CA2274242A1 - Agglomerated silicas - Google Patents

Abstract

Non-dusty silica agglomerates for use in beer stabilisation.

Description

WO 98/28401 PC'>r/GB97/03281 AGGLGMERATED SILICAS
Field of the Invention The present invention relates to a novel granular composition. The present invention more particularly relates to agglomerated synthetic amorphous silicas and their use in stabilising fermented beverages against haze formation during storage.
t3ackground to the Invention Alcoholic fermented beverages, for example beers, have a tendency to produce haze which can be of biological or physico-chemical origin, and a number of products and processes are used for the removal of haze-forming constituents. Whilst gross haze effects are resolved by filtration, flocculation, or centrifugation, secondary haze develops during storage due to interactions between certain polypeptides and polyphenofs which coagulate and precipitate. This haze therefore becomes apparent only at a stage when the beverage is being prepared for consumption and when removal is impractical. A number of organic and inorganic substances can be used to remove the polypeptide and polyphenol haze precursors prior to packaging and so stabilise the beverage; such as tannic acid, polyvinylpolypyrrolidone, bentonite, active carbon and silicas.
Amorphous silica hydrogels and xerogels, and blends thereof, selectively remove polypeptide haze precursors without impairing properties such as body, flavour, colour and head formation; see for example Hough, J.S., "Silica Hydrogeis for Chill Proofing Beer", MBAA Technical Quarterly vol. 13) No. 1, pp 34-39 {1976); Halcrow, R.M., "Silica Hydrogels", The Brewers Digest, pp44 {August 1976 and Hough, J.S., and Lovell, A.t-., "Recent Developments In Silica Hydrogels, for the Treatment and Processing of Beers", MBAA Technical Quarterly, vo1.16, No.2, pp90-100 (1979).
Amorphous silica hydrogels are non-dusty, easy to handle powders. in contrast, amorphous silica xerogels, while being effective beer stabilisers, are extremely dusty and pose difficult handling problems.
The present invention is aimed at delivering low dusting, highly stabilising silica ' gels for use in stabilising beverages. Although the invention is directed to the treatment of beers, which term includes lager, Pllsner, Dortmund and Minato beer, as well as top fermented beers such as ale) porter and stout, it is applicable to other fermented liquids which are liable to generate haze on storage, as well as to non-fermented beverages that may form haze during storage, such as fruit juices and iced teas.
Prior literature shows that silicas either in the form of hydrogels, xerogels and precipitated silicas, and blends thereof, with surface areas ranging from 200 to 1100 m2/g, pore volumes 0.35 to 2.5 cc/g and particle sizes in the ranges 3 to 30 microns can be used to remove protein from beer, and so stabilise the beverage against haze formation during storage. More specifically the use of silica hydrogels with surface areas greater than 700 m2/g are disclosed in 681215928 for the treatment of beer.
Fine particle sized xerogels and precipitated silicas as disclosed in EP-A-0683222, US-A-4515821, EP-A-0287232, US-A-5149,553, have one pronounced disadvantage and that is their excessive dusting when introduced into the dosing equipment normally employed in the brewery. Silica hydrogels, or blends of hydrogels and xerogels containing 30% to 60% by weight of SiOz are practically non-dusting, but these materials are extremely cohesive and as a consequence they require specially designed equipment for them to be handled in bulk.
The use of agglomeration to reduce the dustiness of precipitated silicas, or siliceous materials, is disclosed in US-A-3646183, US-A-4336219, GB-A-2013165, JP 56314/1982, DE-A- 2150346 and DE-A-1807714, US-A-4052334, GB-A-1543576 and GB-A-1365516. These materials find use either as rubber fillers or catalyst supports and as such do not have pore structures suited to beer stabilisation. No prior art discloses the use of agglomerated silicas for beverage stabilisation application.
Standard Procedures The agglomerates, and their component particles, of the invention are defined in terms of their physico-chemical properties. The test methods used to determine these properties are:-i) Surface Area and Pore Volume.
Surface area and pore volume was measured using an automatic BET specific surface measuring apparatus; Micromoritics ASAP 1400 in accordance with the BET method based upon nitrogen adsorption.
Measurement was taken by making reference to the following literature, S.
Brunauer, P.H. Emmett and E.Teller, J.Am.Chem.Soc., 60,309 (1938). Samples were outgassed under vacuum at 270°C for 1 hour before measurement at about '196°C.
ii) Mean Pore Diameter (MPD) The mean pore diameter was calculated in accordance with a cylindrical mode! using:
MPD = 4,000 x PV/SA nm Where PV is the pore volume (cc/g) and SA the specific surface area (m2/g) to nitrogen as determined in (i) above.
iii) Total moisture content The total moisture content was determined from the loss in weight of a silica when ignited in a furnace at 1000°C to constant weight.

