lV~
6550/14
~ he present invention is concerned with a process for the
manufacture of bitter driDks.
Amongst the bitter substance~ which are widespread as
plant constituents having the most diverse chemical structure
and which are used extensively for the manufacture of bitter
drinks, the constituents Or hops (~umulus lupulus) occupy 8
~ignificant position. It i8 primarily the strongly bitter and
soluble iso--scids (al80 denoted as isohumulones) which can
give rise to up to 80% of the bitter intensity in beer and
which are formed in a known manner during the boiling of the
~ wort from the only weakly bitter and almost beer-insoluble
¦ ~-acids (also denoted as humulones). ~owever, this conversion
B f ~-acids into 150-~-acids, which is an isomerisation, does
I not proceed in a quantitstive msnner under the relatively
unfa~ourable conditions of the brewing process and thi~ can
lead to significant losses of yield and, therewith, to a vary-
ing quality of the finished beer. In order to avoid the 1088
of the main bitter substances still occurring in the brewing
process as well as that in the further course of the beer
production, there hsve recently been developed so-called
, "isomer~sed hop extract~" which sre suitsble for addition to
I the beer after the fermentation. Although these iso-prepara-
tions may have, in contrast to umbellifer hops, the same
advantages as conventional hop extracts, namely the possibility
of standardising the bitter value and a greater uniformity and
improved stability, they still do not provide an optimsl
solution for the manufacture of qualitatively superior cold-
; Mez/23.10.1975 - 2 -
l . . . ~ ,
~0'~
-hopped beers, mainl~ for the following reasons:
All pre-isomerised products obtainable today still bring
about a more or less strong turbidity in the beer with cold-
-hopping so that the addition of such products must always be
carried out before the last filtration. ~he iso-extracts
obtainable do indeed represent a substantially more uniform
and better defined material with respect to the bitter substance
mixture present in hops, but they also contain, depending on
the manufacturing process, besides the iso-~-acids other
derivatives of the ~- and ~-acids in varying amounts. These
other derivstives can only be separated from the iso-~-acids
with difficulty and they disturb the bitter substance deter-
minations in cold-hopped beers so that it has hitherto not yet
been possible to agree upon a generally accepted procedure for
the analysis of iso-extracts. Finally, the gushing problem
occurr~ng in connection with cold-hopping can not yet be con-
~idered to be solved.
It has now been found in accordance with the present
invention that the aforementioned difficulties hitherto assoc-
iated with the cold-hopping of beers can be overcome in a
surprisingly simple manner by the use of practically pure iso-
-x,acids. Surprisingly, there can now be manufactured ~uality
; beers which are in no way organoleptically inferior to conven-
tionally brewed beers.
.i
2~ ~he present invention is based on the foregoing finding
and is particularly concerned with a process ior the manufac-
ture of beer or beer-like products which comprises using,
10'~10~0
instead of natural hops or extracts isolated from hops, certain
practically pure iso-~-acids, namely synthetically prepared
compounds of the general formula
,l
H~ (I)
~0
~ '.
wherein R represents a straight-chain or branched-chain alkyl
group containing up to 5 carbon atoms, or physiologically
tolerable salts thereof.
Since the compounds of formula I and their salts afore-
said are also suitable for the manufacture of non-beer-like drinks
having bitter flavour notes, the present invention is more generally
concerned with a process for the manufacture of bitter drinks or
for the bittering of drinks by the addition of synthetically
prepared compounds of formula I or physiologically tolerable
salts thereof to solutions suitable as drink bases.
The present invention is further concerned with bitter
substance solutions containing synthetically prepared compounds
of formula I or physiologically acceptable salts thereof which
1~'3 10 ~ ~
are suitable for the manufacture of bitter drinks, especially
beer and beer-like drinks, as well as with a process for the
preparation of such bitter substance solutions.
