Improve potato quality by minimising mechanical damage

Page last updated: Wednesday, 20 April 2016 - 8:41am

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Factors influencing damage at harvest

Four factors influence the amount and severity of bruising.

Machinery maintenance and operation

The most important factor influencing bruising is the ratio of ground speed to conveyor speed. Bruising is minimised when conveyors are kept full of potatoes.

Increasing ground speed by shifting the tractor transmission to a higher gear can speed up harvest, increase and smooth out the flow of tubers and reduce damage. Individual conveyors are often at the wrong speed relative to the preceding or following conveyor. Harvester and washpack operators should be trained in management of equipment to reduce bruising.

Level of tuber impact

The greater the drop height, the more bruising that occurs. This also leads to a shift in damage from blackspot to shatter bruise. Long impact durations and low velocities - small bumps along the conveyor - result in blackspot and internal crushing, while short impacts and high velocities - drops from the elevator to the bunker - result in internal shattering.

Multiple low energy impacts also cause damage, although not as much as one large impact. Contact between potatoes holds less risk than contact between potatoes and machine parts.

An integrated approach is required to maximise the percentage of bruise-free potatoes. This involves harvesting as close to ideal temperature and soil moisture conditions as possible, while matching the volume of material flowing through the harvester to its capacity. The same approach should be applied to washpacking operations.

Soil and tuber conditions

Soil moisture, temperature and soil type influence the severity of bruising, as does tuber hydration, temperature and specific gravity. See Managing temperature in potatoes to improve quality for more details.

Contact information

Peter Dawson
+61 (0)8 9892 8461