iv) Weight Mean Particle Size The weight mean particle size of the sificas before agglomeration was determined using a Malvern Mastersizer Model X, made by Malvern Instruments, ' Malvern, Worcestershire with MS15 sample presentation unit. This instrument uses the principle of Fraunhoffer diffraction, utilising a low power HelNe laser.
The particuiates are dispersed ultrasonically in water for 7 minutes to form an aqueous suspension and then mechanically stirred before they are subjected to the measurement procedure outlined in the instruction manual for the instrument, utilising a suitable lens in the system.
The Malvern Particle Sizer measures the weight particle size of the particulate. The weight mean particle size (d50) or 50 percentile, the 10 percentile (d10) and the 90 percentile (d90} are easily obtained from the date generated.
v) Beer Stabilisation The proteins in beer which precipitate in the presence of tannic acid, the so called sensitive proteins -see Chapon) L., J.lnst.Brew.) vo1.99, 49 {1993) -are considered to be important poiypeptide haze precursors.
The sensitive protein content of degassed beer was determined using a Tannometer supplied by Bearwell International Systems) 125 St. Mary's Road, Market Harborough, Leicestershire, LE16 DT, England.
Measurement was made at 25°C using a 0.01 % w/v tannic acid solution (Brewtan C., supplied by Omnichem n.v., Cooppallaan 91, B9230, Wetteren, Belgie} by following haze formed in EBC units. The haze formed at a concentration of l0mg/1 added tannic acid was recorded. The results are expressed as the percentage reduction in this haze value following treatment of the beer with silica at 30g/hi either following overnight contact or following 10 minutes contact time.
vi) Agglomerate strength Agglomerate strengths were measured using a Microson XL2020 Sonicator programmable ultrasonic liquid processor, manufactured by Misonix Inc., Farmingdale, New York and supplied in the UK by Labcaire Systems Ltd., Avon.
The Microson XL2020 Sonicator ultrasonic processor has a maximum of 550 watts output with a 20kHz convertor and is fitted with a 3/. inch tapped horn. The processor has variable amplitude control and a microprocessor controlled digital timer integrated with a Pulsar cycle timer with power output and elapsed time displays.
The piezoelectric convertor transforms electrical energy to mechanical energy at a frequency of 20KHz. Oscillation of piezoelectric crystals is transmitted and focused by a titanium disruptor horn that radiates energy into the liquid being treated. A phenomenon known as cavitation, the formation and collapse of microscopic vapour bubbles generated by the strong sound waves, produces a shearing and tearing action. Almost all of the activity takes place just in front of the probe tip.
The generator provides high voltage pulses of energy at 20 kHz and adjusts for varying load conditions, such as viscosity and temperature. It senses ' impedance change and increases or decreases power to the probe tip automatically.
The 3/. inch probe is a medium intensity horn for processing volumes between 25 and 500m1. The maximum ampf itude at the tip of the probe is 60 microns.
Hence, sonicator processors operating at output control setting 10 have 60 microns of amplitude (peak to peak amplitude of the radiating face of the tip) at the tip of the probe.
Therefore, there is a linear relationship between the output control knob (or amplitude adjustment knob) and the amplitude at the tip of the probe, i.e. 6 microns of amplitude per control knob setting. The generator draws energy accordingly to maintain a constant amplitude at the tip for a given output control setting.
This is displayed on the % output power meter and is power in Watts (i.e.: output -%/100 550 watts available = x watts delivered).
A paper given by Mr. S. Berliner, (Director, Technical Services, Heat Systems Ultrasonics Inc.) at the 9'" Annual Technical Symposium of the Ultrasonic Industry Association, entitled "Application of Ultrasonic Processors (Power vs Intensity in Sonification"" provides further detailed information of the principles involved in this experimental technique.