Preferred compounds of formula I are those in which R
represents an isoalkyl group (e.g. the isopropyl, isobutyl or
isopentyl group) although they do not differ substantially from
other members of this class (e.g. compounds in which R represents
the methyl, ethyl, secbutyl or secpentyl group) with respect to
the bitter properties. As physiologically tolerable salts of
compounds of formula I there may be mentioned salts with metals
which are permitted in foods such as alkali metal and aIkaline
earth metal salts, preferably the sodium and potassium salts.
~ he compounds of formula I possess two as~mmetric carbon
atoms and can accordingly be present in the form of racemates
or as optical antipodes. This is, however, not of significance
in connection with the present invention ~hus, formuls I
includes not only cis- but also trans-iso-~-acids and their
mixtures in any arbitrary weight ratio. ~y "practically pure"
compounds of formula I, there are to be understood such
compounds which are substantially free from impurities, espec-
ially free from the accompanying materials present in hops or
in natural extracts or extract fractions. Preferred "practic-
ally pure" compounds of formula I are those which have been
manufactured in a synthetic manner.
The compounds of formula I and their physiologically
tolerable salts are ~uitable for the manufacture of bitter
drinks or for the bittering of drinks of widely differing type;
iO~O
for example, alcoholic and non-alcoholic drinks such as
apéritifs, cordial bitter, beer, bitter liqueurs or bitter-
-tssting lemonades and mineral waters. The manufacture of
bitter drinks can be carried out in a simple manner by the
addition of a suitable amount of a compound of formula I or a
mixture of such compou~ds to the corresponding non-bitter drink
base, expediently in the form of a solution via suitable dosage
aggregates ~he concentration of compounds of formula I or
ph~siologically tolerable salts thereof in the finished drink
can be varied within wide limits. On the one hand, it can be
matched to the desire and custom of the end user and, on the
other hand, it can be kept constant with a high degree of
precision. Suitable concentration ranges of compounds of
formula I or physiologically tolerable salts thereof per 1000 ml
of drink are, for example, shown in the following ~able:
I
i DrinkPossible range Preferred range
Beer5-40 ppm 10-~0 ppm
Aperitifs10-60 ppm 20 '10 ppm
¦ ~emonade6¦ 2-40 ~pm ¦ 5-25 ppm
~he concent~ation of the compounds of formula I or
physiologically tolerable salts thereof in the bitter substance
solutions can likewise be ~aried within wide limits, the upper
limit being determined by the solubility of the compound and
the stability of the solution and the lower limit being prim-
arily determined b~ the expediency of adding the smallest
1~10~ ,
possible volume of bitter substance solution. ~hus, for
example, it is advantageous to choose the concentration of the
compound of formula I or physiologically tolerable sslt thereof
in the bitter substance solution such that by adding one volume
unit (e.g. 1 ml), the bitter intensit~ desired in the finished
drink is achieved. Suitable concentrations of such bitter
substance solutions lie, for example, between 0.1/oo and 10%,
preferably between 1/oo and 5%
By the addition of further flavouring and aroma substances
common in drink manufacture such as sugars, artificial sweeten-
ers, fruit extracts or synthetic aromas, there can be manufac-
tured drink concentrates from which the desired drink can then
be prepared by the end user by dilution in the desired manner
more or less immediately before the consumption of the drink
~he preparstion of bitter substance solutions can be
carried out by dissolving a compound of formula I or a physio-
logicall~ tolerable salt thereof in a suitable solvent, pref-
erably a physiologically tolerable organic solvent such as an
alcohol, especially ethanol, and bringing this solution to the
desired end volume, if desired with the addition of adJuvants,
with aqueous alkali and water As the aqueous alkali, there
is suitable, for example, an aqueous, especially 1-~, solution
of sodium or potassium carbonate, sodium or potassium
bicarbonate or potassium h~droxide, with potassium carbonate
being preferred.
The p~ ~alue of the bitter substance solution can lie
between 6 and 14, but it preferabl~ lies between 9 and 13. As
adauvants in the preparation of the bitter substance solutions,
1 0'3 ~
there may be mentioned, for example, stabilisers such as
alkyleneglycols, preferably propyleneglycol, or glycerine.
