Ask the Troubleshooter
Dave Miller on...
Hop Utilization, Keg Carbonation, and Diacetyl Rests in Lager Fermentations

by Dave Miller
Republished from BrewingTechniques' March/April 1994.

In addition to standard questions and answers, this issue's "Ask the Troubleshooter" presented the author particular challenges, especially one of a slightly more personal nature.


Q: Dave Miller discussed hot side aeration in the November/December 1993 issue of BrewingTechniques. In a side issue, Miller indicated that wort clarity is a factor in beer staling. Miller correctly stated that cloudy first runnings contain a large percentage of lipids. Unfortunately, he mistakenly stated that these wort lipids are the precursor of flavor staling in beer. Lipids are long-chain (C-15 and longer) unsaturated fatty acids. The lipids (of which North American- grown barley contains an inadequate amount) are essential for proper yeast metabolism. Lipid deficiencies can result in fermentation defects such as off flavors, incomplete fermentation, and head retention problems as well as increased incidence of yeast autolysis. One theory holds that the compound 2-nonenal, which is often found in stale beer products, is precluded by the enzymatic oxidation of lipid-based compounds. This long-standing theory has yet to be proven; in fact the high-gravity brewing practices commonly used by large commercial breweries suggests that the high-lipid worts resultant in high-gravity brewing tend to produce more flavor-stable beers. In my opinion, the practice of home brewers recirculating wort, which removes useful wort components, is a poor one and leads to more problems than it solves.

DM: There may be a question about whether lipids are responsible for beer staling, but there is no question that beers made from cloudy worts are less stable than beers made from normal - that is, reasonably bright - worts (1). Of course, as I pointed out in the original column, the question of oxidation is a lot more important if you filter your beer, as all large commercial breweries do. If you never experience oxidation in your finished beers, you don't need to worry about it. However, other reasons exist for clarifying wort before running it into the kettle.

The cloudy first runnings contain not only lipids but also grain husks, which are rich in silicates and tannins. Silicates cause haze, and tannins impart a grainy, astringent character. In addition, first worts produced in a typical home or microbrewery also contain grits, and grits contain unconverted starch, which also can cause haze and off flavors in finished beer. In sum, when you elect not to recirculate your first wort, you are putting a lot more than lipids into your kettle, which is probably why the big commercial brewing companies like Anheuser-Busch and Miller include a vorlauf (recirculation) in their lautering procedures.

As for the question of whether you need more lipids in your wort, the answer is another question: How's your fermentation? Are you experiencing long lag times (yeast use lipids during the growth phase), slow fermentations, or other symptoms of poor yeast nutrition? If not, there is no reason to concern yourself with supplying more lipids or any other nutrient. And if your fermentations are exhibiting any of these symptoms, have you ruled out other causes, such as inadequate aeration of the cold wort? I would not jump into a regimen of trying to improve my yeast's health if it has been working well, and even if it hasn't, I would not jump to conclusions about the cause.

Having said all that, I do know of one instance of poor fermentation that was actually traced to overclarification of the wort. I won't name the brewery, but I can tell you that I heard this story firsthand from several members of its brewing staff. The brewery makes most of its products from a blend of six- and two-row domestic malts and uses adjuncts in quantities from 20% to 30%. Their malt mills and lauter tuns are so efficient that they are able to extract about 98% of the fermentable materials from their grain. Furthermore, they are able to clarify their first worts to the point where they look like filtered beer - no exaggeration. And sure enough, this brewery encountered problems with yeast nutrition. They solved the problem by shortening the vorlauf so that the first worts were slightly hazy, rather than absolutely brilliant. But they did not eliminate the vorlauf altogether. They do not believe that recirculating the wort leads to more problems than it solves. Furthermore, when one considers how imperfectly our grain is crushed, it is clear that the big guys have a lot less to fear from chunks of starchy endosperm or bits of husk getting into their kettles than we do. Yet they still think the vorlauf is important.

