Off-flavor: What is geosmin and how do we deal with it?

Bobby

All right. Sally sells seashells by the seashore. All right. Boom. All right.

Corinne

Welcome to the Salty Talks podcast. This is your go to podcast for information about the aquaculture sector in Maine. So today I'm here with Bobby Harrington, who is a research associate at University of of Maine's Aquaculture Research Institute. And we're going to talk a little bit about geosmin today. So what the heck is that? Bobby, if you want to introduce yourself really quick and then maybe we can get into this geosmin thing.

Bobby

Yeah, well, thank you for the excellent introduction. So I am Robert Harrington. I go by Bobby. Mostly what I do at the Aquaculture Research Institute is I facilitate research based on fish rearing. And so what we mainly focus on is recirculating aquaculture problems, whether that's disease or off flavors, like we're going to talk about today or production growout or feed trials. I help with basically the day to day on recirculating systems. So I build recirculating systems. I repair them, run them, and then I train students and staff here on how to use them. And so that's what I normally do. And then about maybe a year and a half ago, the USDA and University of Maine came together for a collaboration to focus on one of the problems in recirculating aquaculture these days. And that's off flavors. And so right now, I'm running an off flavor testing facility. So we're focused on geosmin and two methylisoborneol.

Corinne

Awesome. So the off flavors that we're talking about here in fish tissue are coming from geosmin. And what did you say the other one is called?

Bobby

Two methyl isoborneol. We also say MIB on that one. Or two MIB.

Corinne

Yeah. Yeah. That's a little bit easier to say than methyl isoborneol.

Bobby

And that's so the MIB is a smaller player in this game. Geosmin is the predominant flavor that people taste and smell, and that's the one we focus on the most. There are a host of off flavor compounds, but the two that we focus on are jasmine and MIB. We'll say MIB for the rest of this. Think it's going to help everybody.

Corinne

Awesome. So starting off with geosmin, I think in general, that's probably not something that most people have heard about, or they might think they don't know what it is. But geosmin is when people say they love the smell after it rains. Right. That's geosmin, that sort of, like, earthy aroma that we all know and love.

Bobby

Yeah, it's often described as earthy or musty. I always describe it as earthy. Other people taste it as musty, but it is one of the components of the smell in the forest after it rains. It's naturally occurring in the soils and waters in our environment, and it comes from bacteria. So when bacteria go through their metabolic processes, they have basically a waste molecule that comes out of that, just like we do when we break down food and go throughout our daily existence and metabolize things. So two of those byproducts are jasmine and MIB. Those just kind of come out in the water in the soils. They are both lipophilic compounds. So that just means that instead of being associated with polar things like water, they want to be associated with lipids. So when you have these molecules come out, they're semi volatile. They can come out in the water and the soils, and they can go into the air, and so we can smell that, but they also can go into lipids. And the closest kind of lipid source that you would find in, like, a stream or a river would be a fish. And so that's what happens in the natural environment, that you sometimes can get let's say, like, excessive concentrations of Gismond and MIB. Typically that will happen if you have a cyanobacteria bloom, which I think a lot of listeners might have seen on a lake, especially in Maine in the summertime. If you have algal blooms, those algal blooms can produce off flavor compounds. They can make the fish in that pond taste like mud or earth. And that's kind of something that everybody kind of has probably tasted when they had catfish or tilapia. The problem in recirculating systems is that we get these bacteria growing in our systems, and it concentrates there because we're recirculating water, we're reusing it for environmentally friendly purposes, and it kind of gives you that Earthy flavor in salmon. And nobody that I've met wants Earthy musty tasting salmon.

Corinne

Most definitely do not want Earthy musty tasting salmon. Really quickly before we get into the geosmin and recirculating aquaculture systems. Is fish the only organism or place that we might be experiencing it, or are we experiencing it in vegetables that might be grown in the ground or drinking water? Wine?

