The Raw Deal With Raw Ales, Seltzer Nutrients and Grain Milling Considerations

Q I read the Raw Ale article by Lars Garshol in the May-June 2018 of BYO And have been Employing This Technique ever since. I do a standard mash and make a separate hop tea that I add to the sparge water. One key during the mashing and sparging process is To Ensure that neither mash nor wort temperature exceeds 76 °C (168 °F). This is to prevent the formation of dimethyl sulfide (DMS). I mash out into a sterilized container, chill the wort, and put into a fermenter. There are no issues with final clarity when Irish moss is added to the hop tea and gelatin finings are added one or two days before kegging.

However, I have noticed some unusual results with the raw ale. Yeast attenuation is extreme (99% apparent). Using standard SafAle US-05 the final gravity (FG) is usually well below 1.003 and most times is between 1.001 and 1.000 with an original gravity (OG) of around 1.040. A good friend of mine brewed a stout raw ale and it finished at 1.003. His stout normally finishes at 1.015. Any thoughts about this topic would be appreciated.

Richard Albrecht
Johannesburg, South Africa

A This question makes me want to try brewing raw ales because the method certainly saves time and really addresses one of those nagging questions to young brewers who don’t think outside of the modern box; how did brewers boil wort before metal working was common? And, of course, the answer is that early brews were not boiled! Try telling that to a youngster who has been piped into Google via their handheld device since they were old enough to crawl. OK, right, you are wondering about the crazy high attenuation you are achieving with raw ales.

Before I actually begin answering the question, I do want to touch on yeast. Your strain selection likely has little to do with your observations. Although different strains may make a marginal difference in your final gravity, what is happening in your wort during and after mashing is so dynamic and so good at producing yeast fodder, that this style of brewing presents some special challenges because malt enzymes are not being denatured by boiling.

Photo by Chip Walton

And this is the topic to really dig into if you want to boost the FG of your raw ales. For all practical purposes, the two enzymes present in malted barley that are relevant to this discussion are alpha and beta amylase. Alpha amylase chops up large starch molecules into smaller chunks, and beta amylase produces maltose and a little bit of glucose from large and small starch molecules. I am going to skip the review and point you to the discussion we had in the November 2020 issue of the “Mr. Wizard” column covering starch conversion.

Your observation with really high attenuation is a great reminder that some of the old brewing chestnuts are more than tired rules. A quick review of wort boiling reminds brewers that boiling kills pathogenic and spoilage microbes, denatures enzymes, coagulates proteins, isomerizes hop alpha acids, helps strip unwanted volatiles like dimethyl sulfide (DMS) from wort, increases wort density, and has a positive effect on finished beer clarity. There are other reasons to boil wort, but these are among the most important.

As a food safety nut and a fan of history viewed through the eyes of a food geek, the killing pathogenic microbes ranks at the very top of the list because this is why beer was such an important beverage in areas without clean drinking water. The fact that wort boiling also kills spoilage bacteria is a nice secondary story because it explains why boiled wort was the perfect media to be fermented by pure yeast cultures. Although clean drinking water is still a concern in many regions of the world, most homebrewers are using potable water for brewing, and the argument that beer is safer than water is not the best excuse to give your wife for pounding pints like your life depended on it! OK, maybe you haven’t done that, but I have unsuccessfully tried that argument and felt pretty dejected by the whole experience.

But the enzyme denaturation story is rock solid, despite all of the changes that have come with modernity. Unboiled wort contains active amylase enzymes that will continue to do their thing beyond mashing. Two interesting things to ponder are the other enzymes that may be present in malted barley and the effect of very long mashing on wort fermentability. I earlier noted that alpha and beta amylase were, for all practical purposes, the only enzymes relevant to this discussion. That’s true when wort is boiled, but in lightly kilned malts, like Pilsner malt, there can be some remaining amyloglucosidase (AMG) activity. AMG is an enzyme that de-branches amylopectin and is used to produce highly fermentable wort for styles like light lager and brut IPA. Another method used to increase fermentability is to use a very long mash. The method you are using allows for residual AMG activity to survive into fermentation (if AMG is present in your base malt) and also allows alpha and beta amylase to continue doing their things for a long time.

