Dr Dario Stefanelli, Team Leader – Fruit physiology, Agriculture Research Division at the Victorian Government Department of Environment and Primary Industries explains how a new non-destructive fruit maturity meter could help growers deliver higher quality pome fruit.
Variable quality in pome and stone fruit has been identified as a major impediment to producer profitability and sales in both domestic and export markets. Supply of consistent quality fruit to consumers is one of the major challenges facing the Australian fresh fruit industry. Fruit maturity is linked, but at the same time not directly correlated, to most of the variables that comprise fruit quality such as total soluble solids, total acidity, flesh firmness, fruit colour and starch content. These are normally determined destructively on a sample of fruit which is not always representative of the variability within and between fruit batches.
Recently, a new non-destructive fruit maturity meter was developed in Italy and is being tested by the Department of Environment and Primary Industries (DEPI Victoria). The DA-Meter from Italy’s Turoni company is an innovative instrument for non-destructively determining fruit maturity by measuring the decline in chlorophyll content immediately below the skin during ripening. As the level of chlorophyll gradually decreases, the level of ethylene increases and this relationship provides an indication of the fruit maturity. The maturity index (or IAD index) decreases in value during ripening of the fruit, until it reaches a minimum value when fruit ripening is complete. Each fruit species and cultivar has specific IAD index according to the different phases of maturation. Consequently a set of reference indices are required for each cultivar, but once established they can be used year after year as IAD values are not affected by agronomic or postharvest practices. This is a major advantage over other non-destructive technologies which require at least annual recalibration. Currently, IAD value ranges at each step of the chain for key varieties are unknown and DEPI is planning research projects that will help identify them.
To optimise maturity and quality during the entire fruit chain the DA-Meter can be used as a tool to:
- optimise crop load and other agronomic practices to obtain a consistent, high quality crop;
- reduce the number of picks and reduce fruit variability at harvest;
- identify and predict the optimal picking window;
- monitor and quantify maturity of stored fruit and determine at any specific time the shelf-life potential of the fruit;
- sort fruit according to maturity, thus guaranteeing optimal, predictable and consistent storage quality whether using normal air, Controlled Atmosphere or ethylene blockers (i.e. 1-MCP);
- increase market flexibility by measuring and predicting suitability of fruit for supplying local, national or export markets and minimising variability in shelf life and market performance; and
- enable retailers to rapidly and accurately measure fruit maturity to manage inventory thus presenting produce consistently at the required consumer preference.
In my opinion fruit maturity could become the quality parameter that allows full integration of information between practitioners at each step in the chain based on an exact reference value provided by the DA-Meter. Monitoring fruit maturity using IAD values along the supply chain will allow the identification of best management practices at each step which will reduce losses due to variable quality and will increase efficiency and profitability. Knowing the ideal IAD value that correlates with quality preferred by consumers will permit real time correlation at each step of the chain allowing fast decisions on the future of each fruit regarding the remaining shelf life and consequently the preferred market. This will increase consumer satisfaction and return sales. Consistent, simple value chain protocols can be created and whole system models implemented to provide a high level of agility for the Australian industry and the ability to respond rapidly and strategically to market contingencies and outside pressures both locally and internationally.
I started using the DA-Meter almost three years ago on both stone and pome fruit. Close collaboration with the University of Bologna team (which has developed the IAD technology) has allowed researchers and data exchange and frequent discussion to further develop this revolutionary instrument. Most of DEPI experiments till now have been on stone fruit with remarkably positive results both in pre and postharvest. Preliminary data on cv ‘Royal Gala’ have also been quite positive in using the IAD index in monitoring maturity in the field as well as a predictive tool for optimal harvest. From my contacts with international researchers some data on pome (mostly apple) are available from overseas. While for stone fruit in Australia the DA-Meter has delivered reliable and consistent results over the years, there are not sufficient data on pome fruit to assert the same. I am personally very confident that, once established for pome fruit, the IAD maturity classes will be as reliable and consistent as they have been for stone fruit. However, considerable industry investment and collaborative effort will be required to cover the broad range of possible fruit species and varieties as well as the various steps in the supply chain. Future research projects should cover all steps in the pome fruit value chain including fruit production, harvest, handling, storage, fruit composition and quality and consumer preferences.
Full adoption of the DA-Meter will help propel the current Australian horticulture supply chain into the 21st century, transforming it into a powerful value chain leading the worldwide horticultural market in terms of volume and quality.