High temperatures and extreme weather events can have numerous impacts on wine grapes and ultimately wine quality. Dr. Andreea Botezatu, Associate Professor and Extension Enology Specialist at Texas A&M University, Texas AgriLife Extension Service finds that changes in ripening patterns are the most common. In high heat, sugars accumulate faster, acids degrade, ripening happens earlier and the result is higher alcohol wines. The challenge is that ripening is not linear. Tannins and maturation of the seeds do not progress at the same pace. Plus, high pH causes color and flavor instability.

Andreea is experimenting with verjus, the juice of green grapes. In North America, grapes from crop thinning are traditionally considered waste. However, in Eastern Europe and the Middle East, green grape juice is used in many culinary practices. Verjus has little sugar, high acidity, and low pH making it a perfect addition to unbalanced wines.

Learn about her current experiment testing both red and white grape verjus against three other acidification methods. Plus, Andreea gives listeners tips on how to prevent that green pepper flavor caused by ladybug taint.

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Transcript

Craig Macmillan 0:00

And my guest today is Andreea Botezatu She is Associate Professor and extension enology specialist at Texas A&M University, the Texas AgriLife Service. Thanks for being our guest today.

Andreea Botezatu 0:11

Thank you for having me.

Craig Macmillan 0:12

We're very interested in some of the work you've been doing recently around effects of warming climates on vines and on wines. You're in enologist. In particular, you've been doing work on wine quality. That Correct? And you've been doing work in Texas, obviously.

Andreea Botezatu 0:26

Yes, for the past seven years or something. Yeah.

Craig Macmillan 0:30

And would you say that temperatures during the growing season in Texas overall have been increasing?

Andreea Botezatu 0:35

I would Yes, the temperatures historically have been increasing. And furthermore, we see a lot more extreme weather events. So temperature records being broken, as well as like I said, extreme weather storms, winds hail, a lot of hail we, we've been having quite a bit of hail in Texas. So these can affect the process of grape growing.

Craig Macmillan 0:58

Absolutely. So definitely, there's been some changes, how has this been affecting one quality, what particular parameters are being most affected?

Andreea Botezatu 1:04

Right. So this is not straightforward answer for this question. Because because several things can happen when you have extreme weather events and temperatures rising. The biggest one that we see here is a changing ripening patterns. So sugar accumulation and acid degradation, they kind of change sugar tends to accumulate much faster, because of the earlier heat we tend to see earlier ripening. So earlier, harvesting sugar accumulates faster acids degrade quite a bit, the ripening is not linear anymore. So we see ripening in terms of sugar, but we don't see that in terms of tannins or aroma compounds or maturation of the seeds. So there's a bit of disconnect there. That's one thing because of the higher sugar accumulation, we tend to see higher levels of alcohols in wine, which is not necessarily a good thing. There's only so much so much alcohol that you want to have in wine that becomes overbearing and unpleasant and the wines will be unbalanced. Most importantly for us in Texas, and I'm sure for any other grape growing region that deals with high temperatures is an increase in pH because of acid degradation. We see grapes coming in with very low titratable acidity, we're talking three four grams per liter, and then pH is of four and above.

Craig Macmillan 2:31

Wow.

Andreea Botezatu 2:32

Yeah, yes, wow, indeed, very, very high pH is that we have to deal with as winemakers as I'm sure your audience knows high pH can cause a host of problems and wine quality problems from microbiological instabilities, compromising one quality that way to color, instability, aroma, and flavor, balance all of that. So that's a big thing that's happening.

Craig Macmillan 2:56

And those high sugars are also problematic just for getting your fermentations done.

Andreea Botezatu 3:00

Absolutely. You can have problems starting your fermentation, you can have problems finishing your fermentation,

Craig Macmillan 3:05

What kinds of things are winemakers doing to try to manage these factors, but and what kinds of things are you looking at to try to manage these factors?

