Ask the Experts

Homebrew expert Brad Smith, author of the Beersmith homebrewing software and the voice behind the Beersmith podcast, tackles questions on sanitation, off-flavors, and conditioned (wet) milling.

What is the difference between cleaning, sanitation, and sterilization of equipment? I’ve seen a lot of brewers use them interchangeably.

There is actually a substantial difference between the terms and how they are applied in brewing. Obviously clean equipment is critical in beer making, more so than for wine or mead due to the low alcohol levels of the beer and high risk of infection.

Cleaning is the first line of defense. Cleaning means removing the dirt and debris from the equipment. If you don’t remove dirt and debris, they can be both a source of infection and a location for infection to fester and grow. Cleaning is typically done after you brew to remove dirt from your fermentors, pots, tubing, and other equipment; and we often clean equipment before brewing again to remove any debris or dust that has gathered in between brew sessions. Cleaning is done with products such as PBW, an alkaline detergent developed for cleaning brewing equipment.

Sanitation is a separate step taken right before brewing. It sanitizes the surface of the equipment to remove any bacteria. It is done after the equipment is already clean and free of dirt and debris. While it is not that important that you sanitize hot-side equipment such as a boil pot, it is critical for equipment that touches the wort or beer after it has been chilled. Any tools or equipment not sanitized can lead to infection.

You sanitize equipment using a sanitizing solution. Common sanitizers used in brewing include Star San, Saniclean, Iodophor, bleach, and IO Star. Bleach is less commonly used these days because it is hard to rinse and can lead to pitting of certain metals. I personally prefer “no-rinse” sanitizers such as Star San and Saniclean.

Interestingly, some brewers also use the term “sterilization,” which is actually inappropriate for brewing. Sterilization is done for medical equipment and some foods using processes that most often involve steam, heat, or very harsh chemicals. A good example is essential surgical equipment, which is often steamed or cleaned using heated gases. Brewing

equipment does not need to be sterilized at the same level as surgical tools. Sanitizing your brewing equipment is sufficient.

My beer has a bit of a creamed-corn flavor to it. What is causing it?

A creamed-corn or cooked-corn flavor is indicative of a compound called dimethyl sulfide (DMS). DMS is a by-product of malting, mashing, and fermentation, so it is present to some degree in all beers. However, it is more easily detected in lighter-colored ales and lagers, as it has a fairly low flavor threshold of 50–175 parts per billion.

All malts have a compound called S-methyl methionine (SMM), which is an amino acid formed during germination and kilning of barley malt as part of the malting process. This SMM is a precursor of DMS. Certain malts, such as 2-row malts, have less SMM than 6-row barley malt, and Pilsner malt has slightly higher SMM levels due to the low temperatures at which it is kilned. The malt house can reduce SMM slightly by under-modifying the malt or altering kilning temperatures. However, for the most part, SMM levels are outside the control of the brewer.

Heating the SMM during the mash produces two by-products. One is DMS, and the other is a related compound called DMSO, which is DMS with an oxygen atom attached. So mashing and sparging barley malt will create DMS in your wort.

Fortunately both DMS and DMSO are volatile and will evaporate if you have a strong rolling boil. So your best defense against a cooked-corn (DMS) off-flavor is, indeed, a long vigorous boil. If you are an all-grain brewer, you want to initiate a strong 90-minute rolling boil, which will eliminate the vast majority of DMS off-flavors. Also be careful not to cover the pot when boiling as this traps the DMS in the wort. Even some commercial breweries have DMS problems if they lack a blower or insulation on the vent pipe for their boil pot because it is common for DMS to condense on the inside of the vent and drop back down into the boiler.

Chilling your beer rapidly after the boil also aids in reducing DMS. If you have hot wort sitting around at high temperature for hours after brewing, some residual SMM will continue to be converted into DMS. However, if you chill quickly, you will reduce the chance for more DMS production.

There is additional DMS that is scrubbed from the beer during active fermentation. The CO2 bubbling up through the beer will take some DMS with it. So a good healthy

yeast starter and strong fermentation will help to further reduce DMS.

A secondary source of DMS is bacterial infection. Bacteria and certain wild yeasts can create DMS. So if you have completed a strong rigorous uncovered boil and chilled your wort quickly but still have some DMS off-flavors, you should examine the possibility of an infection.

In either case, DMS is a very preventable problem. Boil your wort thoroughly for at least 90 minutes, never cover the boil pot, chill your wort quickly, sanitize your equipment properly, and initiate a strong fermentation to avoid DMS.

I’ve heard of a process where you mill your grain while wet? How would you do this, and what is the purpose?

Wet-grain milling, also known by the more formal term “conditioned milling,” is a method that can improve the condition of the crushed grain and reduce the chance of a stuck sparge. Done properly, it produces larger pieces of intact grain husk with less grain powder, resulting in good mash efficiency and a better filter bed for the sparge. It is primarily used for beers with a large portion of non-barley adjuncts.

The goal in wet milling is to raise the moisture content of the grain about 20–30 percent using steam or hot water spray before milling the grains wet. You should not attempt this unless you have a dual-roller grain mill because other grain mills, such as the “Corona”-style mills, will get gummed up with the wet grains.

The commercial method for conditioned milling is to steam the malt before milling. Hombrewers have two options: a steam method and another using hot water to hydrate the malt.

You can simulate the commercial “steam” method using some boiling water with a false bottom or a pot designed to steam vegetables. It’s generally easiest to get the water to a boil and bag the grains in batches if needed. Steam the grain for about 90 seconds, stir it gently, and then quickly mill it while it is still hot.

The other alternative is to spray hot water over the grains to hydrate them. I recommend using a small amount of grain at a time spread somewhat thinly over a false bottom. Spray water heated to 158°F (70°C) over the grain bed for about 60 seconds, allowing the excess to drain through the false bottom. Let the grain sit for 1–2 minutes to absorb some of the water and then quickly mill it.

If the grain doesn’t mill cleanly or the mill gets gummed, then the grain is too wet. Reduce the moisture level by reducing the steam time or hot spray exposure on the next batch of grain.

I will mention that wet milling is really not needed for most malted barley beers. If your grain mill is set properly, you can mill dry malt and brew with it without going through the extra steps of wet milling. Wet milling is most appropriate on beers that have a higher proportion of sticky nonbarley adjuncts such as flaked barley or wheat that could lead to a stuck sparge.