This is all taken from a bit of research I did this morning (mostly via Tom Stevenson)
Terpenes, aka isopentenyl pyrophosphate (IPP), are a chemical compound contributing to aromatics found in most grapes (and wines), though they show themselves most clearly in a few varietals. There are over 400 naturally occurring terpenes in the plant world, but only 40 have been found in grapes or wine.
Some of the different types are listed here
Limonene Used by the fragrance industry, limonene is one of the basic elements of aroma in bergamot and both orange oil and lemon oil, but is closer to orange than lemon. Can also be very resinous.
Myrcene The most herbal-resinous of simple hydrocarbon wine terpenes, myrcene is found in star-anise, coriander, hop, ginger, cinnamon,nutmeg, cardamom, bay leaves, basil, rosemary, sage, peppermint, spearmint, bell pepper, black pepper and grapefruit.
These are the most commonly found terpene compounds in wine and are present in increasing quantities in grapes as they ripen.
Citronellol Found in garden rose, geranium, ginger, black pepper, basil, peppermint and cardamom. Also plays a supporting role to citronellal in the aroma of Lemon Eucalyptus.
Eugenol The most herbal aroma of all terpenoid alcohols, eugenol is found in bay leaves, cloves and allspice.
Farnesol Whilst all the other terpene compounds important to grape and winearoma are monoterpene compounds, farnesol is a sesquiterpene alcohol (i.e., 15 carbon atoms). Farnesol is found in Linden Oil andis a constituent of garden rose aroma.
Geraniol Found in nutmeg, ginger, basil, rosemary, sage, cardamom and grapefruit, geraniol is one of the three terpene compounds principally responsible for Muscat aroma.
Hotrienol Has the aroma of Linden or Lime Tree, but levels higher than 30 ug/lindicate premature ageing, probably due to poor storage conditions.
Linaloöl Also spelt linalol, it is found in lavender, bergamot, jasmine, basil, rosemary, sage, star-anise, cinnamon, clove, nutmeg, coriander, cardamom, ginger, black pepper and mandarin. This is one of the three terpene compounds principally responsible for Muscat aroma.
Nerol Found in orange blossom, ginger, basil, cardamom, mint and mandarin, nerol is one of the three terpene compounds principally responsible for the Muscat aroma.
Citronellal Found in ginger, black pepper, geranium and peppermint, citronellal is however overwhelmingly lemony-resinous in character, representing a minimum of 82% of Lemon Eucalyptus Oil.
Geranial Found in cinammon, clove, ginger, basil and peppermint.
Geranic acid Found in cardamom and peppermint.
Geranyl acetate Found in lemongrass, coriander, nutmeg, cinnamon, peppermint and, of course, geranium. Linalyl acetate Found in lavender, bergamot, jasmine, cinnamon, cardamom, bell pepper, basil, rosemary, sage and peppermint.
Rose oxide Found in Bulgarian rose, but can also be green, geranium-like.
They are found in high concentrations in grapes such as Muscat, Gewürztraminer, Riesling, and other Germanic grape crossings. Also Torrontes is a terpene rich grape.
This is helpful in blind tasting because certain aromas should lead us to certain grapes: If you find geraniol, linaloöl and nerol aromas in a glass, you should be thinking Muscat. Also the number of highly aromatic grapes with these properties is very limited.
Acidity seems to also play a roll in how terpenes are perceived. Higher acid in grapes (i.e. Riesling) lead to lower perception of terpenes, where lower acid in grapes (i.e. Gewürztraminer) lead to higher perception of terpenes.
The method of press will also contribute to the amount of terpenes found in a wine. Free run juice will contain 25-50% of the terpenes of the juice of pressed grapes.
When it comes to bottle aging, the concentration of monoterpene alcohol declines and monoterpene oxides are formed which leads to the loss and alteration of floral aroma.
However, I cannot find information on what else may contribute to terpene flavors in wine. If someone would like to follow up, I'd love to hear about it.
Wow, lot of information. One thing I didn't notice that I know about is Rotundone. It is the terpene that gives pepper its distinctive aroma. They've found rotundone in high levels in Australian Shiraz, Mourvedre, and Gruner (amongst others).
And I should clarify, I should have said detectable levels (since they are actually quite low).
In grapes some terpenes get to their highest level at ripeness (are degredation products) and when in volatile form operate as sort of bird attracting pheromones - the vines basic desire to procreate and find new suitable habitats.
Terpene development/volatile loss are different based on growing climate and exposure to sunlight. Bound forms can be converted to volatile with time (bottle age), heat and/or hydrolysis with glycosidases.
Some exist as compound precursors that convert with age or heat especially in Riesling - vitispirane, TDN (kerosene smell), damascenone. Back to the discussion of petrol as an under ripe or aged characteristic... perhaps both?
Principles and Practices of Winemaking makes an interesting reference to traditional Muscat winemakers heating must to increase aromatic character. Anyone know about this tradition/process/and if anyone still practices it?
Terpenes are a primary component of a plant's essential oils.
As I understand it, terpenes and pyrazines are responsible for wine aromas that are naturally present in grapes, whereas esters are responsible for aromas generated during fermentation. Higher alcohols, fusel oils, acids, and other elements (not to mention wood lactones) are also contributors to aromas.
Some fruit aromas are the result of terpenes, such as limonene, whereas other fruit aromas are the result of esters, such as banana (isoamyl acetate).
This is a good short summary. Also, I believe terpenes can be found in American oak.
One of my favorite out there wine topics.