Australian Stonefruit Grower Magazine Issue 2 August 2016 | Page 36

Research The DA-Meter, from theory to practice By Christine Frisina and Dario Stefanelli DA-Meter technology will increase consumer satisfaction as a result of consistent fruit maturity. T he DA-Meter is a new technology that provides a rapid non-destructive method for assessing fruit maturity from orchard to market. Being non-destructive, the DA-Meter can monitor fruit maturity as it develops in the orchard to predict the optimum harvest date. Different maturity classes can be identified to optimize harvest timing to supply local and export markets of choice. In the packhouse, it will be possible to grade fruit according to its shelf life potential. Overall, the DA-Meter technology creates increased consumer satisfaction resulting from the supply of fruit with consistent maturity. The DA-Meter uses spectroscopy to measure chlorophyll ‘a’ in the mesocarp (just below the skin) of the fruit through the difference in absorbance between 670 and 720 nm (index of absorbance difference, IAD). The best way to determine the physiological maturity of the fruit is to correlate IAD values with the fruit ethylene production rate. The correlation between the IAD and ethylene is cultivar dependent, but once the correlation is performed correctly, the resulting maturity classes should be independent of factors such as location, agronomical practices and growing season. These factors will influence the date in the growing season at which the fruit will reach a certain value but the relative ethylene production at the specific IAD value will not change. Calibrating the DA-Meter for optimal maturity determination The main challenge in determining fruit maturity classes is the correlation between IAD value and ethylene production as it requires sophisticated instrumentation, such as a gas chromatograph (GC) to measure ethylene. In general, this equipment is only available in fruit research laboratories. However, the correlation with ethylene production and the identification of the maturity classes is fundamental to the use of DR DARIO STEFANELLI is is Team Leader at Fruit Physiology, Agriculture Research Division, Victorian Department of Environment and Primary Industries. He can be contacted on 03 9032 7373  or via email: [email protected] the DA-Meter and if not done will reduce the accuracy and effectiveness of the DAMeter. To enable owners of DA-Meters access to ethylene analyses, DEDJTR scientists developed a procedure for the collection of ethylene produced by the fruit that can then be sent to a central laboratory for measurement with GC (see video: Introduction to Ethylene Sampling for Optimal Ripening Prediction with DA Meter and the ethylene sampling protocol below). The procedure uses preevacuated vials for the easy and rapid collection of ethylene samples from fruit. Growers and other handling chain participants can collect the ethylene and ship it to a DEDJTR laboratory for analysis. Central processing of the ethylene samples 36 Australian Stonefruit Grower | august 2016 summerfruit.com.au