In the case of bitter substance solutions for the manufacture
of cold-hopped beers, a so-called gushing inhibitor may be
present as an ad~uvant to prevent the spontaneous overfoaming
of bottled beer. Surprisingly, it does indeed appear that b~
using practically pure compounds of formula I in the cold-
-hopping o~ beers, the cold-hopped beers almost alwa~s show a
substantially slighter tendency to gushing than conventionally
hopped beers. Accordingly, under certain circumstances the
addition of a gushing inhibitor can be dispensed with.
~ he preferred spplication of the process provided by the
present invention lies in the manufacture of beer, In principle,
compounds of formula I snd their aforementioned salts can be
used to manufacture not only top-fermented but also bottom-
-fermented beers. It iB readily possible to obtain the most
diverse types of beer ( common commercial differences between,
for example, lager beer, special beer, export beer, strong beer;
Bock, Double Bock; nutrient beer, diet beer etc), beer
fermentstions (subdiYision by wa~ of different contents of
original wort) or beer t~pes (difference according to colour,
bitterness etc, i.e, light, medium-coloured and dark beers,
e,g, the Pilsener, DortmNnder, Wiener, M~nchner or Kulmbacher
type) using the special customary techniques and the most
extensive know-how present in brewing technology. Moreover,
a particular advantage of the cold-hopping method in accordance
with the present invention, in contrast to conventional methods
of beer production, is that it is possib~`e to manufacture, with
a considerable saving of energy, relatively high-concentrated
~0 batches of smaller volumes (concentrated brews) which, towards
1(~'3~ U
the end of the process, are not only diluted to the desired
concentration but are also brought to the flavour of the
desired beer by the addition of a precisely defined amount of
a compound of formula I or a physiologically tolerable salt
thereof. The infusion process can be preferably used.
The compounds of formula I can be prepared, for example,
by converting a compound of the general formula
~H O
R (II)
HO H
, wherein R has the significance given
earlier,
by reaction with 1-(chloro or bromo)-~-methyl-2-butene
(prenylation) into a compound of the general formula
~ OH
1l
i ~ R
HO ~ OH (III)
;3`
3 10 ~ ~
, wherein R has the significance given
earlier,
oxidising a compound of formula III in methanolic solution by
means of air-oxygen in the presence of lead acetate and a
palladium catalyst to give a humulone or a so-called a-acid
of the general formula
OH O
o ~ H (IV)
OH
, wherein R has the significance given
earlier,
and isomerising a humulone of formula IV by heating under
alkaline conditions.
-- 10 --
lO~iO~O
The manufacture of bitter substance solutions in
accordance with the present invention is described hereinafter
in two Examples. Purthermore, tests for the cold-hopping of
beers carried out on a semi-technical scale according to the
process in accordance with the present invention are described,
Examples and ~ests
Manufacture of bitter substance solutions
1. 0.730 g of iso-co-~-acid (a compound of formula I in
which R represents the group) was dissolved in 8 ml of absolute
ethanol. 6 ml of l-N potsssium hydroxide and 4 ml of propylene-
glycol were added to this solution and the mixture obtained
was finally made up to 50 ml with distilled water. 1 ml of
this bitter substance solution contains the necessary amount
of bitter substance for the bittering of 600 ml of a normal
light lager beer.
2. 1.80 g of pure cis-/trans-iso-co-#-acid were dissolved
in 12 ml of absolute ethanol. ~he resulting ethanolic bitter
substance solution was added slowly with stirring to 15 ml of
a l-N potassium carbonate solution and finally made up to
100 ml at 20~C with distilled water.
Semi-technical te~ts for beer manufacture
with cold-hoPPiDg
1. Test material
Bitter substance cis/trans-iso-co_x-acid
preparation
1~3 1(J~ O
Unhopped beers - with normal concentration
- with high concentration
Water - demineralised, degassed
water
- normal brewing water.