Bobby

That's a super good question. Right? So we've all tasted this, and we've all smelled it and smelled it. People are usually not put off by it unless it's extremely pungent, which it rarely is in nature. They will be in my lab, though, if you ever come visit me. You do taste these things in, like, a lot of root vegetables, especially, like, beets, and you'll get it in wine, and that's typically not considered a good flavor in wine. But I'm not like a Somalia or something, so that kind of question is not best answered by me. But yeah, so we definitely have this in other products. So it's not just a fish issue, it's a food issue. And it's typically with vegetables. We don't mind. I think everybody likes the flavor of beets, and a component of that is geosmin. And I don't know, I guess people at home should also understand basically that we are super tasters for this compound. So we're not talking about really high concentration concentrations either here. We're talking about parts per trillion. The human tongue on a sensitive taster can taste about ten parts per trillion. And you can see a little variation if you if you read on studies of this, that some some people might be able to do eight or six parts per trillion.

Corinne

I probably could do that.

Bobby

You probably could, yeah. Those are the you might be a supertaster. And so in water, you can taste it because there's not a whole lot of background flavors in water. Right. And so you can taste it fairly easily in water, but when it's in a fish, there's a bunch of competing flavors in there. And so what concentration does it need to be in a fish before it becomes an issue? That's always a question that people are asking, and it's taster dependent, and it's fish dependent. So if you have a really strong tasting fish, then jasmine is not going to be as much of a problem there. If you have a light kind of white fish like tilapia, then you start tasting it. And so us being supertasters complicates my job. So now I have to have an instrument that can measure at parts per trillion, which isn't impossible. We we've definitely done it. It's just one of the one of the problems associated with analyzing this molecule or these molecules, I should say. So it's in super low concentrations.

Corinne

Is geosmin at all dangerous or harmful?

Bobby

Yeah. That's always something we want to tell people, is, no, it's definitely not toxic. It's not going to be a problem for anybody. These are in ultralow concentrations as well. Even if they're in high concentrations, it's just going to taste really bad or Earthy. I don't know. I'll leave people to decide whether it's a bad flavor or not.

Corinne

I like some Earthy flavors, good flavor and beets, bad flavor and fish, right?

Bobby

Yeah, exactly. Great. So I think we should get into geosmin and the problem that it causes in recirculating aquaculture systems, but maybe let's just quickly talk about what a recirculating aquaculture system is for those who might not know.

Bobby

systems here at U Maine since: 2015

Corinne

Yeah. It also makes seafood more accessible to people who wouldn't typically be able to afford seafood like wild caught seafood prices. And in middle America, where they obviously don't live on the coastline. And like you're saying, seafood would be harder to get. But there's, like, recirculating aquaculture systems in Wisconsin.

Bobby

I've heard from multiple people in the industry that one of the major goals is to get costs down for Salmon. So to make salmon more affordable. So it's not just like some sort of fine dining level food, something that can compete with maybe chicken and pork? And price wise right now, they're not there yet. But they're going to get there as more and more recirculating systems get online. And this is probably going to take. Ten more years here in the US. Realistically, there's a lot of ambition here but there's a lot of challenges too. And we're I think the industry is trying to do things as clean as possible. I think most industries give the American consumer a bad feeling, right? Like, you know, industries lie to us or something about pollution. Especially when it comes to pollution. But there's something to be said about the aquaculture industry if they need fresh water sources. They need clean water sources so they can't pollute their water source and so it won't be a long term solution. Right. They have the vested interest in keeping things clean and so that's always a good thing.

Corinne

Yeah, definitely. Awesome. So now that I think we have a better understanding of recirculating aquaculture systems, let's move into why geosmin can present a problem in these systems and what we're doing about it. And by we I mean you. Because I'm doing nothing about it.

