Food or edible material: processes – compositions – and products – Fermentation processes – Alcoholic beverage production or treatment to result in...
Reexamination Certificate
1999-12-17
2003-02-04
Sherrer, Curtis E. (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Alcoholic beverage production or treatment to result in...
C426S029000, C426S592000, C426S330400
Reexamination Certificate
active
06514542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to hopped malt beverages, especially alcoholic brewery beverages produced at least in part from malt, and to means for improving the flavor stability thereof. More particularly, the present invention relates to imparting to hopped malt beverages improved stability against the production of thiols associated with the development of a “skunky” odor and flavor in beer that has been exposed to ultra-violet or visible light.
2. Description of Related Art
The process of preparing fermented malt beverages, such as, beer, ale, porter, malt liquor, and other similar fermented alcoholic beverages, hereinafter referred to simply as “beer” for convenience, is historically well established. As practiced in modern breweries, the process, in brief, comprises preparing a “mash” of malt, usually with cereal adjuncts, and heating the mash to solubilize the proteins and convert the starch into sugar and dextrins. The insoluble grains are filtered off and washed with hot water that is then combined with the soluble material. The resulting wort is boiled in a brew kettle to inactivate enzymes, sterilize the wort, extract desired hop components from added hops, and coagulate certain protein-like substances. The wort is then strained to remove spent hops and coagulum, cooled, pitched with yeast, and fermented. The fermented brew, known as “green” or “ruh” beer, is then aged (“lagered”) and clarified, filtered, and carbonated to produce the desired finished beer.
It is well known in the brewing art that when beer is exposed to light of wavelengths between about 300 nm and about 500 nm, the beer quickly develops a so-called “skunky” flavor, which is sometimes also referred to as “sunstruck” or “light struck” flavor. A considerable body of research has resulted in at least partial understanding of the chemical pathways involved. It is widely believed that the photochemical reaction sequence is initiated by the absorption of light by the presence of one or more of the several photosensitizers, e.g., flavins, especially, riboflavin, that are present in beer, which become excited, and, in their excited state, react with the bittering principles in the beer, isohumulones, to form 3-methyl butene thiol (3-MBT), which is understood to be the principal source of the skunky aroma. Only very small amounts of these sulfur-containing compounds are required to be present to impart the skunky flavor to the beverage and render it unacceptable. The riboflavin emanates mainly from the malt, to a minor extent via the hops used in the production of beer, and, according to common wisdom, the action of yeast during the fermentation. (See Tamer et al.
Enzyme Microb Technology
10:754-56, December 1988.) This photochemical reaction is a problem that to some degree has been the subject of a diverse remediation.
More particularly, present understanding is that the reaction sequence is initiated by the absorption of light by riboflavin that is excited and, in its excited state, reacts with the bittering principles in beer, isohumulones, to form excited state isohumulones. The excited isohumulones then undergo a Norrish type I cleavage to give a 4-methyl-3-pentenoyl radical, which, in turn, fragments to carbon monoxide and a 3-methylbutenyl radical. The 3-methylbutenyl radical then reacts with cysteine or other suitable sulfur donors that may be present in the beer to form 3-MBT.
Excited isohumulones can, in principle, also be generated by direct absorption of ultraviolet light. The UV spectrum of trans isohumulone shows a small, but real, absorption of light of a wavelength between 300 nm and, approximately, 350 nm. Flint glass, although it absorbs all light below 300 nm, does not, therefore, completely protect isohumulones from direct UV excitation.
One approach that has been widely adopted relies on primary packaging coloration or opacity either to exclude light or, at least, exclude those wavelengths of light that are particularly problematic. Such attempts to prevent beverages from becoming skunky involve enclosing the beer in opaque cans or in bottles made of protective, i.e., colored, glass—brown or amber being the most efficient (see U.S. Pat. No. 2,452,968). These bottles reduce or eliminate the transmission to the beer of light having a wavelength shorter than about 560 nanometers. Such light is the most harmful because it assists the riboflavin in enhancing the production of the undesirable volatile sulfur compounds.
Brown bottle glass has become a standard for the brewing industry for avoiding the formation of skunky off-flavors, although in some circumstances green glass can be employed, generally with reduced efficacy.
Flint, or clear, glass—apart from the exclusion of a preponderance of ultraviolet wavelengths—is ineffective as packaging for traditional beer products that are susceptible to the formation of skunky off-flavors on exposure to visible wavelengths, although its use is desirable in order to permit the consumer to view the contents of the package.
More recently, chemically reduced isohumulones have been used for bittering in lieu of natural isohumulones. (See Verzele, M., et al.,
U. Inst. Brew.
73:255-57, 1967.) Since skunky thiol is not formed from these compounds, the resulting beers do not develop light struck flavor when exposed to light. Unfortunately, the bittering properties of the reduced isohumulones are not identical to natural isohumulones and, hence, this approach results in flavor modification.
Other methods involve adding light-stabilizing materials to the beverage. (See U.S. Pat. No. 4,389,421.) However, in some jurisdictions, the use of such compounds has not been approved. Further, many brewers are reluctant to use any additives at all, but, rather, use hops or hop extracts in an effort to achieve traditional beer flavor.
Another alternative has been suggested in U.S. Pat. No. 4,389,421. This patent describes malt beverages that have added organic compounds possessing a 1,8-epoxy group and, optionally, another compound having a 1,4-epoxy group. The amount of the 1,8-epoxy compound is at least 0.25 ppb and, preferably, about one to six ppb by weight. Suitable sources of the 1,8-epoxy compounds are said to include 1,8-cineole, or plant essences from cardamom, eucalyptus, peppermint, lavender, laurel, or star anise. A suitable 1,4-epoxy compound is said to be 1,4-cineole. It is taught that the addition of these compounds prevents the development of the “light struck” flavor in a range of malt beverages (for example, beer, ale, malt liquors, etc.).
The problem of skunky flavor has been the subject of research for many years, and such research continues. (See Sakuma et al., “Sunstruck Flavor Formation in Beer,”
American Society of Brewing Chemists, Inc.,
162-65, 1991). This article also deals with the part believed to be played by riboflavin in the reaction that produces the “skunky” flavor and suggests that removing riboflavin from the finished beer may solve the problem.
U.S. Pat. Nos. 5,582,857 and 5,811,144 disclose a process for the production of a hopped malt beer wherein a processing liquid containing riboflavin is hopped to form the desired beverage. The improvement comprises subjecting that processing liquid to an effective amount of actinic radiation of a wavelength adapted to decompose the riboflavin and thereby reduce the amount thereof, whereby a beer having enhanced light stability is obtained. “Process liquid” is defined as any unhopped wort or fermented wort (including green or bright beer) produced using malt.
U.S. Pat. No. 6,207,208, the disclosure of which is incorporated herein by reference in its entirety, is directed to the addition of an adsorbent clay to the process liquid of a brewing process to adsorb, and thereby remove, riboflavin present in the process liquid.
In that application, an improved process is provided for the production of a beer in which process a process liquid having a high riboflavin content is hopped to produce the desired beverage, wherein the improvement c
Maradyn David Jack
McGarrity Michael Jerome
Stewart Robert Joseph
Thompson Donald James
Tinginys Amanda Mary
Labatt Brewing Company Limited
Levy & Grandinetti
Sherrer Curtis E.
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