Talk from Summerfruit Webinar series 2020: Managing fruit quality for export
Stonefruit cultivar performance during cool storage and predicting quality during export - John Lopresti, from Agriculture Victoria
Webinar 2nd September 2020 (56min 48sec)
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Webinar video Transcript
So basically today we'll be looking at cultivar performance, the objectives in light blue - impacts of temperature management. And I'm gonna to show you, a few preliminary prediction tools that we can play around with, to look at the effect of temperature and storage duration on fruit firmness. We'll get going.
And as Mark's mentioned, next week, Glen, will be talking about real time temperature logging, and some software tools. Then the following week, I'll be looking at post-harvest treatments with a focus on the delayed cooling, to reduce storage disorders, and then Christina will cover fruit maturity at harvest and how that impacts on quality.
So I wouldn't really be touching on those today, although you might have questions about it. So today - cultivar performance. Some recent work with some work with recent cultivars, particularly white fleshed, nectarines and peaches. The potential for storage disorders and how it varies with cultivar or variety.
I'll use those interchangeably. Impacts of temperature management during exports. Some examples of commercial simulations we've done for air fright . We've conducted for air freight and sea freight. And then predicting fruit softening using temperature in storage duration. And finally, I'll demonstrate a simple stone fruit shelf life prediction model.
Okay, so harvest and storage performance issues, basically it comes down to three or four factors, and obviously the key one, I believe is variety. Because we've tested probably 12 to 15 different over the three and a half years, and that can behave quite differently, even under the same temperature and storage conditions. Some of them much more susceptible to storage disorders as in flesh browning and mealiness during longterm storage or during a sea freight export. And the reality is this, although we'd probably covering familiar ground in terms of some of our trials, there is very little information about a lot of the new varieties that we're growing specifically for export and the domestic market.
I don't think we're treading new ground, because we really don't know a lot about these cultivars in terms of how they perform after harvest. So we've found some, and you'll see, we found some interesting results. The other issue is that basically a lot of these varieties, we are sea freighting and the reality is that sea freight is taking between three and four weeks, just the sea freight component.
It's not three weeks, it's not 21 days. It's generally well beyond that before they arrived at the importer, overseas. So these cultivars, some of these are unlikely to actually be sea freighted successfully because of these storage disorder issues. And then you might have the importer storing the fruit for one week or more waiting for the right time to market the fruit.
So that is a major issue that duration from harvest right through to when they arrive with the importer can be beyond four weeks. Then we've got harvest maturity, and the inherent variability of the fruit you're harvesting. And this is an example here, just in terms of sugars, that harvest for Majestic Pearl. And this is a graded, this is fruit that has been graded, is ready for export. And you can see the variation in soluble solids, and we've been finding that up to 25% of fruits, in a particular cultivar, is lower than what we would term acceptable in terms of sugars. So there is, you can find quite a bit of variability evening in soluble solids and sugars.
And the other issue that we've had is limited temperature monitoring, particularly before export and after exports, so during importer storage and beyond, into retail. And Glenn's been doing a lot of work in that area, over the last few years.
So I'll vary briefly mentioned harvest maturity because Christine will be going into it, but we've done a lot of work looking at the effects of harvest maturity. So, there's a diagram of September Bright testing and categorizing a batch of fruit by the actual physiological maturity, so this would be considered the onset or commercial maturity, harvest maturity, unripe, I believe. Obviously you can't tell any difference between them visually, but physiologically, they're quite different. And this is the type of data we collect- storage over six weeks at two degrees. And then after each storage period, ripen the fruit and these are the three maturities. So what we determine unripe fruit, commercial maturity, and then overripe fruit, and you can see the difference in behaviour as we move along the storage period. And I said Christine will be talking much more about that specific cultivars and optimal harvest maturities. And then Glenn will be mentioning, will be discussing in detail, export temperature monitoring. And some of, very generally what we found is with air freight we do get variable temperatures over that actual air freight period of 24 to 48 hours. So variable temperatures and spiking temperatures, eight up to 12 degrees over that short period. And we don't really know the effect of these short and high temperature spikes. Although in a little while, I'll show you what the effect is likely to be because we've, we've conducted air freight simulations and you used a few high temperatures to see if there's any impact on quality later on. And then sea freight, the sea freight leg, because of this infestation protocols is always good, below three degrees for 21 days and beyond, but the major issue we found is that see freight leg is taking way too long, greater than twenty seven days and can be up to 35 days between harvest and getting to the importer, which is, in my opinion, a little bit ridiculous. We can't expect the majority of cultivars we're growing to actually store that long and then ripen them properly. That's a major issue.
