Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to the field of brewing.
More particularly, the present invention relates to a method
for brewing a non-alcoholic beer. As used herein, and as
generally accepted in the brewing industry, the term non-
alcoholic beer refers to a brewed malt based beveragecontaining 0.5% or lower ethyl alcohol by volume.
The market niche occupied by non-alcoholic beers has
traditionally been quite small, since throughout history and
to the present, the presence of alcohol has been a natural and
desirable characteristic of beer. The alcohol in beer is
produced by fermenting wort with yeast. Wort is a solution
produced by mashing ground barley malt, with or without
additional fermentable foodstuffs such as corn or rice (known
generally as adjuncts), in a large quantity of hot water, to
extract sugars and other soluble substances such as low
molecular proteins and polysacharides from the malt and
adjuncts. Hops are added to the wort as it is boiled to
provide the bitterness that is a characteristic of beers in
general.
Traditionally, after a wort has been prepared, it is
pitched with yeast and permitted to ferment, until the yeast
has consumed all or substantially all of the fermentable
extract in the wort. The major portion of fermentable
carbohydrates will have been converted by the yeast into ethyl
alcohol and carbon dioxide, and the flavour of the resultant
beverage (after filtration and finishing) will be easily
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recognized as beer. This flavour is essentially a combination
of three factors: the bitterness contributed by the hops, the
distinct flavour of the unfermentable constituents from the
barley malt which are not digested by the yeast, and aroma
substances, generally considered fermentation by-products
contributed by the yeast.
It will be understood, then, from the foregoing brief
discussion, that two of the three things that go into the
flavour of beer - malt and adjunct residues, and hop bitterness
- are introduced during the wort making process, before any
fermentation or ethyl alcohol production has occurred.
Techniques have been developed, therefore, to bring the flavour
components contributed by the yeast into beer without having
the yeast consume the fermentable sugar in the wort and thereby
produce alcohol. Such techniques are generally known as cold
contact brewing, and are utilized in various forms for the
brewing of non-alcoholic beer.
It will be understood, then, that the present invention
relates, in general terms, to a cold contact brewing method.
In the present invention, to enhance the flavour of the
beer, unwanted hydrogen sulphide is eliminated during brewing.
This is one of the most common detractions from the taste of
beer, and is a common sulphur based compound produced as an
undesirable by-product of yeast metabolism during primary
fermentation of beer. Hydrogen sulphide is usually present in
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finished beers at levels of 2 to 15 ~g/l. However, levels
above 5 ~g/l detract from the aroma and palette of the beer.
Hydrogen sulphide levels follow the yeast budding index and
thus rise and fall several times during fermentation; this
makes control of this undesirable flavour compound difficult,
particulary when fermentations have to be prematurely stopped
in order to limit alcohol production. Therefore, a method has
been incorporated for removing hydrogen sulphide from non-
alcoholic beer production in the present invention and thereby
improving the flavour of the finished beer.
Schur, in U.S. Patent No. 4,661,355 describes a PROCESS
FOR THE PREPARATION OF ALCOHOL-FREE DRINKS WITH A YEAST AROMA,
which comprises contacting a prepared wort with a thick,
alcohol-free yeast slurry harvested from a fermentation
process, at a temperature below 3 C, preferably below 0 C. At
these low temperatures, the yeast will not ferment the sugars
in the wort, but after a time of 24 to 48 hours, a sufficient
quantity of yeast aroma substances will have been released from
the yeast to override wort taste. A drawback of the technique
described by Schur is that it is difficult to maintain a near
freezing temperature in the wort during the entire yeast
contact period. As well, at such low temperatures the
metabolic activity of yeast occurs at such a low rate that the
amount of aroma substances released into the beer is not
sufficient to overcome the worty taste. Also, at temperatures
so nearly approaching freezing, ice formation is a significant
problem.
