Note: Descriptions are shown in the official language in which they were submitted.
3051
--1--
BEVERAGE F ILTRATI ON PROCES S
This invention is concerned with preventing haze
development in alcoholic and fruit beverages and more particu-
larly with the removal of haze precursors from such beverages
5 by treatment with positively-charged media.
The develspment of haze in alcoholic and fruit beverages
has long been a distinct problem. The development of haze in the
beverage of course is undesirable from the viewpoint of product
aesthetics and eye-appeal. In addition, haze development can
10 result in loss of product color as well as taste notes. Solution
of this problem has been attempted by several different
approaches. The most commonly employed method for coping with
the haze problem in alcoholic beverages has been a procedure of
reducing the temperatures of the beverage, e.g., beer, wine,
15whiskey, fortified wine products (sherry, brandy and cognac),
rum, certain white and red wines, liquers and cordials, to
cause haze formation at temperatures below about 45F. and
most commonly at between about 20 and 30F. During such
chilling, the haze precursors apparently separate out as the
20so-called "haze" which can be then separated using known
techniques such as filtration. In many cases, such treatment
by chilling is not completely effective and several chilling,
and precipitation, treatments may prove necessary. As an
alternative to chill processing, attempts have been made to
25detexmine the amount of the precursors of haze in the grains
employed in the production of specific beverages, e.g., by
extraction of the malt employed in the production of beer.
As a result of such determinations, grains of low haze-
precursor content can be selected to produce beverages of low
30potential haze. Such procedures are costly and time-consuming.
Although this approach can result in amelioration of the haze
problem, it rarely can result in elimination thereof.
The haze problem has been investigated quite
extensively but the exact nature of the haze has not been
:
i
-- 2 --
established. In beer, the formation of haze is attributed to
the presence of phenolics as described, for example, in MsAA
Technical Quarterly, Vol. 14, No. 4, 1977, p. 250, "Complex
Phenols in Brewing - A Critical Survey" by R.J. Gardner and
J.D. McGuinness, and ~he Brewers Digest, April, 1978, p. 36,
"Determination of Phenolic Compounds in Beer and Brewing
Materials" by Miroslar Dadic. In some whiskeys, haze is
attributable to the presence of steroids which precipitate on
chilling.
In fruit beverages, the haze problem has been treated
primarily through the used of enzymes which hydrolyze the pro-
teins which normally form haze with the phenolic components of
the fruit preparation. Such beverages include, for example,
apple, cranberry, grape, citrus fruit, peach, pear, plum,
apricot and nectarine juices.
For the purpose of this disclosure, beverages to be
treated in accordance with the invention are those derived from
vegetable origin which form a haze on standing and/or chilling,
i.e., are defined as unstable beverages. After treatment in
accordance with the invention, the beverages form litt]e, if
any, haze under storage or chilling at the very least. me
tendency toward haze formation is reduced as a result of treat-
ment by the present process.
BRIEF DESCRIPTION OF THE INVENTION
This invention provides a process for treating un-
stable beverages as defined herein, with a sanitizable or
sterilizable charge-modified high-surface area medium to in-
itiate haze formation in unstable beverages, especially alcohol-
ic beverages. After formation, the haze can be removed by con-
ventional methods, as by filtration using art-recognized pro-
cesses.
In accordance with the present invention there is
provided a process for removal of haze percursors from unstable
æ~3~
- 2a -
beverages which comprises the step of contacting said beverage
with a positive-charge modified porous medium comprised of fine
particulate, the charge being modified with a polyamido-
polyamine epichlorhydrin cationic resin, to form a precipitate
and removing said precipitate from said beverages.
The step for forming the haze can be repeated as often
as required, for example, several timesl to ensure that the
beverage is stabilized, i.e., will not develop haze on cooling
or prolonged standing, although normally one such contact step
is all that is required to attain reasonable stability.
,1~
--3--
In one em~odiment of the invention, the charge-
modified, high-surface area medium is in the ~orm of a filter
medium through which the selected beverage is passed in a
suitable filter device. As the beverage passes through the
5 filter medium, haze becomes evident in the effluent beverage
which can then be filtered using conventional filtration
means. In a preferred form, the filtering device is fitted
with one or several additional filtering media downstream of
the first filter medium to filter the haze formed when the
10 beverage passes throu~h the first filter medium. The
additional filter media can be any of the conventionally
employed filters known to the art, e.g., acid-treated asbestos.
