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Welcome to The Drip (formerly Water in Food), where we keep your mind hydrated with some science, music, and a mantra. I'm your host, Zachary Cartwright, lead food scientist at AQUALAB by Addium
Hosted by Zachary Cartwright, Ph.D.
Lead FOOD Scientist at AQUALAB
https://www.aqualab.com/
Zachary Cartwright [00:00:07]:
Have you ever opened a bottle of wine and thought to yourself, this smells like a barnyard or like a sweaty sock? Welcome to the drip, where we keep your mind hydrated with some science, music, and a mantra. I'm your host, Zachary Cartwright, lead food scientist at AQUALAB by Addium in today's pilot episode, I will be discussing why some wines can have extremely off putting tastes and aromas described as being comparable to a barnyard or a dirty sock, or even a smelly rat or rodent. During my time as a graduate student at Washington State University, I had the opportunity to be in the food science lab of Doctor Edwards, where we primarily looked at wine microbiology and especially wine spoilage microorganisms. My dissertation was on the characterization, vectors and control of a very specific wine spoilage yeast called Britannomyces brexulensis. Now, when you open a bottle of wine, you expect certain aromas. You expect it to be fruity or floral or maybe nutty or oaky, but every now and then, you might open a bottle of wine and have some type of off flavor or off note, especially if you smell something that is like a barnyard or a dirty sock, or even mousy or like a rodent. This could be due to a microorganism known in the wine industry as Brettanomyces bruxellensis, or sometimes shortened to the word bret. Brettanomyces bruxelensis was first isolated from beer back in the 1920s, and wine infections have been reported since the 1950s.
Zachary Cartwright [00:01:49]:
This was primarily in red wines, but this microorganism has also been found in white wines and even sparkling wines at different times. And the way the Brettanomyces bruxellensis gets into a winery is primarily through three different vectors. The most common is used barrels. So barrels that haven't been cleaned correctly, where one winery might use them for a year or two, and then it may get infected at some point, and then it's sold or transferred to another winery, where they start to have issues. Insects are also known to harbor Brettanomyces bruxellensis. It could be on flies and different microorganisms or different insects that may be found within a winery or even out in the vineyard, and then also bulk wine that hasn't been filtered or that hasn't been monitored correctly, or it's been put into a dirty vessel. So Brettanomyces has been found all throughout the winemaking process. It has been found out in the vineyard, on grapes.
Zachary Cartwright [00:02:53]:
Even though this is somewhat controversial in the wine industry, it's been found in grape must very early on in the winemaking process. It's been found all over different types of processing equipment used in the wine industry. You can think of presses and different things used throughout the winemaking process. Brettanomyces has been found in bottled products and even in winery air samples. So it's found all over the winemaking process. And the reason that we're getting these off aromas is because there are compounds in the wine called hydroxycinnamic acids. These are there very early on in the process, and these can be transformed into a wide variety of volatile phenols. And these are called four ethanol, phenol, and four ethyl gaiacol, and several others that some of the listeners may be familiar with.
Zachary Cartwright [00:03:46]:
So as these are produced, some of them at lower levels can have desirable notes. It may smell leathery, or even like bacon or cloves. But when there's too much of this production or certain mixtures of these compounds, this is when we start to get those off putting aromas that we described earlier that are horsey or that smell like a barnyard and so on. So there are other microorganisms that can produce these types of compounds, but only Brettanomyces bruxellensis produces them in enough quantity under enological or winemaking conditions in order to cause a problem. There are other compounds that Brettanomyces bruxellensis can make. These include acetic acid and ethyl acetate. You can think of these smelling like vinegar or nail polish remover. It can produce nitrogen heterocyclic compounds.
Zachary Cartwright [00:04:43]:
And this is where those mousy aromas show up that I mentioned earlier. Britannomyces can also produce isovaleric and isobutyric acid. You can think of these smelling like a really rancid oil. Think of an oil that you've left in your cupboard for years and years that was forgotten about, and then you open it, and then it has that really rancid smell. And then Britannamycin can also produce what are called biogenic amines. These are things like histamine and methylamine and others that can actually cause headaches or even have been associated with migraines. So, as you can see, Brettanomyces bruxellensis bruxellensis, it's a huge problem. When it shows up, it affects the aroma, its off putting and might even have an effect leading to headaches and other problems.
