Patent Application
20100055236
The invention relates to methods for making beer and other malt-based fermented beverages.
Typically, the brewing process includes the following steps, as represented in
During some of these steps, it is known that there is a risk of oxidation of the matter treated, thereby leading to an oxidized flavor which is negative for the final product. For example, oxidation of the mash (mixture of crushed malt and water) may occur at the time of brewing, or else oxidation of the wort may occur during the cooking step. During the brewing per se, the literature indicates that approximately 20 mg/l of dissolved oxygen are absorbed and that approximately 76 mg/l are absorbed until the end of cooking of the wort.
Currently, brewers seek to take as many precautions as possible to avoid oxidation, in particular by avoiding the incorporation of a large amount of oxygen throughout the beer-making process, and more particularly during the steps for producing the wort before the fermentation step in order to improve its organoleptic stability during its storage. With this aim, for example, the company Drummond Brewing Co. uses an on-line system of deoxygenation with nitrogen for reducing the oxygen content, of the water used to dilute its concentrated beers, from 6.5/7 ppm to 0.2/0.3 ppm, and also for the filtration operations (Food Processing, 1993, page 129).
However, brewers also focus on the brewing and wort-cooking phases, these being determining steps for the final quality of the beer. Several techniques using gases make it possible to limit wort oxidation phenomena during the brewing.
The first is to work under an atmosphere devoid of oxygen by inerting with a gas, in order to prevent any incorporation of oxygen into the mash. Thus, it has been shown that inerting the vessels with nitrogen during the mashing and the brewing (gas overhead), but also during the crushing of the malt, improves the reducing power of the wort and, consequently, the stability of its flavor. It also makes the wort slightly less colored (see, for example, D. G. Taylor et al., MBAA Technical Quarterly, 1992, vol. 29). The reducing power of a wort is evaluated by the concentration of free-radical-scavenging compounds (such as polyphenols) therein, and is used to predict the stability of the flavor of a beer.
Similarly, T. Desrone et al. (Bios, 1981, vol. 12, No. 4) have shown that carrying out brewing under CO2 makes it possible to improve the problems posed by excessive dissolution of air in the mash, namely a decrease in the filterability of the wort, and also in the concentration of elements thereof essential for the subsequent fermentation step (sugar, α-amino nitrogen, total nitrogen).
Another technique proposed by the literature for limiting wort oxidation is to degas the ingredients used in the mashing, i.e. the water and the malt grist. Thus, some authors have studied the influence of the presence of oxygen during the brewing on the quality of a wort and of a beer. To do this, malt flour deaerated under vacuum and water through which nitrogen or CO2 had been bubbled were mixed under an inert atmosphere before the brewing. These treatments, which make it possible to eliminate the oxygen in the brewing, reduced the nonenal potential (indicator of the risk of aging of the future beer) of the filtered must, and also the amount of trans-2-nonenal in the beer after aging, whether said aging was natural (3 months) or else accelerated.
The deoxygenation of the grist can also be carried out with gases. Thus, some authors have proposed a new brewing system which makes it possible to reduce the oxygen consumption during mashing by combining three factors: introduction of the ingredients via the bottom of the brewing vessel, degassing of the water and treatment of the grist with CO2 so as to flush the oxygen therefrom.
Moreover, the University of Louvain has evaluated the effect of nitrogen bubbling during brewing (Journal of Agricultural and Food Chemistry, 2002, vol. 50, no. 26). The results show that deoxygenation of the water+malt mixture makes it possible to reduce the nonenal potential of a wort after filtration and after cooking.
In order to be even more thorough with regard to the analysis of the prior art in this field, the studies by Sapporo Breweries Ltd., which proposes in document JP 2000004866 a method for producing malt-based alcoholic beverages by which the reducing power is reinforced in order to increase the resistance to oxidation of the final product and therefore to improve the aging of the latter, may also be mentioned.
Firstly, it is suggested to reduce the oxygen concentration in the atmosphere over all or some of the production steps. To do this, it is proposed:
Secondly, it is suggested to control the stirring speed during the mashing by reducing it to the minimum speed necessary to ensure mixing of the ingredients with the brewing water, so as to optimize the reducing power of the mash.
Prior publications which cite the use of hydrogen may also be mentioned:
This deoxygenation treatment requires the use of a metal catalyst in order for it to be possible for the reactions between the hydrogen and the oxygen to take place. So as not to have to subject the hydrogen to authorization according to German legislation, the treatment is carried out in such a way that there is no trace of hydrogen remaining in the product. For this, the hydrogen is added stoichiometrically as a function of the amount of dissolved oxygen in the water to be treated;
In summary, it may be said that the approach of the techniques used in the existing literature is to flush the dissolved oxygen from the medium under consideration, or else quite simply to put in place, conventionally, an inert gas overhead (“headspace”) above the medium under consideration.
