremarkable exposures ends as a very short life in the consumer’s kitchen — and the quality loss is not visible at the point of sale, which is precisely why it goes unaddressed.

What the damage actually looks like

Ethylene accelerates ageing. In green tissue — leafy vegetables, cucumbers — it drives chlorophyll loss and makes the product more susceptible to rots. Beyond general senescence, several crops show distinctive disorders:

Crop	Symptom
Lettuce	Russet spotting — dark brown spotting along leaf mid-ribs
Carrot	Bitterness from isocoumarin production — reported at concentrations as low as 0.5 ppm within two weeks of storage
Potato	Sprouting
Asparagus	Toughening
Cut flowers	Flower and leaf drop — carnation, delphinium, freesia, gypsophila and Geraldton wax are all sensitive

The carrot figure is worth pausing on. Bitterness at 0.5 ppm is not a theoretical laboratory threshold — it is well within the range a carton of carrots could encounter sharing a cold room with ripening fruit.

Controlling the sources

Most of this costs nothing but discipline.

Separate the classes. Green leafy vegetables should not share storage or transport with ripening apples, pears, mangoes, tomatoes or bananas. Mixed loads are the single most common avoidable exposure.

Use electric forklifts around ethylene-sensitive product rather than gas-powered ones.

Do not leave engines idling in enclosed spaces, including during loading and unloading.

Remove over-ripe and rotting fruit from storage and handling areas promptly. They are strong local sources.

Increase ventilation where practical — on the assumption that the incoming air is genuinely ethylene-free, which is not guaranteed near a loading dock or a road.

Removing what you cannot prevent

Source control has limits. Once produce is sealed in a carton and moving through a chain you do not control, the ethylene it generates has nowhere to go.

The established chemical method is potassium permanganate, which oxidises ethylene into carbon dioxide and water. It does not mask the gas or slow its production — it destroys the molecule.

On format: the Sydney Postharvest Laboratory guidance is that efficient scrubbing depends on spreading the potassium permanganate across as large a surface area as possible — in trays, or within highly permeable bags. Reaction rate is limited by contact between gas and reagent, so a compact mass of media works poorly regardless of how much of it there is.

That is the reasoning behind the sachet format: a permeable envelope holding a thin, distributed layer of impregnated media, placed inside the carton where the ethylene is actually generated rather than in the room outside it.

For cut flowers, silver thiosulfate applied as a stem pulse protects against ethylene by a different route — the flowers take it up and it blocks the response rather than removing the gas.

1-MCP (1-methylcyclopropene) blocks ethylene receptors and is active at very low concentrations. Note on currency: the source material for this section dates from 2000, when 1-MCP was registered in Australia for ornamentals only. It has since been registered for food crops in many markets. Check current registration status for your crop and jurisdiction.

When ethylene is the tool, not the problem

Controlled ripening is the deliberate use of the same gas. Applied under managed conditions, it lets climacteric fruit be presented ready to eat — the reason a consumer can buy an avocado for dinner tonight rather than one that needs four days on the bench.

Fruit	Temperature	Ethylene	Treatment time
Avocado	18 – 21°C	10 ppm	24 – 72 hrs
Banana	15 – 21°C	10 ppm	24 hrs
Kiwifruit	18 – 21°C	10 ppm	24 hrs
Persimmon	18 – 21°C	10 ppm	24 hrs
Tomato	13 – 22°C	10 ppm	Continuous

Commercial ripening generally runs between 1 and 100 ppm at 15 to 21°C and 85 to 90% relative humidity, with the exact combination varying by crop.

Ethylene is also used pre-harvest in the form of ethephon, which releases it in the field — for fruit thinning in apples and cherries, loosening nuts before harvest, colour development in apples, degreening citrus, inducing flowering in pineapples, and promoting lateral branching in potted azaleas and geraniums.

Ripening conditions after Wills, McGlasson, Graham and Joyce (1998), Postharvest, 4th edition, p. 209.

Sources

Jobling, J. (2000). Postharvest ethylene: a critical factor in quality management. Good Fruit and Vegetables Magazine 11, December 2000. Sydney Postharvest Laboratory Information Sheet.

Kader, A.A. (1992). Postharvest biology and technology: an overview. In Postharvest Technology of Horticultural Crops, Publication 3311, University of California, pp. 15–20.

Reid, M. (1992). Ethylene in postharvest technology. In Postharvest Technology of Horticultural Crops, Publication 3311, University of California, pp. 97–108.

Warton, M.A., Wills, R.B.H. and Ku, V.V.V. (2000). Ethylene levels associated with fruit and vegetables during marketing. Australian Journal of Experimental Agriculture 40(3): 465–470. View at CSIRO Publishing

Wills, R.B.H., McGlasson, W.B., Graham, D. and Joyce, D. (1998). Postharvest: An Introduction to the Physiology and Handling of Fruit, Vegetables and Ornamentals, 4th edition. UNSW Press, Sydney.