2.5.1. Flavours in wines

Wine flavours, as the ones from beer, cider, and other drinks obtained by fermentation, is very complex.

It is possible to isolate from grapes more than 400 volatile compounds, by gas chromatography, and 250 of them could be identified (Cordonier and Bayonove, 1978). In addition to the complex composition there is a large complexity of origins. The final wine flavour is the result from a sequence of biological, biochemical, and technological transformations and not only a product from grape fermentation.

Wine flavour, biotechnological sequence and composition.

Variety flavour

As variety flavour it is understood the part of wine flavour that is given by the kind of grapes used.

The history of wine flavour begins in the wine field, were the variety has a very important place versus the interference of the soil, the climate and the phytotechnology (dimension, method of culture, irrigation managing...). This interference is all important in grape composition and ripening.

• Direct effects: for example the nitrogenated managing could increase the grape contents in nitrogenated compounds, amines and peptides and induces a decrease of glucides. This induces a decrease in superior alcohols and esters after fermentation.

• Indirect effects: the wine field and the grapes should be in well-determined sanitary conditions and specialists should control the degree of maturation of grapes. The harvest, transportation, waiting time till processing, and air exposition after smashed are other important factors, in special under high temperature conditions.

Grapes, before the beginning of fermentation process, suffer several treatments: pulling them from stacks, pressing, squeezing, heating, and carbonic maceration...

All this treatments are in the origin of the flavour extraction from grapes and the formation of another ones by grinding grapes, in open air.

Fermentation flavour

After the first manipulations, grapes are transferred to wine vat and suffer alcoholic fermentation. This process has important qualitative and quantitative effects in flavour. In this step, the "wine note" is formed.

In order to quantify, from must to wine we can say that flavour increases about ten times, by the increase of the superior alcohols amount. This value is a function of starting composition, manipulation before fermentation process, fermentation proceeding, like agents and way of doing it.
In a very superficial form, it is possible to say that flavour amount is 1:100 parts of the formed alcohols (about 0.8 - 1.0 g/l) (Rapp et al., 1977).

By qualitative analyze it is possible to say that esters are the most important part of wine flavour. Their amount is considered as a quality index. The "lighter" ones have fruit flavours - apple, banana, and peach - as ethyl propionate, ethyl butyrate, 3 butyl acetate; they are very subtle and fugacious, so they are only noted in young wines, the "primary" ones. The "heavier" esters have a greasy, some times yeast and hazelnut notes, given by ethyl caprylate and ethyl caprate, namely. These compounds are responsible from wine’s "deep note". Ethyl acetate is the most abundant of the esters and gives to wines with natural gas a particular flavour, ethyl lactate is the second most abundant and could be considered a "rounding" flavour.

The most important difference between wine and must is the acetals presents in the first one by the lost of several aldehydes, like hexenal, hexanal (Stevens et al., 1969) , the lactones formation (Muller et al., 1973) and volatile phenols (Dubois et al., 1971).

Post-fermentation flavour

After alcoholic fermentation, wine suffers some maturation operations and sometimes ageing, under controlled conditions, that are specify to each kind of wine. Flavours have some changes during this period; they are "refined", as the wine.

In this step, flavours increase their amount in light products and aldehydes.

Wine flavour classification

• Fruit flavour: it is found in young wines. It could be similar to grape flavour itself or apple, banana, strawberry, raspberry...
• Flower flavour: these notes are heavy, more intense to taste then to smell, and very persistent. A support alcoholic or glucidic should accompany these flavours, to be pleasant. There are wines with rose notes (geranyol, nerol), coriander notes (linalool), and some have complementary notes of cassia, for example.
• Herb and vegetal flavour: this flavour is characteristic of wines done with immature grapes. This flavour is only pleasant if supported with a good tannins content.