How are these byproducts being reduced if not by precipitation?
Maybe they are precipitated but they are smaller and take longer to sink.
Also, chemical reactions are possible. Oxidation is one that we don’t want (except maybe in Barley Wines). Maybe there are others. I don’t know actually.
I don’t think this is correct.
So, essentially, there must be yeast activity that continues beyond mere fermentation, much like diacetyl uptake, that cleans the beer up despite flocculation?
If so, that would upend some current ways of thinking and put us back into some previous thoughts about maturation…interesting.
It would upend not just us, but the professional and scientific literature as well, which advise that yeast activity is best allowed to go to completion warm where yeast is most active, while cold temperatures can then be employed for physical stabilization without expectation of yeast activity. Also mainstream practice for the last 50 years or so, where state of the art lager production process has been a free rise to room temperature, hold until FG reached and no diacetyl detected, and immediate chilling to 0°C for dosing of chillproofing agents, filtration, carbonation and packaging. This could all be misguided, but a lot of research and money has gone into determining best practices.
Perhaps if we find the flavor of a beer is improved by six weeks or more held cold on the yeast, we really should have just held it at room temperature for a couple of days more. Which can be tried next go around with the yeast.
No. Well, no, and a tiny bit yes. Fermentation is finished when all the sugars that are going to be consumed are consumed. The yeast then go dormant. They do have a small amount of metabolic activity in the dormant phase–and this is the “tiny bit yes” I refer to. They consume their glycogen store, which they built up during fermentation, to stay alive during dormancy.
It’s possible that this small amount of metabolism is partially responsible for a beer improving during lagering, but my money is on simple yeast settling due to time and gravity. Yeast removal gets rid of a lot of flavor-active stuff.
When I was brewing commercially I recall filtering a helles. I blindly tasted the pre-filtered beer, right at the valve that fed into the filter, and the post-filtered beer, right at the valve at that came out of the filter. Striking difference. (I actually preferred the pre-filtered helles. Having the yeast still there added a fullness that was missing from the post-filtered beer.)
A factor in my moving away from filtering. It’s been hard for me to learn to accept a little turbidity, but when I did go back and filter a batch a few months ago, it just didn’t measure up in flavor and texture. Raises a question about maturation of beer: when is it mature enough? Can the processes be taken too far? I think so. Like I mentioned above (#17,) you can lager a beer to death too.
I think people use the term “lagering” alternatively to refer to both “cold maturation” and post maturation cold storage for colloidal stability and clarification, which adds to the confusion.
Chapter 4 of Kunze: Beer Production (Fermentation, maturation and filtration) covers these processes in great detail.
Flavor maturation process is accomplished by yeast. Physical stabilization process (optional) is accomplished by chilling augmented by some combination of adsorbants, precipitation, centrifugation and filtration. Since the optimal conditions for these two processes are in conflict, it is best to separate them, and even Kunze recognizes this.
Being German he does, however, betray a romantic attraction to the Märzen process (or some variation of it,) the least optimal method. To the original question in the OP, “lagering” in this sense is absolutely not necessary, quite the opposite.
To further address the OP, the question started “if my beer tastes good…” Stop. If your beer tastes good, you’re done, unless you need to clarify it for your satisfaction. All that has followed is about how to proceed if the beer doesn’t taste good yet.
Yup. This is the ultimate benchmark, and it depends only on your palate. So I might suggest doing what I do: tap that lager as soon as it’s drinkable and enjoyable for you (friends and competitions be damned!), and then appreciate the change you detect over time as it “lagers and matures” (i.e., as it changes as the yeast settles).
+1
But Martin said the beer improved after a time…how do you know if it will get better? FWIW, I am spunding a lager beer that I racked at day 7 (1.015) and expect to try it at day 14 (clear draught system). I will crash and sample again at day’s 16-21 and see what my experience is…
I don’t think science has totally figured it out yet, but we know there is at least:
Non-enzymatic oxidation of unsaturated fatty acids (including through interaction with iron, copper, and
manganese);
Oxidation of higher alcohols to carbonyl compounds;
Amino acid degradation (possibly promoted by polyphenols);
Reactions catalyzed by proline (example from Freshness is the reaction of heptanal and acetaldehyde
to produce E-2-nonenal);
Degradation of bitter acids; and
Reactions involving sulphur dioxide (which apparently provides protection from staling reactions during beer
storage).
