WO2010019077A1

WO2010019077A1 - The filter aid based on microcrystalline cellulose and method of its preparation

Info

Publication number: WO2010019077A1
Application number: PCT/RU2009/000382
Authority: WO
Inventors: Andrey Leonidovich Makarov; Boris Eduardovich Batashov
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-11
Filing date: 2009-08-04
Publication date: 2010-02-18
Anticipated expiration: 2011-02-11
Also published as: RU2008133052A; RU2406566C2

Abstract

The invention relates to the filter aid applied at clarification of beverages containing polyphenols and/or sensitive proteins, particularly at clarification and stabilization of beer. This filter aid is the composite which comprises microcrystalline cellulose and one or more components capable to adsorb polyphenols and/or proteins. Preferably the component capable to adsorb proteins is silica in the form of derivatives of silicic acid: sol, hydrogel (silica gel), or xerogel and the component capable to adsorb polyphenols is cross-linked polyvinyl pyrrolidone. Use of this filter aid considerably improves colloidal stability of beverages even at reduction of the expense of adsorbents. It can be used in addition to kieselguhr with precoat filters and its use is especially effective at membrane (cross-flow) filtration.

Description

THE FILTER AID BASED ON MICROCRYSTALLINE CELLULOSE AND METHOD OF ITS PREPARATION

DESCRIPTION

FILD OF THE INVENTION

The invention relates to a filter aid applied in clarification of beverages containing polyphenols and/or sensitive proteins, i.e. nutritional or medicinal liquids (basically infusions, extracts, juices, wines, low-alcohol drinks and particularly beer and beer-like products) which are obtained from vegetative raw materials by decoction, wringing, extraction, fermentation and similar methods.

BACKGROUND OF THE INVENTION

Usually at fine filtration of beverage liquid passes through a precoated layer of a filter aid. The standard and practically unique filter aid for the precoat filters is kieselguhr. The filtration through kieselguhr is attractive due to high quality of beer, simplicity of technology, and rather low expenses. However, using of kieselguhr has become increasingly a problem.

Occurrences of kieselguhr as a natural mineral material are limited. Thus one must resort more and more to low grade qualities in order to meet the high demand of industry. The result is rising of cost of cleaning and processing of kieselguhr. Moreover kieselguhr is carcinogenic substance and that cause the rising of wage and of expenses for protection of labor and for occupational health service. The filter material cannot be regenerated accumulates as waste, and to a great extent burden the deposits. A classification kieselguhr as hazardous waste makes land filling considerably more difficult and in the developed countries expenses for disposal from used kieselguhr are comparable with cost of the kieselguhr.

At last years new way of a filtration was found: membrane filtration and its preferred embodiment - cross-flow filtration. Turbidity of beverages after a filtration through membranes is lower than at kieselguhr filtrations. Yeast and potentially damaging microorganisms are removed, beverages are practically sterile after filtration and so this process eliminates polishing filtration. Membranes are easily regenerated and costs at their use less or same with than kieselguhr filtration. So many experts agree in opinion that in 5-10 years cross-flow filtration will supersede kieselguhr and become the basic technology on the large breweries.

However at use of membranes it is not possible to accomplish high colloid stability of beverages and particularly beer, it is always worse, than at kieselguhr filtrations. Till now at cross-flow filtration there were no inexpensive ways to manufacture beverages with colloid stability corresponding with that at kieselguhr filtrations. The stability of beverages depends on presence of particles of colloidal structure and they can be removed by filtration only partially. These particles are formed mainly from polyphenols with high molecular weight and sensitive proteins whose molecules react via hydrogen bonds. Haze of colloidal particles develops with the lapse of time and this process accelerates at mechanical influences and especially at change of temperature. To improve the colloidal stability of beverages producers partially remove polyphenols or proteins or both of these by using various adsorbents.