Thus, by use of the present invention, the haze problem
in unstable beverages can be substantially eliminated employing
15relatively simple and economical procedures which readily lend
themselves to incorporation during ordinary processing of the
beverages treated. For example, filtration steps are commonly
employed in beer and wine production and it is possible to
incorporate the present process into the normal filtration
20processing of these beverages by providing the re~uisite
charge-modified, high-surface area medium to the filtration
system in a form adapted to the particular filtration system
employed.
The present invention can be used as the sole means
25 for removal of haze, or alternatively can be used along with
other ~nown methods of haze removal. Thus, a combination of
chill treatment and contact treatment in accordance with the
invention can be used either as separate steps or simultane-
o us ly .
The charge-modified, high~surface area media to be
employed in the present inventio~ are comprised of fine
particulates, such as diatomaceous earth and perlite,
modified with polyamido-polyamine epichlorohydrin cationic
resin. The fine particulates are advantageously supported in
3 ~
--4~
1 a fibex system in the form of filter medium, preferably in
the form of sheets formed from the filter medium.
In accordance with this preferred form of the present
invention, charge modified filter media sheets are prepared
5 utilizing in sheet formation a fiber system for the self-
bonding media matrix incorporating beaten cellulose fibers,
usually a moderately to highly beaten pulp/ to provide a
fiber system having a Canadian Standard Freeness of 100-600
ml. preferably 200-300 ml. or less. The provision of shorter
10 or more fibrillated fiber permits the retention o~ fine
particulates ranging in the preferred embodiments upwards of
50 percent up to 70 percent or more by we ght of the sheet.
The charge modifier selectively employed for the
preparation of sanitizable or sterilizable filter media is a
15polyamido-polyamine epichlorhydrin cationic resin which
resists degradation in such treatment and retains positive
charge potential. Thus, sterilizable filter media may be
formed which are non-toxic, exhibit less than 1.5~ extractables
and are efficacious in use despite autoclaving conditions of
20 e.g., 130C. under 15 lb. pressure for 1 hour or hot water
flushing at 180F. for 1 hour at a flow rate of 225 cc/min.
The filter media sheet, preferably formed by vacuum
felting of a cationically disperse aqueous slurry comprlsing
beaten cellulose fibers and fine particulate shows a unlform,
25 high porosity, and fine pore size structure with excellent
filtration and flow characteristics.
It will be understood that charge-modified fine
particulates in accordance with the present invention can be
used in art-recognized methods to provide the necessary con-
30 tact of the unstabilized alcoholic beverage with the saidparticulates such as the usual filter bed made up of the
particulate matter. However, the invention will be described
in terms of the preferred embodiment which employs sheet
filter media.
~ ~24~8
--5--
1 The results obtained with the positively-charged media
of the present invention are indeed surprising and unexpected
in view of the results obtained with other positively-charged
media. For example, comparable filter media comprised of
5 cationic colloidal silica as a charge modifiex have been used
in an attempt to stabilize alcoholic beverages and the results
obtained indicate non-uniform results, with considerably less
effectiveness than obtained with the present media. When the
charge modifier is cationic melamine-formaldehyde no haze
10 formation occurs.
Since the invention is particularly suitable for
stabilizing so-called "unstable" alcoholic beverages, it will
be described in terms of such beverages in which the lack of
stability is a particularly insidious problem. It should be
15 understood that the invention is also applicable to fruit juices
and other similarly unstable liquid products.
DETAILED DESCRIP~ION OF THE INVi3NTION
. . ~
The filter media sheets of the invention are pre-
pared from cationically modified filter elements, usually in
20 tne form of a cationically disperse aqueous slurry comprising
cellulose fiber and optimized levels of fine particulate such
as diatomaceous earth or perlite. The filter elements may be
cationically modified in the slurr~ and the sheet prepared
dynamically by vacuum felting, and drying, or the filter
25elements may be pretreated and formed into sheet media. A
special feature of the invention is the provision of filter
media sheet in which the level of particulate retained is
enhanced as compared to sheet prepared conventionally.