2, ~est arrangement
Test Ao Unhopped light beer of normal
concentration filtered and
bottled
Test Al Unhopped light beer of normal
concentration filtered,
bittered with cis/trans-iso-
-co--Pcid and bottled
~est Bo Unhopped light beer of hi~h
concentration filtered,
diluted 1:1 with demineralised,
degassed water, imPre~nated
with C02 and bottled
~e~t Bl Unhopped light beer of high
concentration filtered,
diluted 1:1 with demineralised,
degassed water, bittered with
cis/trans-iso-coff-acid,
imPregnated with C02 and
bottled
U
Test C0 Unhopped light beer of hi~h
concentration filtered,
diluted 1:1 with de~assed
brewin~ water (circa TH 6
dH, CH 4-5 dH), impregnated
with C02 and bottled
Test Cl Unhopped light beer of hi~h
concentration filtered,
diluted 1:1 with de~assed
brewin~ water (circa TH 6 dH,
CH 4-5 dH), bittered with
cis/trans-iso-co-~-acid,
imPre~nated with C02 and
bottled
~N B. ~H = Total Hardness;
CH = Carbonate Hardness;
dH = German degrees of hardness]
3. Manufacture of u~hopped light beers
Raw materials ~ormal brewing wster for
light beers, bulking of only
light brewing malt
Yeaæt Auto-propagated in unhopped,
circa 12% wort
Manufacture - Bul~ing: Brew A 20 ~g malt
2~ Brew B 40 Xg malt
Brew C 40 kg malt
- Mashing: infusion process
steeping, gristing, rinsing
50C, pause 30' ~0C,
lO~
heating up to 62C, pause
60' 62C, heating up 70 C,
pause 60' 70C, heating up
75C, pause 15' 75C.
~otal mash 90 litres,
- Refining: pan-full of ssme
volume,
- Wort boiling: 100 min
- Wort treatment: whirlpool,
plate cooler, centrifuge,
aeration,
- Pitching: 6 C with 1 litre
of yeast per 100 litres of
wort, Brew B and C with
2 litres of yeast per 100
litres of wort,
- Main ferment: max.
temperature 9.5C, until
near to the final degree of
fermentation,
- Storage: normal, last
week -1C.
- 14 -
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- 19 -
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1~3 1(~ ~
In Figures 1-3 appended hereto, the fermentation diagrams
of Brews A. B and C are illustrated.
The bittering of the unhopped beers was carried out
according to the flow scheme illustrated in ~igure 4 appended
hereto by a continuous addition of a bitter substance solution
(prepared as described previously) by means of a dosage pump
to an aspired beer bitterness of 25 B.U [Bitterness Units].
In the clarification of the beers with normal and high
concentration, no striking difference with respect to the
filter output can be determined. After the bittering and
after addition of C02, the beers were bottled in the normal
manner via a pressure tank.
~ he results of the analyses of the output beers are
compiled in the following Tables.
- 21 -
lO~i(J~O
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-- 22 --
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- 27 -
~ 3 ~
Striking differences were noted between the individual
beers with respect to froth retention, This was clearly
assessed as normal in te~t Al and as low in the other te~ts.
The beers bittered with iso-co_a-acid consistently have a
substantially better froth retention than the unhopped beers,
this being particularly true in the case of the beers ~ and C
produced by dilution with water. The results of the beer
examination for gushing tendency are very interesting. While
the normally brewed, but unhopped, beer Ao showed a very strong
tendency for spontaneous over-frothing from the bottle, this
phenomenon clearly appeared less with the unhopped beer Bo and
especiQll~ with the beer C0 attenuated with brewing water. In
all three batches, the tendenc~ for gushing can be almost
completely eliminated by bittering with synthetic iso-co-a-
-acids. With all three beers A, B and C practically no
suspe~ded matter was formed by the bittering with iso-co-a-
-acids. This finding was confirmed by measurements carried out
one week after the addition of the bitter substance. It was
shown much more clearly that the iso-co-a-acids provide a
relatively high bacterio~tatic action since, after storage of
the bottled beers for nine weeks, only the samples treated
with the synthetic bitter substances were still blank, while
the unhopped beers already showed a sediment and a haze which,
as could be clearly determined by microscopic examination, was
attributable to a~ infection by Lactobacilli. The cold
stability of the beers bittered with iso-co-~-acids is also
clearly better in all three batches.
