Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-02-25
2003-06-24
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S366000, C568S377000, C568S379000, C568S347000, C426S600000
Reexamination Certificate
active
06583322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Dihydro and hexahydro isoalpha acids having a high ratio of trans to cis isomers, process for the production thereof, and products containing the same.
2. Prior Art
There are four types of isoalpha acids: the unreduced form, called isoalpha acids (isohumulone) (IA), and three types of reduced forms of IA. The latter are dihydro-isoalpha acids (DHIA), also known as “rho”, tetrahydro-isoalpha acids (THIA), and hexahydro-isoalpha acids (HHIA). Each is present as three major analogues differing in an acyl side chain (the co, n, and ad analogues) and as trans and cis and optical isomers. The proportions of analogues depends upon the variety of hops used to make the iso acids. Only IA, DHIA, and THIA have been and are available as aqueous forms. Their structures are shown in
FIGS. 1 and 2
.
IA and THIA do not form insoluble crystalline precipitates upon standing, due to their chemical composition, which includes a keto group on the lower acyl side chain. Commercially available all cis isomer DHIA and HHIA have this keto group reduced to an alcohol. They form precipitates over time, which are exceptionally hard to redissolve. Their solubility in water at pH 10 is about 1%, and much less at pH 7 to 8. The products described herein, containing large amounts of the trans isomers of DHIA and HHIA, are remarkably and unexpectedly soluble in water and overcome this limitation, being soluble in water at all concentrations below about 10% to 40%, depending upon the trans isomer content.
More Detailed Description of the Prior Art
Today, the four types of iso acids used by the brewer are liquids, consisting of their potassium salts in water or propylene glycol. Solids in the form of magnesium chelates have been substantially replaced by the liquids in the last decade.
Because of differences in the concentrations at which the solutions of a particular type of iso acid are most stable against precipitation, the four acid types are sold in different concentrations in different solvent systems. IA is sold as a 30% solution of its potassium salt at a pH of about 10 in water. DHIA is sold as a 35% solution of its potassium salt in water at a pH of about 10.5 and above, from which large, insoluble crystals of DHIA will precipitate over time. THIA is used as a 5% or 10% solution of its potassium salt at a pH of about 9.5 to 10.5 in water; and HHIA is not sold as an aqueous solution per se because of its limited solubility. Because of the keto groups in their side chains, neither IA nor THIA form crystals from saturated solutions, but rather can form gums at the bottom of the container upon cooling and standing. In these commercial preparations, the hop acids, and particularly 30% IA and 35% DHIA, as potassium salts at pH 10 or above in water, act as co-solvents for themselves. The co-solvent effect is demonstrated by the known tendency to precipitate and separate at lower concentrations, as discussed below under the Westermann prior art. However, all forms of hop acids can be solubilized in propylene glycol, as described in Todd (U.S. Pat. No. 3,486,906), and are available in this form, which also adds the advantage of increasing their dispersibility in soft water at pH 10 and above. Propylene glycol and ethanol solutions are the only forms of HHIA available, and their utility is impaired by the requirement of a solvent. The high trans products overcome the need to use propylene glycol or ethanol as a solvent. It should be noted that soft water must be used as the diluting agent for all potassium salt solutions of the iso acids, since calcium and magnesium in the water will form chelates with hop acids and cause a haze and agglomerates and gummy precipitates. Below pH about 9 to 10 in deionized water, the dilute solutions of the prior art DHIA and HHIA do not form a clear solution upon mixing but rather form gummy precipitates upon standing. The high trans products do not.
One common method of adding the hop acids post-fermentation is to dilute them to a 1% or less concentration in soft water to which KOH has been added to bring the pH to 10 or above (Held, Master Brewers of the Americas Association Tech. Quarterly, 35, 132-138, No. 3 (1998). The high pH of the water is essential to prevent the formation of precipitates in the 1% dilute solution, and this has been ascribed to incomplete solubility of the hop acids in the dilute aqueous solution at lower pHs. These dilute alkaline solutions form hazes upon standing, and also form precipitates causing haze after injection into beer or “stringers” of precipitates on the inside of a pasteurized beer bottle. The viscosities of the concentrated solutions make it impractical to inject them directly into beer, and in addition they tend to “shock out” and form particulate matter due to the rapid reduction of pH as they are introduced, plugging the injection nozzle from time to time.
Solid magnesium chelates of IA are well described in Clarke, (U.S. Pat. Nos. 3,765,903 and 3,956,513). Others have added to his basic concept, but all IA chelates behave similarly. Chelates of DHIA and HHIA have never been commercialized. The water-insoluble microparticulate solid chelates are added to water, in which they disperse as a cloudy haze which in turn is added to the unfinished beer. Other chelate preparations are described in Humphrey (U.S. Pat. No. 3,875,316) and Mitchell (U.S. Pat. No. 1,161,787).
Aqueous suspensions of solid micro particles of DHIA and HHIA are described in Guzinski (PCT/US97/04070). These suspensions were made from commercial all cis products (p12, 1 23-24) made by the prior art procedures described herein. They are suspensions. They had the advantage over the prior art commercial solutions of DHIA in that they did not require heating to about 80-90° C. to redissolve precipitates before use. Indeed, one of the major advantages was the ability to redissolve the micro-particles by heating to about 60° C. The redissolved solution was in turn diluted to 1% in soft water at a pH of 10 prior to injection in the beer. Alternatively, the micro particles could be added directly to pH 10 soft water preheated to about 50° C., wherein they would dissolve and form a clear 1% solution within five minutes. The 1% solution, as in the case of the other prior art commercial products, forms a haze upon standing (page 23, line 5), while the high trans product does not. Furthermore, his product, like other prior art products, is not soluble at a 1% concentration in neutral soft water, whereas the products described herein are completely soluble. And furthermore, his product still required heating, albeit less vigorous than 80-900° C. The novel high trans product can preferably be used at ambient temperature, including brewhouse cellar temperatures of 10° C. or less. The commercialization of his product was abandoned because of its limitations in practical brewing use, and particularly the need to heat it and the lack of clarity upon dilution.
DHIA is made from alpha acids by isomerization and reduction using sodium borohydride, first described by Koch (U.S. Pat. No. 3,044,879). A superior process based on Koch was described in Westermann (U.S. Pat. No. 3,798,332), which used an extract made by his earlier invention (U.S. Pat. No. 3,558,326). Goldstein (U.S. Pat. No. 4,324,810) describes a method of making DHIA without the use of organic solvents. Today, manufacturers optionally separate the alpha acids from the remainder of the extract prior to isomerization and reduction, as described in Goldstein U.S. Pat. No. 4,767,640. These investigators produced the essentially all cis forms of the acids.
Todd (U.S. Pat. No. 4,002,683) describes an improved method for separation of alpha acids and subsequent isomerization to IA, which is the preferred method of separating alpha acids from an extract. A less desirable procedure for the separation of alpha acids from an extract and conversion to IA is given in Klingel, (U.S. Pat. No. 3,364,265), who also describes solid salts of IA. Mitchell (U.S. Pat. No. 3,949,092) describes
Guzinski James A.
Mennett Randall H.
Shahlai Khalil
Todd Paul H.
Kalamazoo Holdings, Inc.
Killos Paul J.
Oh Taylor V
The Firm of Hueschen and Sage
LandOfFree
Dihydro and hexahydro isoalpha acids having a high ratio of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dihydro and hexahydro isoalpha acids having a high ratio of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dihydro and hexahydro isoalpha acids having a high ratio of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3115994