Ever Wonder? Can Aged Riesling Really Smell like Petrol?

Wines regularly get described by their aromas – floral, citrus, green apple, melon, herbal, cherry, plum and spice. But, Riesling – can it really including the aroma of petrol?

 A lot of people might assume a bottle of Riesling must have gone bad if they detect an aroma anything like petrol, gasoline or kerosene. But, this actually is a key characteristic of an aged Riesling!

 Not that a Riesling grape straight from the vine will have any such smell, but petrol is an aroma that forms during the fermentation process.

 There is a lot of chemistry that goes on during a wine’s fermentation. And, the development of exotic chemical compounds is one of these.

 As I started with, the fermentation of grapes can result in a tremendous range of aromas – most of which come from the chemical interactions of the juice of grapes and yeast. Other aromas can be introduced during the aging process (e.g., from oak barrels).

 It turns out that a petrol-like aroma is a natural occurrence in aged Riesling. Your glass of wine is not going to smell like a gas can, but there can be “delicate” aromas of petrol.

 Without getting into the chemistry details, the reason that an aged Riesling can smells like gasoline is due to a chemical compound called TDN (1,1,6-trimethyl-1,2-dihydronaphthalene). While the potential for TDN to be produced and noticed in most wines is pretty low, Riesling grapes have the highest chance to exhibit this distinctive aroma. Don’t lose sight of the fact that the primary aromas of Riesling will be tropical fruit, red fruit, melon, citrus and spice. But, there can be this petrol-like aroma compound. And, in combination with the other aromas, it can also result in aromas of honey, beeswax or paraffin.

Sources: GL Sacks et. al. (2012), C Black et. at. (2012)

So, try an aged bottle of Riesling. Not that petrol is an aroma you may desire, but open up mind and your nostrils and see if you can pick out the aroma. It’s not for everyone, but it’s certainly worth trying as you continue on your wine journey. Cheers!

How Fermentation and Aging Affect a Wine's Aroma

Last time we looked specifically at how oak affects the flavor of wine. There we learned that oak can be used in the fermentation process and/or the aging process to add various flavors to the wine. But before you take a first sip of wine, swirl your wine in your glass and then stick your nose into the top of the glass and experience all the wonderful aromas that the wine has to offer.

First and foremost, a wine’s aroma is based on the grape that is used in the wine. So, fruity aromas are those that are up-front. In white wines these aromas can include those of tropical fruits, melons, and citrus. In red wines you’ll find red fruit, black fruit and dried fruit aromas. So, these set the foundation for a wine’s aroma.

Now, let’s take a look at how the fermentation and aging process affect a wine’s aroma. First, fermentation - the process that turns the grape’s natural sugars to alcohol. And, the key ingredient in fermentation is yeast. Therefore, it’s not surprising that the yeast is a factor in a wine’s aroma. While the yeast doesn’t play a major role in a wine’s aroma, it can give a wine hints of fresh baked bread, butter, cream and cheese.

Then there’s the aging process. And, here aging in oak can yield a variety of aromas, some directly from the wood and others from the small amount of oxygen a wooden barrel allows inside. Depending on type of oak and how the barrel is toasted, it can lead to sweet aromas that including vanilla, caramel, brown sugar and butterscotch. The introduction of oxygen in the barrel can lead to nutty aromas. And, a heavily toasted oak barrel can even introduce aromas of smoke, tobacco, cigar and dried leaves.

So, don’t forget ‘smell’ as part of the five-Ss in wine tasting. Try it with your next glass of wine and see how many aromas you can pick out. Cheers!

Ever Wonder Where Fruit Aromas & Flavors Come From in Wines?

When I first became interested in wines, I remember asking if other fruits were used in the production of wines. After all, so many wines smell and taste like a lot of fruits other than grapes. So, if grapes are the only fruits used in wine making, how do all those other aromas and flavors get into the wine?

Well, it turns out that there’s a lot going on during fermentation, not just the yeast converting the grape’s natural sugar to alcohol. There are also chemical reactions going on that create hundreds of aroma and flavor compounds. Wow!

These “compounds” are identical to the compounds that we already associate with smells and tastes. So, when you smell a fruit aroma in wine you are smelling the same aroma compounds that also naturally occur in those fruits. The same is true with flavors.

Other aromas such as vanilla, tobacco, leather, coffee, caramel and toast come from the oak aging of the wines. Depending on the amount of ‘toasting’ the barrel undergoes affects the range and depth of these aromas.

So next time you have a glass of wine take time to smell it in the glass before you sip. You’ll be amazed to discover the aromas of dark fruits in red wines such as berries and plums while white wines can have aromas of apples, pears, melons and citrus. And then sip the wine and enjoy all the fruit flavors it has to offer. Cheers!