Bobby

That's not true. We're all, we're all a big team. All right? So the main way geosmin presents a problem in recirculating aquaculture systems is we've primarily relied on bacteria in these systems to help us. And so the way that works is we have these things called biofilters. And in biofilters, we use Amethia to basically grow lots of bacteria. And these bacteria are mostly just harmless bacteria. They're quite friendly, they do a good service for us and they break down ammonia. So ammonia is a problem in these systems because fish do what fish do. They eat food. And then they poop and then they swim around, right? And so all that waste from the fish has to be broken down. So what we do is we try to remove the solid waste first with some sort of solid filtration, like a drum filter, and we try to get that out as quickly as possible, because the longer that stays in the system, the more ammonia it's going to make. It will make some amount of ammonia and the biofilter breaks that down. So when the biofilter is breaking ammonia down, it breaks it down into nitrite, and then a different set of bacteria will then break nitrite down into nitrate. And nitrate is considered the safer version of this waste product. All right? So it's generally not toxic to fish at normal concentrations. It can present some challenges here and there. And so we have these huge biofilters and these things can sometimes create MIB and Giosman while they're breaking down waste. And this is very system specific and this is regionally specific, and it's also specific to what salinity you're running in your system. So some farms might have no problem with this, and some farms might have a real hard problem with this. And it's probably mostly related to the species of bacteria they have in their biofilters or in other areas of your system that may grow bacteria. And is that something that you can control for, or that's just kind of how it is, that these bacteria are just in some systems and not others. So it's hard to control for it's hard to change the microbiome of your system, basically, is what we're talking about. This is research that's kind of going on everywhere. These microbiomes, how important are these in our guts? How important are these in a recirculating system? Right? Like, these bacteria are understood fairly well, but in practice, in recirculating systems and fish farming in general, poorly understood by, let's say, the average technician. So the average technician is not a microbiologist. They are clearly fish biologists, right? And so it's very complicated. And so how do you change the microbial community in your recirculating system? I don't know. I mean, it's probably set by your input water sources to come in with some level of bacteria. And that's probably where you're starting your community as that input water source comes in. There are some additives, you can add some bacteria that are known to be pretty good bacteria, and you can buy these and add them into your system. People that run aquariums at home might have done this before with several products. So they're basically starter mixes that you can add to these. And I think that the starter mixes are generally pretty good, but whether or not some of them may lead to jasmine, I don't know. It's Part of the research that really needs to be filled out here is understanding these communities. And it's going to be super difficult because they're all different all around the world, and it's all based on our natural environments that we're around that these bacteria are coming into.

Corinne

Yeah. So it seems to be very like it would be a very site specific problem to manage rather than just a general solution.

Bobby

Yeah. Not really a one size fits all solution here. And that's the problem. That's where it gets complicated on this. So geosmin is there and it's a problem, and it's something that we then have to deal with and adapt to, knowing that it's in the system.

Corinne

So does that mean treating water with UV or? I know that depuration...

Bobby

on right now. Or I guess it's: 2022

Corinne

When you say fresh water with depuration, do you actually mean literal freshwater, or you're talking about water that's just not being recirculated?

Bobby

Yeah. When I say freshwater, I'm making the assumption that this salmon system is a freshwater salmon system. Some salmon systems are saltwater driven, which is good. You have a little less off labor problems with saltwater systems, and especially if you're in the brackish water. So salmon are really good. They can live in fresh water. They can live in full strength sea water, or you can have them somewhere in between. And somewhere in between is a good way to grow salmon. And so, yeah, when I'm saying freshwater, I'm saying just a fresh water source. I'm saying a newly unrecirculated water that's going to be low and gizmos coming into this purge tank, and all of the geosmin and MIB is going to work out of the fish over the two week time period and then kind of just be removed. And that's pretty helpful in reducing your geosmin. The problem is it's time consuming and costly. And so in order to get the price point for salmon to be cheaper, we need to figure out less costly. Yeah. Better methods to do that. And it's not only just the price point, it's also environmentally friendly. Like, if we don't need to use more water, that would be great. Yeah.

Corinne

So ozone. Not doing it. Deprivation not the best. Well, it's what we have. We're working with it's effective, but could be better.

Bobby

Right.

Corinne

So that is where you well, you already come into play a lot, but this is where your current research is relevant, correct?