Andreea Botezatu 3:13

Right, so my researcher at A&M, is focused on acidity and acidity management, again with a focus on pH more so than titratable acidity. So over the past six years, we've been looking at two alternative acidification methods. One is enzymatic, it employs the use of glucose oxidase that is a is an enzyme that helps transform glucose into Gluconic acid, thereby increasing the acidity of the wine and increasing the pH. So we've done some research on both reds and whites. And that research has been published in peer reviewed journal. So those are links that I can share with you and now we are working with verjus and that falls within the sustainability category as well because a little bit of background on what verjus is and how it can help. Verjus is the juice of green grapes. It is produced from unripe grapes that are pressed and the juice obtained is called verjus which comes from French, the French language jus vert, green juice. So basically it means green juice. And because it's made from unripe grapes, you can imagine there's little sugar in it, the acidity is quite quite high and the pH is quite low. Traditionally, grape growers can practice this crop thinning practice to manage their crop and crop quality. What they do is they drop some of the grapes on the vine before they ripen in order for all the resources of the vine to be directed to the grapes that are leftover. So the grapes that are getting dropped are traditionally especially in North America considered waste nothing is done with them. They are left on the vineyard floor. I have a European background right and I I grew up with these grapes being turned into virjus, we have a different name for it in Romanian, but same idea. And this juice was used quite heavily for various culinary practices in Eastern Europe and throughout the Middle East. So remembering that I thought, Well, why not try to take these grapes and make verjus out of them and you start to acidify? It is a natural product that comes from the vineyard and it gives added value to the grapes, right?

Craig Macmillan 5:29

And these grapes, are we talking just past verasion, are we talking still in the in the berry green hard pea stage?

Andreea Botezatu 5:36

So verjus traditionally is made pre veraison. There's not a set date for grape thinning or verjus production. It can vary anywhere from 30 days post bloom to 45 days post bloom and the beginning of verasion there.

Craig Macmillan 5:53

So tell me more about this. We make some verjus we collect some berries that haven't been through verasion yet, and then they're crushed, repressed or something. I'm also curious, is this done? Can this be done with both red and white varieties?

Andreea Botezatu 6:03

Again, a very good question. So last year, we had our first experiment with verjus and we made it with white from white grapes on Muscat Canelli. This year, we are making it from both white and red, we're using different varieties. And we're looking a little bit differently at it. So still, we want to see how it affects one quality and wine sensory profile. But what we're doing extra this year, so we're doing red and white. And on top of that we are comparing this method with three different acidification methods, three other acidification methods, both from a chemical and sensory perspective. So we're looking at, you know, the traditional tartaric acid addition that most wineries do, we're looking at verjus addition, we're looking at the GLX glucose oxidase that I mentioned earlier. And we're looking at ion exchange, which is becoming quite popular for pH reduction.

Craig Macmillan 6:57

Tell me more about that.

Andreea Botezatu 6:58

So ion exchange resins are widely used in water treatments, soft water, hard water, depending on what you're trying to achieve. Basically, there, there's resins that have been charged, and they can release either cations or anions. In our case, the resin that we use releases protons or hydrogen ions, and then the potassium in the wine gets reduced. And by releasing protons, increases the number of protons in solution, thereby decreasing the pH. And you basically pump your wines through this ion exchange column that holds the resin and it comes up on the other end.

Craig Macmillan 7:35

If I understand correctly, that's also removing the potassium, which is the buffer that's keeping it high. All right.

Andreea Botezatu 7:40

Some of that, yes, not all of it. Yes.

Craig Macmillan 7:43

Are you doing this at the juice stage, we're doing this just after fermentation. During aging?

Andreea Botezatu 7:48

We are doing this at the juice stage, from everything that I've heard in the industry, it is better to have it done at the juice stage, it has less impact on the final wine quality, but it's gentler, so yes, at all the treatments that we're doing, we're doing them at the juice stage and then fermentation follows sterilization and everything else.

Craig Macmillan 8:08

What kind of quantity or ratio of verjus might we need is in liquid or by weight to get these kinds of impacts that we're after?