My usual way of addressing questions is to leave some solutions to specifically address the problem. I am going to take a different tack on this question and fire off some ideas that could be used to boost the FG of a raw ale. One idea is to alter wort pH after mashing to essentially stop further enzyme activity. This idea will result in a sour ale, but that may not be a problem. You can do this by using a homofermentative lactic species, like Lactobacillus delbrueckii, or by adding acid to your wort to drop the pH below about 4.5. If this sounds interesting, read up on the effect of mash pH on alpha and beta amylase activity.

You can also use crystal, caramel, and a range of roasted grains, to add unfermented carbohydrates, color and flavor to your beers. You may even want to explore separately cold mashing your special malts. Special malts, like Munich and Vienna, contain starch that is acted on by mash enzymes, but roasted grains and crystal malts have very little, if any, starch that will be converted to fermentables and are well-suited for your raw ales.
And perhaps the simplest suggestion is to design your recipe around the fact that raw ales end up being very dry. Look to styles like light lager, saison, Belgian tripel, brut IPA, and dry stouts for ideas on how to brew dry beer with balance. Thanks for the fun question!

Q I’ve been making hard seltzers using the base instructions you provided in the March-April 2020 issue of BYO. But I’ve been thinking about trying to branch out and start to play around with the base recipe, like changing the ABV, yeast selection, and sugar source. One thing I’m struggling with is YAN (yeast assimilable nitrogen) and FAN (Free amino nitrogen) levels. I now understand the difference between the two, but I’m still hearing conflicting numbers for recommended levels and the fact that many nutrients (like the Wyeast beer nutrient blend and the Yeastex product you list) don’t list the YAN/FAN contribution. Do those levels change with different ABV levels or yeast strains? I know in my heart I should just go and trust your recommended dosages, but where’s the fun in that?

Joshua Greenberg
Kansas City, Missouri

A The answer to this question requires an upfront disclaimer about any bias or product promotions that may accompany my answer. I work for BSG (Brewers Supply Group) and we carry several products used by producers of seltzers, and some of these products will be mentioned in this answer because they are most familiar to me. There are many other products available in the marketplace. I don’t do infomercials and want to get the disclosure out of the way up front. Now let me tell you about this great new product!

In all seriousness, there are really two paths that can be followed when it comes to the yeast + nutrient decision making for seltzer production. The easiest path is to select a yeast + nutrient product that has been specifically developed for seltzer production. Since the starting point of most seltzers is a sugar solution somewhere in the 8 °Plato (1.032) to 20 °Plato (1.083) range and the desired outcome from the base fermentation is pretty much the same regardless of what is done after fermentation, for example cleaning up the base, adding acids, and adding flavors, it follows that yeast + nutrient products provide a useful tool to the seltzer maker. Call me lazy, but these products are really attractive to me because someone has already figured out what combination of goodies works the best to optimize the product. The addition rates can be varied by sugar water density (can we just call this “swort” as in sugar wort?), and you can proportionally adjust based on the recommended use rate at a given “swort” density.

Many seltzer makers are happy with these products and are not bothered that the formulations are proprietary. The companies that produce and market these mixes have done the bench trials, invested into the formulations, and keep the information locked down. You want to know more so you can create your own yeast + nutrient blend. There is no silver bullet to this process and I will give you some basics to help you move in the right direction.

The first thing that needs to be addressed is the elephant in the room . . . as in, what’s the big deal with seltzer? After all, Saccharomyces cerevisiae (translated from Latin as sugar yeast from beer) seems like the right organism for the task of fermenting “swort.” But there is a pretty huge difference among the various sugar-containing solutions to make alcoholic beverages. Brewers have things pretty easy because wort contains much more than sugar and great beer can be made without ever having to worry about nutrients, aside from zinc, which really is one of those good-to-great things. OK peanut gallery, I am not talking really high-gravity beers and/or worts with high adjunct ratios, so pipe down!

