AGED SILICA

Abstract: An improved process for chillproofing a malt beverage with silica, the improvement being in the nature of the silica used and the improved results obtained thereby. The silica is aged with ammonia for a prolonged period of time. Better stability with smaller amounts of silica are obtained.

Description: This invention relates to an improved process for chillproofing a malt beverage with silica, the improvement being in the nature of the silica used and the results obtained thereby. Ammonia aged silica is used in accordance herewith. The use of silica for "chillproofing" beer is well known. Reference may be had to the U.S. Patent to McLaughlin et al 4,508,742 dated 2 April l985 and to the background and prior art references cited therein. Reference may also be had to U.S. Patents 3,7l6,493 and 3,959,l74 to Acker at al dated l3 February l973 each of which discloses a method of making an ammonia aged silica. Basically, the problem with beers, ales, lagers, and stouts is one of the tendency of these beverages to form haze or turbidity on storage. Treating the malt beverage with various kinds of silica removes or sequesters the agents responsible for haze formation at reduced temperatures to various degrees. After treatment, the silica is removed. This process is known as "chillproofing". To my knowledge, the only worker in the art who has used an ammonia treated silica for the chillproofing of malt beverages is Heimann, U.S. Patent 2,3l6,24l dated l3 April l943. Heimann (U. S. Patent 2,3l6,24l dated l3 April l943) uses a gel that contains more water than the gels used in this invention. The Heimann uses concentrated hydrochloric acid (the commercial product generally has 36% HCl) diluted with an equal volume of water, yielding approximately l8% acid. He neutralizes this with 40° Baume waterglass solution (37% sodium silicate) which is also diluted with an equal volume of water, resulting in an approximately l8.5% sodium silicate solution. The ingredients for the gel preparation used in a specific embodiment of the present invention are 4l.5% sulfuric acid and 29% sodium silicate. The resulting reaction mixture of the present invention has approximately half the amount of water compared with Heimann's mixture. Those skilled in the art know that this difference in concentration causes the solidification of a gel to take approximately ten times longer for the more dilute system. This is the reason why Heimann makes his gel by one of three methods: l) Precipitation with ammonia, 2) by letting the mixture stand for several days or 3) by heating the mixture to 90 or l00°C. The gel used in the present invention gelatinizes in 30 to 60 minutes. (Data for this difference of gelation time are given in "The chemistry of silica" by Ralph K. Iler, John Wiley & Sons, l979, page 368). The differences in the character of gels is given by Heimann in his patent. On page one, left side line 53, he mentions that the stabilizing effect of his product "cannot be attained when employing an ordinary silica gel prepared with an acid". The gel of this invention is an ordinary silica gel prepared with acid. Prior processes use, in general, higher amounts of silica up to 25 lbs/l00 bbls (112.5 kg/15900 l) of beverage. Briefly stated, the present invention is in a process for chillproofing a malt beverage, e.g., beer, by mixing a slurry of a "wet" ammonia aged silica (which exists of free flowing powder) with the beverage for a predetermined period of time and thereafter removing the silica. The silica is aged at a pH of from 8.5 to l0 for a period in the range of from 5 to 20 hours at a temperature of from 60 to 90°C. The aged product is milled with a fluid energy mill, for example, to a particle size of from 4 to 30 µm, and a water content of 35% to 70% H₂O by weight. Although the aged silica hydrogels used herein exist as free flowing powders, they contain a substantial amount of water by weight and are therefore referred to herein as "wet". The silica, when its water is substantially removed (<5% H₂O) with a suitable solvent, e.g., methyl alcohol, acetone, or diethyl ether, or mixtures thereof, has a surface area of from l75 to 450 m²/g, a pore volume of from l.5 to 2.4 cm³/g and a pore diameter of from l5 to 60 nanometers. The "wet" ammonia aged silica so formed is slurried in water to a concentration of 5% to l5% solids (on a dry basis) by weight and added to the malt beverage in an amount ranging, from about 2 to about 8 pounds dry silica per l00 barrels of malt beverage. Although more or less of the ammonia aged silicas hereof may be used depending on the particular requirements of the brewer, best results are secured with from about 2 to about 8 pounds (0.9 to 3.6 kg) of the silica/l00 bbls (15900 l) of the beverage. Contact between the silica and the beverage is maintained for a period of from l minute to 24 hours. When used herein the term "barrel" (bbl) means a quantity of l59 litres. Figure l is a graph showing the variation of surface area in squaremeters per gram vs. hours of aging. Figure 2 is a graph showing the variation of pore diameter in nanometers vs. hours of aging. Figure 3 is a graph showing the variation of the pore volume in cm³/g vs. hours of aging. As indicated above, the improved chillproofing process of the present invention contemplates adding a particular "wet", ammonia aged silica to a malt beverage, mixing for a predetermined period of time and then removing the silica. The