One of the objectives of the present invention is then to propose novel operating conditions for making beer which make it possible in particular to improve the sensory characteristics of the product obtained. In fact, the current techniques for improving the wort flush away the oxygen present in the water or the atmosphere. However, whatever the means used, a small amount of residual oxygen is inevitable. The present invention proposes to go further, i.e. to prepare the wort in a reducing medium, i.e. a medium with an oxidoreduction potential below what it is when the medium has simply been degassed using a neutral gas; preferably, a negative redox potential will be established, using a reducing gas or a mixture of reducing gases. The amount of degradation precursor molecules formed during the preparation of the wort will thus be significantly reduced, which will result in a decrease in the nonenal potential of the wort and better organoleptic stability of the beer during aging thereof.
As will be seen in greater detail below, the present invention proposes to reduce the oxidoreduction potential of at least one of the media involved in the production line before cooking: for example of the mash before brewing, during the brewing per se, or else of the wort after filtration and before cooking, this being by injecting a mixture of reducing gases (for example a mixture of gases comprising hydrogen) into the medium under consideration.
The introduction of a mixture of reducing gases has the advantage of very significantly reducing the oxidoreduction potential of the medium under consideration, in proportions much higher than what would be obtained by simply degassing using a neutral gas as recommended by the prior art, which is the best prevention of any oxidation reaction. Such a mixture of reducing gases, such as an N2—H2 mixture, is, moreover, sensorily neutral, nontoxic, and authorized in food products, unlike many chemical reducing agents.
Thus, according to the present invention, unlike the prior art, the objective of which was, for example through removal of the oxygen in the water and the mash by bubbling with CO2 or else with nitrogen, to remove a substrate of the enzymatic and nonenzymatic oxidation reactions resulting in the reduction of trans-2-nonenal in the beer, the approach of the present invention goes further since it proposes acting on the redox potential by means of an active gas or a mixture of active gases which does not limit itself to deoxygenating the mash. Thus, a reducing gas or a mixture of gases containing a reducing gas, such as hydrogen, is injected at one or more places so as to significantly lower the redox potential of the wort, as described below.
The invention therefore proposes injecting a reducing gas or a mixture of reducing gases in one or more steps of the method for making beer, this being carried out before the step of cooking (or “boiling”) the wort, the injection making it possible to attain a redox potential value of the medium under consideration which is below what would be obtained when the medium has simply been degassed using a neutral gas.
The method according to the invention may, for example, adopt one or more of the following characteristics:
It may be specified that the gas/liquid contact can be obtained according to one of the methods well known to those skilled in the art, such as bubbling through the liquid to be treated using a frit, a membrane or a porous material, agitation using a hollow-shaft turbine, use of a hydro-injector, etc.
On-line injections can also be carried out on various parts of pipework of the production plants leading from one station to the other in this plant.
Other characteristics and advantages of the invention will become apparent on reading the description which follows. Forms and embodiments of the invention are given by way of nonlimiting examples.
Tepral brewing and filtration tests were carried out with the objective of determining the effect of modifications of the redox potential of the mash, by using gas, on:
To do this, the following procedure was applied for each test: the mash (consisting of 57 g of fine grist and 200 g of water) was subjected to the following temperature increase scheme: 15 minutes at 50° C., increase to 63° C. (1° C./min), 15 minute hold at 63° C., increase to 75° C. (1° C./min), 15 minute hold at 75° C.
The mash was subsequently filtered and the draff was washed with 230 ml of hot water and under a nitrogen pressure. The wort thus obtained was subsequently analyzed. The malt used was a two-row spring malt, of the Pils type.
Six tests were carried out: two control tests, two tests under the nitrogen condition and two tests under the nitrogen/hydrogen (96/4) condition:
The bubbling was carried out using a frit for 20 minutes. Moreover, after addition of the malt grist, the headspace of the vessel containing the grist and the water was swept with the same gas throughout the brewing, in order to prevent any reincorporation of oxygen into the mash.
The redox potential values (Eh) of the water thus gassed were measured with a Mettler Toledo probe. Similarly, the redox potential values of the mashes derived from the mixing of this water with the malt were recorded continuously throughout the brewing. The redox potential values thus measured were related back to pH 7 (by means of formulae well known to those skilled in the art, such as the Leistner and Mirna equation which makes it possible to relate the Eh of a medium of pH=x back to its value at pH 7).
The average redox potential values of the water used and those of the mashes obtained are given in table 1.
The nonenal potential of the worts obtained was measured in the following way: after conversion of the hydroperoxides of the polyunsaturated fatty acids present into trans-2-nonenal by heating under an inert atmosphere, the trans-2-nonenal was extracted with carbon disulfide and quantified by gas chromatography with detection by mass spectrometry.