Anecdotally, I find that the flavors of certain hops (such as Saaz or Styrian Goldings) really improve after maybe a month of cold conditioning. They almost develop a flavor that I would describe as “sparkling.” I have no idea what causes that.
I’ve found the same with s-189. These are my notes last time I used it:
At bottling - smells flawed & homebrewy
1 month after bottling - slight off flavour, caramelly, not really lager-like
3 months after bottling & cold storage - dry, crisp, no off flavour.
8 months after bottling & cold storage - very good, full bodied, like a commercial lager
Received wisdom among homebrewers is that lagers are best fresh, but that hasn’t been my experience, at least with bottled lagers (kegs are probably different). I think there’s continued attentuation in the bottle, though very slow, as carbonation improves for more than 3 weeks and matured lagers are crisper than young ones. While the yeast are metabolising diacetyl & sulphur compounds, there is also a slow chemical reaction between acids & alcohols that creates flavourful esters. This is very important in maturing wines but I’m not sure how much difference it makes to beers.
This idea that there is a purely chemical (apart from yeast metabolism) mechanism for esterification of higher alcohols feels familiar in the back of my brain; I’ve been searching but can’t find a reference in the sources at hand. All I find involve fermentation. Do you have something you could point us in the direction of?
I know this isn’t super helpful, but Bamforth says the following in Freshness:
“It is worth restating here that we should not worry only about carbonyl-containing substances when we consider flavor instability. To take just one example, consider the esters. Some of these increase in level during aging, whereas others decrease. Where does it all end?!”
There is also an article titled “The chemistry of beer aging - a critical review.” I haven’t been able to find a full copy online, but there is a review of it here: A Review of: “The chemistry of beer aging – a critical review” | beer sensory science
And below is the section of the review on esters:
“Changes in ester levels is also discussed. Overall, these changes lead to a loss in the freshness character of beer. Isoamyl acetate (banana) is considered a marquee ester and it, along with many others, undergo degradation during beer aging. In contrast, certain fruity/sweet esters are actually created during aging (such as ethyl formate, ethyl cinnamate, diethyl succinate) and some of these are associated with winy and whiskey flavors (like ethyl 3-methyl butyrate). Some of the compounds associated with these reactions are produced by degradation reactions of iso-alpha acids mentioned previously. Enzymatic activity (in this case, esterases) can also be left over from dying yeast cells, which can further lead to changes in the ester profiles of beer. Increases in gamma-nonalactone (peach, fruity) and other cyclic esters have been associated with staling of beer as well.”
If you look up Fischer–Speier esterification you’ll find a bit of info about how it relates to wine maturation, but I don’t know of any scientific studies looking at the effect on beer. Some wines benefit from ageing partly because the the esters create an interesting floral bouquet, but certain wines are spoilt by the process. Whether beer improves or deteriorates might be a question of style, yeast variety, personal preference etc. If you’re brewing beers that depend on dry hops for flavour, I would think ageing can only make things worse. That’s not the case with lagers though.
I found a full copy of the article: http://depa.fquim.unam.mx/amyd/archivero/ARTICULOGRUPO8_25527.pdf
That’s an interesting article though the few mentions of temperature relate to lagers stored at 25 celsius (77 fahrenheit) or above, rather than true lagering, i.e. cold storage.
Even so, the paragraph on esters does suggest quite a lot is changing:
[quote]Volatile esters introduce fruity flavour notes and are considered highly positive flavour attributes of fresh beer. Isoamyl acetate, produced by yeast, e.g., gives a banana-like flavour. However, during storage, the concentration of this ester can decrease to levels below its threshold level (Neven, Delvaux, & Derdelinckx, 1997; Stenroos, 1973) which results in a diminished fruity flavour of beer. In contrast, certain volatile esters (ethyl 3-methylbutyrate, ethyl 2-methyl-butyrate, ethyl 2-methylpropionate, ethyl nicotinate, diethyl succinate, ethyl lactate, ethyl phenylacetate, ethyl formate, ethyl furoate and ethyl cinnamate) are synthesized during beer aging (Bohmann, 1985b; Gijs et al., 2002; Lustig et al., 1993; Miedaner et al., 1991; Williams & Wagner, 1978). Williams and Wagner (1978) related the formation of ethyl 3-methyl-butyrate and 2-methylbutyrate to the development of winy flavours. The importance of these molecules for the flavour of aged beer was also recently reported using AEDE experiments (Schieberle & Komarek, 2002) and Gijs et al. (2002) confirmed this also for ethyl cinnamate (fruity, sweet). Finally, lactones or cyclic esters, such as c-hexalactone and c-nonalactone (peach, fruity) tend to increase in concentration (Eichhorn, Komori, Miedaner, & Narziss, 1989) and the latter molecule is considered important for the flavour of aged beer (Gijs et al., 2002).
