Re: Fwd: Oak Maturation
- It appears that "the S.G. of oak is approx. 1000 kg/cubic metre" is
incorrect. It probably refers to unseasoned oak. Here is a more
authorative source -
"The ideal ethanol concentration that yields the maximum solid
extraction is approximately 55% (v/v) (Singleton and Draper, 1961).
For the production of lighter products, lower proofs can be used
yielding a product with less extractives and having a different
composition. A barrel for 200 litres has as much as 90 square cm/litre
of wood surface. Evaporation, extraction, oxidation and component
reactions are maturation efffects related to the conditions of the
barrels, and they will increase as more wood surface is in contact
with a unit of beverage (Singleton, 1955). Each mm penetration of the
beverage to the wood will contribute some 9 cubic cm of extracted oak
or 5.4 grams of soluble oak solids, assuming a density of 0.6 g/cubic
cm, and 10X flavor threshold (Singleton, 1995)."
So 5 grams of oak chips/litre of 55%abv is the
recommendation.Duration? From 10 days to 10 months.
This is approx. 2 tablespoons/quart.
For S.G. of woods -
--- In Distillers@yahoogroups.com, "waljaco" <waljaco@...> wrote:
> This is an attempt to quantify theoretically the oaking level, and to
> see how it corresponds with practical experience.
> Aging of wine in oak barrels uses the same basic principles as the
> brandy, whisky and rum industry so I looked up 'Making Good Wine' by
> B.Rankine for information. Here are some relevant excerpts -
> "The surface area per unit volume is a useful indication of
> availability of maturation and extractable oak surface, and details
> are set out below.
> Capacity (litres)-----Surface area(sq.m.)-----Sq.cm/litre
> 500-------------------3.0---------------------60 "
> 200litres (50USgal) is a common cask size and if we assume that the
> depth of penetration is 1mm, and the S.G. of oak is approx.
> 1000kg/cubic metre, the volume of exposed oak in a 200l cask is 9
> cubic cm./litre or 9g/litre.
> "In order to achieve oak flavour without cask maturation, oak chips
> or shavings may be used. The rate of addition depends on various
> factors, including surface area of the chips, the type of wine and
> the oak intensity desired. Addition is usually made during
> fermentation, and the rate is between 1 and 10 grams per litre. Oak
> extracts may be used and their addition can be more precisely
> Time and temperature of storage (which have to be considered together
> is usually 12-18 months and for whites 2-6 months. Temperature of
> storage is usually in the range of 18-24C. with th optimum for table
> wine being 15-20C.
> The number of times a cask may be reused for table wines is between 3
> and 6, after which the casks are usually used for storage of dessert
> wine. Shaving the inside of the cask, removing a millimetre or so of
> surface wood and exposing a new surface, imparts a longer life to the
> cask for table wine maturation and is common practice."
> So the recommendatio is 1-10 grams/litre. Another reference
> recommends 1-5 grams of shavings/litre while a recommendation on an
> oak chip packet recommends 3-5 grams/litre.
> Scotch, Irish whisky and rum are aged for at least 3 years in used
> Bourbon and sherry barrels where extractable material has been
> reduced, while Bourbon whiskey is stored for at least 2 years in new
> charred American oak barrels which have less tannins than French oak
> I measured the weight of oak shavings and found that a heaped
> tablespoon weighed about 3 grams (1/3 oz.), so 3-6 grams/litre or 1-2
> tbsp. of oak shaving appears to be the average recommended amount.
> Another recommendation is to determine the oaking level by tasting
> every 2 weeks until the desired level is achieved.
> See also msg 2883, 5073, 5074, 5082, 5092.
> Caramel (burnt sugar) is also added to brandy, scotch and rum but not
> to Bourbon - see msg 5067.