Defining Minerality, Mouthfeel and Musty Aromas with Gus Zhu

Introduction

Why do certain musty or animalistic aromas, like barnyard or manure, become more acceptable to wine lovers over time? What does minerality really mean when it comes to wine? Why is mouthfeel so important to appreciating wine? How does the colour of wine influence our perception of how it tastes?

In this episode of the Unreserved Wine Talk podcast, I’m chatting with Master of Wine, Gus Zhu.

You can find the wines we discussed here.

Giveaway

Two of you will a copy of his terrific new book, Behind the Glass: The Chemical and Sensorial Terroir of Wine Tasting.

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Highlights

• Why do certain musty or animalistic aromas, like barnyard or manure, become more acceptable to wine lovers over time?
• What’s behind the perception of saltiness and minerality in wine?
• How do we misunderstand sweetness when it comes to wine?
• Why have we developed more complex perceptions of bitterness, and how does it influence our experience of tannins in wine?
• Why is mouthfeel so important in wine tasting?
• How does colour affect our perception of wine?
• What are the most interesting aspects of oak aging in wine, and why is there so much diversity?
• Why is it important to embrace sensory differences in wine tasting?

Key Takeaways

• Why do certain musty or animalistic aromas, like barnyard or manure, become more acceptable to wine lovers over time?
  • Gus says that certain smells, especially in some natural wines, are popular today, even though he doesn’t like them personally, like barnyard. He believes that the wine industry or even the media are trying to promote a certain style of wines and make people believe that many people love that smell and taste.
• What does minerality really mean when it comes to wine?
  • Gus observes that acidity and minerality are such vague terms and concepts that people in the wine industry discuss. When people say minerality, they may be referring to many different things from acidity to saltiness to the taste of flint or wet stone. The term is so difficult to translate in the industry. His sensory professor noted that whenever people don’t know how to describe certain tastes or feelings, they use the term minerality.
• Why is mouthfeel so important to appreciating wine?
  • Gus explains that mouthfeel adds several other dimensions to taste, which makes wine tasting even more interesting. When blind tasting, many people depend on smell but he encourages them to pay attention to the textual, tactile sensations from the wine as well.
• How does the colour of wine influence our perception of how it tastes?
  • Gus says that people usually look at the color first because it’s straightforward, even though we could see colours a bit differently from each other. We are visual animals so we have preconceptions. Even though we want to be objective, we cannot. We could be even more biased when we see things first. For example, there are already studies showing that if you color the white wine as the red wine colour, and you ask people to smell it, they came up with all these descriptors that are related to red wines rather than the so-called white wine descriptors.

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About Gus Zhu

Gus Zhu is the first Chinese national to become a Master of Wine. He works as a research and development scientist at Harv 81 Group, specializing in chemical analysis and sensory studies of aroma compounds in wine, cork, and oak. Gus holds a Master of Science degree in Viticulture and Enology from UC Davis, which he earned in 2017, and achieved his MW qualification in 2019. In addition to his research in flavor chemistry and sensory science, Gus is a professional wine educator, offering tutorials to wine enthusiasts around the world.

Resources

• Connect with Gus Zhu
• Unreserved Wine Talk | Episode 307: Umami, Petrol and Vegetal Aromas Behind the Glass in the Chemical and Sensorial Terroir of Wine Tasting with Gus Zhu
• Unreserved Wine Talk | Episode 206: Minerality in Wine, Great Hybrid Grapes & What Jimi Hendrix Can Teach Winemakers with Aleks Zecevic
• My Books:
  • Wine Witch on Fire: Rising from the Ashes of Divorce, Defamation, and Drinking Too Much
    • Audiobook:
      • Audible/Amazon in the following countries: Canada, US, UK, Australia (includes New Zealand), France (includes Belgium and Switzerland), Germany (includes Austria), Japan, and Brazil.
      • Kobo (includes Chapters/Indigo), AudioBooks, Spotify, Google Play, Libro.fm, and other retailers here.
    • Wine Witch on Fire Free Companion Guide for Book Clubs
  • Unquenchable: A Tipsy Quest for the World’s Best Bargain Wines
  • Red, White, and Drunk All Over: A Wine-Soaked Journey from Grape to Glass
• My new class, The 5 Wine & Food Pairing Mistakes That Can Ruin Your Dinner And How To Fix Them Forever

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• You’ll find my books here, including Unquenchable: A Tipsy Quest for the World’s Best Bargain Wines and Red, White and Drunk All Over: A Wine-Soaked Journey from Grape to Glass.
• The new audio edition of Red, White and Drunk All Over: A Wine-Soaked Journey from Grape to Glass is now available on Amazon.ca, Amazon.com and other country-specific Amazon sites; iTunes.ca, iTunes.com and other country-specific iTunes sites; Audible.ca and Audible.com.

