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TitleAlcohol Textbook 4th Ed
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Table of Contents
                            Front Cover
Table of Contents
Foreword
Section 1 - Ethanol industry today
	Chapter 1, T.P. Lyons
Section 2 - Raw material handling and processing
	Chapter 2 - D. Kelsall and T.P. Lyons
	Chapter 3 - R. Power
	Chapter 4 - D. Radzanowski
Section 3 - Substrates for ethanol producers
	Chapter 5, C. Abbas
	Chapter 6, Nguyen T. T. Vinh
	Chapter 7, O'Shea
	Chapter 8, Piggot
Section 4 - Yeast and management of fermentation
	Chapter 9, I. Russell
	Chapter 10, D. Kelsall, T.P.Lyons
	Chapter 11, W.M. Ingledew
	Chapter 12, D. Livermore, Q. Wang, R. Jackson
	Chapter 13, C. Abbas
Section 5 - Beverage alcohol production
	Chapter 14, T.P. Lyons
	Chapter 15, Miguel Cedeño Cruz
	Chapter 16, R. Piggot
	Chapter 17, R. Piggot
	Chapter 18, A. Head, B. Timmons
	Chapter 19, R. Ralph
Section 6 - Contamination and hygiene
	Chapter 20, N.V. Narendranath
	Chapter 21, J. Larson, J. Power
Section 7 - Recovery
	Chapter 22, P. Madson
	Chapter 23, R. Bibb Swain
Section 8 - Engineering ethanol fermentations
	Chapter 24 - W. M. Ingledew
	Chapter 25 - J. Meredith
Section 9 - The dryhouse, co-products and the future
	Chapter 26, J. Meredith
	Chapter 27, K. Jacques
	Chapter 28, K. Dawson
The Alcohol Alphabet
Index
Back Cover
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Page 1

THE ALCOHOL
TEXTBOOK

4TH EDITION

THE ALCOHOL
TEXTBOOK

4TH EDITION
A reference for the beverage, fuel and industrial alcohol industriesA reference for the beverage, fuel and industrial alcohol industries

Edited by KA Jacques, TP Lyons and DR Kelsall

Page 2

Foreword iii

The Alcohol Textbook
4th Edition

A reference for the beverage, fuel and industrial alcohol industries

K.A. Jacques, PhD
T.P. Lyons, PhD
D.R. Kelsall

Page 224

218 T.P. Lyons

1923). However, when charred oak sawdust was
directly extracted with water or 96o GL ethanol,
the extracts obtained differed markedly in odor
from aged whisky. Moreover, none of the
various fractions of ethanol-soluble oak
extractives contained flavors that resemble
mature whisky (Baldwin et al., 1967). As a
result, it is now generally held that the
maturation process involves not only extraction
of compounds from the oak but also chemical
modifications of at least some of the compounds
extracted from the wood.

For a long time, most of the work reported on
this aspect of maturation of whisky came from
the laboratories of Joseph E. Seagram and Sons
in the US. More recently, accounts of the
mechanisms of Scotch whisky maturation have
been given by Philip (1989) and Perry (1986)
and on the maturation of whisky generally, by
Nishimura and Matsuyama (1989). A theme from
all this work has been the identification of a
number of mechanisms of maturation common
to all whiskies. These divide into addition,
subtraction and modification by reaction. There
is addition of components from the oak wood,
including those derived from lignin, tannins and
oak lactones. There is the subtraction of volatile
compounds from the maturing whisky by

evaporation and adsorption on the charred
surface of the barrel (Perry, 1986). Lastly there
are reaction processes including establishment
of equilibria among acetaldehyde, ethanol and
acetal (Perry, 1986), polymerization reactions
(Nishimura and Matsuyama, 1989) and
oxidation-reduction reactions (Perry, 1986;
Connor et al., 1990). Many of the reactions
involve, and are indeed dependent on, the
components extracted from the wood.

Looking at several of these reactions in more
detail will serve to illustrate the complexity of
the maturation process. The work at the Seagram
laboratories, whilst focused on bourbon, is
directly relevant to Scotch and Irish whiskies for
which once-used bourbon barrels are extensively
utilized for maturation. Changes in the
concentrations of organoleptically-important
compounds during a 12 year storage of a 109o

US proof (54.5o GL) bourbon, on a 100o proof
(50o GL) basis, are shown in Figure 15. The
nature and origin of some of these compounds
have been examined in some detail. Among the
aldehydes, scopoletin and the aromatic
aldehydes syringaldehyde, sinapaldehyde,
coniferaldehyde and vanillin are important.
According to Baldwin et al. (1967), these
compounds could be formed by ethanol reacting

Total solids

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Figure 15. Changes in composition of the vapor at different trays in a Coffey still rectifier used in the manufacture
of Scotch grain whisky (from Pyke, 1965).

