Digging into the Haze, Cacao Nibs Advice and Harvesting Yeast
Q
I love a well-made IPA, whether they are hazy or clear. But I keep coming across mouth-numbing astringent, opaque, gritty versions of the hazy IPAs lately where it seems like the hop pellets are still formed in the beer. I would love to hear your thoughts about what brewers should not be doing when trying to make a highly aromatic IPA.
George Husing
Long Beach, New York
A
It is easy for us “old-school brewers” to joke about the cloudy-IPA style, and dismissively suggest to just do the opposite of what is required to make clear beer. Although there is truth in this suggestion, it requires an in-depth understanding of physical stability that is not exactly common knowledge. In brewing jargon, the term “physical stability” is used to describe how well the appearance of beer holds up to aging. Beers with excellent physical stability do not change in appearance over time. Unstable beers, however, may begin life as crystal clear, straw-colored Pilsners, and morph into an entirely different liquid, that oftentimes include unusual and visually unappealing flakes in the beer and on the bottom of the bottle. Cloudy beers also change over time as cloud particles succumb to gravity and slowly settle to the bottom of the bottle, or react with other compounds in beer to form large, funky looking flocs.
So let’s walk down this path and talk about brewing hazy beers. The primary sources of haze precursors in most filtered beers are the brewing grains and hops. Some beers are hazy because of microbiological problems, but the majority of non-biological hazes arise from reactions between proteins and polyphenols, aka tannins. Less common hazes include starch hazes, beta-glucan hazes and gels, and hazes associated with metal ions from water and/or equipment. And then, of course, there are those hazy, unfiltered beers that are cloudy because of yeast in suspension.
Proteins from grains react with polyphenols from grain and hops, and when this happens the protein-polyphenol complex causes light to scatter and the beer to appear hazy. Barley, wheat, oats, and rye are all rich in protein and typically contain between 8-15% protein. Malted grains lose some protein in the malting process to rootlets (removed after kilning), but the composition by weight is not dramatically affected by the malting process. The nature of these proteins, however, is significantly changed during malting by proteolytic enzymes. The totality of changes to the grain kernel that occur during malting are simply referred to as “modification”, and it is generally true that well-modified grains improve the physical stability of beers.
When German brewers first began brewing lagers in North America, they quickly learned that North American barley had more protein than the barleys they were accustomed to using back in Germany. Malt extract yield, color, flavor, and enzymatic power are all influenced by barley protein. And the physical stability of beer is directly affected by malt protein. For these reasons, German brewers began diluting malt protein with maize and rice.
You want to brew hazy beer, and it really helps to begin with grains that are more likely to contribute haze-active proteins. Think undermodified or unmalted cereals. Flaked oats, wheat, and rye are some of the go-to grains for these beers. And you may want to pick up some rice hulls with these grains because these grains do tend to gum things up!
But proteins alone do not make for hazy beer; polyphenols are also needed to form haze particles. Malted barley and hops are the two main sources of polyphenols in beer, and if you want hazy beer these ingredients are the obvious source of polyphenol. There is a practical limit to the amount of polyphenol contributed by malt because adding more malt increases wort OG. This leaves hops, and hazy IPAs typically have bunches of these green goodies added at various points in the brewing process. More about this later in the column.
Aside from raw material type and quantity, what other things are done to improve beer stability? Intensive mashing schedules, long kettle boils, the use of kettle finings, and whirlpools are brewhouse processes that improve beer stability. Cold conditioning, the use of beer finings, flocculent yeast strains, prolonged storage, filtration, and centrifugation (commercial practice only) are cellar practices to improve stability and promote clarification. And controlling storage time and temperature are both critical to physical stability once beer is packaged. Consider omitting finings, choosing non-flocculent yeast strains, skipping the cold crash, limiting time in the secondary and consuming your cloudy concoction quickly after packaging. A trick is to store bottles cool, but not cold, and to chill the bottles shortly before serving so that the chill haze formation is delayed until it is time to consume.
Science takes time, and there are many unanswered questions about what is really happening with these beers. But the anecdotal evidence points to hops as a key part of this equation, and it seems that large doses of hops, especially when added in the fermenter as dry hops, are very haze-positive. This makes sense because hops contain polyphenols. This is certainly not news, and brewers producing clear IPAs have struggled with hop hazes. What is different is the intensity of the haze.
Some brewers have suggested that adding hops during fermentation interferes with yeast flocculation because of hop oils depositing on the yeast cell wall. Others point to the large addition of polyphenols late in the process. Whatever the explanation, high dry hopping rates (2+ pounds per barrel/1+ ounce per gallon/7.5+ grams per liter) seems to coincide with some of the hazier brews out there. The interesting thing about this explanation is that removing yeast with a centrifuge does not seem to remove the haze, so the yeast flocculation explanation may not be correct.
