It is also a logical, if time-consuming, practice in some cases with white table wines. Whole-bunch pressing leads to a juice with the lowest possible phenolics, very low solids, and fine, delicate flavors. Some hot-climate Chardonnays and Rieslings are made this way. Many varieties, notably Gewurztraminer, are given a number of hours of skin contact after crushing and before pressing. This is a way of extracting more flavors from the grapes - the aromatic compounds known as monoterpenes found in some varieties are concentrated in and just under the skin.
Skin contact requires specially-designed equipment.
Risks associated with skin contacting range from excessive phenolic extraction, with an attendant increase in astringency and premature aging, to increases in the pH of the juice, to the extraction of flavors that aren't that nice after all. Winemakers customarily make additions of specially-prepared pectolytic enzymes to white musts in an effort to increase the yield of clear juice and hasten the settling process. Oxidative handling involves making low or no additions of SO 2 to the must, and making no attempt to protect the juice from air. This allows polyphenol oxidase enzymes to oxidize grape phenols, which eliminates any browning precursors. Primary fruit flavors are also reduced in intensity.