Okay, so let's move on to what we're going to focus on today and in general, what we've found, and this is probably common knowledge in terms of the general storage behaviour by fruit type and variety. If we look at early season varieties, then mid season and then late, you tend to get increasing storage potential, due to reduced softening. So the early season varieties tend to soften more quickly even at lower temperatures. And I'll show you some data demonstrating that, but you also get increasing susceptibility to storage disorders as you're moving to later into the season. With, in terms of type of stone fruit, well the white flesh tend to be, have less storage potential, than your white flesh peach. Then somewhere in the middle, I categorize the yellow flesh peach and white flesh nectarine as to having some average storage potential. And then your yellow flesh nectarine tends to store, have greater storage potential. But again, even though we know that white fleshed varieties tend to be susceptible to storage disorders, in fact, the later varieties, whether they're white or yellow, again, tend to be a little bit more susceptible. And then you've got factors like tree age in the order, whether young trees or older trees. Orchard climate warm weather versus cooler climate orchards or regions. Meltingness versus non melting, although we don't really, as far as I know, really grow melting varieties anymore. So there are other factors, but these are the general, what we've generally observed.
Okay. So in terms of storage behaviour, among varieties, here we have four varieties. So we've got the table here. Very early yellow nectarines - June sweet, an early white nectarine - Polar Light, an early white nectarine - Diamond Pearl, and a mid yellow nectarine or mid to late yellow nectarine - September bright.
These are the harvest firmness when we ran these trials, so they're all around the six to six and a half kilos at harvest. What I'm plotting here is the change in fruit firmness from these initial harvests during storage, so days in storage up to 25 days here. This is storage at two degrees and the final, and you can see how the fruit softens or how much fruit softens from the start. If we call the harvest firmness a hundred, then you can see the differences in how the different varieties behave. June Sweet you lose 60% of initial firmness over that storage period of two degrees. Whereas for example, September Bright, there's very little change in firmness, and then you've got your white, early white nectarines are somewhere in the middle. So you can see what a large difference cultivar or variety makes to storage potential, even at this sort of close to optimum two degree storage period. Down here, we've got storage at eight degrees, which is obviously far above optimum, but just to demonstrate the same effect. Same 4 cultivars. Yes, you lose 50% of your firmness after 12 days in September Bright, but it's the other earlier varieties, whether they're white or yellow fleshed, you're losing 75% of firmness at 8 degrees, which is to be expected. But again, to demonstrate there are differences purely biased on variety. So it's very clear that variety is one of the key aspects of determining storage potential. And although we've done work for a number of varieties, I think there's still a lot of work to be done, to get, to really understand how these varieties perform and which ones are limited, in terms of export. The other thing we've found in a lot of our work is storage disorders, mainly flesh browning and mealiness caused by chilling injury, which is usually related to storage duration. And for example, this photograph is of majestic Pearl, and here we've got a sea freight export simulation. The actual sea freight was 28 days. We conducted at Agribio centre in our cool rooms, and we had different importer storage temperatures. So once the fruit arrived, the simulated importer storage at four, eight and 12 degrees. But as you see ,at the end of sea freight and after, there was no sign of flesh browning, but after four days of importer storage, four to five days, you already got started to get this kind of browning occurring. And it really didn't matter, end of retail and then It was flesh browning consistently. And this picture down here is Flavoured Pearl, which is a white nectarine that comes in before Majestic Pearl, and around the same part of the export chain, no flesh browning. So a big varietal difference with very similar, they come in and around the same time and are both white flesh nectarines, but the performance is completely different. And just highlighting a little interesting, in that we've noticed in quite a few trials, take, have a close look at these. This is after 48 hours of ripening and this trend is very similar across importer storage at 12 degrees, actually reduce the incidence of flesh browning compared to the lower temperatures.
And I'll be discussing that more in, in two weeks when I talk about delayed cooling, post-harvest treatments. I won't go into it now, but just something interesting to notice that the higher importer temperature actually reduced incidence of flesh browning.
And we have developed a one pager with recommendations about, concerning storage potentials, and cultivars by types of white nectarines, white peach, plum, the ones that we've studied. We provide a sea freight flesh browning or storage is disorder risk. What we consider to be maximum storage duration of two degrees and some limiting factors. And we, Christine will have more information. This is about a year old this spreadsheet, and all this is on an information sheet and we will be updating it, particularly these because we've learned a little bit more about these different varieties, what the maximum storage life is, and it is available on the horticulture industry network websites at the moment. So if you want, if you're interested in understanding sort of the variation between varieties, in terms of storage performance, then this sheet may be useful to you.