The state of refinement of a wood pulp fiber is
30determined by means of a "freeness" test in which rreasurement
as the flo~ rate through a forming pad of the fibers on a
standard screen is determined, most commonly utilizing the
"Canadian Standard Freeness Tester". In this method, the
quantity which is measured is the volume of water (e~pressed
35in ml.) which overflows from a recciver containiny an orifice
~ ~2~8
--6
loutlet a~ the bottom. The Canadian S~andard Freeness measu,e-
ments are ~mployed in the present speciLica~ion. Coarse
unbeaten wood pulp fibers produce high drainage rates into
the receiver from the screen resulting in larye overflow
5 volumes, and hence xecord a high freeness. Typical wood
pulps show Canadian Standard Freeness values ranging from
~00 ml. to +800 ml. In paper or filter media manufacture,
such pulps may be subject to mechanical refining processes
such as beating, which tends to cut and/or ~ibrillate the
lOcellulose fibers. Such beaten fibers exhibit slo~ler drainage
rates, and, therefore, lower freeness.
In accordance ~ith the present invention, such
beaten pulp is employed in the self-bonding matrix for the
filter media. The Canadian Standard Freeness of the pulp
15 system will vary with pulp selection, and may be reflective
of varying states of subdivision or refinement, as where
different pulps or dif~erently beaten pulps are combined for
sheet formation, but the beaten pulp will be employed to
provide a composite or average value ordinarily ranging from
20 100 to 60G ml., with lower values, e.g., 200-300 ml. or less
being preferred for higher solids retention.
The wood pulp may comprise as little as 10 percent
by weight with up to 20 to 30 percent, by weight of the total,
being preferred to provide filter media sheet with structural
25 characteristics suitable for industrial filtration applica-
tions.
The amount of fine particulate in the filter media
sheet is dependent to some extent on the performance require-
ments. While as little as 10 percent of a fine particulate
30 will suffice for many purposes, optimum performance is
achieved by utilizing the ma~imum amount of fine particulate.
For industrial filtration, structural characteristics suggest
a practicable maximum of about 70 percent by weight. Of
course, for less demanding applications, somewhat higher
l 1~2~
-- 7
levels will be possible. Generally, levels of 50-70 percent by
weight are employed.
There are various types o-E fine anionic particulates
that are suitable for the intended purpose, including diatoma-
ceous earth, perlite, talc, silica gel, polymeric particulates
such as those produced by emulsion or suspension polymerization,
e.g., polystyrene, polyacrylates, poly(vinyl acetate), poly-
ethylene, (or other such materials as described in Emulsions
and Emulsion Technology, Lissant, Kenneth J., Marcel Dekker,
1974) activated carbon, molecular sieves, clay, etc. Function-
ally, the fine particulate should have a specific surface area
in excess of one square meter/gram and/or particle diameters of
less than 10 microns. In a broad sense, any fine particulate
may be suitable ~such as J.M. Filter Cel, Standard Super Cel,
Celite 512 , Hydro Super Cel , Speed Plus and Speedflow ;
Dicalite 215 and Dicalite 416 and Dicalite 436 ) and may be
evaluated by techniques well-known to the art. From the stand-
point of size, morphology, cost, fluid compatibility and general
performance characteristics, the finer grades of diatomaceous
earth and perlite filter aids exhibiting a mean particle size of
less than 5 microns are preferred. In many cases, mixtures of
more than one type of fine particulate such as diatomaceous earth/
perlite for example, in proportion by weight of from about 80/20
to 20/80 give better filtration performance or better cost/per-
formance chara¢teristic~ than that achieved by the use of any
single type by itself. Similarly, mixtures in all proportions
of relatively coarse and fine particulates, e.g., 50/50 parts
* Trademark
..
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- 7a -
by weight of 10 and 5 micron diameter particulates may be used.
Suitable polyamido-polyamine epichlorhydrin cationic
resins are those of U.S. Patents 2,926,116; 2,926,154; 3,224,986;
3,332,901 and 3,382,096 and may be produced by reacting a di-
carbo~ylic acid with a polyamine dimer to form a water soluble
polymer which is
,S/.