Of materials having the better polyphenols adsorptivity the cross-linked polymer of N- vinylpyrrolidone (cross-linked polyvinyl pyrrolidone or PVPP) more often is used. Despite of high cost owing to the unique properties PVPP has practically superseded all other adsorbents of polyphenols from the market of materials for beverages manufacture. Use PVPP allows removing the most part of polyphenols and improves colloidal stability of beverages but usually it is not enough. Therefore except removal of polyphenols it is desirable to remove fraction of sensitive proteins. For this purpose various forms of silica and its derivatives are most widespread. Of these materials the derivatives of silicic acid (sol, hydrogel, xerogel) and acid- treated alkaline earth silicate are particularly chosen. Hydrogel of silicic acid (silica gel) is most often used because it has low cost and has high adsorptivity. Traditionally manufacturers use double stabilization of beverages by using together cross-linked polyvinyl pyrrolidone and silica gel.

These adsorption methods have fine effect at a filtration through a kieselguhr cake but at use of membranes it is not possible to accomplish high colloid stability of beverages.

According to present invention the effective and inexpensive filter aid was found. Its use essentially improves colloid stability of beverages at membrane filtration and especially at cross- flow filtration and also yields fine results at kieselguhr filtration. This filter aid is the composite which comprises microcrystalline cellulose and one or more components capable to adsorb polyphenols and/or proteins. Preferably the component capable to adsorb proteins is silica in the form of derivatives of a silicic acid: sol, hydrogel, xerogel or mixture thereof and the component capable to adsorb polyphenols is cross-linked polyvinyl pyrrolidone.

DESCRIPTION OF THE PRIOR ART

The technology of using materials which capable to adsorb proteins or polyphenols is widely known to those skilled in the art and does not demand detailed comments. However in accessible publications there are no mentions of using these or similar materials in a combination with microcrystalline cellulose at clarification and stabilization of beverages. Cellulosic filter materials have been known for a long time but they are not suitable for fine filtration because cellulose fibers cannot hold back finely divided substances and reduced to fine particles cellulose is easily pressed at the high differential pressure formed in the filter cake. Therefore crushed cellulose fibers basically is used only like admixture to a filtering layer of kieselguhr, for example as is described in report: J. Speckner, H. Kieninger, Cellulose als Filterhilfsmittel, Brauwelt Nr. 46 (1984) 2058, and for strengthening a filtering layer and especially in filters with a vertical filtering surface.

In publication WO/1986/05511 and in patent US4910182 the use of a mixture of synthetic and/or cellulose fibers with PVPP and silica gel for clearing beer by centrifugation is described but there is no mention of macrocrystalline cellulose.

In patent US6712974 manufacture of the filterable composite absorbents is described. Cellulose is mentioned as one of prospective components but there is no mention of microcrystalline cellulose.

It is necessary to emphasize that microcrystalline cellulose basically differs from cellulose fibers and from products produced by mechanical destruction of cellulosic materials and which have fibrous structure such as powdered cellulose, microfibrilated cellulose etc. Therefore since both publications listed above not mention microcrystalline cellulose when describe use of cellulose as the filter aid; in this case they discuss absolutely other material.

In publication WO/1999/39806 the filtering material consisting of water-insoluble starch, powder cellulose and microcrystalline cellulose is described. Microcrystalline cellulose in this case is used for the purpose of decrease in permeability of a filtering layer. Furthermore there is no mention of application of adsorbents, such as silica or PVPP in combination with microcrystalline cellulose.

The composite of microcrystalline cellulose and silica under the name silicified microcrystalline cellulose is specified in publications WO/1996/021429 and WO/2004/022601 which describe a way of its manufacture and its application as binding and bulking agent for tabletted pharmaceuticals. There is broad list of hypothetical fields of use of this material but these inventions do not disclose its use as filter aid or stabilizer of beverages.