[/quote]
Lagering - Is it worth the effort? George J. Fix
To the average homebrewer, the term “lager” is a descriptor for beer styles; namely numbers 12 (Bock) through 17 (Vienna/Maerzen/Oktoberfest) on the AHA category description list. The one common factor in these styles is the type of yeast used, and not the way they are processed. On the other hand, historically the reverse is the case, and a “lagered beer” has generally been one which has been afforded an extended cold maturation, independent of the type of yeast used. Arnold[1] finds that extensive cold storage goes back to the very beginning of monastery brewing (approximately 50-100 A.D.), if not sooner. This possibly pre-dates the systematic use of what today is a genetically narrow band of microbes called lager yeast[2]. However, this begs the absolutely fascinating open question of exactly when lager yeast entered monastery brewing.
In Bavaria lager beers were also called summer beers because they were brewed from September to April, and cold lagered during the summer months[3]. When refrigeration was introduced near the end of the 19th century, brewing was possible year round. Yet the 3-6 month cold storage still found favor, and 6-9 month cycles were common for high gravity lagers[4].
An interesting twist occurred in the U.S. among ale brewers in the sense that early on extended cold storage was employed by them. Greves[5], an English brewer who visited the U.S. just before the turn of the century, commented on this point. He cited two reasons for this departure from traditional British ale brewing practice. First, he noted competitive pressure from lager brewers, who tended to promote the theme that beer clarity and beer purity were synonymous. Cold storage is one of the best ways to clarify beer, a point that is discussed below. Very likely these influences affected German ale brewers in the Rheinland as well. The second reason cited by Greves was the unfavorable climatic conditions in the U.S., and therefore the need for cold maturation to promote beer stability before distribution. Greves praised the overall quality of American ales, but he concluded that cold storage was not needed in the U.K.
One of the most obvious trends in brewing practice in the 20th century has been the gradual reduction of aging times. “Common beer” using short 2-3 week cycles have been present throughout this century, but it was not until the last part of the century that short cycles were used for premium products. Even Pilsner Urquel, argueably the flagship lager, has been affected by these trends. It was brewed on a six month cycle throughout much of the 20th century. This was cut to three months in the post World War II era, and it is now produced using cylindrical conical fermenters with a short brewing cycle. Critics of this trend cite competitive pressures, and a relatively flat beer market for putting a premium on plant efficiency. Lighter flavored beers were also increasing in popularity during this period. These beers tend to require less aging, the limiting case is water which requires none!
Defenders of short aging periods argue differently. First, given the increased understanding of beer fermentation that has occurred in the last few decades, it is now possible for brewers to reduce green beer characteristics in the main fermentation. In previous periods that was one of the main purposes of aging. Also, there has been vast improvements in yeast management as well as considerable improvements in the quality of brewing materials, most notably malt. These also reduce brewers dependence on aging.
As homebrewers we are free of many of the pressures facing commercial brewers. As a consequence, we can and do put beer quality above any other consideration. Thus, if extended cold storage will improve beer, it will be employed by most homebrewers. On the other hand, it makes little sense to cold lager beer beyond the point where improvements stop. This begs the central questions associated with this article. Namely, exactly what does cold maturation do for us, and how much is enough?
We shall define cold as below 2°C (36°F), although some of the mechanisms discussed below can also take place at slightly higher temperatures.
1. Beer Clarification
The most obvious benefit of cold maturation is the precipitation of haze active polyphenols and proteins. The cold conditions also encourages yeast flocculation. It is my experience that the beer should clarify within the first week of storage. This is possibly why two week cycles for ales, and three week cycles for lagers are so widely used in commercial brewing.
Failure to clarify during the first week of storage is usually due to technical errors. Poor quality malt and/or dysfunctional yeast are obvious culprits. Errors in mashing and sparging cannot be ruled out either. The solution in these cases is not to extend the aging period, but rather to correct original problem.
