The usual house brew started at 1.045 and finished at 1.010. The addition of rice soup bumped the original gravity up to 1.062, and it finished at 1.020. From here the plot thickens.

Next I made two batches identical in terms of grain, but one used half brown and half sweet rice, and the other used all brown rice. The initial gravities were again 1.062, but they finished at 1.010! The addition of brown rice dropped both brews by 10 points and stripped most of the body and mouth-feel out of them. I also had a sort of light, raspy bitterness.

My initial hypothesis was that the rice husks contributed an enzyme specific to some odd little dextrin. I used Danish lager yeast in all of the batches, and, from my reading, lager yeasts like trisaccharides whereas ale yeasts do not.

What did the brown rice eat? Why did it do it? A friend suggested that a nutrient rather than an enzyme might have done the dirty work. Help me out! I've been scratching my head over this for over a year.

DM: Back in the early 1980s, I brewed a lot of adjunct beers using rice and corn meal. You're absolutely right about the stickiness and scorchability of rice. The only tip I can give you is to turn the heat down as low as you can without stopping the boil. But you will still have to stir constantly and use a lot of water -- at least 3 qt/lb.

The question seems to be about the terminal gravities of these three batches of beer. Based on my experience, I'd say that 1.010 is pretty low for a 1.062 beer, but 1.020 is pretty high. I would expect something around 1.014 with my methods (single-infusion mash at 152-153 degrees F for 1 h, no mash-out before sparging). You're right that lager yeasts generally give a lower terminal gravity than ale yeasts.

What could account for the high gravity of your first batch? A high mash temperature may have contributed, but it sounds like an incomplete fermentation to me, possibly caused by lack of yeast nutrients and possibly by something else. Did you change your brewing method at all between batches one and two? For example, did you let all three rice mashes stand overnight before incorporating them into the main mash? Did you add all three batches of rice liquid to the mash, and then sparge as usual, boiling all of the runoff?

What I'm getting at is this: An overnight mash stand after stirring in some crushed malt is a recipe for a Kentucky-style sour mash. All kinds of wild yeasts and bacteria could get going during that rest period, and they might not be killed until you boiled the wort the next day. If that happened, the wild bug(s) might produce a by-product that interfered with fermentation by the brewer's yeast.

Conversely, the low terminal gravity of batches two and three might be explained by a wild yeast or bacteria contaminating your culture yeast. Such bugs often produce the thin body you describe. We have no way of knowing whether the bug was introduced into your brew from the rice mash, though you might be able to guess based on your knowledge of your own methodology.

I doubt that this anomaly in your terminal gravities was caused by a switch to brown rice. However, the raspy quality you allude to was probably caused by tannins in the brown rice husks.

If you want to experiment further with rice, I suggest using rice flakes (or corn flakes) made specifically for brewing. They are expensive, but they will save you a lot of trouble.

If you cook your own adjuncts, I suggest using the methods followed by the major commercial breweries. Basically, you mill the rice to the consistency of coarse flour, then mix it with some crushed malt (about 10-15% of the total amount called for in your recipe), and add lots of water. Bring this mixture to about 158 degrees F, and let it stand for 30 min. Then raise it to a boil, and boil, stirring constantly, for 15-20 min--until the starch is gelatinized. Meanwhile, mix your main mash thick (1 qt of water/lb of malt) at about 113 degrees F. When the cereal mash is gelatinized, stir it into the main mash. The mixture should settle in at starch conversion temperature (150-155 degrees F). If it comes in high, add cold water to temper it; if it comes in low, heat it. Then, the next time, adjust the temperature of the malt mash to get the right temperature for the mix.

As you can see, the main difference between this method and yours is that it brings the rice to a boil after adding the malt. The purpose of adding the malt is to allow the enzymes to perform some liquefaction of the rice starches, giving a thinner "porridge" that is less prone to sticking and scorching.

I really believe, however, that home brewers and microbrewers are better off abandoning the whole project of cooking cereal adjuncts. For small-scale brewers, the savings in time and labor make pregelatinized flakes well worth their price.

My question is, What exactly is hot-side aeration? At what stage of brewing do I need to be concerned with it? How do I avoid it? And what effect does it have on the final product?

DM: First, to correct one statement: Yeast needs oxygen for growth, not fermentation. This is important because I don't want anybody to think they should aerate their beer during fermentation. That would ruin the flavor. You need to saturate the wort with air and pitch your yeast as soon as possible after you have chilled it. But once fermentation begins, no more air should be introduced.

The phrase "hot-side aeration" refers to the hot side of the process, which is wort production. Your understanding is basically correct. Wort contains melanoidins and tannins that are readily oxidized at high temperatures. If air is introduced during wort production--in other words, on the hot side --these substances will be oxidized and later, in the finished beer, they can turn around and give up their oxygen to alcohols that were created during fermentation. An oxidized alcohol is an aldehyde, and aldehydes are the bad guys that are responsible for all the stale, old-beer flavors we have all encountered in far too many imported brews.

