🍷 Centrifuge

A centrifuge is a machine in which a drum spins rapidly. Centrifugal force pushes solids outward against the wall, while the clarified liquid leaves separately. This speeds up settling; in winemaking it is used to clarify, that is, to make juice or wine clear.

In a winery it is used for freshly pressed grape juice, for flotation trub, and to recover wine from the lees at the bottom of tanks after fermentation. Disk stack centrifuges are used for fine clarification of wine.

The principle is the same as in a milk separator, which separates cream from skim milk, also by fast spinning: the heavier skim milk moves toward the outer edge of the bowl. A winery centrifuge removes solids instead of cream.

The method is fast, automatic and continuous, and needs no filter aids such as kieselguhr. Its drawbacks are cost and capacity: the investment is higher than for vacuum rotary filters, although lower running costs offset this, and the volume it can handle is limited. Clarified juice still contains under 1% solids by volume. In a study of icewine, centrifugation lowered some aroma compounds (terpenes by about 13%), but the wines were rated favourably in sensory tests. Natural settling is the simplest and cheapest way to clear a wine, but it is slow.