In the organoleptic testing of the beersJ in which in
each case two beers were compared with one another in a three-
- 28 -
10~3 ~
-cornered sample (three-glass sample), the beers bittered with
iso-co-~-acids were considered not only to be significantly
more bitter in contrast to the unhopped beers but also clearly
better. The bitter intensity appears stronger with beer Bl
than with Al, even stronger with Cl than with Al and stronger
with C1 than with Bl. ~he beer Bl diluted with demineralised
water was significantly superior to that attenuated with brew-
ing water. Between Al and Bl as well as Al and Cl, no clear
preference for one of the beers could be distinguished.
Manufacture of a bitter, non-beer-like drink:
1 part by volume of a base syrup (58,9 Bx), consisting of
Glucose syrup 8~.6 Bx (44 Be) 817 g
Sugar syrup 65 Bx 100 g
Citric acid (5 wt.% in water) 12 g
Potas~ium sorbate 1 g
Colour red (1 wt.% in wa-ter) 40 g
Isocohumulone solution (1% in water *) 10 g
~ Le~ ~4~0~1r;r~s
K ~ ~A _.~ 2 ~
Water 298 g
was diluted with 5 parts by volume of w~ter and the mixture
carbonated in the normal manner with 2.5 parts by volume of
co2.
~) Isocohumulone 1 g
Alcohol 96% 10 g
Potassium carbonate 1 g
Water ~B g
100 g 1% solution of isocohumulone.
- 29 -
The drink obtained was tested by a panel of specialists
and was described b~ them as being of pleasant and refreshing
character with a lasting bitterness, being characteristically
different from a sample bittered with quinine since it was
more reminiscent of bitter beer.
Manufacture of a bitter s~irit:
To 100.0 litres of a 42 percent by volume spirit
(prepared from 43.75 litres of 96% drinking spirit and 59.32
litres of distillad water; volume contraction 3,07 litres)
was added 1,00 litre of herb infusion and 0,50 litre of a 1%
iso-a-acid solution, there being used in each case a compound
of formula I in which R represents the isopropyl, isobutyl or
sec.butyl group. ~ach 100 g of the iso-a-acid solution
contained 1 g of isohumulone, 10 g of 96% alcohol, 1 g of
potassium carbonate and 88 g of wster.
The spirit thus-prepared was tested by a panel of experts
who characterised it as a striking, pronounced, bitter spirit
having a pleasant rounded note. In a test with a corresponding
sample prepared without isohumulone solution, this sample was
rejected as lacking the bitter note and the roundness of taste.
Manufacture of a bitter liauer:
~o 100 0 litres of a 35% liqueur (prepared from 36.46
litres of 96% drinking spirit, 22.15 litres o~ a 6~ percent
by weight sugar solution and 44.63 litres of distilled water;
volume contraction 2.64 litres) was added 1.00 litre of herb
infusion a~d 0,50 litre of a 1% iso--acid solution, there
being used in each case a compound of formula I in which
- 30 -
10'~10~
R represents the isopropyl, isobutyl or sec.butyl group. Each
100 g of the iso-c-acid solution contained 1 g of isohumulone,
10 g of 96% alcohol, 1 g of potassium carbonate and 88 g of
water.
The drink thus-prepared was described by a panel of
experts to be a full, aromatic liqueur having a pronounced
bitter character, It was especially emphasised as a desirable
feature that the bitter note rapidly faded and did not remain
in the mouth for as long as in the case of comparable commercial
products. Compared with the aforementioned drink, a correspond-
ing sample, prepared without isohumulone, was re~ected as
being uncalibrated, insipid and uncharacteristic.