Winemakers deal with fruit musts and must (no pun intended) be more mindful of nutrient levels. Then there are meadmakers . . . I have often wondered if the wide array of things added to honey must has not been in the pursuit of the perfect mead nutrient. Hmmm, if only the Pythons were still creating comedy this could make for an interesting sequel to Monty Python and the Holy Grail! And now we have swort for seltzer, with nothing at all for the yeast cells that are expected to transform this nutrient-empty liquid into a clean base to build upon. That’s why nutrients are needed.

This is a high-level, how-to discussion and the very deep topic of yeast nutrition will be kept brief. Yeast cells need nitrogen to grow because without nitrogen cellular functions simply don’t exist. This is because enzymes are proteins, and proteins are built from amino acids, and amino acids contain nitrogen. DNA and RNA also contain nitrogen. Like Bob Marley wailed, “no nitrogen, no wine.” Yeast also require phosphorous to multiply because phosphorous is a critical cell wall constituent, as in phospholipid membranes, required to synthesize DNA and RNA, and essential for the cellular fuel known as ATP (adenosine triphosphate). And don’t forget the vitamins, especially B-vitamins, enzyme co-factors like zinc and manganese, and minerals like calcium and magnesium that are essential for cellular activity. If this paragraph does not send you to the yeast + nutrient shelf, keep reading!

A great resource to help simplify this messy topic can be found on the BSG website at This is where that disclaimer comes into play. If you follow this link you will find an extremely useful chart that provides several nutrient addition approaches for fruit musts with varying levels of yeast assimilable nitrogen (YAN). Note that all of the addition rates in this table are pegged to 25 °Brix (essentially the same as 25 °Plato or 1.106 specific gravity) must and that there is a statement that reads “Lower Brix grapes need less nitrogen, higher Brix grapes need more.” This point was made earlier, and reinforces the importance of the question you raised about matching nutrients with ABV/swort density.

The very high-risk must category is a good basis for formulating a nutrient blend for seltzers because the risk levels in this table are defined by YAN concentration, and swort has zero YAN. Without calling out product names, the suggested strategy for all of the examples shown in the high-risk must category use a blend of a proprietary yeast food + diammonium phosphate (DAP). Almost all nutrient-rich yeast foods on the market contain a large percentage of lysed yeast cells as the primary source of vitamins and minerals. The DAP component brings simple nitrogen and phosphorous to the party, and a blend of these two general types of yeast foods give yeast a fighting chance to convert swort into something that is fit for consumption.

And that brings up yeast. You need it! The most popular strains being used by the DIY crowd fall into two main categories: 1) Brewing yeast known to be clean and alcohol-tolerant, such as the Chico strain of yeast, and 2) Wine yeasts known to be clean and alcohol-tolerant, especially so-called prise de mousse yeasts that are often used for sparkling wine production. This is where you will need to do bench trials to select the strain that tickles your funny bone.

If all goes well with your nutrient formulation and yeast strain selection, you will produce a relatively clean product from primary fermentation. Two common off-flavors encountered by seltzer makers are hydrogen sulfide (H2S) and sulfur dioxide (SO2). Sulfur dioxide smells like a burnt match and H2S supposedly smells strongly of rotten egg— but how often do we encounter rotten eggs in our modern lives? In any case, you’ll know it when you smell it. These are followed by the perfume-like esters that many describe as sake-like. Although sake-like esters are not unpleasant, they are distracting in a hard seltzer. This is where the big mop called activated carbon comes in handy to clean things up before adding acids, flavor extracts, herbal tinctures, or fruit juices to your fermented base.

This answer really just scratches the surface of the topics raised in your question. If you are serious about this project, the most efficient route will be running dozens of 1-liter (1-qt.) bench trials and collecting as much data as possible. If this is more of a science project than you expected, consider checking out some of the yeast + nutrient blends on the market and finding the product that suits your particular needs.