Okay. So finishing off that section of the talk. So beyond the service supply chain project, this is what I believe we'd have to look at. I've already started, but potentially new R and D is actually benchmarking our latest new cultivars against best performing varieties. So for example, any new white flesh nectarines would be benchmarked against Flavour Pearl, which seems to be a very good and robust variety, particularly for export. And we could conduct cool storage and ripening trials, as we have, already have. Also optimum harvest maturity based on fruit physiology and yeah, there's always more work to be done there. Post-harvest treatments. I've already started to look at optimum cooling practices after harvest to reduce storage disorders. I'll talk about that, but then there's a lot of modified atmosphere liners, and even half in liners are being used at the moment. And we don't really know the effect of these liners on storage performance. And then the impact of a fumigation for air freight on fruit quality. We've done a little bit of work, but again, a lot more. And with temperature monitoring as Glenn will talk about, issue, we have a lot of data about temperatures, fruit temperatures beyond harvest, but before the freight forwarder, or after sea or air freight, into retail and export markets. Our data's limited so would be interesting to find out more about that. So that's the section on cultivar performance. It is briefly outline and what we've been looking at during the life of this project.
Now I want to look at impact of temperature management and storage duration on quality. And some of you might think hasn't all this kind of work been done before, we know the impact temperatures. Post harvest temperatures on fruit. My question to everyone is do we really? I don't believe we do.
We've got some general rules, higher temperatures speed up the rate of firmness loss that's about it as much as we know, and I'll show you that there's some interesting impacts of temperatures and sometimes they're unexpected. So the assumption is that we already know what the effects of temperature management and storage time is. But do we particularly for current export varieties, and we might have a general idea, but a lot of growers and exporters ask very detailed questions. What's the impact of a temperature spike during export on quality? Well, it's hard to say. Has anybody body really done the work? So these are some of the questions we might ask in terms of temperature management. What is, what is the actual impact of poor temperature management? So for example, three days at eight degrees Celsius during export, or 12 hours at 16 degrees during export? What is the real impact, for example, on fruit firmness of those spikes in temperature? An objective measure. Until we started looking at it, I couldn't find anybody doing that kind of work, especially for the cultivars we are growing. What is the impact of high airfreight temperatures on fruit quality? We always worried about temperature management in air freight, but what is the real impact? How long can a grower or importer cool store a variety before it won't ripen properly? That's what we're trying to find out. And what about directly after harvest? Do we cool down to low temperatures or do we delay cooling and do a bit of slow cooling after harvest? What's, and then what's impacted, if it's beneficial in longterm in terms of reducing storage disorders, what's impact on fruit softening, as well as impact of storage disorders?
So there are a lot of questions still to be answered, in terms of temperature management and our cultivars. So what we've done in our work over the last 3 years is we've looked at air freight and sea freight. What we've done is commercial simulation trials, exports simulation trials, because we've had seven dedicated cool rooms at different temperatures available at our Agriculture Victoria, Agribio centre in Melbourne. So we can basically try all sorts of export scenarios because we have access to those seven cool rooms that can be set at different temperatures. So it gives us a pretty good ability to simulate all sorts of export scenarios. And we can do two types. We can do constant temperature storage, say at two degrees for five or six weeks. And then ripen the fruit after each storage period. And as you see, that's an example for Diamond Pearl. Or we can actually simulate real commercial export scenarios, so your freight forwarder, your air or sea freight, the importer storage, distribution and retail, and there are the temperature within those stages in the export chain. So, it's a powerful ability to have, to actually simulate commercial practice. And what we've been doing is we've been, generally being using, through out trials, we've been using fruit packed for export and ready to go. And we pick up the fruit from the freight forwarder. So we are using fruit that is already destined for export markets. So our simulations are quite valid in terms of representing real world commercial practice and outcomes. So I will give you, I will demonstrate firstly for sea freight, some of the commercial export simulations we've conducted. On the left here, this is for Flavour Pearl, and this one's Snowfall, which is a new, white peach, probably I think an early February, white peach and Flavour Pearl is a late December, I think, early January. And as you can see, we actually can simulate over, say a 30 and 40 day period, start of sea freights, simulate sea freight leg. End of sea freight. Then we can try different importer temperatures. I think this is about six days of importer storage, or a week at four degrees and 8 degrees. Simulate the effect and then effect retail at eight degrees here. And then the effect of ripening to say on, once the consumers purchase the fruit, how quickly there's a fruit ripened down to eating firmness.
So this is a ripening phase here. And as you can see, we can see the behaviours of each cultivar during export, based on temperature and we can vary the temperatures. And for example, snowfall here, and then, let me step back. These sea freight legs of 25, up to 30 days, these are not unusual as I've mentioned before. So we actually have been simulating long sea freight legs, because that's what we've found is happening commercially. And in this example, another, just something else to point out is that, so we've got importer storage at four, eight and 12 degrees. And as you would expect during importer storage, the fruit tends to soften more quickly at 12 degrees. But what's interesting is we noticed quite often that at the lower important storage, the firmness actually increases, which is not a good sign. It's indicating to us that at lower temperatures you are starting to get some mealiness and chilling injury, which is actually keeping the fruit quite firm. So we've noticed a spike in majestic Pearl and a few other cultivars. And again, something interesting we've noticed by being able to vary scenarios.
