2.6.2 Intensity
This is simply assessing how strong or ‘loud’ the nose of the wine is, and can give an indication of quality. A nose light in intensity may be expected from a simple, inexpensive wine; a more pronounced nose is generally indicative of higher quality. However, high‐quality reds, in particular, can be very closed in youth. Conversely, there are some grape varieties that nearly always give a very intense nose even in a wine of modest quality, especially aromatic whites. These include members of the Muscat family, Gewürztraminer, and Argentina's three Torrontés varieties. The wine should be aerated by swirling around the glass to reveal the full intensity of the nose.
2.6.3 Aroma Types, Development, and Characteristics
It is perhaps convenient if we consider here the topic of aroma types and development before that of aroma characteristics. However, when making a tasting note, the aroma characteristics might be noted first. Development is assessing, on the nose, the state of maturity of the wine. Wines have a lifespan that depends on many factors, and maturity should not be confused with age. Generally speaking, the higher the quality of the wine, the longer is the lifespan. The finest quality reds including, by way of examples, cru classés from Bordeaux, classic wines from the Rhône Valley, Toscana's Brunello di Montalcino and Piemonte's Barolo may require 10 years or more even to begin to approach their peak. Conversely, a simple branded Bordeaux or Côtes du Rhône or Chianti may be past its best at the age of three or four years.
To understand the concept of nose development, we need to consider the basic types and sources of wine aromas. These are classified into three main groups.
Primary;
Secondary;
Tertiary.
2.6.3.1 Primary Aromas
Primary aromas are those derived from grapes and are generally fruity or floral. A predominance of these on the nose normally indicates a wine that is in a youthful stage of development. Varietal aromas usually belong in this group. Many of the compounds that give varietal aromas remain largely unchanged by the fermentation process. Accordingly, the pronounced blackcurrant or cassis aromas contributing to the nose of a young Cabernet Sauvignon, the overt gooseberry characteristics of a Sauvignon Blanc or the elderflower fragrance of a young Seyval Blanc are considered as primary. Grape compounds contributing to individual varietal characteristics may include methoxypyrazines, norisoprenoids, furan derivatives, lipoxygenase pathway products, and phenylpropanoid pathway products [8]. Terpenes, both mono‐ and sesquiterpenes, are present in grapes and are contributors to primary aromas – they are largely unchanged by the fermentation process and have little impact upon secondary aromas. The concentration of monoterpenes declines as wines age, thus reducing the primary aromas. Maturation and ageing of the wine may also result in them being modified and accordingly contributing to tertiary aromas. Young wines made from grapes that have high levels of monoterpenes, such as the Muscat family, Gewürztraminer and, to a lesser extent, Riesling can have a nose that screams of primary fruit and show overt grape‐like aromas. By way of comparison, Chardonnay, a neutral variety may have less than 1 mg/l of monoterpenes, Riesling up to 4 mg/l and varieties of the Muscat family up to 6 mg/l.
It is worth noting, at this point, that the varieties we all know and love are only a few generations removed from their wild ancestors [8]. During the last 150 years, viticulturists have generally focused more and more on relatively few ‘elite’ varieties, much to the loss of aroma diversity, and possibly also disease resistance.
2.6.3.2 Secondary Aromas
Secondary aromas are the ‘vinous’ aromas resulting from the fermentation – put simply, the smells that are different in wine to those of unfermented grape juice. Many compounds in grapes are precursors of secondary aromas, including free amino acids, phospholipids, glycolipids, aldehydes, and phenols. During the fermentation process, numerous chemical changes and enzyme‐catalysed modifications take place producing secondary aromas. Numerous esters are generated in the process, and the aromas of these are often assertive on the nose of young wines, sometimes imparting pear, banana or even boiled sweet or bubble gum characteristics. Several fatty acids are also generated during fermentation, and some of these, if produced at high concentrations, can be distinctly unpleasant and render the wine flawed or even faulty. These include acetic, isobutyric, isovaleric, butyric, hexanoic, and decanoic acids. Several volatile sulfur compounds may also be produced from their precursors. Some of these are desirable contributors to a wine's aromatics, but others, if they remain in the wine, may also contribute to faults. Also in the secondary aroma group are the by‐products of MLF, and bâtonnage (if undertaken), which may contribute to aromas of butter and cream. Compounds extracted from oak, giving aromas of vanilla, coconut, or toast may also be considered secondary aromas.
2.6.3.3 Tertiary Aromas
Tertiary aromas result from the maturation and ageing process of the wine, particularly in bottle. During this time, there will be many chemical reactions. Following fermentation the wine will already contain some dissolved oxygen (DO), and for wines that are barrel‐matured, more oxygen will be absorbed through the cask. Provided the barrels are kept topped‐up, there will only be a small amount of beneficial oxygenation taking place, which will increase the aldehyde content of the wine. Wines matured in new barrels will absorb the greatest amount of oxygen, together with oak compounds including vanillin, lignin, and tannin. Those matured in second and third fill barrels will also pick up these, but to a lesser extent, for the pores in the wood become blocked with repeated use. Wines that are not matured in barrels may be micro‐oxygenated, and ‘oaked’ in other ways, including chips, beans, and powder.
Wine maturation in bottle results in continuous changes to the volatile compounds of the wine. At bottling time, there will be some DO in the wine, and typically some in the headspace of the bottle. This oxygen present at bottling is rapidly consumed by the wine [9]. During ageing and storage more may be absorbed from the closure itself (particularly if this is cork), through the closure depending upon type, and the interface between the closure and bottle. However, many of the changes that take place during bottle maturation are reductive. These changes take place as the oxygen content of the wine is gradually reduced. It is this process that makes bottle ageing a necessity for the maturation of many fine wines, especially full‐bodied reds. A wine that is not able to be reduced is a dead wine. However, reduced aromas
