ISO-ALPHA-ACID FORMULATION AND ITS USE

Abstract: A substantially stable aqueous emulsion comprises a water-insoluble, reduced iso-alpha acid and a food grade gum in an amount of no more than 2 % by weight of the emulsion. The emulsion is useful as a bittering additive for beer.

Description: Iso-alpha-add formul ation and Its use Field of the Invention The present invention relates to the incorporation of reduced, or hydrogenated, iso-alpha acids into beer as bittering additives, and in particular to formulations of these. Background of the Invention Reduced iso-alpha acids are becoming increasingly popular with brewers because they have advantages over conventional, non-hydrogenated, iso-alpha acid products. Of particular interest is their desirable effects on foam stability and lacing at relatively low addition rates, ie 1 to 5 ppm. Some of these acids have a greater impact on sensory bitterness than do the conventional iso-alpha acids, for instance by a factor of 1.6 to 1.8. Also, when used as a total hop replacement, the beer obtained is less susceptible to flavour instability caused by the action of light. However, a significant disadvantage of some reduced iso-alpha acids, in particular tetrahydroiso- and hexahydroiso-alpha (THIAA and HHIAA, respectively) , is their poor solubility in aqueous media, resulting in handling and dosing problems in the brewery. Attempts have been made to overcome these problems, for example, by dissolving these acids in alkali, and restricting their concentration to no more than 10 wt.%. Under these conditions, however, the acids slowly come out of solution to form a gum phase in the bottom of the container, and this phase separation occurs more rapidly at lower temperatures. Once out of solution, the reduced iso-alpha acids are difficult to redissolve, requiring warming to 55 to 60°C and vigorous agitation to do this. If this procedure is not carried out efficiently the result is a significant, and costly, loss of such acids. It is also known to use solubilising agents for reduced iso-alpha acids. Typically food grade alcohols, such as propylene glycol (typically 15% by volume) , have been used. Phase separation still occurs during storage, but re-dissolution in the brewery is simpler. US-A-3615660 discloses a process for solubilising pre- isomerised and reduced hop extracts comprising mixing with the said extracts gum arabic and an emulsifier. The amount of gum arabic used is at least 7% by weight, and is typically more. Preferably, sorbitol is also used, in an amount of up to 45% by weight. A disadvantage with this process, therefore, is that the " amount of emulsifying/stabilising agents used is very high compared to the amount of bittering acids, the former typically being greatly in excess. Also, the incorporation of these non-hop derived ingredients into beer at such a high amount can be detrimental to its taste. Summary of the Invention According to a first aspect of the present invention, a substantially stable aqueous emulsion comprises a water- insoluble, reduced iso-alpha acid and a food grade gum in an amount of no more than 2% by weight of the emulsion. According to a second aspect of the present invention, a method for preparing beer comprises mixing together beer and an emulsion of the type described above. Surprisingly, the aqueous emulsion of the invention is sufficiently stable for it not to undergo phase separation over a reasonable period of storage, eg. several weeks or months, or longer. If separation does occur, re-suspension is easily achieved even after periods of, say, a year or longer. Its dissolution into beer is both simple and practical and reduces considerably the amount of bittering iso-alpha acids lost during preparation and use in the brewing process, making the brewing process more economical. A further advantage resides in the surprisingly low amount of gum needed to stabilise the emulsion. This means that the amount of non-hop derived ingredients in both the emulsion and the final beer is extremely low compared to the amount of bittering acids or, put another way, per unit of bitterness. This represents a significant advantage over the prior art. Description of the Invention By a substantially stable emulsion it is meant an emulsion from which substantially none of the iso-alpha acid phase separates out other than minor aggregation of emulsified acid globules. These globules are readily and fully re-suspended by gentle agitation, without recourse to heat. The reduced iso-alpha acids used in the present invention are typically selected from THIAA, HHIAA and dihydroiso-alpha acids (DHIAA) , and mixtures thereof. Such acids can be included in the emulsion in an amount of up to 50% by weight, or higher depending on the nature and/or the amount of gum, and optionally emulsifier, used. Typically, however, they are included in an amount of up to 30%, preferably 10 to 20%, by weight of the total emulsion. As each acid imports different properties into beer, with regard to bitterness, foam stability, stability to light etc, the use of a mixture of acids allows the brewer to balance those properties according to the properties required in the final beer. The amount of food grade gum included in the emulsion is no more than 2% by weight of the total emulsion, and is preferably at most 1.5% or 1% by weight. The most preferred amounts of gum are in the range 0.1 to 0.5% by weight, and in particular around 0.35% by weight. Examples of suitable gums include xanthan gum, guar gum, polypropylene glycol alginate, cellulose ethers, and mixtures thereof. The preferred gums are xanthan gum and guar gum, and the most preferred is xanthan gum. As is apparent from the above, the amount of gum needed to emulsify the iso-alpha acids is relatively small. Preferably, the ratio of acid:gum is at least 10:1, and is more preferably at least 20:1 by weight, in practice typically being in the range 30:1 to 60:1. It is preferred to include a food grade emulsifier in the emulsion, particularly when the concentration of the water-insoluble iso-alpha acid is relatively high, to increase the emulsion stability. The amount of emulsifier used tends to be dependent upon the concentration of water- insoluble acid present, and typically varies between 150 and 4500 ppm, preferably between 1500 and 3000 ppm. Suitable emulsifiers include those in the Tween and Span ranges, eg. Tween 80 and Span 60. Mixtures of emulsifiers can also be used. The remainder of the emulsion generally comprises water, as generally it is not necessary to include further stabilising agents for the emulsion. Preparation of the emulsion is both simple and rapid. The preparation comprises mixing the water-insoluble, reduced iso-alpha acid in the form of the free acid into water having a temperature of 50-85°C, preferably 60-80°C. Preferably, the water is deionised water. If an emulsifier is included in the system, the food grade gum is typically mixed into the water first using a high shear mixer. The water-insoluble acid is then admixed with a quantity of the emulsifier, and added to the gum/water mixture. After mixing for a short period of time, which will tend to be dependent on the type of mixer and vessel used but which will typically be less than 20 minutes, the emulsion is ready for packaging. Dosing the emulsion into beer is carried out after fermentation and simply requires mixing beer and the emulsion, either in a container or "in-line" during beer transfer, using conventional brewing techniques. The present invention is now further illustrated by the following Examples. In each of Examples 1 to 3 emulsion stability was assessed visually, and is therefore a qualitative measure. Example 1 Formulations 1 to 8 shown below in Table 1 below were prepared as follows. Deionised water was heated to 80°C. Xanthan gum was mixed into the water using a Silverson shear mixer. THIAA, in the form of the free acid, was admixed with a quantity of Tween 80 (emulsifier) , and then added to the xanthan/water mixture, and mixed for about 30 seconds on the same mixer. The stability of the resulting emulsion is described in Table 1 below. Table 1 THIAA Xanthan Gum Tween 80 Emulsion (%) (%) (ppm) Stability 1.0 0.35 0 good 1.0 0.35 150 v.good 2.5 0.35 335 v.good 5.0 0.35 670 v.good 7.5 0.35 1000 v.good 10.0 0.35 1340 v.good 10.0 0.35 150 poor Example 2 The following food grade gums were tested in the invention at the concentrations (by weight) shown: Xanthan gum 0.35% Guar gum 0.35% and 0.7% Polypropylene glycol alginate 0.5% Methyl cellulose 0.35% In each case, a 10% by weight tetrahydroiso-alpha acids emulsion was prepared as follows: 10.5 g of gum (21 g in case of a concentration of 0.7% by weight) was slowly added to 2640 g of deionised water at 70 to 80°C with stirring using a high shear mixer. Once the gum was fully dispersed, 340 g of tetrhydroiso-alpha acids (88.2% w/w pure), in which 4.5 g of Tween 80 was already dispersed, was added with the mixer operating at maximum speed. After addition of the tetrahydroiso-alpha acids was complete, stirring was continued for a further 10 minutes. The resulting emulsion was then ready for packaging. The results achieved with the different gums are summarised in the Table 2 below. Table 2 Gum (concn.) Evaluation of Emulsion Initial One Week Four Weeks Xanthan (0.35%) v.good good v.good Guar (0.35%) v.good 20% 20% separation, separation, readily re- readily re- suspended suspended Guar (0.70%) v.good good good Propylene Glycol v.good 80% 80% Alginate (0.5%) separation, separation, readily re- readily re- suspended suspended Methyl Cellulose good 70% 70% (0.35%) separation, separation, readily re- readily re- suspended suspended Example 3 A number of emulsions were prepared according to the method outlined in Example 2 above, using xanthan gum at a concentration of 0.35% by weight but varying the concentration of THIAA. Table 3 In most cases, some separation of the emulsion was evident after four weeks storage at room temperature. In all cases apart from emulsion 5, the emulsion was easily re-suspended by shaking for a few seconds. Example 4 Trial beers were produced by taking a commercial beer at high gravity and diluting to sales gravity in the keg. Hop additions were made directly to the keg (the addition rate being 5mg/l) , in the form of a 10% by weight THIAA emulsion (the invention) and two conventional, commercial, 10% by weight THIAA aqueous solution. The trial beers were then carbonated to 1.5 vols. and subjected to routine analysis, foam evaluation and flavour assessment. The results are shown in the Table 4 below. Table 4 In Table 4, O.G. = Original Gravity, P.G. = Present Gravity, and HRV = Head Retention Valve. The flavour properties of the two beers were similar.