Thus sources which teach or disclose the use of microcrystalline cellulose together with absorbents of proteins and polyphenols and in particular with such widespread adsorbents as cross-linked polyvinyl pyrrolidone or silica and its derivatives for using in beverage industry are not found. Furthermore there is no information about individual application of microcrystalline cellulose as filter aid at membrane filtration of beverages. DETAILED DESCRIPTION OF THE INVENTION

In the course of researches it has been searched out that addition of microcrystalline cellulose to adsorbents of proteins and/or polyphenols increases their efficiency and hence improves colloidal stability of beverages. It is especially important at membrane filtration when unlike kieselguhr filtration the action of independent adsorbents is not enough. Microcrystalline cellulose increases adsorptivity both individual adsorbents and their mix.

The composite filter aid of this invention contains basic components:

- microcrystalline cellulose,

- material capable to adsorb proteins,

- material capable to adsorb polyphenols.

The basic and obligatory component is microcrystalline cellulose which is partially depolymerized cellulose produced by chemical destruction of cellulosic-source materials. This material is referred to in the ait by several names including hydrolyzed cellulose and LODP- cellulose because hydrolysis of cellulose is carry out until a product with level-off degree of polymerization (LODP) is obtained. In view of destruction first of all of amorphous portion of cellulose and increasing of end-product crystallinity this material more often is named microcrystalline cellulose. Traditionally microcrystalline cellulose is manufactured by hydrolysis of the cellulosic-source materials with water solution of mineral acid and this material is known since 1875 under the name of hydrocellulose.

In addition to microcrystalline cellulose made by a traditional method for the purposes of the present invention it is possible to use microcrystalline cellulose made in other accessible ways, such as hydrolysis by Lewis's acids, alkaline hydrolysis, alcoholysis, treatment with reagents or oxidizers at high shear stress etc. Also there are no restrictions on methods of washing, bleaching and drying of used microcrystalline cellulose.

From materials capable to adsorb polyphenols it is preferable to use cross-linked polymers or copolymer of N-vinylamids and first of all of N-vinyllactams. Use of cross-linked polyvinyl pyrrolidone as mass product and accordingly the most accessible adsorbent is more preferable.

As the materials capable to adsorb proteins it is possible to use silica in various forms and its derivatives. But derivatives of a silicic acid (sol, hydrogel, xerogel) and acid-treated alkaline earth silicates are particularly preferable. These substances have plenty of Si-OH groups on the surface which are capable to form hydrogen bonds with amino-groups of proteins.

In addition to basic components listed above various additives and impurities can be included into composition of filter aid. It is possible to use powder (fibrous) cellulose and attriting aids serving to grind particles of microcrystalline cellulose. However an opportunity of presence of these additives should be considered separately in each case. For example presence of fibers of cellulose can be useful at kieselguhr filtration for strengthening a filtering layer but is harmful at membrane filtration when they blind narrow channels of membranes. The main requirement to additives and impurities - they should be harmless to health and should not worsen quality of beverages.

The filter aid can consist of two or three basic components what is defined by type of beverage and availability of the auxiliary equipment. In three-component composition the microcrystalline cellulose in a combination with adsorbent of proteins and with adsorbent of polyphenols (for example, with silica gel and PVPP) can be applied at a filtration of beverages containing both proteins and polyphenols (for example, beer). The microcrystalline cellulose in a combination with adsorbent of polyphenols can be used at filtration of the beverages containing small quantity of proteins (for example, wine). At the enterprises possessing the equipment for regeneration of adsorbent of polyphenols (reusable PVPP) it is possible to use a composite of microcrystalline cellulose with adsorbent of proteins at a filtration and to use adsorbent of polyphenols on the auxiliary equipment individually or in a combination with microcrystalline cellulose.

The relative amount of components in filter aid change over a wide range and depends on properties of used materials (particle size, adsorptivity, etc.), and also from conditions of its application and from kind of a beverage, and should be selected individually in each case. Basically the content of each component should not be less than about 1 % by weight. This value is defined by effective amount i.e. the minimal amount of a component which improves the certain properties of composite. However in practice using filter aid with the content of each component not less than 5% is more preferable.