The average nonenal potential values obtained are given in table 2.
These results show that the use of the gases according to the invention makes it possible to reduce the nonenal potential of the wort derived from the brewing. Specifically, it is observed that the nonenal potential of the control is greater than that obtained under the nitrogen condition, which is itself greater than that obtained under the nitrogen/hydrogen condition. Trans-2-nonenal is responsible for the appearance of the “cardboard” taste during aging of the beer. It has a very low perception threshold (0.1 ppb). This molecule is considered by those skilled in the art to be the compound that indicates the intensity of degradation of the quality of the beer due to oxidation reactions. The nitrogen/hydrogen condition therefore made it possible to halve the nonenal potential value of the wort. This lowering of the oxidizing potential is beneficial to the sensory stability of the beer.
The method for measuring the free amino nitrogen consists in heating the wort in the presence of ninhydrin and reading the absorbance of the sample at 570 nm relative to a “blank” sample of distilled water.
The average free amino nitrogen values obtained are given in table 3.
A slight increase in the free amino nitrogen of the wort is observed with the nitrogen and nitrogen/hydrogen conditions relative to the control. The determination of the free amino nitrogen of the wort gives an estimation of the amino acids and of the terminal alpha-amino nitrogen of the peptides and proteins. The nitrogen and nitrogen/hydrogen conditions therefore slightly increase the amount of substrate available for the yeast growth during the subsequent fermentation step.
The other parameters measured were filtration and washing characteristics: filtration rate, washing speed, brewing yield.
No difference was observed for these parameters. The modification of the redox potential of the medium according to the invention therefore made it possible to improve the quality of the wort (lowering of the nonenal potential, slight increase in free amino nitrogen) without, however, impairing the economic parameters, namely the filtration rate and the washing speed, and also the yield.
A lager with an original gravity of 12° plato was produced on a semi-industrial scale of 20 hliters. Nine brewings were carried out using one and the same malt.
Three brewings were carried out for each of the following three treatments: three control mash tubs (brewing under the normal conditions), three mash tubs with reduction of the redox potential using nitrogen and three mash tubs with reduction of the redox potential using a mixture of nitrogen and hydrogen (96/4).
For this, the gas is introduced at various steps (using plugs from Federal Mogul):
The beer-making steps were the following: production of the mash (300 kg of malt+950 kg of water+CaCl2), brewing, filtration of the mash and washing of the draff, boiling, inoculation, fermentation, standing, filtration and stabilization, bottling, pasteurization.
Just as in example 1, the redox potential values (Eh) were measured with a Mettler Toledo probe and related back to pH 7. The pH values were also recorded with a Mettler Toledo probe. The dissolved oxygen values were, for their part, measured with an HQ 30d Flexi analyzer (Hach).
The average redox potential and dissolved oxygen values obtained on the mash before brewing are given in tables 4 and 5.
It is observed that the redox potential values do not decrease very much during the treatment with nitrogen, which is limited to flushing out the oxygen. On the other hand, treatment with a nitrogen/hydrogen mixture considerably lowers the redox potential compared to the control and to the treatment with nitrogen alone.
The dissolved oxygen values are equivalent among the three conditions. They are relatively low in the three cases, doubtless due to the temperature of the mash, which is at 45° C.
These results show that it is possible to have radically different redox potentials while at the same time having the same level of residual dissolved oxygen.
The average nonenal potential values obtained are given in table 6.
These results show first of all that the gas treatment, whatever it is, makes it possible to reduce the nonenal potential of the wort at the end of brewing and of filtration (before boiling). At this stage, the nitrogen/hydrogen condition had an effect that was at least equivalent to that of nitrogen on the nonenal potential (it should be pointed out, moreover, that one of the values obtained with nitrogen/hydrogen was so low that it could not be quantified).
On the other hand, at the end of boiling, the nonenal potential obtained with the reducing treatment with nitrogen/hydrogen is very much lower than those obtained with the “control” and “nitrogen alone” conditions.
These results therefore show that a reducing treatment with nitrogen/hydrogen makes it possible to significantly decrease the oxidation reactions which take place during the production of the worts intended to be fermented. Since this effect is observed on worts having the same initial dissolved oxygen concentration, it is therefore clear that it is indeed the reducing property of the gas which has been the determining factor. It was not in this case an effect due to a simple deoxygenation.
Furthermore, just as in example 1, the modification of the redox potential of the medium according to the invention made it possible to improve the quality of the wort without, however, impairing the economic parameters for production of the beer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0654888 | Nov 2006 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR07/52327 | 11/13/2007 | WO | 00 | 5/13/2009 |