2. Chill Proofing
Extra measures are needed to chill proof beer. Additives like silica gels and polyclar can remove the relevant haze active constituents.[6] I have found that extended cold storage (say 8-12 weeks) at 0-2° C (32-36°F) will achieve the same effect. The recently developed ice brewing procedure provides an interesting alternative. In this process beer temperature is reduced to just below its freezing point so that very small ice crystals are formed. Extensive data[7] has shown that the beer obtained after separation from the ice crystals is fully chill proofed. In commercial practice, where this process is automated, the temperature is reduced to a couple of degrees centigrade below the beer’s freezing point. The latter varies with alcohol content, but it is near -2.3°C, (27.9°F) for beers of normal strength. The contact time with the ice crystals is brief, typically less than one hour. In homebrewing higher temperatures and longer times are used. I have found that holding the beer at -3°C (26.6°F) for 48-72 hours is adequate.
3. Reduction of Diacetyl
The most widely studied green beer compound is undoubtedly diacetyl. There is good reason for this since it can be responsible for some highly unpleasant flavors, especially in packaged beer as it ages. There is ample evidence[8] that the long extended cold storage, in contact with yeast, was the primary tool used by turn of the century brewers to combat off flavors like with diacetyl. In modern practice, there is a decided preference for reducing diacetyl in the main fermentation. This is achieved through proper yeast management, and in particular using yeast which have very low bacterial and mutant levels. It can happen at the fermentation end point that diacetyl levels are slightly above acceptable levels. In this case, best results are usually obtained by kraeusening the beer with fresh wort and yeast, rather than relying on extended aging.
It should be noted that there is much more to flavor maturation than reducing diacetyl levels. For example, research on immobilized yeast reactors has shown that diacetyl can be reduced to normal levels with only a few hours of maturation. Nevertheless, the overall quality of beers produced with these systems has not been impressive.
4. Reduction of Sulfur Compounds
Fermentations conducted at ambient temperatures 18-20°C (65-68°F) should end with all relevant sulfur compounds well below their threshold. Exceptions are usually due to infection by sulfur producing gram negative microbes. These can be found in infected wort and/or in pitching yeast. With lagers fermented at 8-12°C (46-50°F) the situation is more complex[9]. First, the removal of volatile sulfur compounds in a cold fermentation is greatly reduced over what occurs at higher temperatures, and this can lead to a situation where several sulfur compounds are above their flavor threshold.
Lager brewers disagree about how much is too much. However, there is widespread agreement that lager beer will be insipid if all sulfur bearing compounds are reduced below their threshold. In addition, residual sulfur can act as an oxygen scavenger, and this may be responsible in part for the excellent flavor stability of traditional lagers. Nevertheless, most lager beer needs some maturation to reduce sulfur levels, and it has been my experience that objectionable sulfur levels can be reduced to acceptable levels within one week of storage at 0-2°C (32-36°F).
Failure to achieve this reduction can be due to several factors in addition to those cited above. A common culprit is high DMS levels in chilled wort, which may be due to the malt or wort production procedures used.
Yeast related issues tend to have more damaging effects. While there is a difference with respect to sulfur production among strains, pitching rate is even more important. Ideally, lager yeast should be pitched at a rate of 1-2 million cells per ml for each degree Plato; e.g., between 12 and 24 million cells per ml for 12°P (1.048) wort. Under pitching can lead to problems, but so can over pitching. For example, using very large yeast starters, and with this cell counts a factor 5 or more above the ideal, can lead to excessive sulfur levels[10]. It can also create a variety of off flavors due to yeast autolysis. Synthetic fuels are produced using elevated pitching rates, but flavor is not an issue with these products! As with the other defects mentioned above, the best approach is to correct the original problem and not to rely on ageing.
5. Flavor Maturation
This in many respects is the most interesting part of lagering in the sense that the goal is not damage control, but rather taking a sound beer and improving it. Two mechanisms are fundamental. One concerns polyphenols. Extensive data shows that anaerobic cold storage favors the precipitation of phenols in the higher oxidation states. That is, cold anaerobic storage will reduce the beers redox potential. This promotes rounded flavors and a smooth palate for conventional lagering (0-2°C, 32-36°F), discernable improvements will be seen through 6-8 weeks. In the ice brewing process, the times are shorter as noted above.
The second effect is a slow esterification of fusel alcohols. The reduction of higher alcohols promotes a greater elegance of taste, even when these alcohols are below threshold. The esters so formed tend to be of the desirable type, and add to the beer’s complexity. This effect is enzymatic, and depends on having viable yeast present in maturation to keep the beer “alive.” Ideally, this should be between 500,000 and 750,000 cells per ml. This effect also depends on time. When Pilsner Urquell was fresh and brewed on a 3-6 month cycle, it displayed these effects to perfection.