The particle size of used components generally is not critical but nevertheless there are some restrictions. So use of materials with mean particle size less than 1 μm raises resistance of a filtering layer and if the mean particle size will be too greater (approximately more than 500 μm) efficiency of a filter aid will be low. The size of particles is especially important at a membrane filtration since too fine particles occlude membrane pores and large particles are capable to occlude membrane transport channels. For the purposes of present invention in most cases materials with mean particle size from 10 to 100 μm are suitable and most of commercial products for a filtration and stabilization of beverages meet such requirement.

Presence of microcrystalline cellulose in filter aid makes for it ability to form granules that in some cases more conveniently for its use. These granules promptly disintegrate in water or in water-containing liquid and so the size of granules is not important and is defined only by convenience of application of the material. It is necessary to emphasize importance of preparation method of filter aid. The simplest way is addition of composite received by dry mixing or addition of its separate components to a beverage (into the storage tank or into the pipeline before the filter). It leads to some positive results but it is not an effective method because mixing of components occurs in the equipment at the conditions when their concentration is low and respectively efficiency of their interaction is low. The most effective method is preliminary mixing of components in the presence of a small amount of water or a water-containing liquid (beverage) at active mechanical influence and in addition it is desirable to carry out the subsequent drying of the obtained composite.

This co-processing of components causes their active interaction that is unattainable at dry mixing of materials. This fact is interpreted by surface properties of composite components. Particles of all basic components possess set of active superficial groups. These particles suspended in water or in a water-containing liquid form among themselves hydrogen bonds. The part of these bonds is formed directly between particles but the most part includes intermediate molecules or chains of molecules of water. At the subsequent drying the some bonds formed through intermediate molecules of water is replaced on direct bonds between particles and that intensify interaction of microcrystalline cellulose and absorbents. Thus in the filter aid under present invention the particles of microcrystalline cellulose and adsorbents are agglomerated and bound but yet their physical and chemical properties not only remain but also mutually improve.

At preparation of filter aid the content of dry components in a mix may be from 1 to 75 % by weight. The lower value is defined by the minimal concentration where the real interaction of particles occur and the upper value is defined by ability of a damp mix be sheared by mechanical influence without application of the equipment of especial complexity. In practice the using of mixes with the content of dry components in limits from 10 to 40 % by weight is more preferably.

Moreover, owing to co-processing of microcrystalline cellulose with adsorbents its particle- size distribution varies. Usually after production microcrystalline cellulose consists from particles with size from submicron to 1000 microns. Though the particles size is not very critical at filtration through precoat filters but the presence of large particles is undesirable at a membrane filtration. The co-processing of filter aid components reduces content of cellulose particles with large dimension and at that the mean particles size can be regulated by duration of co-processing. Especially this effect appears at co-processing of microcrystalline cellulose with mineral adsorbents with high hardness in comparison with cellulose and such material are the majority of inorganic adsorbents and particularly is silica gel. In the absence of necessity to use adsorbents with high hardness in filter aid it is possible to use the attriting aids which are mentioned above and as these aids various neutral mineral substances can be applied, for example alumina, kaolin, etc.

DESCRIPTION OF THE DRAWING

On graphic chart the relative particle size distributions are presented:

- dotted curve for silica gel before co-processing,

- dashed curve for macrocrystalline cellulose before co-processing,

- solid curve for a mix microcrystalline cellulose and silica gel (1 : 1 by weight) after coprocessing.

One can see that as a result of co-processing practically all large particles of microcrystalline cellulose (more than 100 microns) were disintegrated though the quantity of small particles (less than 1 micron) was increased insignificantly. Particle-size distribution of microcrystalline cellulose approaches to that of silica gel.

INDUSTRIAL APPLICABILITY

Industrial application of the present invention improves colloidal stability of beverages and accordingly increases their storage warranty period, resistance to transportation and to storage conditions. At the same time the consumption of adsorbents may be decreased what is especially important for such expensive material as PVPP.

Furthermore, the industrial tests of cross-flow filtration have shown smaller rising of differential pressure at using filter aid under the present invention in comparison with use of adsorbents without microcrystalline cellulose. As a result working cycle of membrane elongates on 10-30% and that means that equipment productivity increases and that the consumption of expensive reagents for membranes regeneration decreases.

