A mechanical crusher/de-stemmer is often used. The stems are
often removed in red winemaking before fermentation since the stems
have a high tannin content and when unripe, stems can give the wine a
green aroma due to extraction of 2-methoxy-3-isopropylpyrazine which
has an aroma reminiscent of green bell peppers. With Pinot Noir, even if
the clusters are de-stemmed, the grapes are usually left uncrushed
(“whole berry”) to encourage the development of desirable aromas
through partial carbonic maceration (fermentation within the grape