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A PROCESS FOR PREPARING A NON-ALCOHOLIC MALT BEVERAGE is
disclosed by Huige et al in U.S. Patent No. 4,970,082. In that
patent, a combination of four essential process steps is
described for brewing a non-alcoholic beverage. The steps
described by Huige et al include: (i) producing a wort having
a high (14-20%) extract concentration that includes fermentable
sugars; (ii) obtaining a yeast slurry from a previous ordinary
beer fermentation, the slurry containing from 10 - 20% yeast
solids and the remainder beer; (iii) pitching wort with yeast
slurry; and (iv) fermenting the pitched wort for 30 minutes to
10 hours at about 3 C to about 7 C. The thereby obtained
beverage has an alcoholic concentration of about 1% to 2%, but
it is subsequently brought down to less than 0.5% by dilution
with carbonated water. In the Huige et al process, great
emphasis is placed on having little or no oxygen in the
fermenter, to reduce aldehyde formation.
While the product of the Huige et al process is considered
an acceptable non-alcoholic beverage, its flavour
characteristics strongly reflect the make-up of its original
ingredients. In particular, the Huige et al process states 14%
as an essential minimum extract content in the wort which it
utilizes. Moreover, of this 14%, a minimum of 40% is composed
of corn syrup. Therefore, it will be understood that the yeast
fermentation of Huige et al converts only a minimal percentage
of fermentable extract to ethanol and CO2 at the low
temperature at which it is carried out. Accordingly, the
resultant brew will have a fairly high sugar content, relative
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to fully fermented beer that exhibits little or no sugar
(monomer or dimer) content.
In view of the foregoing, an object of the present
invention is to provide a method of producing a non-alcoholic
beverage having a true beer flavour. A further object of the
present invention is to produce such a non-alcoholic beverage
with less sweetness and worty taste than known non-alcoholic
beers by adopting a novel cold fermentation scheme.
In one broad aspect, therefore, the present invention
relates to a method of brewing a malt beverage having a low
alcohol content, including the steps of: (a) preparing a malt
and cereal mash, said mash having a significantly greater malt
content than cereal content; (b) lautering said mash to obtain
an infusion having an extract content below about 14% by weight
and boiling said infusion to obtain a wort; (c) adding a
predetermined quantity of hops to said wort; (d) aerating said
wort to an oxygen content of 15 - 35 mg per litre; (e) pitching
said wort with a yeast slurry to provide a cell count of about
80 to about 180 million yeast cells per ml; (f) fermenting the
pitched wort at a temperature of about 3 C to about 10 C for
1 to 40 hours; (g) removing the yeast from the fermented wort;
(h) filtering the resulting brew; (i) electrolyzing the
resultant brew with a copper electrode to remove HaS; and (j)
adjusting the alcohol concentration of the brew with carbonated
water to a preselected level, and then aging the resultant brew
for at least 24 hours.
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The present invention utilizes as a base a malt and cereal
infusion, boiled to prepare a wort. In contradistinction to
the Huige et al process, however, the wort of the present
invention is prepared utilizing a significantly greater
proportion of malt than of adjunct cereals. Typically a ratio
of two-thirds malt, one-third corn syrup, by weight, is used
to produce a wort containing a higher proportion of flavour
constituents derived from malt. Moreover, in the process of
the present invention, it is important that the total
percentage, by weight, of the malt and cereal extract in the
prepared wort to be kept below 14%. The applicant has
determined that the extract concentration in excess of this
level will result in a finished product, after fermentation,
that will have a taste substantially contributed to by the
presence of unfermented extract from the wort. At wort
concentrations below 14% the amount of unfermented extract in
the beer will be lower and thus contribute less of a worty
taste to the final product.
After preparation and hopping (according to known hopping
methods) of the wort, it is aerated with compressed air or
oxygen to an oxygen content of approximately 25 mg per litre.
This is a significant departure from the prior art, which
specifies that the wort be deoxygenated, or purged with carbon
dioxide to ensure a dissolved oxygen free environment for the
following fermentation. The reason given by Huige et al for
deoxygenation of the wort is to provide a reducing environment
conducive to allowing yeast to reduce aldehydes. However, the
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applicant has observed that it is more effective to focus on
the elimination of H2S during beer processing than providing a
non-aerated wort at pitching. Accordingly, in the present
invention, the wort is oxygenated to a level selected to secure
yeast growth.