~ ~6~438
--8--
1 further reacted with epichlorhydrin. The dimer unit may have
the general formula: -
2 ~(C~l2)2-N~I]x(c~2)2-NH2
5 where x is an integer of 1 to 7, and the dicarboxylic acid
may be aromatic or aliphatic such as adipic, azelaic, digly-
colic, oxalic or malonic acids. The cationic charge is
induced through the amine function in tertiary or quaternized
configuration. Other suitable charge modifying resins, employ-
lO ing a heterocyclic dicarboxylic acid reactant are disclosed inU.S. Patent 3,761,350. The polyamido-polyamine epichlorhydrin
cationic resins are available commercially, as Polycup 1~84,
2002 or S2064 (Hercules); Cascamide Resin pR-920 (Bordon); or
Nopcobond 35 (Nopco)~
In paper production, where cationic charge modifiers
are sometimes used, the objective is reduction of charge
to approximately the isoelectric point to maximize efficiency
in interfelting of fiber. For filtration, maximum charge
is desired to enhance removal of charged particles by
20elect~okinetic mechanisms~ In the present case the surface
charge of at least one of the negatively charged filter
elements i.e., cellulose and particulate is reduced to render
the surface less electronegative and optionally (and prefer-
ably) reversed by the deposition of sufficient cationic
25charge modifiex to render the surface electropositive, to
provide at least certain electropositive regions or sites
within the filter sheet. In order to accomplish charge
reversal, of course, one proceeds through the isoelectric
point, and then positive charge buildup is accomplished to the
30maximum practical level.
The amount of charge modifier employed in the
present invention is thus preferably that sufficient to at
.~ ~rc~e~q~rk
~ ~243~
g
1 least provide a cationically disperse system iOe., a system in
which no visible flocculation occurs at ambient conditions in
the absence of applied hydrodynamic shear forces. The system
therefore comprises essentially discrete fiber/particulate
5 elements exhibiting a positive charge or zeta potential
relatively uniformly or homogeneously distributed in and
throughout the aqueous me~ium. The specific level ~lill,
of course, vary with the system and the modifier selected but
will be readily determined by one skilled in the art. For
10 example, the inflection point on a plot of particulate
retention vs. amount of charge modifier approximates the
minimum level for better performance. Thus, a 2 percent level
is appropriate for a polyamido-polyamine epichlorhydrin resin.
Although additional modifier may be employed to advantage
15 where desired, this level represents the best balance on a
cost/performance basis. Premodified filter elements e.g,,
particulate precoated wi~h charge modifier may of course be
incorporated in any manner into filter sheets with similar
results, and where a cationically disperse slurry is not
20employed, charge modification will be commensurately reduced
by control of modifier leveis.
The charge modification effected is demonstrable in
measurements of surface zeta potential, and in improved filtra-
tion efficiency for negatively charged particles in liquid
25systems.
The slurry of pulp and particulates is forred in any
suitable manner. The sequence of adding these components
to ~ater to form the initial ,slurry appears to be relatively
unim~ortant. The consistency of the slurry will represent
30the highest possible for a practical suspension of the
components, usually about 4 percent. The system is subjected
to hydrodynamic shear forces as by a bladed mixer, and the
charge modifier is then added to the slurry.
~ ~24~
-10-
1 The shear level is not critical i.e., any otherwise
suitable shear rate or shear s-tress may be employed havlng
regard for available equipment, preferred processing times
etc. but is selected and emplo~ed simply to break up the
5 flocs and maintain the system in a dispersed condition during
treatment. Of course, upon the formation of a cationically
disperse slurry, the system is free of floc formation even
in the absence of applied shear.
A~ter charge modification, the slurry is diluted
10 wi~h additional water to the proper consistency required for
vacuum felting sheet formation, ordinarily 0.5 to 2 1/2
percent, depending upon the t~pe of equipment used to form
the sheet, in a manner known to ~he artisan. The slurry is
formed into a sheet and oven dried in standard manner. The
15performance of the sheet is related to the drying parameters
and optimized conditlons may reflect energy considerations or
desired thermal history consistent with minimization of
unnecessary exposure to elevated temperatures, especially as
the decomposition or scorch point for the system is approached.