Procedure A 250mI Pyrex beaker is insulated and fitted with a lid with a 3/4 inch hole in the centre to accommodate the ultrasonic probe and a 1 /8 inch hole to the side to accommodate a temperature probe.
Into the insulated beaker weigh the desired amount of deionised water, and the desired amount of inorganic granule to obtain a final weight of 200 g.
A
magnetic stirrer bar is introduced into the beaker and the beaker is placed on a magnetic stirrer hotplate equipped with a temperature sensor (Heidolph MR3003 magnetic stirrer hotplate with a stainless steel PT-100 temperature sensor and rpm stirrer speed) obtainable from Orme Scientific, Manchester). The beaker contents are stirred on setting 3 (-300 rpm)) the ultrasonic probe is immersed to a depth of 5/8 inch into the liquid and the temperature sensor is inserted into the liquid to continuously monitor temperature.
~ The Sonicator ultrasonic processor is switched on and information on processing time and pulsed mode programmed, as required. Cavitation is introduced to the system by turning the output control knob to the desired amplitude setting, whilst the temperature profile is closely monitored. The %
power output required to maintain the amplitude at the tip is also recorded, according to the setting. When the cavitation process is complete, the stirrer is switched off and the magnetic stirrer bar is removed. Manual stirring is continued with a spatula to maintain dispersion.
+45 micron Wet Sieve Test Method The inorganic particle dispersion is poured through a 45 micron sieve.
Any residue in the beaker is washed through the sieve, using half the amount of initial water. The sieve is then dried to constant weight in an oven at 150°C. The residue which remains on top of the 45 micron sieve is then weighed and expressed as a percentage of the initial weight of inorganic granule. The greater the amount retained on the sieve, the stronger the agglomerate strength of the granule and the more difficult it is to breakdown. An optimum product will have no residue remaining on the sieve.
!t has been found that, for a granule to satisfactorily breakdown in beverage application, it will have less than 5%) preferably less than 2%, most preferably less than 1 % by weight) residua on a +45 micron sieve after ultrasonification on setting 10 (60 micron amplitude) for a period of 7 minutes.
vii) Particle Size Distribution by Sieve Analysis An accurate measure of the true particle size distribution of the granular composition is done using sieve analysis.
1008 of the sample is placed on the top sieve of a series of BS sieves, at approximately 50 micron intervals to cover the particle size range of the granule.
The sieves are arranged in order with the finest at the bottom and the coarsest at the top of the stack. The sieves are placed in a mechanical vibrator e.g.
Inciyno Mechanical Sieve Shaker by Pascail Engineering Co. Ltd., covered with a lid and shaken for 10 minutes. Each sieve fraction is accurately weighed and the results calculated:
% residue = Wt. Of residue * 100 Wt. Of sample Brief Descril~tjon of the Invention WO 98/28401 ~ PCT/GB97/03281 According to the present invention there is provided a process for the treatment of a fermented alcoholic beverage which comprises contacting the beverage with a granular composition comprising 45 to 98 % w/w on dry basis of a water insoluble particulate wherein more than 75% by weight on dry basis, preferably more than 90% ' by weight on dry basis, of the water insoluble particulate is made from an amorphous silica) having a weight mean particle size of from 5 to 30 microns, preferably from 10 to ' 30 microns) a pore volume of more than 1 cc/g, and a mean pore diameter of more than 60 Angstroms, the granular composition having a particle size, as measured by dry sieve analysis, such that more than 75% by weight of the granular composition, preferably more than 95% by weight, has a particle size of more than 45 microns.
Preferably, the granular composition is sieved at 125 and 600 microns so that more than 90% w/w of the granular composition has a parcile size between 125 and 600 microns.
Preferably, the granular composition has a granular strength such that less than 5%, more preferably less than 2%, most preferably less than 1 % by weight, residue is left on a 45 micron wet sieve after ultrasonification on setting 10 (60 micron amplitide) for a period of 7 minutes.
