A term (also known as ‘fining’) used to describe various processes designed to ‘refine’, ‘improve’, ‘clarify’ or make a young wine‘more stable’. By contrast, the terms ‘de-mucilage ’ or ‘clarification ’ are generally understood to refer to processes applied to grape must. In the past, ‘fining’ primarily referred to the removal of sediment from a wine after fermentation (also known as ‘floating fining’). Today, the term encompasses many cellar management practices. Some of these overlap with preservation methods, which are primarily intended to extend shelf life and prevent spoilage.

During fining, suitable substances are added to the freshly fermented wine; through chemical reaction and/or adsorption, these bind suspended particles that can have a negative effect on colour and flavour. These particles are electrically charged, either negatively (such as yeasts and tannins ) or positively (such as proteins and gelatine ). The agents must have an opposite charge in order to bind the sediment particles to themselves. They are added in dissolved form and, together with the undesirable wine constituents, form insoluble flocs that settle to the bottom. 

History

Even the Romans in ancient times were aware of the effect of beaten egg white. In the Middle Ages, some questionable methods (or wine adulteration) were used; for example, ‘colour and flavour enhancement’ using blood. In the famous classic *Von Baw, Pfleg und Brauch des Weins* by the Viennese clergyman Johann Rasch (1540–1612), a number of techniques are described in detail. He explains how to restore a cloudy wine by adding freshly milked milk that is still warm from the cow. It was already known that certain substances, such as sturgeon bladder, gelatine, Spanish earth (kaolin) and charcoal, bind the suspended particles in the wine.

Mode of action

Clarification achieves several effects. Above all, it significantly accelerates the natural settling of sediment. Substances bound within the wine are removed which could lead to cloudiness after bottling. Furthermore, the removal of substances that inhibit filtration facilitates subsequent filtration. Finally, this helps to prevent wine faults altogether, or to eliminate them once they have occurred. A distinction can be made between three groups: physico-chemical substances such as proteins, tannins, crystals (wine crystals) and heavy metals; biological substances such as yeasts and bacteria; and other substances such as dust, filter material and...