As mentioned in the first part of this article, there are a few beers that might benefit from just a hint of astringency. Usually, the slight puckering sensation will offset or complement another character in the beer. (And, of course, we all know that noticeable astringency in most beers is going to be unwanted.) There are a couple ways you can get just a hint of astringency in your beer, if you want it.
Tannins are water soluble. They are more soluble in high pH solutions than low. And, like most water soluble molecules, they are more soluble in hot water than cold. Let’s first review what happens when you use continuous sparging with 170 °F (77 °C) water. In other words, if you sparge in the normal way meant to minimize tannin extraction.
Assuming that you mash out to a grain bed temperature of 170 °F (77 °C), the initial sparge water will hold the grain bed temperature at 170 °F (77 °C). Near the end of the sparge, the temperature of the grain bed will still be 170 °F (77 °C), but the pH will rise to around 5.8. (On a home scale, your sparge water may need to be hotter than 170 °F (77 °C) to maintain the grain bed at this temperature.) If the brewer stops sparging at or below a pH of 5.8, only a minimal levels of tannins will be extracted. If the brewer continues to collect wort over a pH of 5.8, some astringency will result.
Hotter Sparge Water
Now, what happens if you sparge with 190–200 °F (88–93 °C) water? At first, the rate of tannin extraction would be little different than at 170 °F (77 °C). This is because the grain bed would still be full of sugars and the pH close to mash pH (5.2–5.6), below the threshold where tannin extraction is accelerated. Recall that, in decoction mashing, a third of the mash is boiled, and this yields only slightly more tannins than infusion mashing. (It’s a myth that decoction mashing does not increase the tannin concentration at all. It does a little, but not enough — in most cases — to cause overt astringency.)
At some point during the sparge, the combination of temperature and pH would start extracting tannins at a higher than usual rate. Over 170°F (77 °C) and pH 5.8 is the usual “line in the sand” drawn for brewers. However, I’ve never seen the line extended to higher temperatures. Obviously, the pH threshold should be lower at higher temperatures. But where exactly isn’t known (to me, at least). So, it would take some experimentation to discover what temperature and pH would yield the amount of astringency desired. The pH of the grain bed near the end of the sparge would be determined by the volume of wort collected, relative to the weight of grains in the grist. The more wort you collect, the higher the pH would climb.
A better way to add a hint of astringency to your beer is to collect your wort as you normally would, sparging with 170 °F (77 °C) water — and you can use continuous or batch sparging. For a 5.0-gallon (19-L) batch, collect all but the last quart (~1 L) of your pre-boil volume. Then, continue running off wort to a separate vessel. (At this point, you’ll need to use continuous sparging — or something similar. But you can do so even with a batch sparge lauter tun, because you’re not worried about extract efficiency in the late wort.) At some point, the runnings will start to be astringent. Keep running the wort off at a moderate pace and taste the collected late wort as you go. Eventually, it will be distinctly astringent. At this point, take about a quart (~1 L) of this late wort and add it to your kettle. Keep in mind the intensity of the astringency will be diluted.
If you fully sparge the grain bed, the astringent late wort should immediately follow the last bit of “regular” wort. However, especially when brewing big beers, most homebrewers collect a smaller volume than this to save boiling time, or due to kettle space restrictions. Hence the recommendation to collect the late wort in a separate vessel and blend it into the early wort.
When brewing a strong or very strong beer, undersparging — and often drastically undersparging — is common amongst homebrewers. If you are brewing a barleywine, but collecting the same amount of wort as when you make a much lighter pale ale, you are undersparging. In this case, blending some late, tannic wort into the early wort may keep the beer from being a sickly sweet mess. Recall that beer entirely devoid of tannins doesn’t taste right. In this case, the late wort may not be adding actual astringency to the beer; it may simply be adding tannins to below the threshold for astringency. Although not perceived as astringent, their presence may make the big beer more beer-like. (When brewing strong or very strong beers, you’ll also need to produce a highly fermentable wort and run an ordered fermentation.) This is also a consideration, when brewing multiple beers using parti-gyle methods.
The most straightforward way to add tannins to your beer would simply be to add powdered tannins. The winemaking section of your local homebrewing shop should carry this. And, of course, adding powdered tannins lets you measure the amount and replicate the beer, if needed. On the other hand, the mix of tannins in grape seeds and stems isn’t the same as the mix of tannins in barley hulls and hop material. Plus, the tannins you need are right there in your grain bed.
In general, you want the level of tannins in your beer to be below the threshold at which noticeable astringency occurs. In a few cases — such as sour beers, flavored beers, dark beers, or strong beers — a hint of astringency may improve the beverage. (A bit of late wort to deliver less than noticeable astringency in a parti-gyle beer may also be a good thing.) In most cases, collecting some late wort separately and blending it into your “normal” wort can add just a touch of astringency. And, you can regulate the degree by tasting the late wort and determining how tannic it is and how much to blend into your main wort.
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