Page 225

Production of Scotch and Irish whiskies: their history and evolution 219

with lignin in the oak wood to produce coniferyl
alcohol and sinapic alcohol. Under mildly
oxidizing conditions, these alcohols could be
converted into coniferaldehyde and
sinapaldehyde, respectively. Vanillin could then
arise from coniferaldehyde, and syringaldehyde
from sinapaldehyde. The increase in aldehyde
content during maturation is also attributable in
part to formation of acetaldehyde by oxidation
of ethanol. Formation of ethyl acetate probably
accounts for the steady rise in the ester content
of whisky during maturation.

Several other groups of compounds not
described in Figure 14 are also important in the
maturation process. Monosaccharide sugars are
found in mature whisky, and probably arise from
the pentosans and other polysaccharides in the
oak wood. Otsuka et al. (1963) reported that a
mature Japanese whisky contained xylose,
arabinose, glucose and fructose, while Black and
Andreasen (1974) added rhamnose to this list
when they analyzed a mature bourbon. The latter
workers found that the concentrations of
arabinose and glucose increased at a faster rate
than those of xylose and rhamnose over a 12
year maturation period. Salo et al. (1976) also
detected low concentrations of mannose and
galactose in a matured Scotch malt whisky in
addition to the sugars already noted. The
concentrations of sugars in mature whiskies (of
the order of 100 mg/L) are too low to suggest
any sweetening effect on the beverage. Phenols
are also detectable in mature whisky, although
some of these probably arise during mashing
(Steinke and Paulson, 1964) or from malt
produced using peat-fired kilns (MacFarlane,
1968). However, Salo et al. (1976) reported an
increase during a one year maturation of a
Scotch malt whisky in the concentration of
eugenol, which is a major phenol extracted from
oak chips by ethanol (Suomalainen and
Lehtonen, 1976). Also present in mature
whiskies are sterols, which may precipitate in
bottled whisky stored at room temperature.
Black and Andreasen (1973) found campesterol,
stigmasterol and sitosterol in mature bourbon,
in addition to sitosterol-D-glucoside, although
the possibility that some of these were formed
during mashing cannot be excluded. Finally,
reference has already been made to the whisky
lactone, ß-methyl-octalactone, and its origin.

Not surprisingly, the nature and amounts of

compounds extracted from charred oak wood
depend on the ethanol concentration of the
whisky. It is to some extent an advantage to
mature whisky at a high proof, since this requires
fewer barrels and saves on storage space. Until
1962 the US Treasury Department limited the
barrelling proof of whisky to a maximum of 110o

US proof (55o GL). In anticipation of this limit
being raised to 125o US proof (62.5o GL),
Baldwin and Andreasen initiated a series of
experiments in 1962 to establish the importance
of barrelling proof on changes in color and
concentrations of organoleptically-important
compounds during maturation of bourbon
whiskies. Their report in 1973 indicated that
color intensity and congener concentration of
whiskies matured for 12 years decreased as the
barrelling proof was raised from 109o US proof
(54.5o GL) to 155o US proof (77.5o GL). The
one exception was the higher alcohol content,
which remained approximately constant.

Is it really Scotch?

Analysis of the variety of compounds in spirit is
also of interest for reasons of identifying or
authenticating product origins or types. Adam
et al. (2002) investigated whether malt, blended
and grain whiskies could be differentiated based
on content of various metals. While it was not
possible to define a �metal fingerprint� that would
identify a whisky as to origin, malt whiskies had
markedly higher concentrations of copper than
blended or pure grain whiskies. Differences were
significant with malt whiskies containing 385-
480 ng Cu/mL and grain and blended whiskies
contained 131-242 ng/mL. Since malt Scotch is
produced in traditional copper pot stills while
grain whisky used in blending is made in
continuous patent stills, copper content was
suggested as a means of distinguishing a malt
Scotch from a blended product.

Another approach to distinguishing between
malt and blended products is based on the
differences between barley, which is used to
produce malt Scotch and the corn (maize) that
is typically used in production of grain whisky.
Parker et al. (1998) found that the ratio of 12C
and 13C isotopes in volatiles such as
acetaldehyde, ethyl acetate, n-propanol and
others differed among whiskies. This was a

Page 448

JACQUES
LYONS

KELSALL
2003

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