Claims: CLAIMS 1. A substantially stable aqueous emulsion comprising a water-insoluble, reduced iso-alpha acid and a food grade gum in an amount of no more than 2% by weight of the emulsion. 2. An emulsion according to claim 1, which comprises no more than 1% by weight of the gum. 3. An emulsion according to claim 1 or claim 2, wherein the ratio of water-insoluble, reduced iso-alpha acid:gum is at least 10:1 by weight, eg. in the range 30:1 to 60:1. 4. An emulsion according to any preceding claim, which comprises up to 50% by weight of the water-insoluble, reduced iso-alpha acid. 5. An emulsion according to claim 4, which comprises up to 30% by weight of the water-insoluble, reduced iso-alpha acid. 6. An emulsion according to any preceding claim, wherein the water-insoluble, reduced iso-alpha acid is selected from tetrahydroiso-alpha acid (THIAA) and hexahydroiso- alpha acid (HHIAA) , and mixtures thereof. 7. An emulsion according to any preceding claim, which further comprises a food grade emulsifier, eg. Tween 80. 8. An emulsion according to any preceding claim, wherein the food grade gum is selected from xanthan gum, guar gum, polypropylene glycol alginate, cellulose ethers, and mixtures thereof. 9. An emulsion according to claim 8, wherein the food grade gum is xanthan gum. 10. A method for making beer which comprises mixing together fermented beer and an emulsion according to any preceding claim. 11. Beer obtainable by a method according to claim 10.

Inventors: COMBES PETER, PARKER GRAHAM, WESTWOOD KEITH, COMBES, PETER, PARKER, GRAHAM, WESTWOOD, KEITH
Applicants: COMBES PETER, PARKER GRAHAM, WESTWOOD KEITH, WIGAN PRODUCTS LIMITED, COMBES, PETER, PARKER, GRAHAM, WESTWOOD, KEITH
Application year: 1996
Main classification: C12C3
IPC codes: C12C3