Want to keep mangoes fresh? Wax them

Mango farmers will soon be able to extend shelf-life of the fruit by coating them with wax. The low-cost post-harvest technology will help to curb losses in the value chain, ?putting more money into farmers’ pockets

In a few weeks’ time, the sight of rotting mangoes in farms will be stuck with us for some time.

Reason? It is another mango harvesting season and various mango producing counties like Murang'a Kitui, Kilifi, Embu, and Makueni will be awash with the ‘cycles of post-harvest losses in mango value chain' once again.

Mangoes are a seasonal crop with high and low seasons. In most counties, the seasons starts from December and peaks in January to February.

?Post-harvest experts estimate that 40-50 percent of fruits and vegetables produced in Kenya are lost or wasted along the value chain. In Kenya alone, only 80 percent of the mangoes are eaten while still fresh, hence the need to increase their shelf life.

But, this scenario could be averted through the use of simple technologies that mango farmers can adapt and use in the farm to curb the losses of agricultural produce hence supporting livelihoods and food security.

Mr Benson Maina, a Plant Science and Crop Protection master’s student at the University of Nairobi thinks, shelf-life of perishable fruits like mangoes can be extended by coating them with wax.

Mango waxing technology, he explains, slows down the diffusion of water and gas from the fruits thereby reducing their water loss and respiration, hence prolong their shelf-life.

The wax used is a special kind of food grade wax which is safe for food preservation. Maina says the wax replaces the natural wax found on mature fruits and which is often washed off or removed during handling.

“A lot of mangoes goes to waste, especially during a glut. However, with low-cost postharvest technologies such as fruit waxing the losses can be averted,” said Maina.

"Poor storage and diseases are the major causes of post-harvest loss in the mango value chain. There are key processes that occur when fruits are harvested, such as loss of cuticle during the washing and rubbing against each other when in contact …..water loss and respiration which leads to food reserves in the fruit being broken down by the oxidation process."

But if farmers bought this artificial wax, it could help them slow down the rate of oxidation and less loss of water in the mango fruit.

And since respiration and transpirational water loss contribute to the deterioration of fruits and vegetables after harvest, there is a need to safeguard farmers' produce by using innovative technologies.

From last year, Maina has been in the laboratory testing the efficacy of mango waxing technology and how it can save farmers from mango losses. He explains that the initial pilot phase he has conducted at the Embu-based Karurumo Horticulture Self-help Group-which processes mangoes into various products-is causing excitement.

"Traditionally, people never waxed mangoes while other fruits like apples, oranges, and avocadoes are waxed…but after numerous research I realised I could use the same principle in mangoes,” said Maina during the interview.

The study is being conducted by the University and field demonstrations have been carried out to get the view of farmers.

“During the demonstrations, treated and untreated fruits were left with farmers for two weeks and an?assessment was done to check the impact of waxing. Waxing performed way better than untreated ones,” noted Maina.

The project has initiated the process of acquiring certification from local authorities in readiness for roll out. However, says the researcher, "the wax understudies are used elsewhere and is already accepted by the European Union under INS 471”.

He says waxing technology increases the shelf life of mangoes to around 28 days.

Using two kinds of waxes; shellac wax and deco mango wax to compare the appropriate mix to use in his experiments. His extensive research in the laboratories has propelled him to conduct trials among two farmer groups with an average of 50 farmers in the larger Embu County.

Maina explains that after treating the mangoes, he leaves them with the farmers for a period of three weeks to enable them to compare with the untreated ones.

Contrary to beliefs, especially among farmers, the wax used for food preservation is not cancerous because it is developed specifically for the purpose of food preservation.

So how does the waxing technology work?

?"Respiration and transpiration are the major factors contributing to the postharvest deterioration in fruits. Mango, like many fruits, comprises about 70% water which is lost to its surroundings due to water pressure deficit."

The cuticle, which is a waxy layer on the surface of fruits, meant to reduce water loss to the environment, is mostly lost during washing or when fruits rub against each other in storage or transit. Coating fruits with wax compensate for the lost natural wax and provide a barrier to water and gas diffusion by reducing the number and/or the size of lenticels.

This leads to water saturation inside the fruit as well as reducing oxygen diffusing in and carbon dioxide leaving the fruit thereby slowing down transpiration and respiration respectively.

With consumers in urban markets or out of the country in need of fresh fruits and vegetable smallholder farmers, who form part of the value chain need ways to supply them fresh.

But employing postharvest technologies like Controlled Atmosphere is very expensive and out of reach to many smallholder farmers or traders.

Interestingly, explains Maina, coating fruits mangos with wax is a cheap, easy to access and use postharvest handling technology.

Most of the fruits exported outside the country such as avocados are coated with wax to ensure they stay in an unripe state before it gets to the consumer.

“Consumers are so informed and they almost dictate what goes to their food or how that food is grown. But the same consumers need fresh produce,” said Maina.

Waxing technology, adds Maina, would help in cutting logistical costs used by traders in exporting fruits.

"For the mangos especially from Kenya, is transported by air making it very expensive and the fruits become uncompetitive when it reaches the market. Delayed ripening by waxing could help mangos stay for more than 28 days in good condition and therefore sea freight could be adopted, reducing the costs incurred by traders to get the fruits to the market," he said.

The added wax also helps to protect the fruit from bruises and adds gloss to the fruit, continues Maina. Mango waxing is suitable for traders and farmers in the mango value chain.

He, however, cautions that conducting extensive studies to realise the right concentration for coating fruits is key.

Dr Jane Ambuko, a post-harvest expert at the Department of Plant Science and Crop Protection, University of Nairobi says appropriate technologies are key in extending the shelf life of fruits and vegetables.

Ambuko, however, adds that to realise full potential technologies such as waxing must be used together with easily-affordable cold storage systems to ensure better returns for the farmers.

She notes that off-season crops in the country are money spinners for farmers, hence the need for better post-harvest management.

“Lack of access to affordable and easy-to-fabricate post-harvest technologies for handling or storing at the farm level, is to blame for such losses,” said Ambuko.

The researcher’s next stage is to promote the technology among mango exporters. Maina says, "Farmers will be able to get the wax in small quantities which will be affordable. But, as of now, I can't be able to say at how much until we go full scale".

?"We are now moving to the next stage of conducting demos to mango export companies. The long and short of things is, actually, we can use waxing technology as alternative post-harvest loss management for handling mangoes," he explains.

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In Summary

• Mango waxing technology slows down the diffusion of water and gas from the mango fruits thereby reducing their water loss and respiration, hence prolonging their shelf-life.
• Post-harvest experts estimate that 40-50 percent of fruits and vegetables produced in Kenya are lost or wasted along the value chain. In Kenya alone, 80 percent of the mangoes are eaten while still fresh, hence the need to increase their shelf life.
• Waxing technology increases the shelf life of mangoes to around 28 days.

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