That answers your first question: Hot-side aeration is any incorporation of air into hot wort, and you need to be concerned with it at all stages of wort production.

How to avoid it: Don't let your hot wort splash during transfers or fan out as it flows down the side of a vessel. Use hoses or tubing to fill kettles gently from the bottom. Be as gentle as possible when recirculating your wort to clarify it before running it into the kettle. Cool your hot wort in the kettle or else siphon or run it out through a hose or pipe to the heat exchanger. Basically, look at your whole brewing operation critically and decide what changes need to be made to minimize hot-side aeration.

What effect does it have on the final product? The first thing I usually notice when a beer oxidizes is that the hop aroma is gone. Then comes a stage where the flavor seems not quite right, but without any distinct off-flavor. Finally come the stale, cardboard, sherry-like or toffee-like flavors.

The insidious thing about hot-side aeration is that it can cause staling even in a beer that has been carefully handled during fermentation and subsequent stages. A freshly bottled beer may have a dissolved oxygen content of almost nothing and yet oxidize in a matter of weeks if the hot wort was mishandled.

Now for the good news: Brewpubs and home brewers don't have nearly as much to be concerned about as shipping breweries because they keep their beer close to home rather than sending them out into the cruel world where they can suffer all kinds of insults. Storage temperature has a lot to do with how fast beer oxidizes. So does agitation. There really is something to the old saying that beer doesn't travel well. Getting knocked around in the back of a truck does take a toll on packaged beer, and temperature is an even bigger factor. But even at low temperatures, kept absolutely still, beer will oxidize eventually. That is why the best plan is to store it cold and drink it quick.

Another thing you may want to keep in mind is that filtered beer is much more susceptible to oxidation from any source than bottle- or cask-conditioned beers, because live yeast acts as an oxygen scavenger. I don't know whether you filter your beer or not, but if you do, you have an extra reason to be careful with hot-side aeration.

One other factor is a concern, especially if you find that some hot-side aeration is unavoidable in your brewing process. The factor is wort clarity. Be sure to recirculate your wort in the lauter tun to get it as clear as possible before running it into the kettle. Cloudy first runnings have a large proportion of long-chain fatty compounds (lipids) that are precursors of many staling substances. If you can minimize the precursors, you can greatly slow the appearance of oxidized flavors in your finished beer.

ALUMINUM BREW POTS

DM: First of all, I would not pay $100 for an aluminum kettle. For that kind of money, I could get a stainless steel Sankey keg and have it modified to make a first-class kettle, with none of the doubts or disadvantages aluminum carries.

Okay, I ducked the question. I must try to answer it. I have investigated the use of aluminum in every brewing text I could lay hands on, including some very old ones. Regarding aluminum kettles, I came up dry. It seems the metal has never been considered for brew kettles until home brewers came along. I suspect the reasons for this are purely practical. Kettles are the hardest of all brewery vessels to clean, and strong chemical cleaners corrode aluminum. Caustic soda literally eats it up. It is soft enough that hand scrubbing with wire brushes will scratch it badly, which in turn will make the surface harder to clean the next time around. It is no wonder that commercial brewers apparently never considered using it for brewhouse vessels.

On the other hand, there was a time before World War II and even afterwards when aluminum was seriously considered and sometimes used for fermentation tanks. These were the days before CIP (clean in place) caught on, and open fermentors were popular. These tanks had to be cleaned by hand, and aluminum actually had certain advantages over glass-lined steel and pitch-coated wood, which were other common materials. None of the brewing experts of that era, as far as I can determine, noted any kind of metallic taste in beer fermented in aluminum.

Another interesting fact: Although copper was always the metal of choice for brew kettles, iron was used for brew kettles and lauter tuns back in the old days (1800s and earlier), and authorities as recent as Jean de Clerck seriously discuss the use of this material. I myself have seen mild steel rakes in a two-vessel German decoction brewhouse built in the 1930s.

After seeing those rakes, I decided not to replace my old enamelware brew kettle when it started to pit. As far as I could determine, use of the pitted kettle did not cause a metallic taste or haze in my home brews. However, I never tried an aluminum kettle, and I cannot speak positively about it. I can admit to growing doubts about the deleterious effects of aluminum, but the conventional wisdom, questionable as it is, needs to be tested before being thrown out. Any home brewers out there with an aluminum kettle on hand who would be willing to make the experiment?

Meanwhile, my advice to anybody putting together a home brewing setup remains: Copper and stainless are the best materials for a brew kettle. Enamelware works, though it is harder to clean than copper or stainless; it is even cheaper than aluminum. I see no reason to buy an aluminum kettle for home brewing.

DM: Although this question is too general to be answered in a Q&A column, I think every brewer should know something about how the basic materials are made. My book, Complete Handbook of Home Brewing, has a thumbnail sketch of the malting process, but for a thorough treatment--one with enough details to give you an idea of what it would take to malt your own grain -- I suggest Jean de Clerck's A Textbook of Brewing, long out of print but available at some libraries.

FURTHER READING