Q I recently ordered ingredients from a well-known, online supplier. Despite specifying all grains be shipped unmilled, the base malts arrived milled, and the specialty malts unmilled. Rather than delay my brew day, I decided to proceed. I weighed out all of my grains and adjuncts and ran the whole batch through my mill. I had no problem with the mash, hit all of my target temperatures, volumes and gravities, and the batch is busy fermenting as I write. What is the impact of running base grains through a mill twice and is it wise to mill flaked barley and corn?

Tom Volk
Blairsville, Georgia

A To mill once, or to mill twice? That is the question — but why shall a brewer mill at all? Brewers mill malted barley for two purposes, extract yield and husk preservation, and these purposes are opposed in terms of process optimization. Extract yield, measured by comparing wort density and volume to malt weight, increases as grist particle sizes decrease. In a lab setting, malt extract is measured on coarsely milled and finely milled malt samples, and the difference between the two values is one of many indices of malt modification. The lab method uses funnels and filter papers to separate wort from mash solids; time is not so critical because malt labs have lots of these filter set-ups and the time required for the filtration is just part of the method.

When it comes to practical brewing operations, the grist is rarely milled as finely as the finely milled malt used in lab analyses and brewers look to the coarse-ground, as-is (meaning the value is not on a dry weight basis) extract value (CG as-is) as a good indicator of what to expect in the brewhouse. Mill adjustment is one of the first things to look to when troubleshooting low extract yields. Brewhouse efficiency is calculated by comparing the extract yield in the brewery to the CG as-is value.

Extract yield, measured by comparing wort density and volume to malt weight, increases as grist particle sizes decrease.

But extract yield is not the only value to focus on when it comes to efficiently producing a kettle full of wort. Time is money, and the gains in extract efficiency that come with adjusting the crush can easily be erased if wort collection times become too long. This is especially true in a commercial brewing operation where the most expensive piece of brewhouse equipment is the wort separation device (usually a mash tun, lauter tun, or a mash filter). The bottom line is that coarse grist makes for easier wort recovery.

So, you ordered unmilled malt, received some pre-milled and some unmilled, and decided to just mill it all to make things easiest. The good news is that everything turned out OK. If you had ended up with a stuck mash, I would be jumping into a discussion about how milling twice can bash up the malt husk and potentially cause you headaches. To neatly answer your first question about milling twice, try to avoid this in the future unless you are doing something to emulate multi-roll milling or are employing brew-in-a bag mashing.

Your question about milling flaked adjuncts is a really good subject with a bit of controversy surrounding it. For whatever reason, there are some brewers who are dead-set against milling flaked grains. One of the most common justifications given for this view is that milling flakes can end up with a gummy mash that does not make for easy wort separation. The primary point to this argument is that the stuff contained in flaked grains causes issues with run-off, so it’s best to keep most of this stuff in the flaked grains by minimizing extract efficiency. OK, that’s an interesting way to do things, but the other way is to mill the flakes and use less since the efficiency will increase with milling. Another totally radical approach is to mill the flakes and enzymatically address the gummy materials, primarily beta glucans and arabinoxylans, by adding a low-temperature mash rest and/or adding exogenous, cellulase enzymes to the mash.

I am in the mill the flakes camp. Flaked grains do not have any husk to be preserved and the majority of the solids contained in flakes are solubilized during mashing. There is no argument that cell wall constituents from certain flaked and unflaked grains, especially barley, oats, and rye, are quite effective at gumming up the works. The solution to this conundrum is found by varying the grist bill and/or mashing process, versus faking things by reducing yield.

As an aside, starchy adjuncts like rice and corn grits are typically milled finely because these ingredients are almost entirely comprised of starch and fine milling optimizes yield. Similarly, wheat malts and other huskless grains are often milled more finely than barley malts because there is no husk to preserve. Finally, when you do buy pre-milled grains, be mindful about storage conditions because they pick up moisture from the environment more readily than whole grains.

Issue: December 2020