Don’t Overpitch a Session Beer

[This is the second article in a series on brewing session beers. In the first, I discusssed sparging the grain bed for a low-gravity beer.]

In the past, a common problem among homebrewers was pitching an inadequte amount of yeast. The original containers of liquid yeast did not contain enough yeast cells to yield an ordered fermentation of 5.0 gallons (19 L) of average strength or higher wort. They “would work,” but start times were longer than they should have been and sometimes the beer did not attenuate fully. However, some brewers did not want to go through the hassle of making a yeast starter. 

These days, homebrewers have access to liquid yeast packs that have 100 billion cells or 200 billion cells. And of course, we’ve always had access to dried yeast packets that have a large cell count. An 11.5-gram packet of dried yeast, for example, contains over 200 billion cells. And all that is great —  except when you are brewing a session beer. For a low-gravity beer, the amount of cells in a commercial yeast packet might actually be too high.

Generally, the problems associated with overpitching are less troublesome than the problems associated with underpitching. However, in a session beer, overpitching can detract from the beer’s character. Overpitched beers may attenuate to a greater degree than you want. With a session beer, you already expect a low finishing gravity because of the low starting gravity. So “extra” attenuation is unwelcome. You can moderate this somewhat by adding more crystal or caramel type malts to your recipe or mashing for a shorter time at a higher temperature. However, higher pitching rates also increase your overall attentuation. 

In addition, the yeast character from ale strains is mostly developed in the early growth phase of the beer fermentation. Fewer esters are produced once the yeast has reached their maximum density and are fermenting compared to when the population is still growing. So, overpitching can minimize the yeast character of a session beer. And given that many session beers are low-gravity, English-style ales, this character will be missed. Even in a non-English-style beer, some yeast character in a low-gravity beer gives it more overall aroma and flavor — something that can be lacking if the beer is not brewed well.  

For a low-gravity ale, I recommend pitching even less than the typical ale calls for. The general rule of thumb for ales is to pitch a million cells per mL per °Plato. So, for example, 5.0 gallons (19 L) of 12 °Plato (SG 1.048) beer — one that should produce a beer around 5.0% ABV — would need 227 million yeast cells. However, 5.0 gallons of a 9 °Plato (SG 1.036) beer — one that should produce a 3.5% beer — only needs 170 million cells. Pitching 200 million cells to a beer like this would not be drastically overpitching, and you’d probably get away with it. However, if you wanted to purposely underpitch to develop more yeast character, 130 million cells would be a better target. That’s 75% or the amount the general rule would suggest (and in line with the pitching rate of many commercially produced ales). 

Fortunately, it is easier to deal with having too much yeast than too little. If you have a 200 billion yeast cell container of yeast, and you want your pitching rate to be less than that, just pitch part of the package. If you wanted 130 million cells, for example, you want to pitch (130 million cells/200 million cells =) 0.65 or 65% of the yeast in a 200 billion cell package. Be sure to shake the package so that the yeast is evenly distributed before dividing it. You could perhaps utilize the unused yeast to make bread, or another yeast starter, if you were concerned about wasting it.

Alternatively, you can use a yeast pitching calculator to determine the size yeast starter that would be required. Then, pitch a small amount of yeast to the starter — NOT the whole pack — and let that grow. Recall that 8.0 fluid ounces (240 mL) of yeast slurry is generally adequate for 5.0 gallons (19 L) of 12 °Plato (SG 1.048) beer. So, if you were making a 1.0 qt. (~1 L) yeast starter, about 1/20 of that volume — 0.4 fluid ounces (12 mL) of yeast slurry would be required. I nearly always make a yeast starter because I can assess the health of the yeast based on the vigor with which they ferment the starter wort.

Brewing a high-quality low-gravity session beer requires every bit as much attention as brewing a big beer. The “tricks” are just different. For starters, don’t use too much sparge water on your grain bed nor pitch too much yeast to your wort. More session beer posts are in the works.

Beer Foam (Part 5: Brewing Considerations)

DSCN2679Most of the time, brewers give comparatively little thought to foam. We brew our beers and foam appears on top of them. There is no single ingredient or procedure that creates foam, it simply emerges when a beer is brewed properly. However, there are things you can do when brewing that affect foam production and stability. It pays to understand these things, especially if your foam isn’t always what it should be. [Read more…]

Top 10 Steps Towards Brewing Better Beer

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The first five of which I’ll post today.

When I started brewing, information of how to make the best quality beers was just starting to emerge. These days, there is an abundance of information on homebrewing, and sometimes it can be overwhelming. Sorting important information from minutiae or the latest fad can be hard. As such, I’m going to present what I think are the top 10 most important aspects in brewing. This top ten list is presented as both an informed opinion on what the most important aspects of brewing are, and an argument for their ranking.