In terms of air freight, we've run two decent trials. And I'll show you, I'll show you some results from both of them. A few graphs here, but I'll take my time. They're pretty clear. Cut. Once you see what's going on. So this was airfreight simulation. What we did was we simulated air freight over 24 hour period, three different temperatures. So basically the period where, from the freight forwarder, onto the plane and then off the plane. And we simulated eight degree air freight temperature, a 12 degree and a 16 degree. That's a poor temperature management scenario, during air freight.
Polar Queen, a white peach, very susceptible to storage disorders, but nevermind. So the first graph here is what occurred in terms of flesh firmness with fruit that had no storage disorders. So clean fruit, good quality, all the way through to four weeks. And as you can see there was an effect of high air freight temperatures, which is 16 degrees, 12 and eight degrees. The 8 degree air freight temperature, well the fruit basically remained at four degrees over the four week storage periods, simulated importer storage remained pretty much at that, six to seven kilos firmness, whereas these air freight at high temperatures did impact on softening, as we would expect. Although realistically, the importer wouldn't keep this fruit for longer than a week. And after wake at four degrees after air freight, there was a difference with the 16 degrees, but not really with a higher air freight temperature of 12 degrees. Eight to 12, probably similar result for that 24 hour period of air freight. So can we then, the spike in temperature, of that 24 hour period, does make a difference. But only really at that really high core temperature management 16 degrees.
What was interesting though with fruit with storage disorders? The change in firmness over that four week period was much less. And as you can see, even at 16 degree air freight temperature, you only got down to about four kilos. When this occurs, that abnormal softening, I've called this, that the fruits has a problem and that there are storage disorders associated with that fruit. And here we have the flesh browning incidents from zero to a hundred percent. As you can see, after the first week of storage, at the importer, you started getting very severe flesh browning. But again, what's interesting just note, is that, there was, after two weeks at four degrees, the fruit that was air freighted at 16 degrees had much lower incidents of flesh browning, which gives us a clue to what we might want to do directly after harvest in terms of cooling and I will talk about that in a few weeks.
Now, with Flavour Pearl, we also did air freight simulation. Three temperatures for 24 hours of three different air freight temperatures. But in this case, there was very little difference in terms of loss over four weeks at four degrees, and the fruit ripens pretty much normally, and similarly, regardless of air freight temperature. And this is the actual physiological maturity measured with a DA meter and very little difference in maturity, physiological maturity over that storage period. So Flavour Pearl is an unusual variety. It's a very robust variety. The maturity drops during cool storage, but there's little change in firmness, but it does ripen very quickly, and similarly. And it wasn't very, there was very little impact of air freight temperature. Again, this highlights how important cultivar variety is in terms of storage performance. I think that's all I wanted to say there.
So that's how we run our commercial simulations. Now we're going to look at some shelf life model and then prediction.
So what we've been able to do is store fruits, different varieties, at seven different temperatures and see their behaviour over the different storage periods. And this is an example from Majestic Pearl. The low temperature storage, and then 8 degrees, 12, 16, and you can see the different behaviour and the short storage period as related to differences in temperature.
So we collect all this data and we're able to model actual commercial export scenarios. And I'm going to do that now. So what we have here is an Excel spreadsheet, with a model based on our experiments, our temperature and storage experiments behind the Excel spreadsheet. I'm not going to show you the model, but I'm not sure how you, what you can do with this model. So here we have the harvest maturity, so you can modify this depending on the variety and in what harvest, what firmness and harvest maturity. The duration of each step in the export chains, so harvest to freight forwarders, sea or air freight duration, importer storage, distribution retail, and the consumer phase. You can vary the temperature of each of those phases / stages. And then you can get average firmness or the change in firmness as you move along the export chain. And this is the accumulation, I'm not gonna talk much about it, but this is the total degree hours, accumulated above zero as we move along the chain. So I'm going to double click on it and hopefully it works.
It won't because I got to go back. So I'm going to escape, double click. And here we go, zoom in. And so we can have a look and play around with it. So I'm going to run a sea freight scenario that is probably pretty common, and we've done it to assume a harvest firmness of seven kilos. So I'll put that in. So let's assume a standard air freight scenarios in terms of durations we know. So harvest to freight forwarder, we don't believe that you can get, a grower can get the fruits to the freight forwarder before, any earlier than four days. So let's just say, ideally, they managed to do it in four days. Then, I believe that the average sea freight period is about 25 days at this stage, but let's say 22, just for the sake of this example. Okay, so we've assumed three degrees, average temperature between harvest and freight forwarder. Two degrees, it is more likely to be one degree, but let's say two degrees during sea freight for 22 days. And so at the end of sea freight, the firmness has dropped from seven to 5.7 kilos. And this is average firmness. Then let's say the importer would, once they store the fruit for five days and stores the fruit at five degrees, sorry, three degrees for 5 days. The fruit therefore dropped from 5.7 to 3.4 kilos.
