Some molecules are realised easily than others, but once at gaseous state, they give very intense aromas. What influences mostly these scents is first the temperature, the evaporation surface and the volatility of the substances and even the solubility of the mucus in our nasal cavities. It means that more a substance is soluble, more intense it will be the scent.
Each substance has its own structure, represented with a chemical name. Some of them come directly from the grapes, such as in the case of the terpenes of the grape peel, others change during the fermentation, such as many secondary compounds, while others come from many combinations which are created during the evolution process.
The aim of the taster is not to recognise wine according to its chemical structure, but feeling a particular feeling, which can be floral, citrus, fruity, vegetal, earthy or spiced and any number of scents.
For example the aroma of aged red wine is described as spiced with cinnamon notes and it is a description more suitable than the chemical name cinnamic aldehyde. Generally the wine scent is classified in three groups of scents: primary, secondary and tertiary aromas. Its origin can be very different, because it may come from grapes, but also from fermentation, maturation or ageing process. The wine aroma rarely reveals intense notes belonging to all these groups, in fact there are different proportions depending on the pedoclimatic environment and the character of the vine, the type and evolution of wine.
The primary aromas or varietal are those which come
from directly from the vine, as you
can guess from the name itself. In this group we can find the terpenes, which
belong generally to the grape peel, among hundreds of molecules there are
linalool, geraniol and nerol.
Hints of musk, sage, rose, peach and other flowers and fruits are often linked to terpenes and definitely characterise the scent of wine. The main aromatic vines (gewürztraminer, brachetti, malvasie, moscati) create wines which reflect exactly the aroma and the taste of the grapes. Then there is large series of grapes defined as partially aromatic which are: riesling, sauvignon blanc, chardonnay, kerner, sylvaner, prosecco, merlot, cabernet sauvignon and others which have an intense olfactory personality.
The vine is the fundamental element to determine the primary aromas of wines and when you taste a young wine, these aromas describe the olfactory profile along with the secondary ones.
Some substances which are created during the fermentation processes, in particular in the pre-fermentative and in the post-fermentative phases, establish the secondary aromas. Among the former we can remember those that are created during the pressing, when they are detached from their main molecule thanks to the intervention of specific enzymes, becoming volatile and therefore responsible for some fragrances. The second ones generally give the wine fragrant hints of flowers, fruit and vegetables. If you visit a winery in autumn, when the fermentation is taking place or, even better, if you witness the drawing off, you can perceive in the air an intense aroma of new wine, a vinous scent that immediately leads to a very young red wine when tasted just tapped.
The scent of a new wine is always the result of primary and secondary aromas, If the vine used has an intense olfactory personality, the primary aromas prevail and guarantee an easy identification, while if are the secondary to overlap, the scent is less representative of the grape types and the structure is more balanced.
The secondary aromas are realised during the alcoholic fermentation, which is often carried out in steel vats.
The tertiary aromas appear during the maturation and ageing processes of wine.
If is it true that the steel does not influence the transformations which happen during the rest period of the wine in the autoclaves, its permanence in the barrels is fundamental to determine the tertiary aromas. The factors the most influent are the time of permanence in wood barrels, but also the origin and the type of this material, which guarantees the constant and slowly passage of oxygen and aromatic substances. At the same time it is very important the size of the barrel: the barrique works quicker on the wine structure than a big barrel, because the relationship between its surface and the volume of wine is greater. Moreover the wood of the small barrels undergoes a roasting process which enriches the aroma. During the maturation process in big barrels or in barrique, primary and secondary scents tend to diminish and to be dominated by the more advanced tertiary ones. Hints of jam and dried fruit, dried and faded flowers with spicy, ethereal notes, blending with those already present and constantly evolving, create a particular and complex bouquet.
The primary aromas do not disappear. In fact, sometime, it is possible to trace the original grape also sipping an aged wine, thanks to the incredible imprint of the vine. The discovery of an aged wine bouquet requires time and patience. Due to the long permanence in bottles, the scent may be close and so it is necessary to oxygen it in a glass, to help the release of the odorous substances.