improved silica is an ammonia aged silica gel which is aged for a much longer period of time than Acker discloses (see US-A-3 959 174). The starting silica is a hydrogel and any of the known methods for forming such hydrogels may be used. The aging conditions to which the starting gel is exposed are: (a) Contacting the silica, preferably a silica hydrogel with an ammonia solution in water with a 8.5 < pH < l0.0, preferably 9<pH<l0. (b) The contact time of the ammonia with the gel ranges from about 5 to about 20 hours, preferably from about 8 to about l5 hours. (c) The temperature during contact is from 60° to 90°C., preferably 70° to 80°C. (d) The aged product is milled to an average particle size of 4 to 30 micrometers (preferably 7 to 20 micrometers) and has a water content of 35 to 70% by weight (preferably 55% to 68%). The aged gel has the following properties: These properties were determined after the removal of water by washing the water-containing product with methyl or ethyl alcohol, diethylether or acetone or mixtures thereof and drying the product in vacuum. This is necessary because the properties were determined on the dry or substantially water free product, and drying without a proceeding removal of the major amount (e.g., 98%) water with a solvent or solvent mixture destroys the pore structure. Surface area: l75 to 450-m²/g, preferably 200 to 350 m²/g. Pore volume: l.5 to 2.4 cc/g., preferably l.75 to 2.25 cc/g. Pore diameter: l5 to 60 nanometers, preferably 25 to 45 nanometers. Reference may be had to the annexed drawings which graphs showing the variation of various important physical properties with the hours of ammonia aging. These graphs show aging for a minimum of about 5 hours is critical to the development of the desired properties of surface area, porosity and pore volume. While the maximums of each occur at slightly different periods of aging, the useful and ideal values are obtained in the broad range of 5 to 20 hours, and preferably from 8 to l5 hours. Figure l shows how the surface area varies with time of aging. While less than 5 hours gives a larger surface area, maximum pore volume (Figure 3) does not occur until after 5 hours. Also, maximum porosity (Figure 2) which measures pore diameter in nanometers does not occur until after 5 hours of aging. Beyond l0-l5 hours of aging the changes in the properties illustrated in the several graphs do not change materially. It is desirable to reach a balance which occurs at about 8 hours where the more important pore volume (Figure 3) and porosity (Figure 2) have gained near maximum value. The surface area is not as important, and although large surface area is desirable, the maximum values of the other properties are more critical of achievement, and hence some surface area is sacrificed for these values. The aged silica product of this invention is added to beer, preferably as a 5% to l5% slurry, by weight, in water freed from dissolved air, and carefully mixed. After a contact time of between one minute and 24 hours (preferably between 3 and l20 minutes) at a temperature less than about 25°C., silica is removed from the beer by centrifugation and/or filtration and/or sedimentation. The treated beer is then processed in the regular way. When the malt beverage is chillproofed in this way with the product of this invention it will be more clear than without this treatment and will not, during the time of normal storage, develop any haze at temperatures between 0°C. and ambient temperatures. The product and treatment will not influence foam stability, color, taste, flavor or other properties essential for its quality. The product as it is used in this invention appears to have a chemical and/or physical structure different from other silicas prepared by acid washing. This is - together with surface area, pore size, pore volume and water content - the main reason why the product of the present invention has a higher chillproofing ability than any other silicas. To illustrate the preparation of the ammonia aged products hereof, 36° Baume sulfuric acid is combined with 32.l° Baume sodium silicate and allowed to set to a hydrogel. The gel is sized and washed with hot water. (See U.S. Patent 4,097,302 by H.J. Cohen et al dated 27 June l978). Aging with ammonia is accomplished with an aqueous solution of ammonia at 60° to 90°C. at a concentration corresponding to an alkalinity at a pH between 9 and l0. The aging lasts several hours. The properties of the gel changed in the following way: The present invention uses gel with a pore size distribution as obtained after 5 to 20 hours of aging. (See Figure 2). It is clear that a washing of gel to neutralize the acid in the precipitated gel as described by Heimann cannot create the same pore structure as the five to twenty hours aging described here. A "wet" aged gel prepared as above was used for the stabilization of beer. The correct silica dosage is predetermined in accordance with standard brewing practices. Depending on the desired stability, it was found to require from 2 to 5 lb/l00 bbl (0.9-2.25 kg/15900 l) of beer. The beer was a lager beer that was not previously chillproofed or pasteurized. EXAMPLES l) A slurry of the test silica in water (l0% SiO₂ by weight) was prepared. 2) The slurry was deareated by blowing carbon dioxide bubbles through the slurry for l5 minutes. 