Okay, so this is just demonstrating, and this is for Majestic Pearl, this particular scenario, and then we might say the retail, the distribution retail then takes two days and eight degrees Celsius. So the consumer by, after that time, fruit firmness is basically down to almost eating firmness of one to one and a half kilos. And then the consumer, leaves it on their bench at 18 degrees for let's say one day before consumption. Well it's eating firmness and beyond. So this little Excel calculator demonstrates the power of modelling shelf life and storage life. And so you can vary, we can run through another scenario very quickly.
We'll leave that at 4 degrees. Let's say air freight is more realistic. I, sorry, we can run an air freight scenario. Sorry. We've just done a sea freight. So lets say air freight - two days at 12 degrees. Okay. You might be surprised that there's very little change in firmness over that six days at those temperatures. Well don't be because that's what you tend to find. You don't see the effect of high temperatures until later on in the export chain, you won't to see it straight away. It's just to behaviour of our cultivars. That's how they'd behave. But then the importer storage, let's say six days and say 4 degrees. So after air freight, the importer stores it, stores the fruit for six days at four degrees and the fruit has dropped down to five kilos. Then the, let's say distribution might take three days and it might be 10 degrees, on average rather than eight. See the impact there of that temperature's only seen at the end of the export chain where the fruit tends to soften rapidly, even at eight degrees, it's 1.9 and then the consumer obviously has maybe a day or a bit to consume the fruit.
So I just want to demonstrate that to you, this kind of approach where, a grower, exporter, importer or retail, can you use this sort of calculator to determine how quickly fruit will soften, but then there is another way of looking at it. And this is what is more likely to be used by someone along the export chain, whether it's an exporter or importer or retailer. And to determine the remaining shelf life or storage period. So that previous calculator was just to play around with temperature and storage durations to understand how firmness changes with those parameters. This is actually useful in terms of predicting what is going to happen to your fruit based on what's already happened to it.
So I'm going to run again each one and use some examples. And hopefully this is interesting for you just to have a look how this can work, noting that the Queensland department is actually developing a mobile app for Mangos and Stone fruit, for industry, which incorporates some of these calculations into a very simple user interface.
This is just showing you in a bit more detail, but will not be the final product. So say you're a, an importer and what you've got here is again, you've got harvest to freight forwarder, number of days, the temperature in each stage, and this tells you that the reminding storage period. Now as the importer, what you would need to know is what, how many days, if you want to estimate remaining days, the shelf life as an importer, while you actually need to know this information and you might obtain it from your exporter, just from temperature monitoring. And then once the fruit arrives, you could actually estimate shelf life and storage life. And you do that by inputting a desired firmness. At which point you'd want to, need to sell the fruit as an importer. So you might say, I can keep the fruit until it 4 kilos, and then I have to move it on to the retailer. So, the power of this is actually, you can select the minimum desired firmness as an important, for example.
So let's say five kilos. Right, so let's assume that five days at three degrees. So this is importer doing the calculation. Then you know that the fruit took 23 days to get to you at two degrees. You've got a problem. Your minimum firmness of five kilos has already been reached, right. So this is the issue. So let's change it to 21 days, right? You will receive that fruit at one kilo, so you've got , sorry, that's not kilos it's days remaining. So, under these conditions for this particular, this is majestic Pearl, at a harvest maturity of about six kilos, I think this model is based on, and you can vary that, but this is six kilo harvest maturity. If you want to, if you want to know how quickly you need to offload the fruit before it gets to five kilos, we've got one day remaining before you have to sell the fruit. But if you can hold the fruit until it's four kilos firmness, you've got five days at 3 degrees, and you can see that. If you've sorted for two degrees, you've got two to three days remaining. So you can play around with storage time and storage temperature, and a minimum firmness to actually determine how much time you've got left before you have to get rid of the, or on-sell the fruit. And again, if you can hold the fruit until 3 kilos, then you'll find that you've actually got, (and get rid of that) , when you receive the fruit, you've got nine days to play with before you have to sell the fruit. So it's quite a powerful calculator because you can play around with these different scenarios. If I increase that to 27 days and you can keep the fruit until it reaches 3 kilo firmness, you've got five days rather than nine. Again, demonstrating the power of it and you can do the same as a retailer. You do the side thing, except now that, now that you're a retailer, so you can hold the fruit until it drops down to two and a half kilos before it has to be sold. And if we do the same thing, five days, 21 days, and this is just telling you that the fruit still fine if you continue, the importer stored it for three days, you've got as a retailer, three days to sell the fruit before it gets too, it reaches this firmness. And that's a firmness that the consumer would want to purchase at and consume after a few days of buying it. So I just want to show you what's possible and ideally we will have a mobile app, a much simpler app where you can just put in some temperatures and storage periods and it gives you a warning about how many days are left of shelf life based on those temperatures and storage durations.
Okay. So I'm going to move on, and we're probably nearly there. I'm nearly done.