Transcript

Natalie MacLean 00:00:00 Why do certain musty or animalistic aromas, like barnyard or manure become more acceptable to wine lovers over time? What does minerality really mean when it comes to wine? Is it a taste? Is it a texture? What the heck is it? Why is mouthfeel so important to appreciating wine? And how does the colour of wine influence our perception of how it tastes?

In today’s episode, you’ll hear the stories and tips that answer those questions in Part Two of our chat with Gus Zhu. You don’t need to have listened to Part One from last week first, but if you missed it go back and have a listen after you finish this one.

By the end of our conversation, you’ll also discover what’s behind the perception of saltiness and minerality in wine, why we’ve developed more complex perceptions of bitterness and how it influences our experience of tannins in wine. How we misunderstand sweetness when it comes to wine. What are the most interesting aspects of oak aging wine, and why there is so much diversity in it, and why it’s important to embrace sensory differences in wine tasting. All right, let’s dive in.

Natalie MacLean 00:01:09  Do you have a thirst to learn about wine? Do you love stories about wonderfully obsessive people, hauntingly beautiful places, and amusingly awkward social situations? Well, that’s the blend here on the Unreserved Wine Talk podcast. I’m your host, Natalie MacLean, and each week I share with you unfiltered conversations with celebrities in the wine world, as well as confessions from my own tipsy journey as I write my third book on this subject. I’m so glad you’re here. Now pass me that bottle, please, and let’s get started.

Welcome to episode 308. Two of you are going to win a copy of Gus’s terrific new book, Behind the Glass The Chemical and Sensorial Terroir of Wine Tasting. These are fascinating concepts. You’ll love the book. All you have to do is email me and let me know that you’d like to win. I’ll choose two people randomly from those who contact me. If you haven’t won a book yet, now is your chance and keep listening, as my goal is to offer lots more books and other prizes with every episode. Makes me feel like Oprah. I’ll announce more winners next week. Just email me at [email protected].

In other book news, if you’re reading the paperback or e-book of Wine Witch on Fire: Rising from the Ashes of Divorce, Defamation, and Drinking Too Much or listening to the audiobook, I’d love to hear from you again at [email protected]. I’ll put a link in the show notes to all retailers worldwide at nataliemaclean.com/308 .Okay, on with the show.

Natalie MacLean 00:03:07 So why do certain aromas like musty or animalistic ones become more acceptable to wine lovers over time? Is that even the barnyard, the so-called euphemistic name, sometimes for manure or whatever in Burgundy? Do we just accommodate or is there a sense of taste or smell becoming more evolved that we grow to like these or are we just accommodating to them or what’s going on there?

Gus Zhu 00:03:30 Okay, so this could be a bit personal and this is nothing scientific to me. I just think that certain weird smells, especially in certain natural wines which seems to be popular nowadays. Honestly, to myself and to some people around me, certain weird smells like barnyard, those kind of smells we cannot accept. So I have a feeling is that it is the wine industry or the media try to promote certain style of wines, like natural wines, that they make people believe that quite a lot of people love those kind of smell and taste. But I’m not sure about that.

Natalie MacLean 00:04:11 I’m with you.

Gus Zhu 00:04:12 I’m not sure about that. And the one thing that is related to my book is that certain smells in natural wines. Let’s say this is I have a glass, not a natural wine, but in this glass there are some weird smells associated with compounds like isovolaric acid. You don’t have to remember the term, but certain type of smell or certain type of compound, right?

Natalie MacLean 00:04:36 Does that translate to something isovolaric acid. Is that like manure? What is that?

Gus Zhu 00:04:43 A stinky smell in general.

Natalie MacLean 00:04:45 Okay stinky.

Gus Zhu 00:04:47 There are so many different types of stinky smell and also sweaty or some people say some really bad cheesy smell. And some other compounds also are responsible for it but let’s not dig into that. But more importantly, those kind of compounds, certain people are very sensitive to it. Certain people are not. So when you taste certain natural wines to people, to certain people overall they smell those kind of wines as less stinky as compared to you. So we need to be aware of that. If they love certain smell is either they got used to it, they started to appreciate that, or it is simply because they do not find them that stinky.

Natalie MacLean 00:05:30 Wow. Yeah, I can imagine a dinner party. Here’s the stinky wine you love. Would you like some more of it?[laughter]

Gus Zhu 00:05:36 [laughter] Well, it’s a stinky one that I found stinky. But you don’t find stinky. That is as you like it.

