Norwegian aquavit differs from the other Scandinavian and German aquavits in that it undergoes a maturing process stored in 500-litre used sherry casks. With the maturing in sherry casks there is a controlled and late oxidation. The maturing is a vital stage in the production chain, and closely resembles the process used for whisky and cognac.
The barrel store at Arcus, which occupies two storeys and has a floor space of about 5 acres, contains aquavits for maturing in used sherry barrels from Jerez in Spain. Each barrel holds 500 litres, and there is a total of 8,500 barrels in the store. At any given time there is over 4 million litres of aquavit maturing here.
During the maturing process there is an evaporation of water and alcohol, on average 2-5 per cent a year, and thus a slight rise in concentration of the aquavit. Further, an extraction of the oak phenols and aroma compounds augments the aquavit’s complexity.
All the barrels are registered in a separate database, which contains information about age and other properties of the barrels. This information source is accessed when selecting the appropriate barrel for maturing of the individual batches. New barrels give a lot of colour, an aroma from the oak staves, and sherry notes. The older barrels give minimal or no colour, and are used for maturing table aquavits. The oldest barrels still in use are nearly one hundred years old.