So to summarize temperature, duration and quality. A good temperature management during export is still critical though. I've tried to use some unusual results from higher temperatures compared to a lot of temperatures. But in the end of the day, good temperature management is critical. But temperature impacts on quality can depend on the variety and the storage durations. So you have to take those into account. and then we've also seen that, for example, short bursts of the warmer temperature during export, during the post harvest chain, could potentially be beneficial. And that's why we've looked at delayed cooling after harvest, which I'll talk about in a few weeks and you'll see that there are some benefits potentially not fast cooling or immediately cooling, fruit. Simulation trials that we've conducted have provided insights into storage potential of the different varieties we've looked at under realistic commercial / export conditions. But more monitoring, temperature monitoring is required during grower handling, cooling and packing as well as after air and sea freight during the import of storage and retail, because we really don't know what's going on at those stages in the export chain, with temperatures. And we've seen that the real impact on quality, due to temperature and storage time, can be understood using shelf life prediction.
So the next step for us is to develop these models further for different varieties. And we're looking at doing at least six varieties by the end of the project or producing models, six varieties. We were hoping to do commercial validation this season, but with the coronavirus and lockdown, we will probably have to do simulated validation in our own cool rooms rather, because we're unlikely to get overseas. And industry probably requires a simple to use real time eyeball app which has been developed. And just finally, I think this kind of work, especially with the sea freight is very relevant at the moment because it looks like it will be quite difficult to air freight a lot of our cultivars this season because of limited flights into our export markets. So we are going to have to sea freight a lot of these cultivars. And so knowing that storage potentials and whether they can actually make the journey and still ripen properly and be good, have good eating quality for the consumer is really important and timely.
Okay. I think that's it. Thank you very much.
Yeah, if there's any questions just to type them into your chat box or Q&A box below. Look, something I've heard just to kick this off if there aren't any, is this thing called kill zone that I've come across just recently about fruit?
Can you tell us a little bit about that and is that really, looking at what you've done? A fair way of gauging a problem with fruit moving in and out of a kill zone.
So, Kills zone, and most growers and exporters have heard of it, is this region, temperature region of about three to seven or eight degrees where many cultivars, older cultivators, generally appear to be highly susceptible to chilling injury. If they spend a period of time at that temperature, and even if they then drop back down to below three degrees, they tend to be more susceptible to storage disorders. Now we have seen a little bit of that with the new cultivars, and we're not particularly sure that it's always relevant, but with that, the recommendation is to play it safe and ensure that you do keep your fruit out of that. Now what's interesting about that is that the problem with how we have handle out fruit from harvest, fruit to the freight forwarder, is the fruit generally can go through that kill zone one or two times before it gets to the freight forwarder, you know if you think about immediate cooling, then you pack the fruit warms up again, and then you cool down again. And we were thinking that we generally want to avoid any movement through that kill zone, even with our newer cultivars, so that then we have to consider, how do we handle fruit to avoid too many movements through that kill zone? And that's where potentially delayed cooling comes in. So I would consider it based on old work and even some of our work, that's still an important issue and it is still highly relevant, for the cultivars and post harvest practices, current post harvest practices.
So while the work has been done on export fruit, could the app be adapted to the domestic market? Looking at the supply chain, grower to market agent, DC, retailer and predict the retail shelf life for domestic markets?
So there's no reason why those models and the app can't be used for the domestic market. Basically what you're doing is replacing that stage that is air or sea freight export will be replaced by domestic, a domestic stage, transport or something like that. So yes, that app very applicable to both export and domestic market. The project has been focused on export cultivars, but obviously most of these export cultivars are still, not all of them, but the majority is still sold in domestic market, and there's actually not a reason, if you've got temperature, if you're monitoring temperatures and the length of a big stage during, across the domestic market, yes you can use those tools to predict remaining shelf life very easily.
Okay, another question, John. Great presentation. Does the shelf life prediction vary for fruit held at constant versus fluctuating temperatures, even if these temperatures may average the same over time? That's a nice, that's a good question. who ever asked that and I haven't shown the data. We've actually studied the effect of temperature fluctuation in one or two trials, I think it's two trials we've done. Where we've looked at different fluctuations scenarios over say a three week storage period, fluctuations from 8 degrees to zero, zero to 8. four to two. But, every scenario adds up to the same degree hours. So they've undergone the same type of temperature, overall average temperature, but just in different types of, different fluctuations. And we haven't seen, we didn't see any difference in the end result. So it appears that the order of the fluctuation, whether you had a high temperature first then a low temperature, or vice versa, doesn't act on firmness for example, but the thing it doesn't act on is storage disorders. And again, as I highlighted in the talk these shortish spikes of higher temperature appear actually to be beneficial , reduce storage disorders. Now, I don't want to come across as sounding like we don't need good temperature management. I'm always worried when I say it's a spike in temperature might actually be good in reducing storage disorders. It's a controlled spike. It's not just random spikes along the export chain or domestic market, because of poor temperature management. That's what you don't want. But, In terms of controls in higher temperatures over a short period, as I'll demonstrate in a few weeks, it's probably, can be beneficial to some cultivars. So we didn't go back to the original question. We didn't see any real impact of the order of temperature fluctuations on firmness change during storage periods, no .
