Carbonating Thoughts, Star San Water Temperature, and Sprouted Grains

Q Can I “bottle condition” my homebrew in a 1-gallon (3.8-L) keg or growler?

Chris Morrow
Milledgeville, Georgia

A This is a great question and one I always like answering. Beer can be conditioned, a.k.a. naturally carbonated, by capturing carbon dioxide produced by yeast in a conditioning tank, bottle, can, or keg. The most common home method of conditioning is in bottles, hence the general term bottle conditioning. In past discussions about this method, I have focused on the how. This answer is going to focus on the safety aspects of “bottle” conditioning, starting with keg conditioning.

Kegs are great for a variety of reasons, including convenience, minimal packaging labor, relatively low cost, and their safety features. Most homebrewers and beer consumers don’t think much about pressure safety when it comes to beer kegs because we very rarely hear about exploding kegs. Commercial beer kegs are not only designed to withstand pressure much greater than that used for beer dispense, they are also built with an integral rupture disk to prevent explosions. Beverage gas regulators also include a pressure relief device that vents gas pressure above ~55–65 psig. This gives commercial-style kegs three levels of protection.

Cornelius kegs used by most homebrewers have a pressure relief valve on the lid (the thingy with the pull tab) and are also protected by the beverage gas regulator; still a belt-and-suspenders level of safety! Outside of gross negligence, there is not much that’s going to cause a keg to blow up. Plastic kegs are a different product and all brewers need to know about their kegs because plastic kegs have exploded and resulted in at least one death. That’s a topic for another day.

Bottles are different than kegs because glass bottles do not contain relief valves and do indeed have pressure limits that are sometimes exceeded. But like kegs, we don’t hear too much about bottles exploding in the commercial marketplace. The rate of bottle failures is likely higher for homebrewers who don’t have labs or packaging quality assurance measures. Most commercial beer is carbonated before packaging or bottle-conditioned to a level that aligns with the pressure rating of the bottle because no one is keen to blow up glass beer bottles. However, there have been some high-profile bottle failures in the market associated with diastatic yeast, high levels of fermentables in fruit beers, and some near-misses related to hop-creep. In all of these examples, beer carbonation levels resulted in pressures exceeding the bottle pressure ratings.

What about growlers? Well, most of the growlers used to fetch beer from your favorite local places that do growler fills are not rated for any internal pressure greater than atmospheric.

Let’s pause here and review a few carbonation basics. Most beers in the world contain about 2.5 volumes of carbon dioxide, or about 5 g/L. The equilibrium headspace pressure of beer at 38 °F (3.3 °C) containing 2.5 volumes of carbon dioxide is about 11.25 psig; it doesn’t matter if the beer is put into a bottle, can, keg, or serving tank, the pressure needs to be 11.25 psig to satisfy the level of carbonation at this temperature. Because packaged beer is in a sealed container, pressure increases with temperature. The carbon dioxide contained in the beer in this example increases the headspace pressure to 29 psig when the beer is warmed to 68 °F (20 °C), and then to 56 psig when the beer temperature rises to 104 °F (40 °C). (Note that this does not appear like a linear relationship because we normal folk use gauge pressure instead of absolute pressure.)

Technical details aside, a hot bottle of beer is packing about 95 psig of pressure if the carbonation is pushed to 3 volumes (6 g/L) and the temperature rises to 122 °F (55 °C) in the back seat of your car on a hot and sunny summer’s day.

Back to your question. There are no safety concerns at all to condition in a keg, even if you somehow managed to over-carbonate your brew and heat it up 122 °F (50 °C). And if your hot, gassy beer is in a Corny keg you may have some beer foam in your car when the relief valve blows, but nothing more than a beer mess. The same beer in a growler? No bueno! Depending on the type of bottle and its history (new versus used), that hot bottle in your car may up and explode. And if that does happen, just hope you are not in the car.

Here are a few factoids that I hope will help folks with glass safety:

1. Screw-top growlers are intended for short-term transfer of beer from tap, back to a refrigerator, and into a glass. Tales about cold growlers of ale blowing up in the fridge are not something floating around the web, so it’s safe to say that this is not a problem.
2. Growlers are known to burst in cars when beer tourists are hauling home precious pints, take a long pit stop for lunch, and return to their car only to discover a pool of beer and shattered glass in the back seat.
3. Heavy-duty growlers are really just large versions of re-usable flip-top bottles. These containers are made from much thicker glass than growlers and are designed to contain carbonated liquids over a wide-range of pressures, including the high temperatures used for pasteurization. No problems bottle-conditioning in these types of containers.
4. For all practical purposes, liquids are non-compressible. However, liquid density does change with temperature because liquids do expand with temperature. This is why bottles should never be filled completely full. Although the effect of temperature on volume is negligible, for example 1.000 gram of water occupies 355.000 mL at 4 °C (39 °F) and 355.331 mL at 70 °C (158 °F), a bottle of beer without headspace can result in bottle failure when no headspace is available for expansion. Easy enough, just don’t fill a flip-top full and expel all gas when closing . . . accidentally been there, done that, and can attest to bottle failure within an hour as the beer warmed.
5. Re-used glass bottles fatigue with time, especially if they are heated to sanitize. Commercial bottling lines designed for use with returnable bottles use in-line scanners to detect fissures in glass that are signs of fatigue and reject these bottles before the filler. Homebrewers don’t have glass scanners, so it’s a good practice to visually inspect bottles. When I began homebrewing, returnable glass bottles were common and we would collect good-looking bottles for use at home. One-way glass bottles are the norm these days and are not designed to be used multiple times. Bottle failures are much more problematic when these single-use bottles are used for homebrewing.

