**2. Port wine production and styles**

Port wine is subjected to an extensive set of legislation and regulations. According to the Decree-Law n°173/2009 of 3rd of August [4], the IVDP, located in Oporto city, has the responsibility of promoting and perform the quality control of Port wine, as well as the amount of Port wine that can be produced annually, regulating all the production process, and the protection of the denominations of origin Douro and Port and the geographical indication of the Douro Region. The panel of expert tasters of IVDP is responsible for the certification and approval of wines and wine spirits, as well as the granting of the guarantee seal [5].

In the Port wine vinification process, the alcoholic fermentation is stopped, between 6% and 9% (v/v) alcohol content, according to the Port wine style and sweetness desired. Therefore, the wine is runoff from the skins, and it is fortified with a wine spirit containing 77% (v/v) of ethanol to raise the alcohol concentration to 18–22% (v/v). The average proportions of wine spirit added are 115 L for each 435 L of fermenting wine. The wine spirit allowed to be used in Port wine production required rigorous quality standards regulated by the laboratories and panel of tasters of IVDP. The sensory characteristics evaluated by the panel are turbidity, colour, aroma, and taste. The analytical parameters (ethyl carbamate,

**123**

**Figure 2.**

**Table 1.**

*Port Wine: Production and Ageing*

*DOI: http://dx.doi.org/10.5772/intechopen.94900*

**Sweetness Specific gravity (g/cm3**

*Port wine classification according to their sugar content.*

*Port wines styles and categories according to [1, 7].*

total higher alcohols, acetaldehyde (ethanal), ethyl acetate, methanol, 2-butanol, 1-butanol, allylic acid, cyanidric acid, calcium, copper, iron, alcohol content, total acidity, and density) must be below of the allowed limits described in Regulation n° 84/2010 [6]. Contrasting with most other fortifying spirits, the wine spirit used in Port wine production is not highly rectified; therefore, it contains many flavourants, especially higher alcohols, and aldehydes and this fortification process results

Port wine can be extra dry, dry, semi-dry, sweet or very sweet, according to the levels of unfermented sugars remaining (**Table 1**) that is dependent on the time of

**, 20°C) °Baumé (ºBé) Sugar content (g/L)**

There are four main different styles of Port wine, designated as Tawny, Ruby, White and Rosé (**Figure 2**). Port wine intended for Tawny style are obtained from different wines in different stages of ageing. During the ageing in the wood barrels, the red colour of the wines gradually develops into tawny, medium tawny or light tawny, with an aroma of dried fruits and wood [1]. In this style, there are some special categories like Tawny Reserve, Tawny with Indication of Age (10, 20, 30 and 40 years) and "Colheita". This last category is an exception, as these wines are from a single vintage [7]. All these wines are ready to drink when they are bottled [1]. Port wines that belong to Ruby style are wines that the evolution of their deep red colour is limited and the fruity character is maintained [1]. Within this Port style, special categories

Extra dry <0.9980 0.0 <40 Dry 0.9980–1.0079 0.0–1.3 40–65 Semi-dry 1.0080–1.0179 1.4–2.7 65–85 Sweet 1.0180–1.0339 2.8–5.0 85–130 Very sweet >1.0340 > 5.0 >130

in a high concentration of acetaldehyde in these initial wines.

wine spirit addition to stop the alcoholic fermentation [1].