Natalie MacLean 00:05:43 Absolutely. Again, your cultural assumptions, your genetics, everything sets the stage for this. So you’ve explored both sourness and saltiness when it comes to wine tasting, two overlooked aspects often. How do these interact? How do they play a part? Like, I personally find it hard to differentiate in wine between a so-called salty taste versus acidity versus the even more vague concept of minerality. And maybe we’re referring to very similar sensations or tastes. But let’s talk about saltiness first. What is it when it comes to wine?

Gus Zhu 00:06:19 So if you talk about pure saltiness, just as salt as we eat every day right, that is sodium. That’s sodium chloride. And they do exist in certain wines. It’s just chemical analysis. People do not analyze them. There are certain things by law, people need to analyze. Alcohol you have to analyze before you can label and ship and sell the bottle. But salt, people never analyze them. But to me, actually, this is something I personally I will do in the future is that I would analyze salt in certain wines because people ignore that part. And, you know, like a bit of salt in food can greatly change the taste. So I think in certain wines that tiny amount of salt can change the taste. So that’s my personal project.

Natalie MacLean 00:07:11 That’s a great project. Are there certain wines that generally tend to have a saltier character than other wines or regions or grapes?

Gus Zhu 00:07:19 Yeah, that is the thing that we cannot say for sure. So in the book, I did mention that I believe certain wines, like in Sherry region, where they even let wind blowing from the ocean into the cellar, they could induce some salt into the maturation barrels. And also, just based on my classmates’ feedback, I have a Greek classmate. They have some outdoor fermenters for their wines in Santorini island and they say if every day after a few hours, if you just touch the outside jacket of the fermentation tank is an obvious layer of salt. You just touch it and there’s salt in your hand. And there are some other things I cannot say, because it’s kind of like a winemaking secret that winemakers can kill me, but you could introduce…

Natalie MacLean 00:08:13 There are protection programs. [laughter]. Adjustments they’re making. All right.

Gus Zhu 00:08:21 No, they are not adding salt deliberately, but they could introduce a tiny bit of sodium through certain winemaking processes. So anyway, I got gone too far on that. But just purely for salt, that is something that could exist in very small volumes in certain wines. And I personally do believe they could change the taste of wine. Having said that, when you refer to all the others, such as acid, minerality, those kind of feelings, those I cannot explain how to say by mixing them together, because minerality and those kind of sensations are such vague terms and vague concepts that people talk about. So I can only explain as in the book in isolation. And I did say, when people say minerality, people may refer to many, many different things to themselves. So that is why minerality, the term is so difficult to translate in the industry because people are referring to different things for minerality. But having said that, my sensory professor said one thing I want to quote her, because I think it’s pretty true for the commercial world, is that people tend to be like whenever they don’t know how to describe certain taste or feeling, they use the term mineral.

Natalie MacLean 00:09:56 [laugher] I love it. I love it. The Emperor has no clothes. I find that when I’m tasting and someone says minerality, I immediately think well this wine has lots of acidity, but I don’t know what you’re referring to. Do you think or maybe you just don’t even want to define it? To me, minerality should be more of a texture or a feeling than a taste. Like I’m not tasting minerals. So minerality, I don’t know. I think of that lick-a-mate. I don’t know if you have it where you grew up in China, so I don’t know if you had it there, but there was this candy that bubbled on your tongue. And to me, that’s the closest thing I can think of that like might be minerality. Sort of a vibrancy, whatever. I’m not even sure.

Gus Zhu 00:10:39 As you mentioned, it really also depends on people’s background. To me, my reference point for mineral are two things. One is that kind of cold spring water because they came from the mountain, right from the cave, and it gave me the feeling. But to my feeling is always the temperature. Whenever I drink something cold, I feel that kind of minerality. The other thing is the smell. So certain people do think certain smells reminds them of some minerals or herbs or whatever rock, to me yes I can sort of understand that. So for a certain smell, if you relate that to flint or those kind of burnt matches or those kind of things.

Natalie MacLean oo:11:14 Sulfur.

Gus Zhu 00:11:16 Sulfury type of things. People refer that to mineral, which is also understandable if you have related experience.

Natalie MacLean 00:11:29 Right. Wow. Now the book also touches on the complexities of sweetness perception. How do we misunderstand sweetness when it comes to wine? I mean, first of all, people usually say well if you like sweet wine, you’re just not that evolved.  But I really dislike that because I think some of the most complex wines in the world have a good amount of sweetness, including German Riesling and the ranges of German Riesling. What’s your take on sweetness and why?

Gus Zhu 00:11:56 That’s something even though this is more like a technical book, which I hope it’s not too technical, but it does have quite a few concepts that I want to introduce to people in terms of all the other things related to wine, like history, like culture. They do influence our perception to a certain taste, like sweetness. The sweet taste genetically by itself is not that complex. It’s not as complex as bitter because we have more genetics genes responsible for different compounds for bitterness anyway. But for sweetness, it’s more of a cultural thing. So people say they do not drink sweet while they some people still drink sweet and sweet stuff.