Your point about high-gravity brewing is mistaken. American breweries did not adopt high-gravity brewing to get more-stable beer. They did it to get more output from their equipment. If you brew and ferment 16 °P wort and then dilute the finished beer to the equivalent of 11 °P right before packaging, you have increased the capacity of your plant by almost half without having to buy any new buildings, tanks, or refrigeration equipment.

Regardless of whether lipids are the cause, cloudy first worts in the kettle lead to less stable finished beers. With imperfectly crushed malt and primitive lauter tuns, small-scale brewers have to work hard just to get their first worts to the slightly hazy stage, never mind brilliant. Furthermore, cloudy first worts contain other substances that are deleterious to finished beer, including starches, silicates, and tannins. Finally, even large commercial breweries that have experienced the "lipid deficiency problem" have not abandoned wort clarification. Although it is possible, using high-adjunct worts and excellent equipment, to overclarify a wort, it is questionable whether this can be done in most small-scale breweries.

A postscript, for readers who may be interested: At the Saint Louis Brewery, we recirculate our wort for 30-45 min, which is sufficient to remove almost all the grits and chunks from the stream and bring the wort to a state where it looks reasonably clear, though not as clear as filtered beer. The real trick, however, is to maintain wort clarity during sparging. The grain bed tends to expand as the runoff thins, so we have to gradually increase the runoff rate - in effect, the suction on the filter bed - to keep it compressed as sparging goes on. By the way, we have absolutely no problems with yeast growth or fermentation that would suggest a lack of nutrients, even in our lowest gravity (1.037) beer.


Q: I am currently brewing 7 gal of raspberry mead. I was hoping to find an alternative to bottling when it is done. Will a stainless steel container work with mead?

DM: If you plan to put your mead in a soda keg, it will probably work. The reason I say probably is that numerous grades of stainless steel exist, and they differ in their resistance to corrosion. I don't know the grades of stainless steel that soda kegs are made from. Most grades, however, tolerate mild acids quite well. Mead is essentially a mild acid, similar to wine in pH, so you will probably be fine. If you have any doubts, call the manufacturer of your soda keg and ask a few questions. With any luck they'll tell you that your keg is made from 304 or 316 stainless steel. Those are the best grades for fermented beverages and the ones used for winery tanks (beer kegs are usually 304).


Q: On the question of using aluminum brew kettles discussed in a previous issue (2), there are two thoughts that you did not mention.

First, although you mentioned that caustic (high-pH) cleaners will "eat" aluminum, I believe that acidic (low-pH) solutions will also affect aluminum adversely. I remember hear-ing in my chemistry courses that aluminum is one of the most reactive metals on the periodic chart. Also, notice that if aluminum foil is put over any food containing tomatoes (low pH) - pizza, lasagna, or just plain tomatoes, for example - the foil will be eaten away within days.

Second, some medical studies on Alzheimer's disease patients seem to indicate that aluminum is somehow associated with Alzheimer's disease. I have not read these articles and have only heard this information second hand, but I have heard it enough to warrant my concern with the use of aluminum in my cooking practices. I have also refrained from drinking beer from aluminum, but that's a foregone conclusion even without health concerns added to the pot.

On the process of boiling rice without scorching it, I would try using a double boiler. This would bring the temperature of the rice pot down to 212 °F as opposed to 450-500 °F.

DM: Your comments about aluminum and acid are well taken, though it should be emphasized that it takes a pretty strong acid to react with aluminum. Mildly acid solutions such as beer do not react appreciably. In Alzheimer's disease, as I understand it, the nerve cells of the brain deteriorate and form large tangles. These tangles contain an abnormally high concentration of aluminum and some other substances as well, a fact that has led some researchers to speculate that there might be a link between dietary aluminum intake and Alzheimer's disease. As far as I know, however, this link has yet to be established, and the latest thing I read on the subject suggested that Alzheimer's disease may be hereditary in nature. Because Alzheimer's is a disease that is worldwide and has been known since antiquity, it would seem unlikely that the use of aluminum cooking and storage containers is the cause. Anyway, I drink canned beer frequently.

Your suggestion about a double boiler is good. Just make sure it's big enough, because every pound of rice or corn meal needs at least 3 qt of water.