Andreea Botezatu 8:19

Right? So it depends on what we're trying to achieve. We asked that question with our study last year. So we had two treatments last year one to see how much verjus we needed to add to drop the pH by one point. So let's say you start at 3.6, we're gonna bring it down to 3.5. How much verjus do I need to add to achieve that and the other one, the other treatment was to target pH. So again, you start at 3.6, but you want to drop it to 3.3. We did both. And it turned out in our experiment that we needed to add 2% by volume verjus to drop the pH by one pH point. And then for the target pH we needed, we added about 10 to 11% verjus to get to the target we wanted. So you know it depends on what you're starting with the pH you're starting with a depends on the pH of your verjus. And that makes a big difference. We're working with lower pH verjus this year compared to last year. So that might change things a little but this is what we got so far between two and 10%. With a pH is that we worked with.

Craig Macmillan 9:24

If I remember correctly during that latter phase before verasion when we get past like lag phase or so what's happening with the reduction in acidity is that the malic acid is getting metabolized basically as an energy source tartaric may come down a little bit during that period, if I remember right, so if I am picking things early, like pre raisin, I'm assuming there's going to be a quite a bit of malic acid in that juice.

Andreea Botezatu 9:50

That's right. Yes.

Craig Macmillan 9:52

And is that going to affect what I do from winemaking perspective?

Andreea Botezatu 9:55

Well, for whites, very little for reds. I think it's absolutely a positive thing because most winemakers will want to put their reds through malolactic fermentation. And that's problematic. Now here with a high pH is because if you have a malolactic fermentation with a high pH wine, you can run into a million different problems and have really serious quality issues. So by adding this natural malic acid from the grapes, you allow then your winemakers to run their malolactic fermentations at a safe pH and get that effect of roundness and softness and all the sensory properties that come with it.

Craig Macmillan 10:34

Are there things that growers can do in the field, we're talking about the bears up, so the things that other things that we can do in the vineyard to help ameliorate some of these are things that people experimenting with, or winemakers are interested in having vineyard folks experiment with.

Andreea Botezatu 10:48

I mean, in the vineyard, there's only so much you can do once your vineyard has been planted. Water management is very important. And it helps a lot makes a big difference. Water stress can can have quite the impact on grape quality and Vine health as well. So water management is a big thing. And then canopy management is another one, you want to make sure that your grapes are a little bit shaded, they're not completely exposed to the sun, so you avoid sunburn and heat and light exposure. These are things that some grape growers can do. Some grape growers in Europe, as far as I know, plant grass coverings to reduce the evapotranspiration, the soil level to maintain water in the soil as well some modify their canopy structure, raise the trunk. So there are a few options. But I would say water management and canopy management are the most important ones. However, there is something that can be done and is actually being done actively in various parts of the world. As temperatures change. grape growers are changing the varieties that they're planting to adapt to these higher temperatures and different weather patterns. So they're looking at varieties that are a lot more heat tolerant. And that's a big change, that's a big change. And that's going to have a big impact.

Craig Macmillan 12:07

Just to go back for a second, when we talk about irrigation management, what you're talking about is not stressing the vines overly you want them to be happy,

Andreea Botezatu 12:14

You know, vines, like a little bit of stress. So but not as much as we see with these types of temperatures here. So yes. Keep them somewhat happy.

Craig Macmillan 12:25

So there's some things that we need, we need to stay on our game, basically in the vineyard - monitor, monitor your your evapotranspiration, and also the plants status and all that kind of thing. Because I have seen vines and heat, you know, basically collapse. Yes. And, you know, it's all the chemistry in the grape just goes nuts. They're like at the last minute, you know, and you're like, Oh, we're doing great and everything goes to heck. what Oh, what about shade cloth? Are people using shade cloth?

Andreea Botezatu 12:51

Yes. So the answer is yes, you can use that. And another thing that they are using this has nothing to do with temperature but rather hail they use hail netting to protect their vines from from hail.

Craig Macmillan 13:03

Oh, interesting. Interesting. I've heard about that in Europe, and I've never seen it in the United States.

Andreea Botezatu 13:07

Yeah, well come to Texas.

Craig Macmillan 13:08

I'm gonna I do I need to come to Texas. I got a friend there who's a bit of culture tonight. He keeps saying you gotta come check it out. You gotta come check it out.

Andreea Botezatu 13:14

Well, I feel sometimes that like we are the main lab for grape growing in the world, because we've we've already done all this work because it's hot here anyways. So we started this 20, 30 years ago. Like we can teach the world a thing or two about grape growing in hot climates, really.

