Red wines Gran Reservas are those whose maturing time is at least 60 months. Of those 60 months, at least 18 must pass them in a barrel.
In the case of white and rosé wines, these times are 48 months in the case of maturation and have been a minimum of 6 months in barrels.
In these wines the scrap or woody part of the bunch separates from the grape to avoid the transmission of bitter flavors in the maturation process.
Sometimes in the bottling sulfur dioxide is used to avoid vinegary bacteria.