Zachary Cartwright [00:05:36]:
So when I was in grad school, I wanted to study different vectors or different ways that Brettanomyces bruxellensis could end up in wine and then give winemakers tools to reduce this yeast from occurring and causing problems. So the first study that I looked into was looking into winery practices that may encourage a wider dispersal of Britannomyces. And one of them that really stood out to me was the practice of spreading grape pumice out into the vineyard. So this is often done because grape pumice can be used as a fertilizer or a soil conditioner, and it's generally a waste product. So after producing wine, all this pumice is left over, and winemakers have to decide what to do with it. So often they throw it out into the vineyard. But keep in mind that Britannomyces can survive alcoholic fermentation, and it has been previously detected in pumice. So my hypothesis was that the pumice could be infected with Brettanomyces bruxellensis, and then possibly through some other known vector, like insects.
Zachary Cartwright [00:06:45]:
Then Brettanomyces bruxellensis could be put onto grape clusters, where it's also been found, and then end up back into the winery. So I wanted to study the survival of Brettanomyces in this winery waste under vineyard conditions which had not been studied at all before. And so the objective here was to monitor the survivability of this yeast and pumice. So, basically, I set up this big experiment. I collected all different types of pumice. I inoculated some with Britannia myces and also had some as a control as well. And then I picked several vineyards throughout the state of Washington to put these controlled samples into the vineyard. So these samples were in very specific containers that had a filter, so it would allow the pumice to experience the environment that it was put in while keeping the Britannomyces at bay, and make sure that we were not infecting anything.
Zachary Cartwright [00:07:43]:
And then I would regularly go out every three or ten weeks or so and check on these pumice samples and bring them back into the lab and analyze them to see if Brettanomyces bruxellensis was still there or not. And what I found is that Brettanomyces bruxellensis could survive for an extremely long time. We looked for over 130 weeks in some cases, and Brettanomyces bruxellensis was still there, it was still present. So I would bring the samples in and use a very special type of media that can help any Brettanomyces bruxellensis in that sample to grow. And what we found is that there were still pretty big populations of Brettanomyces bruxellensis, even after months and months of being out there in the vineyard. So it's very likely that Brettanomyces bruxellensis can survive a long time. But this project was extremely hard to do, because I would go out there and these samples were covered to protect them from, you know, any animals or anything. But I went out a few times, and when I uncovered samples, there would be mice right next to them, and in another sample nearby, there'd be a snake right next door.
Zachary Cartwright [00:08:50]:
So I had to be really careful uncovering these samples. But it was a fun project, and overall, it did show that Britannomyces could survive in pumice. So, this is all summarized in a publication called the Survival of Britannomyces Bruxellences in great pumice and reduction of populations by application of heat and sulfites. This is published in the Australian Journal of Grape and Wine Research, and this was published back in January of 2018. And I'll make sure to add a link to that publication in this podcast description. The second study that I looked at involved oak barrels. So, Brettanomyces has been looked at pretty thoroughly in oak. It's known to be a primary threat to barrel aged red wines.
Zachary Cartwright [00:09:38]:
And populations of this yeast can persist pretty deep in oak barrels. It's been found up to an eight millimeter depth. And part of the reason for this is because it can metabolize celebios, so it can use some of the sugars available in the oak to survive. And pretty large populations have been found in infected oak. So what we wanted to do is look and see if there is a practical way that winemakers can remove Brettanomyces from oak. There have been other methods that have been investigated, things like microwaves and ultrasonics and ozone. All of these have been investigated, and they do have a pretty good effect, up to a certain limit or a certain depth within oak. But more conventionally, heating is used in order to limit contaminations.
