Assertion: wine's contact | /r/HasProperty | essential
Facets:
value: for color extraction
type: PURPOSE
Source sentences:
text: Most red wines derive their color from grape skins (the exception being varieties or hybrids of non-vinifera vines which contain juice pigmented with the dark Malvidin 3,5-diglucoside anthocyanin) and therefore contact between the juice and skins is essential for color extraction.