Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-05-03
2002-12-03
Ford, John M. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S598000
Reexamination Certificate
active
06489509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aqueous potassium sorbate solution exhibiting successively stable hue, a production method and a storing method of the same, and a method of producing potassium sorbate.
2. Description of the Related Art
Sorbic acid and its salts have antiseptic and antimicrobial activities and are substantially nontoxic to the human body in normal concentrations in practical use. These compounds are therefore useful as food additives. Of a variety of known processes for producing sorbic acid, a commercially important pathway is a process of polymerizing crotonaldehyde and ketene to form an intermediate polyester, and decomposing the polyester to yield sorbic acid. Sorbic acid obtained by this technique contains a variety of colored substances and other impurities and is generally subjected to a purification operation such as treatment with activated carbon, distillation or recrystallization, and is then subjected to a neutralization reaction with potassium hydroxide to thereby yield potassium sorbate. The above-prepared potassium sorbate is in an aqueous solution state and is generally further subjected to a drying process to evaporate water to thereby yield powdery potassium sorbate, or is further subjected to a granulation process to thereby yield granular potassium sorbate. In actual use as a food additive, however, potassium sorbate is dissolved again in water and is used as an aqueous solution.
In general, potassium sorbate increases in color and odor over time after its production and is deteriorated in quality. Potassium sorbate in an aqueous solution state particularly strongly has this tendency and is deteriorated in quality in a short time, and the solution itself is colored. A powdery or granular potassium sorbate obtained by drying such a colored aqueous potassium sorbate solution is naturally colored and does never exhibit a recovered hue.
Regarding dried potassium sorbate, a variety of measures to prevent deterioration in quality have been taken and many proposals have been made. Such proposals include, for example, a production method, in which colored substances are removed in the production process to thereby improve hue immediately after production, and a storing method, in which a storage container is sealed with an inert gas or a moisture-impermeable packing material is used. However, each of these techniques is directed to dried potassium sorbate, and no effective solution on potassium sorbate in an aqueous solution state has been proposed. Accordingly, the aqueous potassium sorbate solution must be immediately dried and granulated to yield a dried product in conventional production methods.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an aqueous potassium sorbate solution exhibiting successively stable hue, and methods of producing and storing the aqueous solution.
Another object of the present invention is to provide an aqueous potassium sorbate solution and methods of producing and storing the same, which are useful for obtaining potassium sorbate exhibiting satisfactory and successively stable hue.
A further object of the present invention is to provide a method of producing potassium sorbate exhibiting satisfactory and successively stable hue.
To achieve the above objects, the present inventors focused attention, among a series of production steps for potassium sorbate, on a step for the neutralization of sorbic acid with potassium hydroxide and on the resulting aqueous potassium sorbate solution obtained in this step. They found that there is a link between deterioration of hue and dissolved oxygen contained in an aqueous solution, when potassium sorbate is stored in the state of an aqueous solution. This finding suggested that colored substances are formed by an action of oxygen dissolved in the aqueous solution. Finally, the present inventors found that deterioration of hue during storage as an aqueous solution can be prevented by controlling the dissolved oxygen concentration in the aqueous potassium sorbate solution to a specific range and that this type of aqueous potassium sorbate solution can yield potassium sorbate exhibiting satisfactory and successively stable hue (color).
Specifically, the present invention provides, in an aspect, an aqueous potassium sorbate solution having a dissolved oxygen concentration of 3.0 mg/l or less.
In another aspect, the present invention provides a method of producing an aqueous potassium sorbate solution, which includes the step of degassing an aqueous potassium sorbate solution to thereby control the dissolved oxygen concentration in the aqueous solution to 3.0 mg/l or less.
In a further aspect, the invention provides a method of producing an aqueous potassium sorbate solution, which includes the step of allowing sorbic acid to react with potassium hydroxide in the presence of water. In this method, the reaction is performed in a system in which the oxygen concentrations of a gas phase and of materials to be reacted are reduced to thereby yield an aqueous potassium sorbate solution having a dissolved oxygen concentration of 3.0 mg/l or less.
The invention provides, in yet another aspect, a method of storing an aqueous potassium sorbate solution, which includes the step of storing an aqueous potassium sorbate solution having a dissolved oxygen concentration of 3.0 mg/l or less in such a condition that the oxygen concentration of a gas phase above the liquid level of the aqueous solution is less than that in the atmospheric air.
The invention provides, in another aspect, a method of storing an aqueous potassium sorbate solution, which includes the step of storing an aqueous potassium sorbate solution having a dissolved oxygen concentration of 3.0 mg/l or less in a container composed of an oxygen-impermeable material.
In addition and advantageously, the invention provides a method of producing potassium sorbate, which includes the step of drying an aqueous potassium sorbate solution having a dissolved oxygen concentration of 3.0 mg/l or less to thereby yield a powdery or granular potassium sorbate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A feature of an aqueous potassium sorbate solution of the present invention is that the aqueous solution has a dissolved oxygen concentration of 3.0 mg/l or less. If the dissolved oxygen in the aqueous potassium sorbate solution is out of the above-specified range, the aqueous solution markedly becomes colored over time. This is provably because colored substances are formed by action of oxygen contained in the aqueous potassium sorbate solution. In other words, minimized oxygen prevents the formation of colored substances to thereby reduce hue change over time.
The aqueous potassium sorbate solution is obtained by allowing sorbic acid to react with potassium hydroxide in the presence of water. Material sorbic acid is not specifically limited and includes any sorbic acid obtained by a known or conventional method. Sorbic acid is generally produced by, for example, a process in which crotonaldehyde is allowed to react with ketene in the presence of a catalyst such as a zinc salt of fatty acid to yield a polyester, and the polyester is hydrolyzed with an acid or alkali. The above-prepared sorbic acid generally contains a variety of impurities and requires a purification operation to remove the impurities. The purification operation includes, but is not limited to, treatment with activated carbon, distillation, recrystallization, and other known or conventional operations, and combinations of these operations.
Potassium hydroxide for use herein includes any potassium hydroxide which is pursuant to industrial standards and is commercially available, of which an aqueous potassium hydroxide solution is preferred for its easiness in handling. The concentration of such an aqueous potassium hydroxide solution is, for example, from about 45% to about 50% by weight, and preferably from about 49% to about 50% by weight.
A reaction (a neutralization reaction) between sorbic
Kamei Noboru
Kouno Mitsuhiro
Daicel Chemical Industries Ltd.
Ford John M.
Tucker Zachary C.
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