Hopefully this helps to clarify some of the big points about haze. Your question opens the door to opinions about the astringency found in some of these beers. I’ll just say I am not a big fan of that character, and I am not a fan of beers that have vegetal and grassy notes from the extreme use of hops. This is where hop selection becomes important. Not only hop variety, but specifics about the variety and different preparations made from given varieties.
Selecting hops after harvest is not an option for homebrewers and most smaller craft breweries, but this does not mean that you cannot select hops. Hops that don’t smell great are not magically transformed when added to beer, so if you open a bag that smells strong of onion or garlic and you do not want that aroma in your beer, don’t add the hops. This sounds simple, yet can be frustrating and expensive when contemplating not using something you purchased. Choosing hop products is another option. If you want lots of hop aroma, but not so much hop matter, consider using lupulin powders, hop extracts, or Type 45 pellets. And it is up to the brewer, not the recipe written by someone else, to decide how much hops to add.
Several years ago, some were seemingly obsessed with IBUs and beers became more and more bitter, to the point where many of these brews were unpleasant and unbalanced. There is a similar thing happening today where brewers and beer lovers are talking about hopping rates in pounds per barrel as if super high hopping rates are a badge of honor. I suggest focusing on aroma and flavor quality and not trying to figure out how to top the hopping rate charts. But if you are after the extreme in hop flavor and aroma, the sky is the limit. Just remember that wort and beer losses increase with hopping rate, and brewing these beers can be very expensive if concerns about efficiency are thrown out with the bath water!
In summary, consider the following brewing tips:
• Derive about 20-25% of total wort extract from unmalted cereals
• Omit the Irish moss
• Select yeast strains with low flocculation properties
• Do not cold crash after fermentation
• Add hops late in the boil, in the whirlpool, and late in fermentation
• Consider chilling beer to drinking temps immediately before consumption
• Leave the bread flour in the cupboard
Q
What is your best procedure for adding cacao nibs to an all-grain brew?
Patrick Kiefer
Greenleaf, Wisconsin
A
With any brewing ingredient it is helpful to consider what the ingredient contributes to beer, how the contribution is best transferred from the raw material to the wort and/or beer, if there is any benefit to cooking the ingredient, and if there are microbiological risks associated with the ingredient or flavorant, e.g., used oak barrels. Wort is prepared like it is because malts must be mashed to convert starches into fermentables, hops need to be heated to isomerize alpha acids into iso-alpha-acids, and “sterile” wort is required for bacteria-free fermentation.
Cacao nibs contribute a range of aromas and flavors that can be described as chocolatey, nutty, malty, and fruity, among others. Most of these compounds are water soluble, and arise from Maillard reactions that occur during roasting. This means that cacao nibs do not need to be soaked in solvents, such as ethanol, to yield their goods, or transformed, like hop acids, by cooking to improve solubility of the flavor-active compounds. And despite the crucial role yeast and bacteria play in the fermentation of cacao pods, which frees the beans from the pod and develops flavor, roasted cacao nibs are not associated with beer spoilers because the relatively long and hot, drying and roasting processes is a thermal kill step (there are aerobic bacteria on the surface of cacao nibs, but are not a major concern for beer spoilage).
The easiest and most common way to use cacao nibs is like hops used for dry hopping, and the contact time can be empirically determined by periodically taking small samples for tasting. A couple of weeks is usually what it takes to get good flavor extraction. I prefer this general method for all brewing ingredients that do not need to be mashed or boiled because the aromas and nuanced flavors of these ingredients fade if added prior to fermentation because carbon dioxide gas scrubs volatiles from fermenting beer.
A variation on this theme is to add the featured ingredient; in this case cacao nibs, to a smaller fermenter or container, fill with beer or another liquid, and make a concentrated stock that can be used for blending. The advantage to extracting the flavors in a smaller volume of beer or other liquid is that it allows for more control over the flavor intensity in the finished beer. This method works especially well when using potently flavored ingredients in a recipe for the first time. Whether the ingredient is cacao, coffee, vanilla, oak, fruit, or spices; it is nice not having to worry about adding too much or too little. And when you use special ingredients in this fashion you can really focus on maximizing flavor extraction because it is easier to filter or strain smaller liquid volumes, especially if you use a solvent that is not subject to oxidation, as is the case with beer. Water or alcohol teas are the most common, and the simplest way to improve flavor extraction of these types of ingredients is by reducing the particle size. Cacao nibs are fairly brittle, so they can be turned into a powder using a blender or coffee grinder; don’t attempt to mill this ingredient because the fat content will gum up your malt mill.