Craig Macmillan 13:34

And that's a really good point is that there's resources in other parts of the United States or the parts of the world that that may apply to your world. If you're in a different region as your region changes, then I've definitely learned that over time, I will look out for other sources outside of California. I'm in California, I'm on the Central Coast, California, which has traditionally been a very cool area. And we're gonna see if that continues, which then leads back to your point. So changing varietals, or varieties, I should say changing varieties, what direction are people going in? What's the what are people thinking?

Andreea Botezatu 14:09

Right, So people are looking at heat tolerant varieties. And these two, again, both come from hotter regions, southern regions, so we're looking at Spain, southern Spain, Southern Italy, Greece, some of the Georgian varieties as well. Some seem to be doing quite well. I can give you some examples of varieties that we have in Texas,

Craig Macmillan 14:30

Please.

Andreea Botezatu 14:31

We've planted a lot of Tempranillo, Mouvedre, Vermentino, Aglianico, Montepulciano, Sagrantino does fantastic here Tannat. does very well here as well. Albarino on the wine, white side, I said Vermentino we have some Russanne and Marsanneare doing okay, but southern Italian Spanish Portuguese varieties are quite the stars.

Craig Macmillan 15:00

That's interesting, and how are how are winemakers feeling about this? I mean, are they excited? Are they? Are they having a great time? I mean, Tannat was a very exciting variety about 10 years ago and have made some really nice wines in California, are people getting into it? Are they excited about it?

Andreea Botezatu 15:15

So winemakers are very excited about all of that the problem is not the winemakers, it's the consumers who are not not familiar with these varietals, they don't have name recognition, so convincing the consumers to try them and buy them and come back for them that that is the main problem that we are having now. But I think we're making a lot of progress. And actually, some of my research is focused on that as well. So name recognition and pronunciation and comfort in purchasing or choosing a wine that's hard to pronounce and submitted an article for publication, or looking at that just today.

Craig Macmillan 15:49

Just today, timely as today's headlines. Well, I'll be looking for that I'll be looking forward to that yet to people, you know, people will have to be kind of familiar with it, you know, they have to kind of recognize it over time, I think that can can definitely happen. I mean, I was thinking about SSangiovese in the United States, I'm thinking about Syrah, even in the United States, that was one that wasn't that labeled that much 30 years ago. And now we've got a whole fan base nationwide for that variety. And so maybe that same kind of thing will happen. And I hope so finding the plant for the place is huge, you know, and so if things are changing, we may want to think about finding different plants for that place.

Andreea Botezatu 16:25

I mean, look at Bordeaux, right? They Bordeaux, in France, they were approved to use six new varieties, which is extraordinary considering how long they only stuck with a traditional Bordeaux varieties. So now they are allowed to grow six new varieties, four reds and two white. So that's that's quite something. And that's not the only place where that is happening.

Craig Macmillan 16:47

Yeah, that's, that's very interesting. It will also be interesting to see if we have breeding plant breeding programs along these lines as well. That's an even harder road to hoe, because there's no history with it with a plant like that. But it's an interesting idea. I need to find a grower I need to find a plant breeder to talk to. So changing gears a little bit. There's something else that you've been working on that I'm really fascinated by. And that is Ladybug taint. And we are talking about the ladybug, we're talking about high sparrow.

