Flotation

flotation is a technique of must clarification borrowed from the ore refining and concentrating industry. It is based on the tendency of grape solids to adhere to rising bubbles. If very small bubbles of air are introduced at the bottom of a vat of must, easily oxidized phenolics in the juice will react and some will be removed along with the other suspended solids which are carried to the top of the tank by the finely divided air bubbles. Oxidized phenolics, which are brown, not removed by flotation will probably be adsorbed and removed with the lees after fermentation. (It is also possible to use compressed nitrogen instead of air.) The advantage of this technique is that the resultant wine resists further oxidative browning. However, there must be no yeast or fermentation activity in the must as this prevents flocculation. Flotation is best suited to large wineries where the process can run continuously.