Bobby

Yeah, yeah. So when we got some new instruments, we wanted to help the industry detect geosmin and MIB. The whole idea was there's a lot there's a lot of these farms starting up. Nobody I mean, it's a real high capital cost anyway to start one of these farms. It's very technical. The last thing any one of these farms needs to do is start an analytical lab as well. Getting these samples analyzed at a private lab would probably be about $120 or something like that per sample. So it's a little expensive, and it's kind of a complicated method. So I can understand why that is. What we were trying to do is create a geosmin and MIB testing lab to help not only the researchers that are trying to solve these issues, the problems to these issues, but also to be a service to the industry members out there so they can send in samples to us and we can analyze them. Rather reduced costs. And then help them give them advice on how they might be able to mitigate it. Although they probably know their systems way better than I do, but I can talk to them about kind of the specifics on these compounds. So that's kind of what we're trying to do. When we started, we did realize, and we knew that the method was a little time consuming. I think another lab that we knew was doing, like, ten samples a day, which is not much. So one of our goals for this lab was to increase the amount of sample throughput. But also, I have a lot of jobs, so I can't just be in a lab crunching out samples all day. And being a chemist, I have to also go work on recirculating systems and help with projects and do other things.

Corinne

And take care of your new puppy.

Bobby

Yeah, and take care of my new dog. There's things in life that one wants to do besides analytical chemistry. And so we wanted a method that just kind of was a little more automated, and so we came up with a new method for analyzing these odorants. And I guess if I'm going to get into the nitty gritty of it, it uses a sorbet material that looks a little bit like a piece of rubber on the end of a stainless steel probe. And the Xorbit material some people have heard of it referred to as steamy SPEME, which is solid phase microextraction.

Corinne

SPEME

Bobby

Yeah, of course. Good old steamy,. So solid phase microextraction is just a super fancy word. Basically, it's a material that absorbs organic molecules. And so it's really cool for extracting these organic molecules from water. Fairly easy to do. And so if we want to just test the system water, we have a method now that's excellent. The problem with the old SPEME method was that it was a little fiber. It was like this little teeny, really coarse horse hair kind of thing, and it had limited space for attaching these molecules. And so you could sometimes overload that steamy fiber. You can overload it with your sample if you had a high concentration sample, because you have to remember, we're not just extracting at this point, geosmin and MIB. We're extracting all the volatile and semi volatile compounds in our sample. And so then we have to tease it out in our gas chromatograph, in our mass spectrometer. What we didn't like about the fiber was that you can overload it, and that's also a little brittle. And then they have this thing called a SPEME stir bar, right? Solid phase microextraction stir bar. And it's just like this little bar that can be magnetically stirred, and it has a plastic coating with a steamy coating on top of that. And so that got rid of that whole brittle problem, and there's not enough space for all your molecules to fit on there. That's great. Now it's working great, but it really created the problem of it's super hard to automate because you're spinning a stir bar and a beaker of water. And how do you automate that? The probe thing that was created is really great. It's able to be automated. It has the same detection level as the other speedy methods, but it's automatable, and it's super environmentally friendly. The only chemicals we use in the analysis are some NaCl, some regular salt, some pure salt, and we also use a little trace amounts of methanol. And so that's pretty good for an analytical analysis. There's a lot of analysis out there that people would probably be surprised. There's a lot of waste involved in chemistry. And so one of the big movements is like green chemistry, is to try to keep the methods just as good as they are or improve them, but also improve their environmental impact. And so that was kind of a cool component of this. Of this method that we developed. How does this method work moving forward?

Corinne

Like, is the plan to, I guess, have other labs doing this as well?

Bobby

Yeah. So we can now at our lab, we can do more samples per day, so if people start sending us samples, we can get a quicker turnaround time for them. I'm not in competition with anybody. The more people that can analyze this and that can help with the problems, the better. I think for us, the best thing to do is now get the word out about what we've done. And so people in the industry know kind of, hey, we're a valuable resource to you. If you want a reduced price analysis on water samples or fish samples, you can send them over to us, because I do both water, and we can test it on fish. Fish tissue is a little bit more difficult to analyze, but we can still do it. And I think I'm going to publish a paper on that one earlier this year, hopefully.