The last thing I will say about glass safety relates to eye protection. Wear safety glasses whenever using a counter-pressure bottle/growler filler! Wear safety glasses or face-shield and gloves if a bottle-conditioned bottle/growler blows up and you decide to open all bottles from that batch. Assuming that all bottles/growlers were filled from a bottling bucket dosed with priming sugar, it’s a safe assumption that all bottles contain about the same pressure. If one bottle/growler failed, others may follow and you do not want to be near a bottle when it fails without proper protection. Brew safely and happiness will follow!

Q A friend and I were recently bottling some homebrew together and we found ourselves having a bit of a debate. I had mixed the sanitizer (Five Star Star San) into hot tap water. He told me that I should be using cold water. Does it make a difference? If so, why?

Jim Wiggins
Savage, Minnesota

A Star San is in the family of sanitizing detergents known as acid-anionic surfactants. These solutions typically contain an acid, such as phosphoric or lactic acid, and a surfactant. In the case of Star San, phosphoric acid is combined with the surfactant dodecylbenzenesulfonic acid (DBSA). Let’s get the debate settled before digging deeper; both of your methods work just fine! Acid anionic sanitizers do their job over a wide range of temperatures and do not rely on heat for their efficacy. No precautions related to temperature are indicated in the Star San safety data sheet (SDS).

I want to address a more general question: What are acid-anionic surfactants and where are they used? In general terms, these compounds are negatively charged (anionic) molecules that have a hydrophobic end and a hydrophilic end. It’s the combination of hydrophobic (water repelling) and hydrophilic (water attracting) properties in a single molecule that give these compounds excellent dispersion properties as well as making them foamy. This just sounds like a garden-variety detergent, so what about the sanitizer function? While DBSA is an excellent detergent, its tendency to disrupt cell membranes with its hydrophobic molecular tail also provides broad-spectrum antibacterial properties.

One downside to DBSA is that it is not as effective in killing yeast and molds. Acid-anionics are used in a wide range of applications, including food and health care, because they are safe, effective, and have residual activity. These properties make products like Star San similar to quaternary ammonium compounds, aka quats or QACs, but unlike quats, acid-anionics typically do not damage beer foam.

Two handy properties of DBSA are its stability during storage and its compatibility with stainless steel. This means that clean solutions can be stored in stainless steel fermenters, kegs, or brew kettles and used in the future. pH is the key parameter to check because DBSA loses its antibacterial properties when the pH rises above about 2.5. In general, if the solution looks clear, was properly dosed when originally made, has not been diluted with water, and has a pH less than 2.5, it is good to go. Looks like you guys can trade beers and call this debate a draw!

Q I have been seeing rolled, sprouted grains at the store. What is the deal about the grains being sprouted and, more importantly, can these be used for something tastier than a bowl of breakfast oatmeal?

Frank Modesto
Harrisburg, Pennsylvania

A Sprouted grains have been used for thousands of years for cooking and brewing, with malt being the ultimate sprouted grain product. The history of food and cooking is largely comprised of stories of trial and error, and the consumption of sprouted grains naturally began without people knowing anything about biochemistry or nutrition because those sciences had not been developed and grains don’t require any intervention to sprout when given moisture and time. More recently, people have been focused on differences between the bioavailability of nutrients in grains before and after sprouting. No big surprise to us brewers, germination modifies the grain endosperm (energy reserve) and has an effect on all sorts of parameters. Long story short, sprouted grains can definitely be used for much more than a hot bowl of oatmeal.

For starters, what are these sprouted products popping on store shelves and where can they be found? Although there is no standard definition of sprouted grain, these products are definitely not germinated like malt. Based on observation and chewing, my assessment is that the products I have tried are probably soaked, briefly sprouted, dried and flaked. To put this in the context of brewing malt, these sprouted grains are similar to chit malt.

If you have never knowingly consumed foods made with sprouted grains or never noticed these products at the store, go to the whole or healthy foods aisle at your local grocery store and look for products like sprouted bread (Food for Life is one company that has been in this market segment for about 50 years), sprouted quick oats, and sprouted rice. Just like brewing malt there is a very wide range of these products on the market.

Taken to the extreme you can also find sprouts (often bean or pea sprouts) in the produce section, but these products are well on their way to becoming plants. In fact, you can sow these in soil instead of casting upon a salad! By the way, there are all sorts of sprouted legumes, but sprouted cereals like oats, rye, wheat, teff, barley, and rice are the products that are probably of most interest to brewers.

So, what’s the big deal with sprouted grains; sort of sounds like clever marketing to help sell grain, right? It turns out that there is more than a name to go along with these products. When cereal grains germinate, enzyme systems activate and begin converting the energy reserves within the grain endosperm into simpler compounds that can be used by the embryo, rootlets, and acrospire (shoot) during transformation from seed to plant. In practical terms, cell walls are softened, vitamins are made more available, amino acid levels rise, and starch hydrolysis begins. And just like malt modification makes it easier for brewers to produce wort, sprouted grains make nutrient assimilation easier on humans. But we are talking about brewing here, so let’s leave the grocery store and enter the brewhouse.

Any rolled grain you can buy in your local market probably has a brewing analogue and can be used directly in brewing. Have a recipe calling for a pound of flaked oats and want to give sprouted oat flakes a try? Go for it and just sub pound-for-pound. Don’t expect much of a flavor change, instead pay special attention to things like extract yield, ease of wort separation, mouthfeel, and foam stability. Keep in mind that there is no standard for sprouted grains and some of these products are certainly more modified than others. In general, expect them to be a bit easier to use than raw grains, especially when used at rates above 10–20%. Experimentation in the brewhouse continues to push the limits of beer, so when the patchouli aisle gives you sprouted oats, make beer not war!

And to all those folks who like a bit of patchouli, so do I.

Written by Ashton Lewis