Definitions for "Treading"
This is the classic image of a group of people stomping on grapes. The technique (almost extinct now) was used to crush the grapes, to improve the color of the wine and to speed the start of fermentation, rather than to press the juice out of the grapes, as many people may think. It was particularly important for making Port, which is deeply colored, and benefited greatly from the technique. Some Port producers still hold to the tradition, but most opt for modern wine making techniques which yield similar results, with greater control.