6. Dry Hopping
As Greves noted in his paper, the addition of hops during cold maturation was a uniquely American practice. The most important historical examples showing the benefits of this procedure was (arguably) the Ballantine Ales, back in the days when Ballantine was an independent family owned brewery. Their flagship product was Ballantine XXX, which was dry hopped during a cold three month maturation period[11]. This ale was noted for its full and attractive hop aroma, which was accompanied by a well defined but mellow hop bitter. Dry hopping will always achieve these effects, at least for a short period. The problem is that the aromatic compounds are unstable, and can quickly disappear. Ballantine XXX in its prime was a national beer, and subject to market abuse. Yet, typically around 5,000,000 bbls. were sold each year. The hop aroma was its signature, and hence the stability of it was a crucial point. The extended cold contact time played a fundamental role since it was during this period that the aroma compounds became bound up in the beer. Nugy8 suggests that one month of cold contact time with hops yields one month of stability for the aroma compounds. This is consistent with what has been reported about the Ballantine ales, and it is also consistent with my own brewing experiences.
7. Carbonation
The traditional carbonation of lagers takes place during cold storage. Beer is transferred from fermenters to maturation tanks with approximately 1% (by weight) of fermentable sugars present. The secondary fermentation which takes place creates sufficient CO2 to saturate beer. It has been my experience that 2.8-3.0 volumes of CO2 will be dissolved at equillibrium. Thus, it is desirable to take pressure and temperature readings so that adjustments can be made to desired levels. A 3 month cycle for this method is ideal if the beer is held under an appropriate counter pressure. I have found that 1 atmosphere (14.7 psi) is adequate.
I have personally not seen any difference in foam quality that can be attributed to the way beer is carbonated, either forced or natural. However, it has been my experience that people who are sensitive to carbonic acid, and dislike gassy beers, tend to prefer (by a wide margin) the flavor of the beers made with traditional carbonation when CO2 levels are in excess of 2.4 vols. The reasons for this are not altogether clear, but it could be that the traditional carbonation has CO2 more tightly bound up with other constituents.
Conclusion
To lager or not to lager is a question to which brewers will likely come to different answers. I recommend that brewers not blindly follow the rigid rules set up by others on this matter, but rather be guided by test brews. I have found the following to be useful.
(a) Do three batches of your everyday beer and lager for 3, 8, and 16 weeks, respectively.
(b) Do three batches of your favorite high gravity beer and lager for 3 weeks, 6 weeks, and 9 months respectively.
(c) Do two test batches, one being forced carbonated and the other carbonated by the traditional method.
It is of course desirable to control for extraneous effects. This is hard to do in a homebrewing content. However, the key items to control are yeast, brewing materials, and oxidation. In particular, the test brews should be staggered so that they can be bottled at the same time (or nearly so). If this is done, then it is my experience that what ever bias that may exist will not be significant enough to alter conclusions.
I realize that this program requires a lot of brewing, but then it also gives us an excuse to do more brewing, as if any of us needed such a reason!
[1] Arnold, J. P., Origin and History of Beer and Brewing, Wahl-Henius Institute, Chicago, 1911.
[2] Casey, G. P., Presentation at Rocky Mountain Microbrewing Symposium, Univ. of Colorado, Colorado Springs, Feb. 1999.
[3] One Hundred Years of Brewing, Arno Press, New York, 1974.
[4] A. Zimmermann, Brauereibe Briebslehre, Buffalo, New York, 1904.
[5] J. A. R. Greves, “On Some Recent Advances in Brewing in the United States,” J. Institute of Brewing, Vol. III, 1897.
[6] G. J. Fix and L. A. Fix, “Analysis of Brewing Techniques,”
Br. Publ., 1997.
[7] G. J. Fix “Principles of Brewing Science,” Br. Publ., to appear, October 1999.
[8] Nugy, Brewers Manual, Jersey Printing, 1948.
[9] G. J. Fix, Sulfur Flavors in Beer," Zymurgy, vol. 15, No. 3, 1992.
[10] Cahill, G., P. K. Walsh, D. Donnely, J. Am. Soc. Br. Chem., Vol. 57.2, 1999.
[11] George Lever, former Ballantine brewmaster, personal communication