The grapes arrive at the winemaking facility and are tossed in the receiving hopper that evenly feeds the grape clusters into the crusher/destemmer. With mechanical harvesting or for the estate's finest wines, the grapes may go first to a sorting table or conveyer belt so that workers can remove any rotten, under-ripe or lesser quality grapes from the batch. White wines can be made from grapes of all skin colors as long as the skin contact during crushing is as short as possible. The grapes then fall into the crusher, which breaks the skins without crushing the leaves, stems, skins, and seeds which would otherwise impart harsh tannins to the juice. The crusher is a horizontal cylinder, with dull propeller-like blades that separate the stems from the berries as they pass through. The wall of the crusher is stainless steel with holes the size of the berries that allow them to fall through. The resulting must is sprinkled with the smallest possible dose of sulfur dioxide. SO2 is a naturally occurring component in all wine, however this small addition is important for many reasons: it prevents the growth of bacteria and unwanted wild yeasts, and inhibits oxygen reactions that can cause undesirable browning of the juice (as occurs when a sliced apple is left on the counter) and loss of sought after aromas.