Zachary Cartwright [00:10:31]:
So most wineries use either hot water or steaming in order to sterilize that barrel and to hopefully remove any Brettanomyces bruxellensis that may be there. So the objectives of the second study was to better define the Brettanomyces bruxellensis populations and the depths that they could be found at to determine the effects of different barrel factors. So, oak species, toasting level, age, and even the location of the stave within the barrel. And then to better define heating recommendations, and to give the wine industry different time and temperature combinations that can reduce Brettanomyces bruxellensis. So, for this study, I ended up purchasing a wide range of different oak barrels. These were smaller than the normal size barrels that you may see in a winery, but this allowed me to conduct the research in a more timely manner and to be able to do this in more of a lab setting. But these were still pretty big barrels. I'll have to look up the correct size, it's not ringing a bell.
Zachary Cartwright [00:11:36]:
But several gallons of wine fit within each barrel, and these barrels were filled with different wines. Some were infected and some were not. And then these were allowed to sit for quite a long time to make sure that a thorough Britannomyces infection occurred. After that time, the barrels were disassembled into their individual staves and cut into very specific four millimeter layers so we could look at different layers and decide whether or not Britannamyces was present or not. Part of my research also involved scanning electron microscopy pictures, or SEM pictures, and we were able to actually take pictures of Brettanomyces bruxellensis cells at very deep depths within the oak. And we were the first to do this and even see some different structures that the Brettanomyces bruxellensis may have been producing that helped it to penetrate further. So we will make sure to show some of those pictures and link them again to the podcast description, and they'll be in the publication that I mentioned here in a second. So once we had these oak staves taken apart, then we did subject them to different types of steaming trials, and we even put temperature probes at different depths within those staves so that we could monitor the heating of the blocks and correlate that heat back to the populations of Brettanomyces bruxellensis that we were looking at or finding.
Zachary Cartwright [00:13:09]:
The key discoveries for the second study was that the resident populations of Brettanomyces bruxellensis in oak depended on several different factors, primarily on oak species. So we found that there were larger populations, greater penetration depths and faster recovery of Brettanomyces bruxellensis in french oak barrels compared to american. And this really has to do with the pore size in the oak and the ability of Brettanomyces bruxellensis to get to a greater depth, because at a greater depth those populations are more protected from heat treatment. We also found that longer wine contact time resulted in greater depths of yeast penetration into oak staves. And that makes sense if you think about it. If you allow the wine to sit in the barrel for a longer amount of time, this gives the microorganism more time to move deeper into that barrel. Or if you think about stave location, staves at the bottom of the barrel are always in contact with the wine, whereas staves at the very top of the barrel close to the bunghole are going to experience less contact time due to evaporation of the wine over time. We also found that maintaining a temperature greater than 55 degrees celsius at all infected oak depths for five to eight minutes was necessary in order to prevent any recovery of the microorganism and using steam Brettanomyces bruxellensis was prevented after nine minutes if the microorganism was found at a depth less than 4 mm, but that twelve minutes of steaming was actually necessary in order to remove the microorganism if it was up to 9.
Zachary Cartwright [00:15:00]:
This is much longer than what most wineries were currently using and probably still do. Most wineries maybe use three up to five minutes of steaming, but we found that closer to twelve minutes is really necessary if you have an infected barrel in order to remove this unwanted microorganism. So just as a takeaway from all of this work in grad school at WSU, the takeaway here is that there are extra steps that winemakers can consider in order to prevent their wines from being spoiled by Britannomyces bruxellensis. And hopefully this research can help winemakers, especially when Brettanomyces bruxellensis pops up and starts to cause a problem. There are extra steps and other vectors to consider to make sure that you're having as clean of a process as possible. I should mention though that some Brettanomyces is sometimes favorable by different consumers. Small amounts of those compounds that I mentioned earlier can add in the complexity of the wine and are sometimes wanted by different consumers. So it really depends on the market.