Natalie MacLean 00:12:39 What is it, talk sweet drink dry. No. no. It is the other way. Yes, exactly. There we go.

Gus Zhu 00:12:47 So it’s very cultural, but I just want people to be aware of the fact that lots of the very, very classic wines, they are sweet wines. And this is easy to understand because wine came from Europeans. The wine culture basically come from European countries. And in European countries, they didn’t have abundant resources of sugar, like beet or sugar cane those kind of things, to industrialized sugar production in the past. So grapes are one of the most important gold for getting sugars energies from. So people respect sweet wines and those kind of, you know, raisined or botrytis wines more simply because sugar was precious in the past and people do do not want to admit they like to eat and drink sweet, simply because Coca Cola is a cheap product and is everywhere nowaday.

Natalie MacLean 00:13:57 Sure. And junk food. The sweetness of junk food. But to your point, like the highest ranking of all Bordeaux, as you know, Chateau d’Yquem above, even Chateau Lafite and Margaux and all the rest of them right at the top of the pyramid in the 1855 classification. I mean, that’s a sweet dessert wine from Sauterne.

Gus Zhu 00:14:18 Exactly. So I always quiz people on two fun facts for the wine world. One is, as you just said, Chateau d’Yquem. So I asked people which one has the highest classification status in the world. And people may say Chateau Lafite or some others. No, it is Chateau d’Yquem is even superior than the first growth. The second fun question I ask people is that what is the longest living, highest priced wine in the world.

Natalie MacLean 00:14:49 It’s got to be a sweet wine.

Gus Zhu 00:14:50 It used to be the Egon Müller TBA for the longest time. Nowadays, is not.

Natalie MacLean 00:14:55 A sweet German wine okay.

Gus Zhu 00:14:56 Exactly. Nowadays is not because Domaine de la Romanée-Conti became number one. But if you think about it. Burgundy, it’s all the Burgundy fashion nowadays. But if you think about like which one lives the longest as the top price wine in history, that is the sweet German wine.

Natalie MacLean 00:15:16 Right. Sugars are preservative, as is tannin, alcohol and so on. But then you mentioned TBA. And for those who who may not be familiar Trockenbeerenauslese. Thank you for giving me a chance to say that. I got to say quickly before I muck it up. But yeah, that makes a whole lot of sense that that would be a preservative. So that’s sweetness. And what about bitterness? You said it’s more complex. How does that relate? What do you cover in your book as it relates to bitterness and wine.

Gus Zhu 00:15:44 So because evolution wise, animals and humans, we need to be sensitive to bitterness in order to test if this thing is the plant or whatever we eat is poisonous or not. Before we have a chance to swallow or we decide to spit them out. Otherwise, if you swallow, we can still sort of get it out, but it’s much harder. So it’s a defense system, but it’s not a singular compound that can be poisonous. So if you think about how animals survive, they have to be sensitive to a wide range of compounds that could taste unpleasant, like bitter. And then they recognize it’s poisonous. But throughout evolution, especially for human beings nowadays, we just need to read the instructions and rely on food safety programs to just say okay this is all safe to drink, safe to eat. So we don’t need to rely on the taste. Or sometimes it’s a sense of smell to judge if this thing is good or not. So some of the genes we had got lost, but we do need a quite a wide range of genes to detect different compounds as bitter.

Natalie MacLean 00:17:09 And then in bitterness, like we still talk about, even though we just dispelled the myth of the tongue map, but we still talk about a bitter finish. So is that really not happening? Or it’s just that that’s that last perception before we swallow. And because the taste buds have the capacity for all tastes, not just bitter, but we’re just getting it strongly at the back for some reason.

Gus Zhu 00:17:33 That needs a bit more research. But my personal understanding is that especially for, let’s say red wines and in certain white wines, the tannins could feel bitter to certain people.  So when you put the wine on your palate, there are so many other things like fruitiness and sour and all those kinds of alcohol, everything that mask those kind of tiny bitter sensation. But after you swallow or after you spit out the residuals, you can start to see that bitterness from certain phenolic like tannins. That is what people generally agree. It is those kind of residual tannins and phenols that gives the bitter taste. But I think this field needs more study.

Natalie MacLean 00:18:24 I’m getting that as the end of a lot of questions here, but that’s good. It shows just how much needs to be done. So tannins, that sort of furry mouth feeling we get when we drink over steep tea or eat walnuts or drink tannic wine, it can give us the perception of bitterness but do tannins themselves have a taste or are they just astringency, a tightness like a textural thing.