The aerated wort is then pitched with a yeast slurry
harvested from a completed fermentation. The wort is pitched
with a large quantity of yeast possessing a viability of at
least 90~ and a cell count of 80 to 180 million yeast cells per
ml. The wort is then fermented at from 3 to 10C for 1 to 40
hours. The applicant has determined that a 6 hour fermentation
at 6C is usually sufficient to provide in the brew an
acceptable level of yeast flavour components, and to ferment
a sufficient quantity of the fermentable sugars in the wort to
reduce the sweetness of the brew to within acceptable levels.
After fermentation for the desired period of time, the
yeast is quickly removed. It is essential that yeast removal
be accomplished as efficaciously as possible, to prevent
continued fermentation and to maintain product uniformity.
Accordingly, it is preferred that the yeast be centrifuged from
the partially fermented brew by a centrifuge that has been
adapted to handle a high solids load in a short period of time.
The beer is then chilled to 0C, which precipitates out many
colloidal substances such as proteins, and treated with a
silica gel that functions as a flocculant to clarify the beer.
The clarified beer is then acidified to a pH of below 4.3 using
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a food grade acid such as phosphoric acid, the selection of
which will be a matter of choice for the skilled brewer. By
bringing the pH of the partially fermented brew down from its
naturally occurring pH of about 5.2, which is in the neutral
range, to about 4.3, which is very mildly acidic, a more
acceptable beer taste is obtained, closer to that of fully
fermented beer.
At this point in the process of the present invention, the
alcohol concentration will be significantly above the target
level of 0.5%. Therefore, carbonated, deaerated water is then
added to the brew, to bring the alcohol concentration to a
level just above the target level. The brew is then aged at
0C for 24 hours minimum, and is filtered through a layer of
course and fine grade kieselguhr to further clarify it and
remove any haze particles after which carbonated deaerated
water is added to adjust the alcohol content to the precise
concentration desired.
The bitterness of the beer is then adjusted to produce a
beverage that is well balanced in its flavour congeners. At
this stage, any minor colour changes desired may be made using,
for instance, caramel.
As a final step in clarifying the beer and eliminating any
unwanted taste components, the beer is electrolysed by a copper
electrolysing unit. This unit gradually dissolves minute
amounts of copper ions into the beer, to rid the beer of any
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hydrogen sulphide that may be present. This process is carried
out in an electrolytic cell by passing beer between two
electrolytically purified copper plate electrodes. The
electrodes are housed in an insulated pipe such as, although
not limited to, a polychlorylvinyl pipe with an inner teflon
coating to prevent leakage of the applied current through the
housing during use. The beer is passed through this pipe on
its way to the filter. The cell also contains a power supply
capable of applying 24 D C with a continuous and repetitive
reversing of polarity. The reversing polarity is controlled
by a solid state repeat cycle timer. This continuous switching
of polarity prevents the electrodes from excessive surface
damage or coating while acting as a cathode, and allows for an
equal disillusion of the electrode while acting as the anode.
During this process, the sulphur of the hydrogen sulphide is
precipitated out as copper sulphide, and the associated sulphur
flavour is thereby eliminated.
The applicants have discovered that by electrolytically
ridding the beer of H2S, a substantial advantage is gained, and
to a large extent, the cold fermentation process is made more
practical than was previously the case. That is, a large
quantity of viable yeast is required to be added to the wort
for fermentation, and a natural by product of yeast growth is
H2S. Due to the presence of such a large quantity of yeast,
H2S will tend to build up quite quickly in the fermenting brew,
and will remain dissolved therein, because of the low
temperature at which the fermenting brew is maintained.
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The beer is then filtered one more time to remove any
precipitant. The filtered beer is then carbonated to the
desired level, bottled or canned and pasteurized.
It is to be understood that the examples described above
are not meant to limit the scope of the present invention. It
is expected that numerous variants will be obvious to the
person skilled in the brewing art, without any departure from
the spirit of the present invention. The appended claims,
properly construed, form the only limitation upon the scope of
the present invention.