The list will cover things that are important to brewing quality beer. I’ll ignore economics, among other things, and just focus on what is most important to making outstanding beer. I will assume that the brewer can already manage to produce a drinkable beer. Incredible foul-ups or intentionally ruining items farther down the list could ruin a beer, and argue for a different ranking of items, but I’m trying to help brewers who are actually attempting to brew good beer and can reasonably hit the temperatures, volumes, and durations required on an average brewday.

I’ll start this list at the top, rather than doing the usual countdown, because I want this list to be an argument. (And by argument I mean a set of statements meant to support a central thesis, not a shouting match.) And, it is easier to understand my logic if start at the top. 

[Read more…]

Russian Imperial Stout (VII: Fermentation: Yeast Strain and Pitching Rates)

RISphotoIn most cases, the thing that separates a good Russian imperial stout from a bad one is a well-run fermentation. In order to conduct a good fermentation, you need to select the right yeast strain, pitch an adequate amount of it, and create a healthy environment for the cells.

[Read more…]

A “Trick” to Boost Your Pitching Rate

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Use your favorite liquid yeast strain for flavor and aroma, then use a neutral yeast strain to shore up your pitching rate.

Pitching rate, the number of yeast cells used to inoculate a given volume of wort, influences several things in the brewing process. Higher pitching rates lead to faster fermentations — they start faster and finish faster. Higher pitching rates also lead to finishing gravities closer to what is predicted by a forced fermentation test. In other words, the yeast utilize all the carbohydrates that they can. In contrast, in severely underpitched beers, the yeast may quit early and leave fermentable carbohydrates behind, resulting in a higher final gravity (FG). Low pitching rates are frequently the cause of stalled or stuck fermentations.

For “characterful” yeast strains that produce plenty of fermentation byproducts, higher pitching rates are associated with “cleaner” beers. Some Belgian ale strains produce an estery, “spicy” aroma when slightly underpitched, but produce a cleaner beer when pitched at a higher rate (to a well-aerated wort). Temperature also plays a major role, with higher temperatures leading to more fermentation byproducts.

This is true of White Labs WLP530 (Abbey Ale) and Wyeast 3787 (Trappist High Gravity) yeast — larger than optimal pitches, thorough aeration, and low temperatures (within the usual ale fermentation range) lead to clean fermentations. It is also true that the “banana ester” level in German hefe-weizens can be manipulated this way.

Homebrewers who are concerned about their pitching rate generally consult a pitching rate calculator, then make a yeast starter of the suggested volume. However, if your brewday arrives and you haven’t made a starter, there is a way to “cheat” that may come in handy occasionally.

[Read more…]

Barleywine (VII: Fermentation I)

This article is part of a series on barleywine.

 

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Conducting an orderly fermentation is key to brewing a quality barleywine. The biggest key to doing this at home is to make an adequately-sized yeast starter and pitch enough yeast.

Making the wort for a barleywine can be trying. Sometimes the amount of grain required is more than your mash tun can hold. Sometimes you can’t collect all the wort you’d like because your kettle is too small. And for most all-grain versions, you need to boil the wort for an extended period of time. Even though wort production can be a chore, the part of brewing a barleywine in which the brewer can exercise the most influence on the quality of the final product is the next step — fermentation. If you make a yeast starter that is large enough, your fermentation can be handled like most ale fermentations, especially for smaller barleywines. For the largest barleywines, you may need to use some additional techniques to get all you want from the yeast,

 

Your Goals

Once the wort is chilled and in the fermenter, it’s time to let the yeast transform the wort into beer. In a barleywine fermentation, you have several goals. As with any fermentation, you want active fermentation to begin quickly. If your barleywine has a cap of kräusen and your airlock is gurgling between 8 and 16 hours after pitching the yeast, you’re doing great. If it takes longer than 24 hours to start, you may be headed for problems. (At a minimum, this could lead to a sluggish fermentation that takes longer than it should to finish). Likewise, once started, you want the fermentation to keep moving steadily until the beer’s target final gravity (FG) is reached. Most barleywines should finish in the high teens through the 20s. (The BJCP gives FG 1.018–1.030 for English barleywines and FG 1.016–1.030 for American barleywines as the proper range.) For beers at the lower end of the barleywine OG range (OG 1.080–1.090), this means you want a maximum apparent attenuation of around 75%. For heavier barleywines, apparent attenuation up to 80% is OK. The biggest key to achieving this is to pitch an adequate amount of yeast. Choosing an appropriate yeast strain is also important.

[Read more…]