Gus Zhu 00:18:45 Those are what we call the tactile sensations. Those are textural things. Mouthfeel thing. So other than the 5 or 6 basic tastes, we also have different feelings toward those kind of tactile, textural things. And that is almost like our skin. Our hand touch this we feel is hot or cold. We can position certain things, but for the mouth and for our tongue and all over our mouth, the trigeminal nerve will sense those kind of sensations so we can feel the burn from chili peppers. We can probably feel burn from alcohol for certain people. And we can also feel like in China we have a special pepper called the Sichuan peppercorn. And the Sichuan peppercorn makes you feel numb. So there’s also a numbing sensation from certain food. So it’s all interesting. And that is why people eat them and drink them, because it gives us a multiple different sensations. That makes us exciting, I guess.

Natalie MacLean 00:19:48 Yeah, absolutely. The diversity of taste and texture. So tannins technically don’t have a taste, is that correct?

Gus Zhu 00:19:54 No. But wine is always a combination of all sorts of taste and smell and everything. So it’s hard to isolate. If you can isolate tannin and just taste it, you will feel that it is only a tactile sensation. But rarely any food or drinks has tannin in isolation. Well, probably we can go back to the real traditional tannin industry because the word tannin came from like tanning the animal parts and to make the leather. So if they extract those kind of plant based tannins to do that and we just taste it, maybe it has less of the aromas but more of the pure taste of tannins.

Natalie MacLean 00:20:37 We have a lot of weird homework coming off this episode. So, to taste and smell. But I get what you’re saying, everything’s a combination, and therefore you start getting tasting notes like dusty tannins. So. Okay, I see where they’re coming from. Why is mouthfeel so important? Is it because it just adds to that, sort of. You’ve got the flavours. You’ve got the aromas. And then you’ve got the textural element of the mouthfeel. Is there anything else you want to say about mouthfeel?

Gus Zhu 00:21:05 It’s very simple. As we discuss it, just add another or add several other dimensions to your taste, which makes wine tasting even more interesting. But the other thing I would say is that nowadays, a lot of people love to play the game of blind tasting: guessing the grape varieties, guessing the vintages, even guessing the regions without knowing what the wine is in the glass. But I will say some people rely on smell heavily just by smelling in front of the glass. But I would always encourage people to pay attention on the palate, because it has lots of the clues for you to play that blind tasting game came from the aroma and the taste and the tactile sensations from the wine. So get everything from the wine, not just smelling the wine.

Natalie MacLean 00:21:55 Yeah. And I always say to my online students, full bodied feels like – doesn’t taste like – what feels like cream. Medium bodied, homogenized milk, 3%. And then light bodied skim milk. Because you’ve got to get a sort of weighted feeling when we talk about mouthfeel.

Gus Zhu 00:22:13 I tink those are good references.

Natalie MacLean 00:22:15 Cool. What do you mean when you talk about flavour scalping?

Gus Zhu 00:22:20 Some people say some of the flavours were kind of mute or not that obvious, but it was supposed to be more pronounced. And those are not necessarily flavours. And in the book, I really pay attention to separating flavours from aromas, because when some people say flavours, it’s just the aromas. But when some people say flavours is a combination of everything they taste, including the taste on the tongue. So it’s more about the aroma themselves that is kind of mute due to many different reasons. It could be that simply the wine making is not that good, or it could be there are some other things such as cork taint, the TCA, those kind of compounds that actually attack our nose and make us not able to smell other aromas. So when a wine is tainted by cork taint, people say, oh, it is the quality that destroys those aroma compounds. No, the aroma compounds are there, but it actually destroy our nose temporarily so that we cannot perceive lots of the aromas hidden behind.

Natalie MacLean 00:23:34 Okay. That’s fascinating. I never knew that. Now, you write a lot about colour. It’s one of the things that we perhaps minimize in the wine world when it comes to wine tasting, we kind of say, okay, that’s pale yellow, that’s dark red, whatever, ruby. How does colour affect our perception of wine, especially as it relates to how we perceive its taste?

Gus Zhu 00:23:56 Colour is, first of all, easy. It is the easiest thing. So people usually look at the colour first because it’s kind of straightforward even though we could see colour a bit differently from each other. But it’s easy as compared to smell or taste. But there’s one thing that is very important to understand is that we are visual animals. We are visual beings. So we have preconceptions. We use our sight to prejudge a lot of things, which is nothing there’s nothing wrong with that. We always, always have these kind of things. Even though we want to be objective, we cannot.

Natalie MacLean 00:24:36 We’re busy sorting things like there’s just so much information in our environment, we’ve got to handle it some way.