In accordance with a preferred embodiment of the
invention, filter media sheets are formed from filter elements,
i.e., particulate and a self-bonding matrix of cellulose pulp at
least one of which is charge modified, the pulp being a system
incorporating beaten pulp to provide a Canadian Standard Free-
25ness of up to 600 ml., preferably less than 300 ml. e.g.,100-200 ml. the charge modifier consisting of a polyamido-poly-
a~ine epichlorhydrin cationic resin, and being applied in a
proportion to reduce electronegativity of the surface, preferably
to achieve charge reversal beyond the isoelectric point, e.g.,
30to an add-on level of about 2~ by ~7eight. Filter media sheets
so~ prepared may be autoclaved, hot water flushed or other~7ise
treated at elevated temperature to sanitize or sterilize the
structure.
l 16~
1 For the purpose of the invention, it is sufficient to
merely contact the selected unstabilized beverage with the
positively-charged particulates and the haze forms as a result
of such contact. The manner of contact is not critical and
5 usually is selected as a matter of convenience. F~r example,
the most convenient method employs filter media, the preferred
form of the described particulates, and contact s accomplsihed
by merely passing the unstabilized beverage through the filter
medium in a suitable filter device with haze forming in the
lObeverage after passing through the medium. The formation of
haze is usually completed within a short period after contact.
For example, the haze is substantially completely formed within
about a minute, and even less, ater contact and can then be
removed, e.g., by filtration using filters suitable to removal
50f the haze. If desired, haze formation can be allowed to
proceed for long periods of time, even to 16-20 hours before
filtration, but the increased amounts of haze formed are not
significant so no advantage is realized by long standing. On
the contrary, the more desirable would be shorter standing time
20for haze formation, usually for time periods of about one
minute before final filtration of the haze to produce stabilized
beverage.
To assure beverage stability, particularly when treating
large volumes of beverage, in particular on continuous basis,
25the filtering system employed can include a series of the
positively-charged filter media to provide successive contacts
with the treated beverage and these media may optionally be
separated by second filters to remove haze, resulting in
successive exposures of the unstabilized beverage to the
3necessary contact step required by this invention. The number
of such positively-charged media necessary to accomplish the
re~uired result can, of course, be readily determined by
~ tB2~8
-12-
l routine experimentation and will be determined in part by the
rate of flow of the beverage through the positlvely-charged
media in the series. For most purposes, a series of two such
filter media should suffice to precipitate substantially all of
5 the haze components. To maximize the effect of each, the filter
media should be spaced to provide sufficient time for haze
formation to occur after the beverage passes through each
positively-charged medium, say l/2 to one minute during which
most haze will have precipitated. The arrangement of
lO successively-placed media can then be followed by suitable
filter means to remove haze from the stabilized beverage which
results.
Employing the positively-charged filter media in
accordance with this invention, the unstabilized beverages
15 form a more abundant and finer haze than obtained by the usual
chilling processing. For example, using a preferred filter
medium, the turbidity of an unstabilized beverage (blended
whiskey) increases from about 2 NTU to 8 NTU on passing once
through the medium at ambient temperature whereas the same
20 beverage, on chilling to 50F., showed a turbidity of slightly
more than 4 NTU. In both instances, final filtration through
an asbestos filter gave liquid product of a turbidity o~ less
than l NTU. The product stabilized in accordance with the
invention showed remarkable long-term stability when compared
25with the chill-hazed product. Under accelerated conditions of
storage, the latter showed twice the instability as measured
by turbidity measurements.
~he following examples further illustrate the invention.
The filter sheets useful for the present process are
30prepared in accordance with the following procedure: all sheets
were prepared utilizing Weyerhauser Coho Kraft pulp, beaten~to
the levels indicated below, and Grefco Dicalite 416 Perlite,
having a mean particle size of 3~9 microns.
~ r~Je ~k
2~
-13-
1 The charge modifier employed in these runs was
cationic polyamine-polyamide epichlorhydrin resin (Hercules
Polycup 18$4, about 100000 mol. wt.; about 150A particle size).
The total input weight (bone dry basis) of the
5component materials was 80 grams, exclusive of charge modifier.
A constant proportion of pulp (30 percent by weight, or 24
grams) and particulate (70 percent by weight, or 56 grams) was
maintained. The components were added to water in a 1 liter
polyethylene bucket, with strong agitation, to ~orm an aqueous
slurry at two percent consistency, and the charge modifier
added. (The system was subjected to hydrodynamic shear by
action of a Hei-Dolph stirrer (Polyscience Inc.), having 4
propeller blades, rotating at about 700 rpm on setting 2.)
