Ask Mr. Wizard

Reduce tannins during the steep


C. Zurich • Baltimore, Maryland asks,

In using specialty grains with extract homebrewing, what is the best method to get the most flavor and color out of the grains but still reduce tannins? Some recipes say to steep grains until water comes to a boil and remove, while others say to bring water to 150° F and steep for 30 minutes. I just made a Belgium ale in which I steeped the grains in 170° F water for 30 minutes and then sparged with 170° F water. Was this temperature too high for the steep and did it release unwanted tannins?



The two most influential factors affecting the extraction of tannins from malt into wort are pH and temperature. All-grain brewers are very careful not to allow wort pH to reach more than about pH 6 during sparging because tannin extraction increases with pH. In all-grain brewing wort pH typically rises during the last stages of wort collection and is one of the factors letting the brewer know that wort collection should be stopped.

When a relatively small weight of specialty grains is steeped in a large volume of water, the result is a very thin mixture. The pH is only slightly affected by the malt (pale malts tend to lower the mash pH during all-grain mashing to about 5.4 pH). This means the pH of the solution during steeping will be higher than the pH of a normal mash, which has an oatmeal-like consistency.

To combat this problem the pH of the steep can be adjusted to around 5.4. Although all-grain brewers typically use calcium sulfate (gypsum) or calcium chloride to lower mash pH, these salts lower pH by reacting with phosphates from the malt. Steeping mixtures don’t contain much malt and lowering the pH with water salts can be difficult. Food-grade lactic or phosphoric acid are alternatives to water salts; both of these acids are sold in homebrew stores.

The key to adding acids is to add them slowly with continual stirring and monitoring with a pH meter or pH paper. I recommend adding a small amount while stirring the pot, checking the pH, and continuing until the pH is around 5.4.

Temperature also affects tannin extraction. This relationship is pretty simple. If you don’t want to run the risk of getting too much tannin in your wort, keep the temperature just below 170° F.

This is where the answer to your last question begins. You ask whether steeping and sparging released “unwanted tannins” in your beer. For starters, all beer contains tannins. Some tannins are implicated in haze and some lend astringent flavors to beer.

The type most homebrewers are concerned about are those affecting flavor. In any case, it is up to the brewer to decide if the level of tannins in their beer is too high. The (in)famous decoction mash is frequently recommended when a brewer is in search of more malt flavor. Decoction mashes boil malt and — among analytical brewers who are not afraid of rocking the boat with unpopular ideas — are known to increase the astringent character associated with tannins. In general I wouldn’t consider 170° F dangerously high with respect to tannin extraction. However, if you believe your beers may suffer because of too much astringency, consider adjusting your steep pH and lowering the temperature a few degrees.

Response by Ashton Lewis.