Brut Reserve ... a French term for sparkling wines, it indicates very low level of sugar up to 15 grams per litre. There is no sugar present in Brut integral or Brut zero Champagne. However the reserve indicates the wine is special due to its rare vintage such as a longer maturation in oak, and some wineries still use them in the original sense.Still wines are stored in reserve from each vintage to blend into a future champagne base.