3) Contact of the silica slurry with air could redissolve oxygen from the ambient air. Small amounts of air influence the taste and the stability of beer so that the contact with air was kept to a minimum. The slurry was added to the beer. 4) The silica slurry was carefully mixed with beer and the contact time was kept at one hour. 5) The beer was filtered over a pre-coat of diatomaceous earth and pasteurized using standard industrial procedures. The stability of treated beer has been determined by measuring haze at 0°C. after chillproofing. The beer was stored for 24 hours at 0°C. and the haze was measured. This was followed by storage at 25°C. for seven days and by cooling for 24 hours at 0°C. The haze was measured again and the beer was stored at the higher temperature for another seven days. The heating and cooling cycle was repeated until the haze was higher than 2 European Brewing Congress (EBC) units. The data were graphically interpolated to determine the number of days at which a haze of exactly 2 EBC units can be expected. The longer the time in days to achieve 2 EBC units, the higher the stability. The results also depend on the age of the unstabilized beer. Because of this, the comparative tests were always done on the dame day, so that results are always given for only one pair of chillproofing agents. The same chillproofing agent shows different results on different days with a given beer. Sample silicas being compared: A) A "wet" silica powder containing 67% water was prepared following the English Patent No. l,2l5,928. The material has been compared on a dry basis. When the dosage is given below as 3 lb/l00 bbl. (1.35 kg/15900 l), the amount of the wet product used was actually 9 lb/l00 bbl. (4 kg/15700 l), i.e., the 3 lbs. (1.35 kg) is calculated on the water free basis. B) A silica aged with ammonia for nine hours as described above. The material was dried and milled after aging. Particle size was approximately 8 microns. C) A "wet" silica powder aged with ammonia for nine hours as described above. The product was milled without drying. Water content was 62% and the particle size was 2l µm. D) A silica similar to C. The particle size was l6 microns. Stabilities After Chillproofing and Pasteurization (expressed in exposure days at 25°C.) A) At 3 lb/l00 bbl (1.35 kg/15900 l) (dry basis) ll days B) At 3 lb/l00 bbl (1.35 kg/15900 l) (dry basis) l4 days A) At 5 lb/l00 bbl (2.25 kg/15900 l) (dry basis) l5 days B) At 5 lb/l00 bbl (2.25 kg/15900 l) (dry basis) l8 days C) At 2 lb/l00 bbl (0.9 kg/15900 l) (dry basis) 25 days B) At 2 lb/l00 bbl (0.9 kg/15900 l) (dry basis) l9 days C) At 3 lb/l00 bbl (1.35 kg/15900 l) (dry basis) 29 days B) At 3 lb/l00 bbl (1.35 kg/15900 l) (dry basis) 22 days D) At 2 lb/l00 bbl (0.9 kg/15900 l) (dry basis) 37 days B) At 2 lb/l00 bbl (0.9 kg/15900 l) (dry basis) l9 days D) At 3 lb/l00 bbl (1.35 kg/15900 l) (dry basis) 38 days B) At 3 lb/l00 bbl (1.35 kg/15900 l)(dry basis) 22 days The data show clearly that the ammonia aging creates a dry product (b) that is more active than the acid washed product prepared according to the English patent No 1 215 928. It also shows that the wet ammonia-aged product is more active (per lb (0.45 kg) of pure SiO₂) than its dry counterpart. The l6 µm product by this invention is more active than the 2l µm material. Example D illustrates the best mode of carrying out the present invention. The test did not show any change in flavor, taste, color, pH or any other properties of the beer when it was treated with our ammonia aged silicas.

Claims: An ammonia aged silica prepared by aging a silica hydrogel with ammonia at a pH of from 8.5 to l0, for a period of from 5 to 20 hours and at a temperature of from 60° to 90°C., milling the product to a particle size of from 4 to 30 µm, said milled product having a water content of from 35% to 75% by weight, said silica, when substantially water free having a surface area of from l75 to 450 m²/g, a pore volume of from l.5 to 2.4 cm³/g and a pore diameter of from l5 to 60 nm. An ammonia aged silica as defined in claim l wherein the aging period is from about 8 hours to about l8 hours. An ammonia aged silica as defined in either of the preceding claims, wherein the temperature of aging is from 70°C. to 80°C. An ammonia aged silica as defined in any one of the preceding claims, wherein the particle size of the milled product is from 7 to 20 µm. An ammonia aged silica as defined in any one of the preceding claims, wherein the water content of the milled product is from 55% to 68% by weight. An ammonia aged silica as defined in any one of the preceding claims, wherein the surface area is from 200 to 300 m²/g. An ammonia aged silica as defined in any one of the preceding claims, wherein the pore volume of the milled product is from l.75 to 2.25 cm³/g. An ammonia aged silica as defined in any one of the preceding claims, wherein the pore diameter of the milled product is 24-45 nm. A process for chillproofing a malt beverage which comprises a) adding a slurry of an ammonia aged silica as claimed in any one of the preceding claims in water free of dissolved air at a solids concentrate of from 5-l5% by weight to a malt beverage at a concentration of from 2 to 8 lbs per l00 bbl (0.9-3.6 kg per 15900 l) malt beverage b) contacting the silica with said malt beverage for a period of from l minute to 24 hours and c) removing the silica from the malt beverage.

Inventors: VAN DER HEEM, PETER
Applicants: SCM CHEMICALS, INC.
Application year: 1987
Main classification: C01B33
IPC codes: C01B33, C12C5, C12C7, C12H1, A23L2