Talk from Summerfruit Webinar series 2020: Managing fruit quality for export

Christine Frisina, from Agriculture Victoria, presents: Are the fruit on your trees really ready to pick?
Webinar 9 September 2020 (40 min, 29 sec)

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Video: Harvest maturity impacts fruit quality, Spring 2019

Christine Frisina from Agriculture Victoria discusses how important it is to have ethylene production occurring in stonefruit prior to harvest.

Presentation - Harvest maturity impacts fruit quality (from Stonefruit Research Roadshow August 2019)

Presentation - New fruit monitoring technology (from Stonefruit Research Roadshow August 2019)

Video transcript: Harvest maturity impacts fruit quality, August 2019

So one of the key things we found from this work so far, is the maturity of the fruit is really important to the outturn. The fruit produces its own ethylene naturally. And if there's no ethylene when the fruit are actually picked from the tree, they're likely to be compromised in their outturn in some form, whether that's through flavour or through internal injuries that that can happen. If the fruit has ethylene when it's been harvested on the day it's picked, then those effects aren't as definitive.

So hopefully with this knowledge we can then take this and be able to get an understanding that the harvest time of the fruit is really important and that consignments of fruit, whether they go to domestic or export markets, will have a much more positive outturn and there will be much less effect of those storage times and treatments on the fruit quality.

I took samples of the fruit from complete unripe to full ripe, and we worked out development stages throughout that timeframe. We were able to define ethylene production rates for these fruit, when it occurred and when it boosted. We were able to define three clear stages of fruit development as defined by this ethylene production. The first stage where there's no ethylene production is the stage that's critical to not harvesting your fruit. There's a second stage where the fruits just starting to produce this ethylene. We call that onset. It is very very small amounts but it's there and it's consistent. And then there's a climacteric phase of ethylene production where there's a big flush of ethylene and that's usually the stage where people like to eat their fruit. It's already started to soften and it's got those really full rich flavours and aromas that go with stone fruit.

So in summing up, if you are able to harvest your fruit with ethylene production before they come off the tree, then you will have high quality fruit going into your markets.

Topics:

Comparing stonefruit maturity, quality and volatile composition (aromas)

Variable maturity at harvest affects fruit responses to shelf life, cold storage and consequent quality through the handling chain. Fruit composition and flavour volatiles in particular, are a fundamental element of fruit quality and therefore consumer acceptance. The fruit volatile profile is affected by fruit maturity on the tree, during postharvest storage and consequent ripening.

This project aims to generate knowledge of the interaction between harvest maturity measured by the DA-Meter, storage and ripening behaviour and resultant effects on soluble solids content (SCC i.e. brix - fruit sweetness index), firmness and volatiles profile. This project is linked to the stonefruit trial orchard in Tatura and to 'optimal ripening protocols' to which will deliver preliminary data on the varieties used and will add important information for the protocols.

This project will identify maturity classes to optimize harvest timing depending on the market of choice, with particular emphasis to export, for up to 10 nectarine and peach varieties. The project will generate cold storage and ripening protocols.  The results will provide knowledge to optimise fruit quality and consistency on domestic and export markets. Consistent, high quality fruit will increase consumer demand and provide a point of difference for Victorian stonefruit increasing both domestic and export markets by at least 5% equating to an increase in export value alone of $15 to $20 million per annum.

Video: Introduction with Christine Frisina, February 2018
Christine Frisina Stonefruit PhD

Christine Frisina, from Agriculture Victoria (Agribiosciences in Bundoora, Victoria), discusses the work on comparing stonefruit maturity, quality and volatile composition such as the interactions between aromas and cold storage.

Picking fruit for optimal flavour and storage - presentation by Christine Frisina at the 2017 Stonefruit Research Roadshow (slides only)

Video: fruit volatiles in stonefruit and pear associated with aroma in post harvest storage

Allessandro Cecarelli, PhD student from the University of Bologna, Italy, in collaboration with RMIT University and Agriculture Victoria, talks about changes in fruit volatiles in stonefruit and pear associated with aroma in post harvest storage.