Do warm temperatures encountered early in the chain have less impact on remaining shelf life than if encountered later in softer fruit? Good question, Andrew. So when you get back, so warmer temperatures - with stone fruit, the even warmer temperatures early on you don't see the impact until, and this, now I can start, since I've given the presentation, we're looking at what we call degree hours, post harvest degree hours, so basically above zero. And we're finding that you, regardless of where the temperature you've got early on, you need to accumulate 1200 degree hours or beyond before you see most cultivars begin to soften, right? Assuming commercial maturity. And we found that across the board that, this 1200 to 1500 hours degree hours, before softening appears is pretty consistent. Now, all that means is that if you store your fruit at eight degrees after harvest, obviously, you're going to accumulate those 1200 degree hours very quickly, and then you will see softening. So it would probably take you four days at 8 degrees and then the fruit will soften. Obviously two degrees to accumulate1200 hundred hours takes three to four weeks. So that's where storage duration comes in and temperature, that's how it impacts. So I would say with stone fruit, you generally see the impact of those higher temperatures during the ripening phase. Not. Not during the low temperature storage phase. That's why, just say for example, you delay, used delayed cooling, so you store your fruit at 12 degrees for two days after harvest. And then cool it down to one degree for export. There will be very little impact of, on firmness loss until the other end when the fruit moves to a higher temperature, say during distribution at four or six or eight degrees, then you will see the softening start to take off. And so you are seeing the impact of that earlier warmer temperature only after import and at high temperatures during distribution. So hopefully that answers the question, Andrew. So it's a really important point because, and the model tells us that if you get, as we just saw, an airfreight temperature spike during air freight, you won't see an impact on firmness after that air freight leg, once the importer receives it. If the fruit was seven kilos before air freight, even at a 12 degree air freight temperature, it was still be six and a half to seven kilos, but you might see it impacted that higher temperature later on when the fruit is softening. And whether that's an issue, it depends on how quickly it's retailed. The consumer might see it in the form of the fruit ripening more quickly in the fruit bowl. Again, my observations, I believe that we get a little bit carried away by these spikes of higher temperature, because they don't necessarily, for most cultivars, they don't necessarily make a change firmness to the extent you will be able to detect it at say after sea freight or importer. The detection, the softening, the effect on fruit softening occurs later on. Anyway, that's my observation. Don't holding me to that, but the data shows that pretty clearly.
One more question. So Antar, says hi John, What about the impact variation of levels of oxygen, O2 and CO2 and humidity inside the liner? Is there any work in that area?
Well, that's, I, we've avoided looking at that work because that's a whole other opening up a can of worms, but really we want, the next stage in this work is to actually combine some of what we've been doing with testing various liners and measuring CO2 and O2 levels.
I've done some very preliminary work and I don't even remember the liner. It's a commercially available liner. And we've stored some mixes of yellow nectarines for 45 days in liners at low temperature. And then ripened them. It wasn't a true experimental trial. It was just a basic suck it and see, and it seemed to work. We didn't measure atmospheres in he liners. We just had a shot at it with a small sample and yes, the fruit remained firm. They seemed to ripen okay. I didn't really taste the fruit, if there was any off flavours that can occur in long term storage. So I really can't recommend anything at the moment because we haven't done proper experiments with the cultivars we're growing now and the newer cultivars, and measured oxygen and carbon and CO2 properly and then ripen the fruit to see what impact it has on eating quality and flavour at the end. And that's what you need to do, taste the various liners available. So I hope that we can indeed do that work, form because it's critical, especially even in terms of the impact of fumigation when you've got fruit in liners and whether fumigation is working properly or not. That's another issue as well.
Likelihood of flesh disorders in white nectarines and peaches increases with increasing sea freight duration
During export of summerfruit via sea freight the period between harvest and arrival in export markets can be as much as 35 days. Susceptibility to storage disorders such as flesh browning and mealiness in early to mid-season white nectarines and peaches increases with greater sea freight duration and importer storage period. For these cultivars a harvest to importer storage period of more than 4 weeks is likely to result in a commercially unacceptable incidence of flesh disorders that directly impact on fruit marketability. Further research is required to determine the maximum export duration allowed for these cultivars before storage disorders are likely, and currently air freight is recommended for early to mid-season white-fleshed cultivars.
