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Last Updated: Mar 6, 2026Must
Must
Grape must refers to the freshly pressed, unfermented grape juice which contains the fruit’s skins, seeds and sometimes stems (collectively referred to as pomace). It is the first step in winemaking, which serves as the base for fermentation by yeast into alcohol. Its name is derived from the Latin phrase “vinum mustum”, which means “young wine”.
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Yeast
Yeast in wine is a microscopic, single celled fungus, typically Saccharomyces cerevisiae, which triggers fermentation by transforming the sugars in must into ethanol and carbon dioxide. Yeasts are essential for converting grape juice into wine and they determine its final alcohol content, aroma and flavor profile.
TCA
TCA stands for 2,4,6-trichloroanisole, a chemical compound that causes "cork taint". It forms when natural fungi in corks or wooden barrels interact with chlorine in cleaning products, resulting in musty, moldy or wet cardboard aromas in wines.
Sediment
The term "sediment" signifies the natural, organic by products of the winemaking and aging process. It is made up of grape solids (skins, seeds, pulp), dead yeast cells (lees) and tartarate crystals (wine diamonds).
Assemblage
Assemblage is the French term for the process where winemakers combine different base wines that vary by grape variety, vintage or vineyard parcel, to create a balanced and complex final wine.
Yield
The yield signifies the amount of grapes or wine produced from a specific vineyard area, commonly measured in tons per acre in the US, or hectoliters per hectare in Europe. Lower yields are associated with better quality, while higher yields produce lighter and less concentrated wines.
Saccharomyces Cerevisiae
Saccharomyces Cerevisiae is the major yeast species involved in wine fermentation. Also known as "wine yeast" or "baker's yeast", it converts the sugar in grape juice to ethanol and carbon dioxide, creating wine.
Racking
Racking refers to the process of transferring wine from one tank or barrel to another using gravity rather than a pump to separate clear liquid from sediment.
Fermentation
Fermentation is a natural biochemichal process where yeast consumes the natural sugars in grape juice and converts them into alcohol, carbon dioxide and heat. At the end of fermentation, grape juice is converted into wine.
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