Videos: Measuring fruit maturity using the DA meter

Fruit maturity is measured with a DA meter (IAD) to guide harvest logistics.

  • The DA meter measures the flesh greenness by reflectance of two wavelengths (670 and 720 nm) of light, near the chlorophyll-a absorbance peak.
  • The reflectance is expressed as an index of absorption difference (IAD) scaled from 0 to 3 (green).
  • Comparison of IAD with fruit ethylene production for many cultivars has shown a strong inverse relationship supporting the DA meter as a tool to measure fruit maturity.
Measuring fruit maturity: DA Meter

Dr Dario Stefanelli introduces the DA Meter (non-destructive fruit maturity measurements) and the concept of measuring fruit maturity in the field to determine harvest timing.

Video transcript

Hi, I am Dario Stefanelli, a researcher in tree fruit physiology in the agricultural research division. My project specifically is regarding training and quality of fruit for increasing production, increasing quality and consumer acceptance.

As part of these project., we are trying to introduce a new technology that is to be used for measuring a fruit maturity to help growers to understand when is the correct time for harvesting. That is a good, on my opinion, 60 to 80 percent of the reason why fruit are not of a high quality on the shelves in the supermarket.

So this new technology allows us to measure fruit to maturity. And through this machine over here that is called a D.A. meter. It was invented in Italy at Bologna University from Professor Costa's group. And this machine is sort of a portable, near Infra-red metre about it know measures in the chlorophyll wavelength. And it works as a difference of absorption, meaning that it shoots a light in the fruit and it bounces back. And the difference in the two wavelengths, then it measures a index of absorbance difference. And that number is the number that is going to tell how a fruit is on the ripening development from birth to harvesting.

Measuring Fruit Maturity DA Meter in the Field

Dr Dario Stefanelli discusses using the DA meter in the fruit orchard to determine fruit maturity.

Video transcript

To be effective, the DA meter, needs to be brought in the field. And it needs to actually have the fruit measured directly in the field. It is a non-destructive measurement that, as we said before, tells the grower how mature is their fruit? So the DA meter needs to be attached to the fruit from this small area where the lights come from. It needs to be very close to the fruit and then push the centre bottom. And it takes the measurements on two sides of the fruit. And in this way, it's going to tell us how the fruit is mature or not. And we can read in the centre part of the screen, we can read the value. In this case it is quite high, meaning that the fruit is highly immature, but we already did know these part. However, by monitoring the fruit, then monitoring the ripening of the fruit directly on the tree, it allows the grower to understand when is the correct moment to harvest the fruit according to their correct development.

So the fruit, we need to measure several fruit in the orchard. To have correct measurement, we would say that something like, we should tag twenty five fruit at least, randomly in the orchard, and those, they need to be followed along the entire season to understand how the development is. But to understand how the orchard is going to bring in that the spatial variability and tree variability that normally happens, that is one of the main reason of different quality, we need to measure other seventy five fruit randomly in the entire orchard for a total more or less of a hundred fruit. That would give us a nice number, a nice statistical number to understand when we average it what is actually happening as maturity in the entire orchard. We need to do this weekly. If we collect data and we are able to create the nice ripening curve. And it is possible to predict with two to three weeks in advance, depending on the variety, to predict the harvesting, the correct harvest time.

DA-Meter protocols in the field Observations and Results - presentation by Dr Dario Stefanelli at the 2017 Stonefruit Research Roadshow (slides only)

Scientific instrument called a D.A. meter Photo: DA-Meter Measuring harvest maturity.

This research project, SF15001 Comparing Stonefruit ripening, quality and volatile composition, was funded by Agriculture Victoria with co-investment from Horticulture Innovation Australia Limited using the Summerfruit levy and funds from the Australian Government.