Photos: Example of flesh browning symptoms in white nectarine after simulated export via sea freight and importer cool storage
Fruit maturity at harvest impacts on subsequent ripening and flesh disorders
Harvest maturity is considered a key determinant of proper fruit ripening resulting in maximum eating quality after storage. It is also likely to impact on the susceptibility of fruit to flesh disorders after a long storage period as encountered during export via sea freight. For export markets summerfruit tend to be harvested relatively immature to minimise the risk of premature softening during export and to meet the demands of importers for firm fruit that may be held in storage for several weeks prior to marketing. For most current cultivars an optimum harvest maturity has not been determined to ensure proper ripening after export and to minimise flesh disorders, whilst also reducing the risk of premature softening.
Graph: ‘Immature’ Majestic Pearl fruit ripened at 24°C with little change among circled fruit after one day of ripening suggesting that flesh firmness at harvest was too high for proper ripening to proceed.
- Cultivar influences fruit quality after export
- Likelihood of flesh disorders in white nectarines and peaches increases with increasing sea freight duration
- Fruit maturity at harvest impacts on subsequent ripening and flesh disorders
- Changes in fruit firmness along the export chain can be predicted
- Preliminary cultivar recommendations for sea freight
Video: Introduction to Stonefruit Simulation Research
As part of this project and focused on stonefruit, what we're looking at is a few areas. One is taking some of these import and export cultivars and looking at the storage potential. So simply storing them or simulating sea freight and import and storage in the importing country using the same temperatures that they would use in during export and looking at their performance, at the cultivars performance in terms of ripening, changes in flesh firmness and any physiological disorders like flesh browning that may occur. And we're looking at mainly white fleshed peaches and nectarines, some yellow nectarines as well as some plums. And this will provide industry with, or will give them some idea of how long these cultivars can be stored for before we see some problems coming up. So we do understand that there are some issues with some of these cultivars, but we're just confirming them by doing these storage trials. There's two other areas where we're sort of specifically looking at. One is what kind of post-harvest treatments we can apply to these cultivars to potentially reduce the severity of the physiological disorders. And also looking at what effect the current post-harvest treatments such as dis-infestation has on subsequent quality in export markets, so a sort of two pronged attack. And the final area we're looking at is to actually try to predict remaining shelf-life during export based on temperatures occurring during the export chain, and the duration of the export chain. And so we're hoping to develop a model that is cultivar specific, that you can plug in your export temperatures, time it's taking to get to importing markets, time that fruit is stored in the importing country, and the model will be able to tell you what the remaining shelf life is of that fruit.
What we found is because these cultivars seemed to be quite susceptible to chilling injury and flesh browning, that impacts on the predictive ability of the model that we will develop. So, we've taken a step back now and really considering which cultivars can be exported by sea freight and, if potentially there's going to be some quality issues with chilling injury, for example, then do we strictly stick to airfreight, which is obviously a much shorter timeframe?
Stonefruit Research Roadshow August 2019
Presentation from Stonefruit Research Roadshow August 2019
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- Predicting fruit quality and shelf life
- Simulated sea freight and quality prediction – Majestic Pearl
- Fruit quality issues – SSC and cool storage
- Air freight temperature vs flesh firmness (kgf)
- Stone fruit pre-conditioning – a solution?
- Preliminary cultivar recommendations – Extended storage
Video: observations from research on cultivars, flesh disorders, harvest maturity, and predicting fruit firmness.
- a number of cultivars have limited cool storage potential
- simulations indicate risk of chilling injuries for these cultivars
So far, it's two and a half years into the project, and I guess the key story that's come out of the work we've been doing is that many of the cultivars we are exporting into Asian markets, particularly the white fleshed peaches and nectarines, seem to be under-performing in the sense that their storage potential is limited in terms of storage duration at low temperature, which is what is required for sea freight export. And sea freight export usually takes three to four weeks once it leaves Australia and gets to Asian markets. For example, China. And during that time, we're simulating that sea freight export and we're finding at the end of the sea freight leg that we're observing some physiological disorders commonly known as chilling injury. And the main symptom is flesh browning and loss of texture, So the loss of eating quality. It's quite a concerning because these cultivars have been planted out in quite high numbers, high volumes, and they are import and export cultivars. So I guess what our aim now is to determine what are the factors influencing the severity of these disorders. And that's within sort of a research sphere, but then there's the logistics of how does the industry shorten the export duration from harvest right through to the importing country? Because at the moment it's it's probably five to seven days from harvest to the freight forwarder, and then we're looking at probably four weeks sea freight durations, so you're already at five weeks storage, low temperature storage, but five weeks storage duration before it even gets the importing countries.
The Serviced Supply Chains project is funded by the Hort Frontiers Asian markets Fund, part of the Hort Frontiers Asian strategic partnership initiative developed by Hort Innovation, with co-investment from Agriculture Victoria, the Department of Agriculture and Fisheries Queensland (DAFQ), Montague Fresh (summerfruit), Manbulloo (mangoes), Glen Grove (citrus), the Australian Government plus in-kind support from University of Queensland and the Chinese Academy of Sciences.