Q
Can I be adding an unwanted flavor to my beer by the starter I’m adding? I saved the trub from my previous brew fermented with Wyeast 1056, and have used it 4 times. I mix up two liters (2.1 qts.) of distilled water, add 200 grams (7 oz.) of light dried malt extract, boil that for 15 minutes, cooled, add my trub and let the yeast do their thing for 24 hours + (67-70 °F/19-21 °C in a dark closet) before adding it to the cooled wort. Any comments are appreciated.
Chuck Hamstreet
Leavenworth, Washington
A
I have a routine when preparing to answer questions for my column, and this routine begins with editing questions that come into BYO magazine from email, social media, and snail mail. It is tempting to edit your question because your use of the word “trub” can be interpreted two ways. In the context of your question, I read “trub” to mean yeast solids that fall to the bottom of the fermenter after fermentation. But trub specifically refers to the protein-polyphenol-hop acid complexes that precipitate from wort during wort boiling and wort cooling. Although there is some trub in yeast solids, most brewers do not refer to harvested yeast as “trub.” I am not taking this digression into semantics to nitpick, rather I want to draw attention to a term that is often misused. And this misuse can lead to confusion about brewing advice that pertains to wort boiling, trub, yeast solids, and the meaning of life. So, without further ado, onto your question!
To paraphrase, you are harvesting yeast at the end of fermentation, storing it for an unspecified time period, and growing it up in a starter before re-pitching into a fresh batch of wort. Harvesting, also known as cropping, and reusing yeast is quite common, but, as you suggest, can be problematic. Harvested yeast with low viability, with excessive trub, and dilute crops can lead to issues when re-pitched. The good news is that these challenges are fairly easy to overcome.
Towards the end of fermentation, yeast cells, at least those with good flocculation properties, begin to stick together to form large flocs of cells. So-called top fermenting yeast may form thick yeast layers on the top of the beer, and so-called bottom fermenting yeast flocculate and sink to the bottom. Depending on the yeast strain and the type of fermenter used, many top-fermenting strains will end up on the bottom of the fermenter. Whether harvesting yeast from the bottom of the fermenter (most common method) or the skimming from the top, it is important to harvest the yeast shortly after fermentation has ended and the yeast has risen to the top or settled to the bottom. Prolonged storage in beer, especially warm beer, reduces viability. Chilling beer after fermentation often precedes yeast harvesting and some breweries store yeast for a few days at the bottom of the fermenter as yeast flocculates. The rule of thumb is to harvest the yeast as soon as possible following sedimentation.
Yeast is not the only thing that settles from beer in a fermenter. Trub also settles, and trub is not the tastiest stuff in the brewery! Cone bottom fermenters are very handy when it comes to dealing with trub because they allow for trub removal before most of the yeast cells settle. It is common practice in commercial breweries using conical fermenters to blow the cone several times during fermentation; this helps remove trub, early flocculating yeast, and dead cells from the beer before the yeast cells doing the heavy lifting flocculate and settle. If you ferment in a carboy or bucket, this practice is not possible because there is no cone on these flat-bottom vessels. One relatively uncommon practice to address this limitation is racking beer about 8 hours after pitching, and before active fermentation begins. This allows for trub to settle before the stirring action of fermentation mixes the trub up and into the fermenting beer. Trub can also be skimmed from the top of the fermenter by encouraging blow-off through high fermenter fills, or by actively skimming the fermentation.
The bottom line is that cropped yeast should be fresh and trub free. But some yeast strains have poor flocculation properties. These strains may not be sufficiently dense to re-pitch without adding lots of beer with the yeast into the next brew, and one very useful solution to this problem is to prepare a starter with the yeast available. This is the method you describe. Your DME weight and starter volume produces wort at about SG of 1.036 or 9 ˚Plato, and the 2 liter (2.1 qts.) volume is perfect to pitch into a 20-liter (5.25-gallon)batch of wort. No problems at all with this method as long as you are using yeast from a good brew with reasonable viability and minimal trub. Some brewers use this method to revitalize yeast that may have been stored for too long since the propagation step yields healthy, cells with lots of vigor.
But I do question the necessity of a propagation step when using yeast strains that are very well behaved, such as Wyeast 1056 (American Ale) or White Labs WLP001 (California Ale). This strain is known for clean and rapid fermentations, and good flocculation. You should have no problem harvesting enough yeast slurry from normal gravity brews (I don’t suggest re-pitching yeast from brews with OGs higher than 1.064/16 ˚Plato without a propagation step) to pitch into another batch. A good rule of thumb: Pitching volume is 10-15 mL of thick slurry per liter of wort.
