Energy Transfer No chemical reaction takes place without energy being used or released. In winemaking, the phosphate radical is the major energy releaser. Energy is stored in this radical from reactions which give off energy and, when required in reactions, the phosphate gives up its energy.

Enzymes Organic catalysts produced by living cells. They do not depend on the cell for their livelihood, but can perform their reactions outside the cell. Most fermentative reactions take place outside the cell. Unlike inorganic catalysts enzymes are destroyed by boiling and inactivated by freezing (the principal behind deep freezing foods). Many enzymes require a co-enzyme to act as an energy provider for the reaction, or as hydrogen acceptors in oxidative reactions. Some metals act as activators for enzymes which explains the need for calcium and magnesium in the must.

Esters are produced by the condensation of an acid and an alcohol. They are sweet-smelling compounds and are responsible for most of the flavor of a wine. Some esters are obtained from ingredients and, since they are volatile, boiling should not be used for flavor extraction if possible. Other and more important esters are produced during the reduction reactions that take place in the bottle. For a good bouquet and flavor, succinic and malic acid esters are important. Some of the former is produced during fermentation, but the wine will benefit if additional succinic acid is added prior to maturation. Apart from the right blend of ingredients time is essential to obtain a good flavor and bouquet and it is for this reason (as well as tannin reduction in red wines), that wines should be allowed at least one year

Ethyl Pyrocarbonate is an unstable compound formed when bottle fermentation occurs. It is formed by the joining of alcohol and carbon dioxide. On opening the bottle the rate of loss of carbon dioxide (or rate of bubble formation) is inversely proportional to the concentration of ethyl pyrocarbonate. Thus a good sparkling wine retains its fizz for a long time because the bubbles can only form as the decomposition of ethyl pyrocarbonate takes place.

Exponential Feeding A system of sugar additions to a must so that a high alcohol content can be achieved. If all the sugar is added at the start of fermentation, there is a great danger that the sugar will inhibit or even kill the yeast. By adding small amounts of sugar each time the specific gravity falls to 1-005, the yeast learns to tolerate alcohol concentrations which normally would kill it. In this way, a slow, steady ferment is encouraged. This aids quality by not causing the vaporization of esters.

Extraction of Alcohol Tannins and many of the natural pigments are insoluble in water. To overcome this, ingredients rich in such compounds are left in contact with the must until sufficient extraction has been obtained. This is necessary with berried fruit, currants, dried fruit, flowers, gooseberries, grain, grapes, leaves and stone fruit.See Alcohol, See Extraction of Color ;

Extraction of Juice Following the pulping or crushing of fruit, the juice can be extracted by pressing. The yield can be increased by the use of cellulose enzymes.

Extractors are pieces of equipment designed to facilitate the obtaining of juice from fruit and to increase this yield. They can work on the principles of either pressure or steam.