I have been putting of writing a blog about the Congener of “Leafy” is the Fresh Section of the Grassy Group. Why? Because I thought that “Leafy” is about as specific as describing your BMW 7 series as a “Car”. I mean, which leaf on which plant and in what status of it’s life?

So first thing I did was consult the internet to find out what a “leaf” is. Turns out there are whole sections of the internet dedicated to just this topic. Hundreds, no thousands of Biologists seem to get all streamed up about “leafs”. Never Knew.

Anyway, if one reads the wikipedia website on “leafs” one gets a pretty good idea what a leaf is.

Polytrichadelphus pseudopolytrichum - leaf structure by George Shepherd
Polytrichadelphus pseudopolytrichum – leaf structure by George Shepherd

What I read is that leafs are pretty nifty little buggers. They absorb light and CO2 and make glucose and something called “leaf alcohol”. This is used by the plant to make food out of light and Carbon-Dioxide. Some leafs produce all kinds of other chemicals as well, even pheromones, to attract insects or repel them. Anyways lots going on there.

The light comes from the sun. The CO2 from your car. The water comes from the ground of from the rain. Then all the stuff in shuffled into cells. Eh presto other stuff is made and the channel like thingies that make up the structure of the leaf transport the stuff, which is now food, to where ever it is needed to make “oak tree trunks”! Hey did I just tie up the cooperage world to the leafy world?

Just some insights. Lattice is a leaf vegetable. So is Spinach. Both taste very different. So which “leafy” note did the people that drew up the flavour wheel intend. Let’s consult the 2001 Journal that describes the origins of the Flavour Wheel. Origins of Flavour in Whiskies and a Revised Flavour Wheel: a Review By K.-Y. Monica Lee, Alistair Paterson* and John R. Piggott

For the “Leafy” congener the chemical compounds of hexanal, trans-2-hexenal, 2- and 3-hexenol are identified. These compound originate in the lipids that are in the malted barley.

Hexanal is a 6 Carbon molecule with an aldehide functional group. Trans-2-hexenal is also a 6 Carbon molecule with an extra double bond. 2-Hexenol has an OH group at the end. Same goes for 3-Hexenol. So these molecules have the “same” 6 carbons but the functional groups differ and the location of the functional groups differ. This does imply a totally different set of characteristics for flavour and Aroma.

Oh, some have cis- and trans- versions of the same molecule. Meaning, same basis structure only “flipped”. (Not rotationally symmetrical) This means double the fun in chemical properties.

Hexanal is described on PubChem as:

Characteristic fruity odor (on dilution)
Strong, green grass odor
Sharp, aldehyde odor

Characeteristic fruity taste (on dilution)
Green, woody, vegetative, apple, grassy, citrus and orange with a fresh lingering aftertaste” 

~ PubChem 2017

Trans-2-Hexanal is also called “leaf aldehyde”. It is a flavouring agent and it seems readily available. Who knew.

2-Hexanol and 3-Hexanol are not well described on PubChem but they are on the “leafy” page of “The Good Scents Company”.

I am trying to combine all that I read into something simple. But I cannot. The chemicals that are given as the origins of “leafy” seem also to describe “apple”, “melon” etc. It seems that the concentration in the liquid is key to determine what one smells and tastes. That really doesn’t help me at all. It has given me a new problem to solve.

Apparently the concentrations of a compound influence what one smells? Ah Crap! Now I need to find out how THAT works.

Anyways, leafy is indeed a “congener”, but not a very specific one. Good to know. It also explains why not many people use “leafy” in notes. Too non-descriptive?