Zachary Cartwright [00:16:10]:
But generally within the US, Brettanomyces bruxellensis and these off aromas that I mentioned are not welcome. Today's episode is sponsored by AQUALAB. AQUALAB is a partner that solves moisture related challenges in the food, pharma, cannabis and cosmetic industries, using our scientific expertise, proprietary technology and software platform to improve product safety, quality and profitability for our clients since 1987, AQUALAB's ultimate goal is to provide a platform for complete moisture control and drier optimization. As data acquisition becomes easier and more affordable, we are meeting our clients desires for maximizing efficiency and product consistency by providing actionable insights and process automation. A link to AQUALAB's brand new website will be in this podcast description. In future episodes, I plan on inviting a wide range of scientists and industry experts to discuss their work in the food, pharma, cannabis and cosmetic industries. Since having a job in a scientific field can be really tough and demanding, one of the key questions I will be asking each guest on the show is how do they relieve the tension and the tightness and the stress of their jobs, and how do they maintain a work life balance? Personally, I do this primarily two different ways, through music and also through yoga and movement. When it comes to music, I incorporate this into my life through djing and recently through music production.
Zachary Cartwright [00:17:46]:
I've been djing in local clubs and venues and djing at weddings for well over seven years now, and although some people may be more familiar with my original stage name of DJ Grapevinyl, I changed it to catalyst a few years ago once I started playing a wider range of music because of my love for music, im going to ask each guest on the show to recommend one of their favorite songs and then I will add a link to that song in the podcast description. I will also be recommending a song myself as well, most likely something I recently heard that I just cant get out of my head or occasionally an original track that I've been working on. Today's track is something I released earlier this year with some help from my friend Christian Martinez and is a remix of an original song by Eric Burton. If you've never heard of Eric before, he's the lead singer of the Black Pumas. This is a group that has six Grammy nominations over the course of the last three years. I had the opportunity to meet Eric when I was doing my undergraduate studies at New Mexico State University. He's an extremely talented individual. We knew that even at that time, my friends and I knew even listening to him then, that one day he was gonna make it.
Zachary Cartwright [00:19:01]:
He has an incredible voice and I was very lucky for him to send me some of his original tracks when we were in school together. So I took one of those tracks. It's called soulmates and I made a house remix to it. So we're going to listen to the first verse and the chorus of the song together. Check it out.
Christian Martinez [00:19:28]:
It's been a while since I've been to the water when I looked to the sea I wondered where you were my friend, how have you been? Time hasn't been too kind with us I remember when you and I won't force about being free cause we could not see what it might look like to see the world be on both shales what it might feel like to walking now step on seashells can you dig it like a five foot shovel dig it like a fine bulldozer dig it like a pirate for gold can you dig it? When you were gone I missed your humor it's not fun being funny for others I won't make you laugh again like when we'd make our silly faces fate is finally fell on through I was always supposed to be with you but we cannot end let's never ever ask questions like what it might look like to see the world be on bookshelves what it might feel like to walk and not step on seashells. Can you dig it like a five foot shovel? Dig it. Or can find Bulldozer?
Zachary Cartwright [00:21:38]:
And finally, to round out each episode of this podcast, I will be offering listeners a mantra. A mantra is something that we use in yoga. It can often be a single syllable, a word or a phrase that you repeat to yourself to help you feel calm, to motivate yourself, or to express something that you believe in. Think of the little engine that could using the mantra I think I can. I think I can. To overcome the seemingly impossible task of getting through difficult terrain to its destination, this episode's mantra is, I am capable of great things. I can and will do great things. And I'm just going to repeat this three times.
Zachary Cartwright [00:22:19]:
And maybe you, the listener, can say it to yourself, either in your head or maybe even say it out loud. Alright, here we go. I am capable of great things. I can and will do great things. I am capable of great things. I can and will do great things. I am capable of great things. I can and will do great things.
Zachary Cartwright [00:22:47]:
As you move into the rest of your day, your week, your year, just remember that you are capable of great things and that they will come to you as you keep your positive attitude. Come back to this mantra when you need it. It's right there in the background at any time. Thank you so much for listening to this episode. I'm really excited to see where this goes and I can't wait to get some guests involved. My name is Zachary Cartwright and this has been the pilot episode of the.
Christian Martinez [00:23:13]:
Drip, brought to you by AQUALAB. Shovel digit like a fine bulldozer, it like a party for gold.