Andreea Botezatu 17:14

Yeah, we're actually talking about ladybugs and this has been the subject of my PhD research and my postdoc work. So I've spent six, seven years looking at ladybugs and how they can affect wine quality. So for a little bit of background I have to start and be with some science. There is a group of compounds called methoxypyrazines that are naturally occurring in the world naturally occurring in plants. Many vegetables contain them bell peppers, for example, will have high levels of methoxypyrazines Peanuts, peas, green beans, some fruits contain them as well and grapes within a category of fruits, some grape varieties will naturally produce methoxypyrazines. These compounds smell like bell pepper in green beans like the vegetables that couldn't contain them. So at low quantities, low concentrations in grapes. These compounds methoxypyrazines can contribute to the paucity of the wine to complexity of the aroma profile and flavor profile of the wines. If however, these quantities increase, the concentrations increased, they can become overpowering and dominate the profile of the wine and you don't want your wine to smell like bell peppers and nothing else. Really, that's no fun. Another source of methoxypyrazines in the world is insects, in particular, lady beetles, ladybugs, and within the ladybugs category there are some species that are more apt at producing them but also infesting Vineyards, one of these species is called Harmonia axyridis, or the multicolored Asian lady beetle also known as MALB. Now this is a species that has been introduced into North America from Asia as a method of bio control against aphids in the 1960s mistaken and in time, it has established populations here and it has begun to spread so as the bio control method is very successful, it does what it's supposed to do but once the aphids are gone and the soybeans are picked harvested, then it looks for other sources of food and it can migrate into vineyards so these are the beetles will fly into vineyards they don't damage the grapes they don't bite into they don't want the grapes but they do feed on grapes that happen already open or cut for the sugar is you know is exposed in any way the flesh is exposed in anyways. And what happens is that if you pick the grapes with these lady beetles in them and you bring them into the winery with lady beetles in the menu, process them with lady beetles in these way they will also secrete something that's called hemolymph. It's basically their blood and this hemolymph will contain again Methoxypyrazines at quite high concentrations, these Methoxypyrazines get into wine, they tend to wine. So the wine will smell like bell pepper and green beans and potatoes and peanuts. And what's also interesting is that the ratio of these Methoxypyrazines is different in the hemolymph of lady beetles, as opposed to the ones naturally occurring in grapes. So there's one particular Methoxypyrazines , that's dominant in grapes, that's isobutyl Methoxypyrazines IBMP, whereas in ladybugs, it's the isopropyl Methoxypyrazines , and that's dominating. And that can be also a method of diagnostic, you know, if you're looking at a wine that smells like that, and you're not sure, where did they come from, if IBMP is the dominant one, most likely there was a lady beetle infestation there, if IPMP is the highest one, and it's just the grape and weather conditions or whatnot.

Craig Macmillan 20:51

Arectheir control measures, cultural things are their chemical things in the vineyard. And then the subsequent then moving to the next step is what what can wineries do when the grapes come in? Can they inspect the fruit?

Andreea Botezatu 21:05

Absolutely. So in the vineyard, there are some sprays that can be applied to get rid of the lady beetles. However, you have to be careful as a grape grower with pre harvest interval there. SO2 has been tested as a spray in the vineyard against a lady beetles as well and used to be very effective, which you know, it's very helpful because it's SO2 we sprayed and it was already added anyway. So that helps to have some natural products natural essential oils that have been tested, they were shown to be quite effective at repelling lady beetles. And then there's the same yo chemical, the push pull traps. So you want to have compounds that repel the lady beetles in the middle of your vineyard, and then compounds that attract the lady beetles outside of your vineyard. So it's a push pull system. That's what can be done in the vineyard. And then once grapes are harvested on the winery side, we need to make sure if we are aware that there was a lady beetle presence in the vineyard, we want to make sure we sort our grapes, very, very careful. I mean, it doesn't take much to taint the wine one lady beetle per kilogram of grapes is more than enough. So you got to be very careful when sorting to make sure we get rid of all lady beetles. And also what's important to remember is that even dead lady beetles can taint the wine. So even if you spray them kill them, if they're still coming in, they still have the potential to taint the wine. And that's one thing that's the first step that you can do as a winemaker, if still after that you have an issue with Ladybug tainting your wine, there are some things you can do. They're not extremely effective. So juice clarification has been shown to help a lot. Thermo vinification has been shown to help actually one very good method at reducing pyrazine levels in wine is Flash détente. That is very, very successful. And we have that here in Texas. And we have some wineries that use Flash détente are not necessarily for methoxy partisans for other purposes as well. But very successful at doing that. Some refinding treatments more or less successful. In my research, I looked at my plastic polymers and silicone and they worked, but you need to find a form of application to apply them industrial, you know, commercially. So right now we're not there yet.

Craig Macmillan 23:20

And these techniques were wondering would apply to both red and white wines.

Andreea Botezatu 23:24

Well, fining is more difficult with reds because of the loss of color. So it's easier with whites, but Flash détente on the other hand is better with reds than with whites. So thermo identification Flash détente would be better suited for it.

