The eco-friendly way to preserve mangoes

Saturday February 17 2018

Dr Jane Ambuko, a scientist at the University of Nairobi's Department of Plant Science and Crop Protection demonstrates how the innovative cooler works.

Dr Jane Ambuko, a scientist at the University of Nairobi's Department of Plant Science and Crop Protection explains how the innovative cooler works. The mango cooler helps the farmers aggregate their produce together for some time. PHOTO | LEOPOLD OBI | NMG 

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Under the searing sun of Eastern Kenya, tens of mango farmers ferry their produce to the markets hoping that a serious buyer will soon show up with a good price for the perishables.

Usually, the mango harvesting season that falls between January and early March is a terrible period for thousands of small-scale farmers growing the fruits for lack of ready market.

Buyers, mostly middle men, wait until farmers become desperate before sending their trucks to the fields so that they can buy the fruits at throwaway prices, sometimes as low as Sh3 per fruit.

“For many years I have harvested mangoes but end up giving them to hawkers to sell and pay me later. I also advise them to eat as they sell which is a better deal compared to leaving them on the farm to be eaten by dogs and birds. It’s better to get some little money than nothing at all,” one farmer said.

Members of the Masii Horticultural Farmers Cooperative in Machakos County are have a way to reverse the situation.

The farmers recently adopted two low-tech post-harvest innovations for storing fruits and vegetables which could save them unnecessary wastes by prolonging the shelf life of their fresh farm produce.

Elizabeth Muia, a farmer who owns over 200 mango trees, has brought her first batch of the harvest of about 394 kilos to the aggregation centre. The aggregation centre serves both as a collection point for the fruits and refrigeration centre.

“We established the aggregation centre in 2015 and constructed a charcoal cooler. We borrowed the idea from a neighbouring group- but the cooler was not operational until few months ago when the University of Nairobi researchers come and refurbished it,” said Elizabeth, adding that the varsity also introduced a brick cooler.

Intermittent power supplies and lack of proper storage facilities mean that a lot of farm produce often goes before it arrives in the market. But with such eco-friendly off-grid innovation farmers can manage without electricity. 


“The biggest challenge is transporting the fruits to centre since some of us use motor bikes yet the roads are bumpy so by the time they delivered at the centre the fruits are damaged and are therefore rejected,” said the farmer.

The zero energy brick cooler and charcoal cooler which refrigerates the fruits without electric power has been a huge help to the farmers.

Advocates of the innovation say it can reduce pressure on the off-grid farmers to get rid of their produce besides helping them aggregate their produce at one point which makes transport easier.

Dr Jane Ambuko, a scientist at the Department of Plant Science and Crop Protection who is heading the project, says they are emphasising on the low cost post-harvest technologies such as low-cost cold storage technologies to boost farmers resilience and income.

“The technologies slow down deterioration of the fruits while preserving quality. The brick cooler can hold over 50 crates which is about 3,000 fruits while the charcoal cooler can store over 160 crates,” said Dr Ambuko.

The charcoal cooler can be constructed just like a house, but its walls made charcoal is sandwiched by chicken wire mesh.

The zero energy brick cooler on the other hand can be constructed of bricks – a double brick wall (inner and outer wall) while putting sand in between the walls.

The structure also needs adequate water and drip pipes with water flowing into the sand or the charcoal. “Due to water scarcity in this area we constructed roof gutters to harvest rain water which is stored in tanks for use in the drip line,” Dr Ambuko explained.

Dr Ambuko says the farmers can diversify into growing other horticultural crops such as French beans to enable them put the facility to full use.


Daniel Nyalita, a field extension officer in Mwala sub-county in Machakos County, says the facilities can keep fruits for over 15 days as the farmers shop for the appropriate buyers.

“Mango cooler helps the farmer aggregate their produce together for some time. It ensures high quality fruits for sale while maintaining the freshness of the fruit,” said Mr Nyalita.

He admits that food waste is a huge challenge because traders take time before they come yet the neighbouring local markets are flooded with the mangoes resulting to poor prices and huge losses to farmers.

“Compared to other food crops, mangoes are more resilient to the area’s hash terrain which make them a cash crop,” said Mr Nyalita.

Benson Maina, a researcher at the University of Nairobi, explained that before the fruits are stored into the coolers they are sanitised using substances such as Jik to kill bacteria or fungi on the fruit.

The substances are also used for cleaning the crates, he said. “One can use 37 ml of jik then mix with 20 litres of water for cleaning the fruits before storage. Calcium hypochloride which comes in a pellet form can also be used for the same purpose. Dissolve 0.8grams for every litres of water,” Maina explained.

After sanitisation the mango can be waxed. “Waxing controls the environment inside the produce, just like putting a bandage on a wound, it controls respiration and water loss. Waxed mangoes look fresh because they lose very little water,” he said.

“Traditionally, people never waxed mangoes but other fruits such as oranges, apples and avocadoes are waxed.”

The project is supported by the University of Nairobi’s post-harvest project funded by the Rockefeller Foundation under the Yieldwise programme.