These facts are verified by examples of using filter aid at filtration and stabilization of ^■ beverages (in this case beer) which are given below.

EXAMPLES

All examples are adduced only to evidence utility of the present invention and cannot be considered as exact recommendations for use. At an application of the invention the dosage of filter aid and content of its components should be selected pursuant to beverage grade and individual conditions of manufacture.

All experiments were carried out with beer of one grade but different parties. However comparative experiments (with and without microcrystalline cellulose) were always carried out with beer from one party.

In all experiments it was used microcrystalline cellulose obtained by treatment of cotton- gauze waste by gaseous hydrogen chloride (RU2007131393). As adsorbent of polyphenols PVPP Divergan® from BASF and as adsorbent of sensitive proteins silica gel Cδstrosorb® from CWK were used. For membrane filiations installation BMF-RX 300 QS from NORIT was applied.

Samples of filter aid prepared as follows: dispersion of microcrystalline cellulose in water (weight ratio of water to microcrystalline cellulose was 3 : 1) was treated with high-speed mixer (5000 rpm) until formation of product reminding sour cream then adsorbents with additional quantity of water were added (weight ratio of water to silica gel was 1 : 1, weight ratio of water to PVPP was 3 : 1). The obtained blend was mixed within 10 minutes then it was dried.

Turbidity of filtered beer was defined in EBC units (European Brewery Convention).

For examine colloidal stability of beer two basic tests were executed which allow defining colloidal stability of a beverage and predicting its warranty storage period:

- Chill haze - beer during testing is cooled to -4°C and maintained at this temperature of 40 minutes as a result there is a sedimentation protein-polyphenolic complexes. Parameter of colloidal stability is change of beer turbidity after cooling in comparison with turbidity of not cooled beer.

- Alcohol chill haze - the test carries out similarly to the test for chill haze but in ethanol presence that decrease solubility of protein-polyphenolic complexes and accelerates their sedimentation. The addition of alcohol is 5 ml to 100 ml of beer.

Also the tests were carried out which are not allowing precisely estimating colloidal stability of beverage but these tests give the additional information on base of which it is possible to estimate efficiency of adsorbents:

- Sensitive proteins — change beer turbidity (ΔEBC) after addition 10 mg of tannin to 100 ml of beer this test allows to estimate the content of sensitive proteins in beverage.

- Saturated ammonium sulphate precipitation limit (SASPL) - addition of saturated ammonium sulphate solution to beer forms precipitate of both sensitive and foaming proteins.

- Tannoids - indirect definition of the content of active polyphenols in beer at the expense of their bonding with polyvinyl pyrrolidone. Examples 1 - 5

During these laboratory experiments the beer passed through a filter with precoated kieselguhr layer. Into beer stream before the filter it was batched kieselguhr and adsorbents (examples 1 and 3) or kieselguhr and preliminary prepared composite of adsorbents with microcrystalline cellulose (examples 2 and 4) or with powder cellulose (example 5). Beer was examined after subsidiary polishing filtration on standard technology. The test data are given in Table 1. The analysis of data evidences efficiency of using of microcrystalline cellulose both in combination with silica gel (compare examples 1 and 2) and in combination with silica gel and cross-linked polyvinyl pyrrolidone (compares examples 3 and 4). Application of composite materials in both cases improves colloidal stability of beer. At comparison of results of examples 4 and 5 it is visible that use of powder cellulose unlike microcrystalline cellulose does not improve colloidal stability of beer.