Q: I have a question about using unmalted adjuncts. Could you briefly explain gelatinization and liquefaction of the starch in these adjuncts? I am particularly fuzzy about the temperature needed and the technique used in creating usable starch from these adjuncts. Do you need different temperatures for rice, rye, wheat, and barley? Could you refer me to some good references on this process?

DM: Gelatinization is the physical breakup and dispersal of starch molecules in water. Gelatinization is essentially what happens when you make gravy. The flour or cornstarch gelatinizes and thickens the mixture. It is a physical phenomenon and involves no breaking of chemical bonds. Liquefaction, on the other hand, is the breaking of long starch molecules into shorter molecules that are soluble in water. It is a chemical process and is brought about in the mash tun by a-amylase.

Different adjunct starches require different temperatures to gelatinize; wheat is the lowest at about 150 °F, and rice is the highest at about 190 °F. In practice, any kind of adjunct grits are boiled before being added to the mash, so the exact gelatinization temperature is not important. The best description I know of the flaking process is found in The Practical Brewer (3). This book is found in many large libraries.


Q: I recently became head brewer at the Yakity Schmackity Brewery. I'm having terrible problems with trub clogging the butterfly valves of my unitanks. Are there any preventive measures that I can take, and, if you experience this at your brewpub, how do you extricate the trub? Are there any sophisticated tools that you use to dig out the sclibb that's stuck in there? My finger's getting pretty raw, and I'm constantly spraying yeast all over the brewhouse. I find this somewhat embarrassing (just how do you explain impaction to your friends?), and I'm in need of remedial help. Having read all your technical articles, I knew you'd be my salvator. Some friends have suggested various proctological measures, but I'm hesitant to inflict undue bodily harm on my fermentors. Looking forward to your brilliant reply.

PS: Why do they call you the Troublemaker? DM: I almost cut this letter, but I'm a page short for this month's column, and besides, I can't turn my back on a neophyte beer proctologist.

The real problem, of course, is a lack of training. Bill Siebel and his crew do a fine job with water chemistry and wort lipids, but when it comes to real brewery work, you have to dig for information. Take my word for it, I've done more digging than anybody. Instead of your sore finger, I suggest a table knife swiped from the pub's kitchen. If you engrave your name on it, you can even pretend you actually paid for it. As an alternative, you could try an electric drill. It's faster, but it's hard to get out when the dam breaks.

Regarding yeast spraying, various theories exist. Some mathematically minded brewers insist that the amount of yeast sprayed when you break an impaction is directly proportional to the number of people watching through the glass. It follows, therefore, that if you always do your proctoscopies at 6:00 a.m. on Sunday morning, you'll never have to wash sclibb off the walls again. However, I believe that life is more like Jurassic Park than like a computer model - all hell is likely to break loose anywhere, at any time, and that goes double for breweries. If you subscribe to this notion, it follows that you should always do your trub extrication at 12:30 p.m. on Fridays, when the pub is overflowing with lunch customers. You may get the stuff out with nary a squirt, but if not, at least you haven't wasted the big show on a handful of servers and kitchen workers.

The long-term solution to your problem is to find an eager young home brewer and train him/her as your assistant. Then you can hang out at the bar doing The New York Times crossword puzzle while your loyal helper works out the problem.

As for the title of this column, I deny everything. Mallery shredded the documents as soon as I signed the contract. Have you been talking to my wife?


(1) Narziss et al., MBAA Technical Quarterly 30 (2), 48-53 (1993).

(2) Dave Miller, BrewingTechniques 1 (4), 12-17 (1993).

(3) Lawrence H. Bradee, "Adjuncts," in The Practical Brewer, 2nd ed., Harold Broderick, Ed. (Master Brewers Association, Madison, Wisconsin), p. 47.

Dave Miller was a home brewer for 15 years and has been brewing professionally since 1991. He is currently brewmaster at The Saint Louis Brewery, St. Louis, Missouri, USA. He is the author of four books and numerous magazine articles and is a contributing editor of BrewingTechniques.

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