Craig Macmillan 23:38

In your experience. Do you think you're seeing an increase in Ladybug infestation? And is that possibly tied to the changes in climate?

Andreea Botezatu 23:46

Well, yes, we see a change in patterns. I don't know if necessarily an increase they seem to be moving from certain places and arriving in other places. So places that didn't used to have ladybugs have them now and then they move out certain areas. So yeah, there's a shift so people need to know about them. grape growers need to be aware of this problem and monitor their vineyards for ladybugs, you know, you don't think about it. They're cute little things and people seem to like them, oh, they're just ladybugs, but they can be quite quite detrimental, especially in particular species, which is quite easy to identify it has that M on the pronoun. So very easy to spot and to be aware of. So yes, grape growers need to keep an eye out for lady beetles in places where maybe they never used to have them before. Just something to be aware of.

Craig Macmillan 24:39

If we're talking about one particular species, is this an issue with other species in the order of Coleoptera?

Andreea Botezatu 24:47

To a much lesser extent, this one is worst one Coccinella septempunctata the seven beetle can summon spot beetle can also taint wines but we just don't see them in vineyards as much they're not as much of an issue as Harmonia.

Craig Macmillan 25:01

Interesting, we're getting close to our time here on both topics. Let's start with climate winemaking. And then let's talk about lady beetle. What is one thing that you would tell growers or winemakers regarding that topic and let's start with, with the warm wine.

Andreea Botezatu 25:17

Growers, I would advise them to choose their varieties carefully. When they initiate a vineyard when they start on the plan of vineyard and be very careful about their water treatment. To winemakers, I would say focus on pH rather than sugars focus on acidity. And also for those winemakers who look at malolactic fermentation in red as a given, I would urge them to reconsider. I personally don't see a reason why malolactic fermentation has to happen, especially if you have issues with acidity, it doesn't always benefit the wines. So and there are there are options out there to inhibit malolactic fermentation if you choose to do so there are several compounds that can help with that and help stabilize the wines from from that perspective. So I really, really encourage winemakers so at least think about that, start considering that as an option. Maybe start experimenting, you know, small amounts not necessarily go full on on not running malolactics, but start slow and see how it goes and see how that affects or changes the wine quality and wine stability.

Craig Macmillan 26:23

What about the lady beetle? What's the one thing you would tell both growers and winemakers about the lady bettle.

Andreea Botezatu 26:28

Do your best that so that it doesn't get into winery it's much easier to prevent than to fix the wines. So be very, very careful in the vineyard. Watch out for ladybugs and take them seriously if you see them.

Craig Macmillan 26:43

Action, early, early action, I think it was under chilled shift the closer to the crusher and the farther from the bottle you can fix a problem the more success you'll be. Well it looks like no farther from the crusher ahead of time. And closer to the crusher, after the crusher might be the solution. Where can people find out more about you?

Andreea Botezatu 27:04

Oh, I can share links to my Texas A&M page, my YouTube page. I have a YouTube channel where I post I have several different playlists where I post different videos related to enology wine quality, I can share with you the links to my peer reviewed papers on ladybug taint and pH management so they can find them on your website.

Craig Macmillan 27:27

That would be great. Yeah, but at least things will be on the show page. As always. Folks, I want to thank you for being on on the podcast. Our guest today was Andrea Botezatu. She's Associate Professor and extension technology specialist with Texas a&m University, Texas AgriLife service. This has been very enlightening. I think a lot of us are thinking about this, especially places that have been growing Pinot Noir and Chardonnay for a long time. A lot of people are thinking about this.

Andreea Botezatu 27:52

Well, you're welcome. And it was a pleasure being here. I just want to finish if I may with an observation that I had winemakers and grape growers from California contacting me about verjus research so they're very excited about that. I'm glad that we are getting to talk about this and maybe more people will hear about this and start thinking about about these options.

Craig Macmillan 28:15

Absolutely. Absolutely.

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201: Balance Hot Climate, High Sugar Wine with Green Grape Juice aka Verjus

Sustainable Winegrowing

201: Balance Hot Climate, High Sugar Wine with Green Grape Juice aka Verjus