Gus Zhu 00:24:42 Exactly. So when we look at wine, I will say we could be even more biased [laughter] when we see things first. For example, there are already studies shown that if you.  I also have a white wine here, right? If you colour the white wine as the red wine colour and you ask people to smell it, they came up with all these descriptors that are related to red wines rather than the so-called white wine descriptors.

Natalie MacLean 00:25:10 Like the red wine or the red fruits, instead of the sort of peach, apricot, apple kind of white wine descriptors.

Gus Zhu 00:25:16 Exactly. And also the M & M. The chocolate little things.

Natalie MacLean 00:25:22 M & M.

Gus Zhu 00:25:22 M & Ms. And they did studies on M & M. They are all the same flavours, but if you…

Natalie MacLean 00:25:30 On no. I eat the red ones first for no reason [laughter].

Gus Zhu 00:25:34 Right [laughter]. And you would assume, especially for kids, you would assume that they have a preference towards things because they have preference towards the colour. And if even they are certain adults who are not familiar with the product to do experimentation on, they would assume the yellow ones would have more lemon flavour versus those kind of chocolatey ones would have more chocolate flavour even though they are all the same flavour.

Natalie MacLean 00:26:02 Oh my gosh. Another big myth busted here. And there are certain movie stars who require only certain colour M&Ms be in their  movie trailer on set. Well, they’re just creating a lot of nothing work for…

Gus Zhu 00:26:16 No, no, no, they’re all relevant. We are living in the visual world. So like, I always embrace my preconception on things because I see that thing first. And I don’t do anything to just deliberately go against that. It’s how we naturally behave.

Natalie MacLean 00:26:34 That’s true. I just like to be judgy when it comes to movie stars, but that’s something different.

Gus Zhu 00:26:38 Of course.

Natalie MacLean 00:26:42 [laughter] So if you were colourblind sy you didn’t couldn’t perceive the red green colour blind attribute, how would that change the way you experience wine? Does it?

Gus Zhu 00:26:50 I would say there’s nothing you can do if you’re really colourblind. For example, certain people are not crazily colourblind. They may have difficulties judging from red to green, but they can see a difference. But certain people, unfortunately, a very tiny amount of the population, they really cannot see a lot of colours.  It’s kind of rare, but you shouldn’t feel so sad because you can enjoy the sense of smell. You can enjoy the sense of taste. You don’t have to say this white wine has to be like a lemony or this red wine has to be some purple ish colour. You don’t have to because most of the time we put the wine in our mouth, we enjoy the liquid. So that’s true. Don’t worry too much. And again, there’s nothing you can do if it is something deeply genetic. For example, I didn’t mention in my book because I cannot just put that photo in my book due to copyright issues. But if you think about that many years ago, there’s a huge social media thing on a dress. Some people look at us white and gold and some people look at black and blue, and people were debating. People were even fighting among families. I’m like, unless you have a technology to just change your genetic immediately now, you will still see the colour as you see. It’s genetic. It’s not because you think in a weird way.

Natalie MacLean 00:28:25 Wow. Yeah, I do remember there’s a huge uproar on that. People calling other people crazy that they couldn’t see clearly. This is a white dress. I mean, what’s wrong with you?

Gus Zhu 00:28:35 Yeah. And now science explained. It’s not fully explained, but it explained that certain. So I’ll try to explain in a very simple term. Certain genetics will give your expression of the proteins in the eyes differently. So certain people at certain position in the eye will express certain proteins. Some other people will express another type of protein. So they are hugely different. That will influence the way we see certain colours. So because of the expression of different proteins, we will see certain people see more sensitive to red light as compared to a certain people will be more sensitive to green light. So with all these kind of combinations, people will see that dress differently.

Natalie MacLean 00:29:23 I love it, that’s great. That’s going to settle an argument once and for all at this Thanksgiving this year. I can’t wait to bring it up again. Now your book delves into oak ageing and you’re quite a specialist on this, the chemistry of oak aging. Maybe talk about what is the most interesting aspect of oak aging for you. We’ll get to a couple other things as well for oak.

Gus Zhu 00:29:47 I just mentioned something in the book because now I understand more about oak. Oak is worth another book to write about.

Natalie MacLean 00:29:56 It’s a big topic.

Gus Zhu 00:29:57 Yeah. But basically what I want to say is that there are differences in oak. Just like in wine, there’s just so many different factors that contribute to the differences. For example, different oak varieties, species, different forests, different growing environment, they can hugely change the flavours of oak. And also people when people make oak, they use different toasting levels using different ways of controlling the temperatures. And those will change the flavours a lot. So I would say if a winemaker or as a wine consumer would taste wine with oak or we marry wine with oak it is almost like getting to a relationship or getting to marriage where there are hundreds of people you could choose from. But how do I say this? Okay, let’s just say boys and girls, okay? There are hundreds of girls out there. There are hundreds of boys out there, and you try to find the perfect match. But it doesn’t mean that it has to be this girl or this boy. There are just so many different options. So we have so many different grape varieties and from different growing environments. We also have different oak species from different terroir. So there’s just so many options out there I want the people to be aware of.