The slurry was subsequently diluted to 0.5 percent consistency
15and vacuum felted into a sheet ranging from about .160 to .200
inch thickness ~depending upon retention) in a nine inch by
twelve inch hand sheet apparatus utilizing a 100 mesh screen.
The sheet was subsequently removed, dried in a static oven at
350F. until constant weight was achieved, and the final weight
20recorded. Comparison of the final sheet weight with the total
input material weight allowed determination of total solids
retention in the sheet.
Using this procedure, the following filter sheets can
be prepared. All sheets showed good flow characteristics.
3o
~ rr~J~ ~a~k
~ ~6~3~
1 TABLE I
Pulp Charge Solids
Sheet Freeness Modif ier Retention
No (CSF) Content (Wt.%) Percent
660 2 73 . 8
2 660 2- 74 . 5
3 660 2 88 . 5
4 520 2 86.1
S 2 0 2 8 6 . 9
6 400 2 86.1
7 400 2 8609
8 320 2 87 . 2
9 320 2 ~
200 2 88 . 2
11 200 2 92 . 4
5l2 llO 2 91. 6
13 llO 2 93. 0
3o
~ 1 ~0ZA~
-15-
1 EXAMPLE l
Blended whiskey was stabilized by treatment with
activated carbon tl lb. of carbon per lO00 wine gallons)
and diatomaceous earth. It was filtered through a 4-inch
5 disc using lO psi of air pressure in a pressure vessel.
The results obtained with 2 filter media (Filters 1 and 2)
prepared in accordance with the present invention ~sheet 12
in Table l) are given in TABLE l. Also included are the
results with Filter 3 (a positively-charged filter medium ln
lO which as charge modifier is present cationic colloidal
silica) and Filter 4 (a commercial fil~er medium consisting
of diatomaceous earth, cellulose and acid-washed asbestos
fibers).
Filter
-l ~ 3 4
Filtration time (sec.) 38 90 75 23
pH (initial = 4.1) 4.3 4.3 4.5 4.6
Color (KV) (initial = 85) 5~ 33 59 75
Turbidity (JTU) 6,3 2.8 .27 .18
20 Turbidity (after 24 hrs) 6.5 2.8 .33 .19
When the procedure is repeated with a comparable filter
using melamine-formaldehyde as charge modifier, haze formation
does not occur.
3o
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1 EXAMPLE 2
The procedure of EX~PLE 1 was repeated employing a
Scotch whiskey. Filtration with Filter 1 gave a turbidity of
1.5 JTU and, after 24 hours, 2.8 JTU. The filtrate was
5 recirculated through Filter 1 three times after which the
turbidity values were .37 and .~, respectively.
3o
6~3~
-17-
1 EXAMPLE 3
Unstable rum based liquer samples were passed through
selecte~ filter rlledia and turbidity was measure~ of the effluent
sample. Results a~^e recorded in Table II.
Table II
N.T.U.
Untreated 0.55
Filter A 0.46
Filter B 0.70
Filter C 0,40
Filter D 0.35
Filter A = cationic melamine-formaldehyde resin
modified silica-cellulose filter.
Filter B - Filter 2 in Example 1.
Filter C = Filter 3 in Example 1.
Filter D = anionic silica-cellulose filter.
Only Filter B caused haze formation, the remaining
merely filtering haze present in the untreated samples.
g 1~24~8
-18-
1 EXAMPLE 4
Unstabilized whiskey was filtered through Filter
2 (EXAMPLE l) at .room temperature at the rate of 620 ml/mm
sin disc and 15 psi pressure. The turbidity of the unstabi-
5 lized whiskey was l.9 NTU, and the ~iltered (stabilized)pxoduce had a turbidity of 8.0 NTU.
The same unstabilized whiskey was chill-hazed by
cooling to 50F. to obtain stabilized product of a turbidity
of 4.6 NTU.
Filtration of both stabilized products with an
asbestos filter brought the turbidity to a typical level of
0.4 NTU.
The product stabilized in accordance with the
invention after 2.5 months at 50F. showed an ~TU o 1.4 and
15 the chill-stabilized product, 2.6.
3o
