WINETECH Technical Yearbook 2019

WINEMAKING WITH STEMS

Alcoholic fermentation is the backbone of winemaking. It therefore follows that all processes, physical factors and components of the process will have an influence on the result of the fermentation. Whether stems are absent or not during fermentation is one of these influences. Although it is generally referred to as a stem, it consists of the pedicel, with the berries attached to it, the central axis or rachis to which the pedicels are attached and the peduncle where the bunch is cut from the shoot. Together these parts of the stem are 2-5% of the bunch mass. The appearance of the stem changes during ripening from green to brown due to lignification, which also has an influence on the chemical composition of the stem. As result of this change, the stage of picking the grapes will have a great influence if it is decided to ferment undestemmed grapes. CHARL THERON: Private consultant KEYWORDS: Stems, whole-bunch fermentation. APRIL 2019

PHOTO 1. Red wine fermentation.