Natalie MacLean 00:31:15 Yeah, it just gets really confusing, right? But wonderfully diverse. I mean, that’s the point of it. What is the Maillard reaction when it comes to oak toasting? You just talked about toasting there.

Gus Zhu 00:31:26 So my reaction in simple terms is actually sugar reacting with proteins on high temperatures. So when we do cooking, we almost all experience Maillard reactions almost every day if you love to cook. But for oak, the heating part and especially the breakdown into sugar part may cause some Maillard reactions but in these proteins. Where did the protein come from? It is wine. So you have the sugar and heating part in oak, but then you need wine protein if there’s any left in it to interact with the oak. So I will say for oak reactions this is more of a how to say combination of different sources. Whereas we do see the real Maillard reaction happen in one type of wine which is traditional method sparkling, especially Champagne. If you think about the Champagne usually –  of course, nowadays some people do not add sugar at all –  but usually they add a tiny bit of dosage, the sugar. And then you also have the proteins, amino acids, released from the long lees aging process. So those with long term without heating, there’s no heating in the Champagne, but just long term aging in that bottle, you could have more and more Maillard reactions.

So that is the interesting point to me as well because lots of people, because of our preconceptions, think oh Champagne is so wonderful because of all the bubbles. But you know what to me is not only because of the bubbles. Champagne is so fascinating because it’s also a drink that contains more umami taste and all this kind of complexity from the Maillard reactions. And that’s actually making me feeling Champagne or all traditional methods sparkling wines are fascinating to drink.

Natalie MacLean 00:33:27 Yeah. So the Maillard does it have a certain taste? It’s the sugar in them. The proteins combining. When they combine it, you’re just getting that umami savory deliciousness. That’s the reaction?

Gus Zhu 00:33:39 Yeah. The only predictable part is that it will become more complex, but Maillard reaction is just a reaction. After the reaction, we will have thousands or even millions of different compounds created from that reaction. So it’s kind of unpredictable in terms of specific taste or smell, but it’s definitely becoming more complex. And again, that’s why we cook. Otherwise we would just eat certain things raw [laughter].

Natalie MacLean 00:34:08 Yeah. And for those who are listening, Maillard is it M A I L L A R D? I’m not pronouncing the L’s like I did at first. Okay, cool. My goodness at the time has flown and I’ve gotten maybe halfway through all the questions here, Gus, as I thought.

Gus Zhu 00:34:15 No worries.

Natalie MacLean 00:34:19: Your book is amazing. Is there is there anything that we haven’t touched on that you’d like to mention? Any areas specifically that you wanted to highlight?

Gus Zhu 00:34:36 Yeah, I think we touched a lot of things. Even just half of the questions were probably like we talked about many other interesting things in daily life. So I want to emphasize on the fact that after reading the book first, again, chemistry is fun. I hope it’s easy for you to understand the chemistry part of the book. And I try to relate all these kind of examples into our daily life. So it should be pretty straightforward. But if not, I will welcome feedback. But the other very important thing is that we are different from each other. We live in our own sensory world, whether it’s because of genetics or is because how we brought up or how even just at the moment how the surrounding environment influence our taste. So pay attention to your own sense of smell, sense of taste. Pay attention to what you see from your own eye, but also appreciate the fact that other people may likely smell, taste and see things and hear things differently from your perspective.

Natalie MacLean 00:35:39 I love that. That’s a recipe for human understanding and world peace. I think they are right in that wine glass.

Gus Zhu 00:35:46 And enjoy.The most important thing. Enjoy your own sensory world.

Natalie MacLean 00:35:50 Absolutely. So the book is Behind the Glass. Gus, this is fabulous. Where can we find you in the book online?

Gus Zhu 00:35:57 To me, I just find me on GusZhu.com. Very straightforward. My name.com. But more importantly, I think that the website link to the official website of the publisher’s website, Academic du Vin Library. And it has my book and you can order on it or order on some other platforms like Amazon. I think the e-version, Kindle version will be available soon.

Back to Academie du Vin. I feel very lucky to work with the publisher by chance, and because it’s a legacy of the great Steven Spurrier. So I’m now in Napa. And Napa, California wine industry basically got its fame because of him. So I feel really lucky to contribute to a little tiny piece to the library that he founded.

