Getting your valuable mangoes from your farm to the consumer is an essential part of the supply chain. It usually involves considerable transport distance and time. However, the conditions that the fruit are exposed to during this phase can reduce the quality of the fruit.
- High temperatures can cause premature ripening
- Excessive gas build-up in the transport container (e.g. carbon dioxide) could slow down the loss of green colour during ripening and result in green-ripe fruit
- Weak cartons or rough roads can cause carton collapse and compressed areas on the fruit
- Rough roads or driving too fast can cause vibration or bouncing of the fruit resulting in rub marks on the skin; i.e. small brown areas on the skin where fruit have rubbed against each other or the carton.
Why is this important?
Honey Gold mango fruit are susceptible to under skin browning (USB), a bruise-like symptom just under the skin that does not affect flesh quality. Honey Gold fruit grown in the hotter production areas of the Northern Territory and North Queensland are particularly susceptible, but other cultivars such as R2E2 also develop USB.
We frequently observed that USB was a lot worse in Honey Gold fruit that had been road-freighted from the Northern Territory to South East Queensland compared with fruit that were not road-freighted, so we started to look at what was happening during transport.
We saw that the sharp edges of some tray inserts caused rub marks on the fruit and that USB often developed around these rub marks. We confirmed in further trials that we can reduce USB after road-freight by wrapping the bottom half of the fruit in bubble wrap or small squares of plastic to act as slip sheets between the fruit and the insert, carton, or adjacent fruit.
Based on these results, Honey Gold growers in the Northern Territory refined their harvesting systems to minimise damage to the fruit. They also started using softer expanded polystyrene inserts. These reduced USB on the bottom of the fruit in direct contact with the insert. However, they did not reduce USB where the fruit rubbed against adjacent fruit or the sides of the carton. This was because the low profile of the insert did not hold the fruit in position very well.
We have looked at several other insert designs from The Netherlands, The United Kingdom and China. We have also tested whether we can reduce the transfer of vibration from rough road surfaces up through the pallet to the fruit. Preliminary laboratory and commercial trials identified possible leads associated with carton design. We hope to progress these leads pending project approval.
The research and development program to reduce USB on Honey Gold mango has taken a whole-chain approach, including investigating how we can grow more robust fruit, and improving harvesting, packhouse, and transport practices. Key improvements via night harvesting, slower cooling after harvest, and minimising physical damage at all stages from harvest onwards has significantly reduced USB in commercial consignments from about 20% to less than 2% of fruit being affected.
Article submitted by Peter Hofman, Hung Duong, Andrew Macnish and Philippa Bryant from Queensland Department of Agriculture and Fisheries (DAF), Daryl Joyce from DAF and University of Queensland, Gavin Scurr from Piñata Farms and Ted Winston from Tropical Horticulture Consulting.
Acknowledgements: Project MG13016 is funded by Hort Innovation using voluntary contributions from Piñata Farms Pty Ltd and matched funds from the Australian Government. The Queensland Government has also co-funded the project through the DAF. Additionally, the generous cooperation of Honey Gold growers, and Piñata Farms staff is gratefully acknowledged.