Preferably also, the granular composition has a total moisture content of less than 40%, preferably less than 30%, more preferably less than 20%.
Amorphous silicas which can be used in the present invention may be prepared via an acid gel route or an alkaline precipitate route.
Siaecific Description of the Invention Examples of the preparation of agglomerated synthetic amorphous silicas will now be gmen to illustrate but not limit the invention.
Preparation of 8gaiomerates Silica gels having the properties shown in Table 1 were agglomerated individually at 2008 powder batch size (laboratory scale) with deionised water using a Sirmon CV6 mixer, supplied by Metcalfe Catering Equipment Ltd., 8laneau Ffestiniog, Wales. The resulting wet agglomerates were then dried in an oven at 150°C for 4 hours, gently forced through a 600 micron screen and sieved at 125 microns to collect the greater than 125 micron fraction. Each silica 1 to 5 was agglomerated this way to produce agglomerates A to E.
As an alternative route to prepare the agglomerates, approximately 1 kg of the silica powder was dry compacted using an Alexanderwerk roller compactor with a feed rate setting at number 3, supplied by Alexanderwerk AG-D-42857, Remscheid-Kippdorfstrasse 6-24. The strength of agglomerate prepared in this way depended on the pressure applied to the rollers. The silica cited as silica number 1 in WO 98!28401 PCT/GB97/03281 Tabte 1 was agglomerated in this way at 15 bar (code F) and 50 bar (code G).
Example H was also produced with silica number 1 and was made even harder by multiple passes at 50 bar. The prepared agglomerates were classified and sieved as ~ described for the wet route structures.
Aaalomerate strength The strength of the prepared agglomerates was determined as outlined earlier.
Table 2 records these strengths as the energy required to reduce 50% of the structure to less than 45 microns particle size. The results of Table 2 show that a wide range of strengths is attainable, the strength being a function of the physical characteristics of the silica particles making up the structure, as well as pressure applied and number of passes made through the aggfomerator.
deer Stabilisation Agglomerated silicas of greater than 45 micron agglomerate size will only be effective in beer stabilisation if they break down to deliver particles of 20 micron or less. The results shown in Table 3 for an adjunct lager, serve to illustrate this effect.
Thus samples coded G and H were measured for their effectiveness at removing sensitive protein from a beer, before agglomeration (i.e. as large particle agglomerates), and following de-agglomeration by dispersion in a beer sample.
The samples were prepared from a common feedstock (i.e. silica example 1 in Table 1 ) under conditions designed to deliver different agglomerate strengths. The results of Table 3 show that when agglomerated to large particle size the stabilising effectiveness of the silicas is lost. Agglomerate G gives better performance than H due to its weaker structure (cf. Table 2) partially breaking down during addition to the beer.
Application of shear to the system (i.e. magnetic stirrer bar) serves to deaggiomerate sample G
such that it is once again able to deliver effective protein removal. The strength of sample H is such that the gentle shear forces applied are insufficient to return the primary particles and hence it fails to deliver the pre-agglomerated protein removal.
Table 4 shows, on a beer different from the bear tested on Table 3, that an input of sufficient energy to reduce the agglomerates to small particle size (cf.
Table 2} is effective in delivering the beer stabilising performance of the pre-agglomerated particles. Example O (prepared from silica example 4 of table 1 ) is a poor stabiliser in both pre and de-agglomerated forms due to not having a suitable pore structure for beer stabilisation, i.e. having a mean pore diameter of less than 60 Angstroms and a pore volume of less than 1 cm'/g. All of the remaining samples are good stabilisers and recover their performance following de-agglomeration.

