Homebrew expert Brad Smith, author of the Beersmith homebrewing software and the voice behind the Beersmith podcast, looks at what can cause unintentional bitterness in beer.
Brad Smith 9 months ago
A Craft Beer & Brewing Magazine reader recently asked us the following question:
My last beer has a sharp harsh bitter finish to it. It’s not a hoppy flavor but tastes more like a harsh tea or overdone coffee finish. What did I do wrong?
I’ll cover two possibilities. Based on your description, the most likely cause is excessive tannins, though it is also possible you used an excess of grains from the “harsh zone,” which I’ll describe in a minute.
Tannins are a form of polyphenol that naturally occurs in malted grains and is derived primarily from the grain husk. During the mashing and lautering process, some tannins are extracted from the grain husks, although in most cases the tannin level remains below the flavor threshold that most people can detect.
Excessive tannins can be extracted in your beer if you allow the pH to be driven too high (above 6.0) either when steeping grains in an extract brew or when lautering an all-grain brew. In the extract case, the usual cause is using too much water when steeping your grains. For extract brewers steeping grains, I recommend keeping your water/grain ratio below about 4 qts/lb (8 l/kg), as higher ratios can result in the pH above 6.
For all-grain brewers, tannins are most frequently extracted near the end of the sparge/lautering process when the last runnings rise above a pH of 6. To counter it, first you want to manage your mash pH and keep it in the 5.2–5.6 range while mashing. For most batches, I end up adding some lactic acid to bring the pH down close to 5.2 when brewing, and you can use software or an online calculator to estimate your mash pH acid adjustment both for the mash and sparge water. Second, you want to avoid very long sparges, especially on light colored, low-gravity beers.
While tannins are one potential cause of your problem, the other problem could be use of too many grains in the “harsh zone.” The “harsh zone” is a concept Randy Mosher introduces in his recent book, Mastering Homebrew. In the book, Randy notes that very few grains are malted and produced in the color range from roughly 80 to 250 Lovibond. The reason for this is that malts produced in this “harsh zone” have many harsh flavors including strong tannic, coffee, burnt marshmallow flavors that can easily overpower other malts.
That’s why malts such as Special B, very dark caramel malts, dark brown malts, aromatic malts, and even light chocolate malts should be used very sparingly. Some even come in “debittered” or “dehusked” versions to try to soften their flavor. Using more than a few percent of malts from the harsh zone can give you excess tannins and other harsh burnt flavors that could ruin your beer. I use them only in small percentages and only when I have a specific purpose, such as to add depth to a complex porter or imperial stout. You should avoid using grains in the “harsh zone” when brewing most beer styles.
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