Natalie MacLean 00:36:44 Absolutely. It’s quite a tribute. Steven Spurrier, UK based wine writer. Very elegant. He hosted the 1976 Judgment of Paris, where California bested the best of France in a blind tasting by French judges, wine judges. So he left quite a legacy, including the Academie du Vin, which is collection of world’s best wine books on different regions and aspects of wine. And we’ll put a link to Academie du Vin and where people can find you online, Gus, in the show notes. So thank you so much for taking the time to join us here today. That conversation was fascinating and

Gus Zhu 00:37:21 There are so many more we can talk about.

Natalie MacLean 00:37:28 I know.

Gus Zhu 00:37:22 We should go to Canada or come to Napa. We’ll have a drink and have not a drink, several drinks to talk things.

Natalie MacLean 00:37:31 Absolutely. This is fantastic. So I’ll say goodbye for now. Thank you so much, Gus.

Gus Zhu 00:37:36 Thank you, Natalie. Cheers.

Natalie MacLean 00:37:37 Cheers.

Natalie MacLean 00:37:40 Well, there you have it. I hope you enjoyed our chat with Gus. Here are my takeaways. Number one, why do certain musty or animalistic aromas like barnyard or manure become more acceptable to wine lovers over time? Gus says that certain smells, especially in some natural wines, are popular today even though he doesn’t like them personally, especially barnyard. I don’t really either. He believes that the wine industry and even the media are trying to promote a certain style of wine and make people believe that lots of folks love the smell and taste. Open to debate.

Number two, what does minerality really mean when it comes to wine? Gus observes that acidity and minerality are such vague terms and concepts that people in the wine industry discuss frequently. When people say minerality, they could be referring to many different things from acidity to saltiness to the taste of flint or wetstone. The term is so difficult to translate, his sensory professor noted. And I love this, that whenever people don’t know how to describe certain tastes or textural feelings, they use the term minerality. It looks like the emperor has no clothes.

Number three, why is mouthfeel so important to appreciating wine? Gus explains that mouthfeel adds several other dimensions to taste, which makes wine tasting even more interesting. I agree fully. When blind tasting, many people depend on smell alone, but he encourages them to pay attention to the textural, tactile sensations from wine as well.

And number four, how does the colour of wine influence our perception of how it tastes? Gus says that people usually look at the colour first because it’s straightforward, even though we see colour a bit differently from each other. We are visual animals living in a visual culture so we have preconceptions and biases based on this. Even though we want to be objective, we really can’t. We can be even more biased when we see things first before smelling them. For example, there are already studies that show if you see the colour of a white wine that’s presented as a red colour because they’ve added some food dye or something like that, and you ask people to smell it, they will come up with descriptors that are related to red wines rather than so-called white wine descriptors.

All right. In the show notes, you’ll find a full transcript of my conversation with Gus, links to his website, and book the video versions of these conversations on Facebook and YouTube live, and where you can order my book online now. No matter where you live, I will find you. And so on.

If you missed episode 206, go back and take a listen. I chat about minerality and wine, great hybrid grapes and what Jimi Hendrix can teach winemakers with Alex Zecevic. I’ll share a short clip with you now to whet your appetite.

Aleks Zecevic 00:40:40 Minerality definitely impacts the flavour, but I think it also impacts the texture. And this wine to me, although it has a lot of flavour, it’s mostly about texture. It doesn’t have tannins, but it has this grip that I think comes from minerality and also the high acid you feel. It caresses your palate. And then, because of the acidity, you get this like mouthwatering sensation right after you swallow and the wine just lasts. You can really taste it for like minutes.

Natalie MacLean 00:41:15 You won’t want to miss next week. When we chat with Tony Edwards, author of The Very Good News About Wine, which focuses on the surprising health benefits and risks of wine. You’re going to be happy about this conversation because there’s been a lot of scary headlines, and we’re going to pick through all of them, including many that are based on junk science.

If you liked this episode or learned even one thing from it, please email or tell one friend about the podcast this week, especially someone you know who’d be interested in learning how to improve their ability to taste wine and food, and to identify aromas and flavours or just to say wine has a lot of minerality. If you give up, it’s easy to find my podcast. Just tell them to search for Natalie MacLean Wine on Apple Podcasts, Spotify, their favourite podcast app, or they can listen to the show on my website at natalie maclean.com/podcast. Email me if you’re a sip, tip, question, or have read my book or are listening to it at natalie@natalie maclean.com.

In the show notes, you’ll find a link to take a free online food and wine pairing class with me called The Five Food and Wine Pairing Mistakes That Can Ruin Your dinner and How to Fix Them Forever at nataliemaclean.com/class. And that is all in the show notes at nataliemaclean.com/308. Thank you for taking the time to join me here. I hope something great is in your glass this week, perhaps a wine that makes you feel all tingly all over because of its minerality or its acidity or its saltiness or whatever the heck you want to call it.

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