Food or edible material: processes – compositions – and products – Inhibiting chemical or physical change of food by contact... – Treating liquid material
Reexamination Certificate
1997-07-08
2003-05-20
Sherrer, Curtis E. (Department: 1761)
Food or edible material: processes, compositions, and products
Inhibiting chemical or physical change of food by contact...
Treating liquid material
C423S335000, C423S339000, C426S423000
Reexamination Certificate
active
06565905
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a silica gel used for improving the haze stability of beer, a method of manufacturing the silica gel and a method of stabilization treatment of beer using the silica gel.
Conventionally, a method of stabilization treatment of beer using a silica gel which can prevent the generation of haze in beer is known. The preparation of a silica gel having various physical properties for use in the stabilization treatment is disclosed, for example, in the examined Japanese Patent Publication No. 63-38188 and the Japanese Patent laying-open Nos. 5-70120 and 5-97421.
However, since the conventional silica gels can insufficiently prevent a haze from being generated in beer, a large quantity of the silica gels are required for providing a desired effect, which increases the cost as well as the industrial wastes resulting from the manufacture of beer. Therefore, the physical property values of the silica gel, contributing to enhancement of the haze inhibiting effect, required to be strictly selected.
The specific surface area, the pore volume, the average pore diameter and other physical properties of the silica gel are dependent on one another: when either one of the physical properties change, the other ones also change. In the conventional art, even if a certain physical property is improved to increase the haze inhibiting effect, the other physical properties possibly change dependently to act against or lower the haze inhibiting effect, and, as a result, the silica gel provides only an insufficient haze inhibiting effect. Therefore, if the physical properties of the silica gel contributing to enhancement of the haze inhibiting effect are found and arc all improved when preparing the silica gel, the haze inhibiting effect could be remarkably enhanced.
SUMMARY OF THE INVENTION
An object of this invention is to provide a silica gel having the physical properties contributing to enhancement of a haze inhibiting effect improved in a well balanced manner.
Another object of this invention is to provide a method of manufacturing a silica gel which can prevent the generation of haze of beer.
A further object of this invention is to provide a method of stabilization treatment of beer using a minimum quantity of silica gels.
To attain these or other objects, the invention provides a silica gel for stabilization treatment of beer prepared by calcination at a temperature of 400-800° C. between 10 seconds and 10 hours. The silica gel has a specific surface area of 700-1000 m
2
/g, a pore volume of 1.1-1.6 ml/g and a average pore diameter of 6-10 nm.
If the calcination temperature is lower than 400° C., the silica gel provides an insufficient adsorbability. If the calcination temperature exceeds 800° C., although the surface of the silica gel gains an improved quality, the specific surface area and the pore volume tend to be lowered because sintering is effected. Further undesirably, the specific surface area, the pore volume and the average pore diameter or other physical properties of the silica gel cannot be easily controlled to the optimum values required in the invention.
If the calcination time is shorter than 10 seconds, the quality of the silica gel surface can be improved only insufficiently. Even if the calcination time exceeds 10 hours, a further improvement in the surface quality cannot be expected and this is ineffective in cost.
According to the invention, the silica gel desirably has a large specific surface area. If the specific surface area is less than 700 m
2
/g, the silica gel cannot provide better adsorbability as compared with the conventional silica gel. However, the silica gel having a specific surface area greater than 1000 m
2
/g cannot be easily manufactured industrially, and this is not practical.
Furthermore, if the average pore diameter of the silica gel is less than 6 nm, the adsorbability of the silica gel remarkably deteriorates, while if the average pore diameter exceeds 10 nm, the specific surface area cannot be kept 700 m
2
/g or larger. Additionally, since the specific surface area, the average pore diameter and the pore volume are mutually dependent, the pore volume adequate for the industrial manufacture of the silica gel is between 1.1 ml/g and 1.6 ml/g while the average pore diameter and the specific surface area are controlled in the aforementioned ranges.
The present invention also provides a method of manufacturing a silica gel for stabilization treatment of beer. In the method, first a silica hydrosol is prepared by reacting silicate with inorganic acid such that the SiO
2
concentration is between 10% and 20% by weight, and is gelled, forming a silica hydrogel. The silica hydrogel is washed with water, hydrothermally treated with water having a pH of 2-8 at a temperature of 20-100° C. and acid treated with either inorganic or organic acid having a pH of 2-5. The washed, hydrothermally treated and acid treated silica hydrogel is ground into particles having a mean particle diameter of 5-30 &mgr;m, dried at a temperature of 100-1000° C. for 1-100 seconds, and calcined at a temperature of 400-800° C. for 10 seconds to 10 hours.
The present invention further provides a method of stabilization treatment of beer, in which the aforementioned silica gel is contacted with beer, and subsequently is separated from the beer.
As aforementioned, according to the invention, the calcination temperature is between 400° C. and 800° C., the calcination time is between 10 seconds and 10 hours, the specific surface area ranges from 700 to 1000 m
2
/g, the pore volume ranges from 1.1 to 1.6 ml/g and the average pore diameter ranges from 6 to 10 nm. Both specific surface area and average pore diameter have relatively large physical property values. The inventors found as a result of their earnest researches that when a certain degree of average pore diameter is assured, the larger the specific surface area is, the more the adsorbability per unit weight increases, and adjusted and determined the manufacture conditions in order to increase both the specific surface area and the average pore diameter. In general, the silica gel having a large specific surface area tends to have a small average pore diameter. In this case, a haze causing component does not easily permeate the pores in the silica gel, the adsorptive surface area of the silica gel is not substantially large, and only insufficient adsorption effect can he obtained. According to the invention, however, the silica gel has a large adsorptive surface area and a relatively high adsorbability per unit weight. Therefore, even a small quantity of silica gels can provide an excellent haze inhibiting effect.
In the method of manufacturing silica gels according to the invention, the silica hydrosol is prepared by reacting silicate with inorganic acid such that the SiO
2
concentration is between 10 and 20% by weight and gelled. Excessively low SiO
2
concentration would lengthen the period of gelation time, increase water content, and deteriorate an efficiency in the subsequent washing and drying steps, which is industrially impractical. Excessively high SiO
2
concentration could excessively accelerate the gelation process, and the silica hydrogel having uniform physical properties could not be obtained. As the silicate, sodium silicate, potassium silicate, ammonium silicate or other is available: sodium silicate is most used industrially. For the inorganic acid, sulfuric acid, nitric acid, hydrochloric acid or other is, available: sulfuric acid is generally used.
Subsequently, by washing the silica hydrogel with water, inorganic salt is removed. When the washed silica hydrogel is hydrothermally treated with water having a pH of 2-8 at a temperature of 20-100° C., the average pore diameter and the pore volume are increased. In this process, if the silica hydrogel is washed with water under the conditions corresponding to those for the hydrothermal treatment, the washing and the hydrothermal treatment can be carried out simultaneously. For the conditions of the hydrothermal tr
Ishiwata Yoshihisa
Ito Mutsuhiro
Okada Akihiko
Yamamoto Shinji
Fuji Silysia Chemical Ltd.
Sherrer Curtis E.
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