UNIT 2 – Issues related to the components of wine

The main components of wine after bottling

Compound	Task and specification
Water	Main component of wine
Ethylic acid	A product of the alcoholic fermentation. Quantity is from 10 to 16% in Volume
Tartaric acid	To be found in the grapes and in the wine
Malic acid	To be present in the grapes and the wines that haven’t undergone the malolactic fermentation
Residual Sugars	To be found in quantities of 1 to 5 g/l or higher in special wines
Sulphur dioxide	Conservative substance typically present in wine, with different chemical forms and different roles
Colloids	Substances to be found in the grapes and in the wines (i.e. proteins)
Phenolic compounds	Responsible for the colour of wine and for the sensorial characteristics
Aromatic compounds	Responsible for the aromas of wine

Main chemical alterations happening during the transport of wine

Tartaric acid: it can undergo precipitation if the temperature of wine gets lower or if it hasn’t stabilized properly

Malic acid: if it is found in the wine, it can trigger anomalous fermentations but only if the temperature is higher than 18 – 20 °C

Acetic acid: if the temperature is higher than 15 – 18 °C and with oxygen, it can rapidly add up and trigger acetic fault

Colloids: they can merge up and precipitate if the temperature is lower than 4 – 5 °C

Residual sugars: they can be fermented by bacteria or faulty yeast if the temperature is higher than 15 °C

Sulphur dioxide: molecular sulphur is the form the most likely protects the aromatic profile of the wine from alterations (biological and chemical). It decreases when temperatures are high as well as when oxygen is available

Issues related to alternation happening during transport at high temperature

When temperatures are high (higher than 20 °C and subjected to the time of permanence) anomalous fermentation of the malic acid (if available) may happen thanks to the action of malolactic bacteria or by the residual sugar
In addition, other metabolites may develop because of Brettanomyces (polluting yeast having a slow fermentation action) with subsequent production of carbon dioxide and issues related to the cloudiness of the bottled wine
If the closure is made of cork, or if the bottle is kept vertically, with high temperatures it may dry up so its quality is compromised with possible losses of the product or production on acetic acid
High temperatures lead to a fast action played by sulphur dioxide with subsequent losses of quality
High temperatures enhance the flocculation of proteins so wine gets cloudy

Issues related to alternation happening during transport at low temperature

In the case of low temperatures (lower than 8 °C and subjected to the time of permanence)
There is the possibility that tartaric acid (if it hasn’t been stabilized earlier in a good way through the use of cold techniques or using auxiliary products (like meta-tartaric acid) creates some sediments in the bottle
For red wines, low temperatures may loose up the colour with colloidal substances creating precipitations

Other issues about wine transport

Breakages: bottles may break down if they are not properly packed. Should only one bottle in the box break down, it is still a problem since it could spoil the labels of all the other bottles. In addition, the spilt liquid can undergo microbial alteration (acetic hue and moulds) that attack the other bottle in the box
Corks may get altered (they can swell or dry up)
The loss of aromatic intensity along with the feelings of freshness of young wines
Decrease in the general quality of the wine itself