Corinne

Yeah, you are.

Bobby

y this next year or this year: 2023

Corinne

That's awesome. I am looking forward to when that paper comes out.

Bobby

Yeah. It's going to be rad.

Corinne

Yeah. I'm going to add it to my list of fun and exciting reading that I do in my free time.

Bobby

I'm sure it'll get several reads worldwide.

Corinne

A couple dozen, maybe.

Bobby

I'll be happy with that.

Corinne

Yeah.You should have named your puppy SPEME.

Bobby

I named my dog Beryllium Ten.

Corinne

Oh, that's almost as good.

Bobby

Yeah. Only chemists get that kind of stuff, I suppose.

Corinne

Do you call it beryllium ten every time or

Bobby

I don't think he understands that syllables in a name. Right. So we call him Bucky for short. But that's a good one. Yeah. His online handle for his for his, you know, his fee collar exploits is beryllium ten, then. But if you are interested, if you're out there and you're in the aquaculture industry and you're interested in geosmin and MIB testing, just contact me at the University of Maine, robert.harrington@maine.edu and I could do some testing for you, reduce costs and help you work through any off flavor problems that you might have. Because sometimes this is the problem in research systems, but it also can be an issue in pond aquaculture as well. So there's other people that are interested in this besides people that are in salmon aquaculture specifically.

Corinne

Off flavor problems.

Bobby

Yeah, they could have a couple meetings, right? You'd be surprised. Right. There's, like, communities of odorant analyzers out there that I actually didn't really know about until about a year and a half ago when I got into this specifically. Yeah, they do all sorts of things with, like, flavors of butter, awesome flavors of wine, all sorts of things out there. So fish is just one of the many foods that have off flavor problems. Every food kind of has it, but yeah, it's pretty exciting. It's pretty fun. It's pretty interesting, too, to see what other food chemists are up to out there.

Corinne

Well, it's speaking of food, speaking of fish, this is an Aquaculture podcast I do have. Probably the most important question of today's podcast is what is your favorite type of fish to eat?

Bobby

Did you ask everybody this, too?

Corinne

No, actually, I somehow have not asked anybody this. You're the first.

Bobby

Yeah. Good. Well, I'm going to be super boring here. I'm going to say brook trout. I know I'm a marine science person, and people expect me to say angular fish or some, like, extreme, like, you know, deep ocean, you know, weird fish that they've never heard of. But I like brook trout.

Corinne

Is anybody eating deep ocean fish?

Bobby

Nobody nobody eats those things. Maybe somebody out there is. But yeah, no, I'm a brook trout fan. I grew up in Maine fishing for brook trout and the streams and yeah, I enjoy it. A real pretty and rather cool fish.

Corinne

I respect that. I actually, myself, am a trout person. I would say rainbow trout.

Bobby

And they're fun to grow, too, in recirculating systems. Trout in general are really fun. Right now we're doing a steelhead project, and I think you're going to interview Matt Hawkyard, dr. Hawkyard on that. So maybe he'll fill you in on that kind of stuff. But yeah.

Corinne

Awesome. Well, thanks, Bobby, for coming on the podcast today and teaching us a little bit about geosmin and MIB. I'm going to call it MIB. geosmin and MIB.

Bobby

Yeah. And just so everybody at home is not having a conviction fit on this one, it could be pronounced geosmin for geosmin. Yeah. We were having a debate about this before we started, so if you're out there and you're really particular for that, we decided to go with the idea that you don't call it geology. No, you call it geology, so maybe geosmin, but I think it's a tomato tomato thing, I guess. An expert in the analysis of geosmin. I don't care how it's pronounced. I suppose I like that.

Corinne

Yeah. Well, thank you for taking time to talk with us today. It was awesome.

Bobby

This was fun. Great.