Table 1 : Physical larol~erties of the silicas i~rior to ~,galomeration TVM 7.5 8.6 8.6 22.4 7.5 ' Surface Area (m(lg)766 295 319 662 304 Pore Volume (cc/g)1.3 1.8 1.1 0.4 1.2 Mean Pore Diameter68 244 138 24 158 (A) Particle Size (microns) D10 5.3 6.1 5.1 2.8 4.8 D50 11.9 11.5 10.7 8.7 8.8 D90 25.5 20.8 20.6 19.5 15.6 Table 2 ~ Agatomerate strenr~th - Ener4v to reduce 50% Qf structure t-o less than 45 micros A B C D E F G H

Energy (Joules)1,500 3,000 800 550 14,000850 900 18,900 Table 3 ~ Effect of Particle Size on S nc~tivp prot in Removal Pre-agglomeration Agglomerated De-agglomerated G H G H G H

Particle 11.9 11.9 125-600 125-60032.5 238 Size (microns) Reduction 62 65 30 12 60 22 in Sensitive Protein Table 4 ~ Beer Stabilisation % Redmction in Sensitive Protein A B C D E F G

Pre-a lomeration73 62 71 10 67 73 73 ~De-agglomerated74 ~ 60 70 ~ 8 65 76 72 ~ ~

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Claims (10)

Claims

1. Process for the treatment of a fermented alcoholic beverage which comprises contacting the beverage with a granular composition comprising 45 to 98% w/w on dry basis of a wafer insoluble particulate wherein more than 75% by weight on dry basis, of the water insoluble particulate is made from an amorphous silica having a weight mean particle size of from 5 to 30 microns, a pore volume of more than 1 cc/g, and a mean pore diameter of more than 60 Angstroms, the granular composition having a particle size, as measured by dry sieve analysis, such that more than 75% by weight of the granular composition has a particle size of more than 45 microns.

2. A process as claimed in Claim 1 in which more than 90%, by weight on dry basis, of the water insoluble particulate is made from said amorphous silica.

3. A process as claimed in Claim 1 or 2 in which said amorphous silica has a weight mean particle size of from 10 to 30 microns.

4. A process as claimed in Claim 1,2 or 3 in which the granular composition has a particle size, as measured by dry sieve analysis, such that more than 95% by weight has a particle size of more than 45 microns.

5. A process as claimed in any one of the preceding claims in which the granular composition has a granular strength such that less than 5% by weight, residue is left on a 45 micron wet sieve after ultrasonification on setting 10 (60 micron amplitude) for a period of 7 minutes.

6. A process as claimed in any one of Claims 1 to 4 in which the granular composition has a granular strength such that less than 2% by weight, residue is left on a 45 micron wet sieve after ultrasonification on setting 10 (60 micron amplitude) for a period of 7 minutes.

7. A process as claimed in any one of Claims 1 to 4 in which the granular composition has a granular strength such that less than 1 % by weight, residue is left on a 45 micron wet sieve after ultrasonification on setting 10 (60 micron amplitude) for a period of 7 minutes.

8. A process as claimed in any one of Claims 1 to 7 in which said granular composition has a total moisture content of less than 40%.

9. A process as claimed in any one of Claims 1 to 7 in which said granular composition has a total moisture content of less than 30%.

10. A process as claimed in any one of Claims 1 to 7 in which said granular composition has a total moisture content of less than 20%.