Table 1

Data of laboratory tests of filter aid efficiency at filtration through precoated kieselguhr layer

Examples 6 - 15

In these laboratory experiments beer passed through membrane filter. Into beer stream before the filter it was batched adsorbents (examples 6, 8, 10 and 12) or filter aid (examples 1, 9, 11 and 13). In examples 14 and 15 the silica gel or composite of silica gel with microcrystalline cellulose was accordingly added to beer and after filtration additional stabilization of beer by the reusable cross-linked polyvinyl pyrrolidone was carried out. The results of tests are shown in Table 2. It is visible that using filter aid under the present invention decreases the turbidity and improves colloidal stability of beer even at expense reducing of the adsorbents. Table 2 Data of laboratory tests of filter aid efficiency at membrane (non cross-flow) filtration

* - reusable PVPP (the additional stabilization after filtration) Examples 16 - 19

In these industrial experiments the adsorbents (examples 17 and 18) or filter aid (example 19) were dosed out into beer stream that was circulate thru cross-flow filtration equipment. From the analysis of the tests data which are mentioned in Table 3 one can see that using of filter aid under the present invention appreciably improves colloidal stability of beer even at reduction of the expense of adsorbents and also reduces its turbidity after a filtration. In comparison of examples 18 and 19 it is visible that application of filter aid results in prolongation of membrane working cycle on 24 % in this case.

Table 3

Data of industrial tests of filter aid efficiency at cross-flow filtration

Examples 20 - 24

In these laboratory experiments beer after kieselguhr filtration (control examples 20) was stabilized with PVPP (examples 21), with PVPP and silica gel (examples 22) or with filter aid (examples 23 and 24). It is visible that using filter aid under the present invention decrease^'s the turbidity and improves colloidal stability of beer even at expense reducing of the adsorbents.

Table 4

Data of laboratory tests of filter aid efficiency at stabilization after kieselguhr filtration

Claims

CLAIMSWe claim:

1. The filter aid applied at clarification and/or stabilization of beverages containing polyphenols and/or proteins, wherein said filter aid consist of microcrystalline cellulose and one or more components capable to adsorb polyphenols and/or one or more components capable to adsorb proteins.

2. The filter aid according to claim 1, wherein microcrystalline cellulose is partially depolymerized cellulose which made from cellulosic source material by any accessible way, such as acid or alkaline hydrolysis, alcoholysis, treatment with reagents or oxidizers at high mechanical stress, etc., and is washed, bleached and if necessary dried by any accessible ways.

3. The filter aid according to claim 1, in which the component capable to adsorb polyphenols is preferably cross-linked polymer or copolymer of N-vinyllactam and more preferably cross- linked polyvinyl pyrrolidone.

4. The filter aid according to claim 1, in which the component capable to adsorb proteins is preferably one of forms of silica or its derivatives, and more preferably it is one of derivatives of silicic acid: sol (silica sol), hydrogel (silica gel), xerogel or acid-treated alkaline earth metal silicate.

5. The filter aid according to claim 1, in which the content of each component is not less than 1 % and preferably is not less than 5% by weight.

6. The filter aid according to claim 1, in which mean particle size of each component is in the range of 1 to 1000 μm and preferably in the range of 10 to 100 μm.

7. The filter aid according to claim 1 in the form of granules.

8. Material according to claim 1, wherein the term beverages means nutritional or medicinal liquids (basically infusions, extracts, juices, wines, low-alcohol drinks and particularly beer and beer-like products) which are obtained from vegetative raw materials by decoction, wringing, extraction, fermentation and similar methods.

9. The method of preparation of filter aid according to claim 1, wherein said method comprises the co-processing of components in water or in aqueous liquid (beverage) under high shear stress and the content of dry components in the mix is from 1 to 75 % and preferably from 10 to 40 % by weight.

10. The method of filtration and/or stabilization of beverages, wherein the filter aid according to claim 1 is used.

11. The method according to claim 10, wherein equipment for membrane or cross-flow filtration is used.

12. The method according to claim 10, wherein equipment for filtration through precoat filter is used.

13. The method according to claim 12, wherein the filter aid according to claim 1 is used in addition to the basic filter material such as kieselguhr.

14. The method according to claim 10, wherein after filtration the additional stabilization is carried out by treatment of beverage with adsorbent of polyphenols.

15. The method according to claim 14, wherein the filter aid according to claim 1 is used as adsorbent of polyphenols.