Ask Mr. Wizard

A Look Inside Crystal Malts


Morrey Thomas — South Carolina asks,

In an article I recently read online (from the September 2000 issue), you discussed caramel/crystal malts and the fact that these malts offer non-fermentable sugar chains. Does the addition of caramel/crystal malts offer any fermentable sugar at all, or does the stewing and kilning process render all of the sugars non-fermentable?


Morrey, thanks for letting me know that my material from 2000 is still being read today! Crystal, also known as caramel malts, do contain a mixture of fermentable sugars, non-fermentable Maillard reaction products, and starches that can be hydrolyzed during the mash by alpha and beta amylase. Not all crystal malts are produced in the same fashion and some are less thoroughly crystalline in nature than others. I have never seen any data from crystal malt producers that directly addresses your question, but there are some indicators that can be used to better understand the differences among crystal malts being produced by various maltsters.

Before jumping into this discussion, let’s take a few steps back and review how crystal malts are made. The most common method is drying “green malt” (green malt refers to germinated malt containing about 45% moisture) in a roasting drum using a special process that includes a “stewing step” that proceeds drying. Green malt is loaded into the drum roaster, heated to about 149 °F (65 °C), and held for sufficient time for malt amylases to convert malt starches into a combination of fermentable and non-fermentable sugars; essentially the malt starches are mashing inside of the malt kernel during the stewing process. The sugar-rich malt is then kilned or dried using specific time and temperature profiles that allow the maltster to control color and flavor development. During the kilning cycle, malt sugars and dextrins react with amino acids in the various chemical reactions that are collectively known as the Maillard reaction. Maillard reaction products, often abbreviated MRPs, range in aroma and color intensity as the reaction is allowed to continue and as kilning temperatures increase.

Crystal malts can also be produced on a malt kiln by controlling air flow, moisture within the grain bed, and malt temperature to achieve similar results as drum roasting. Process control is much better in a roasting drum, however, and the uniformity of crystallization tends to be better in drum-roasted crystals in comparison to those produced on kilns. This difference can be visually assessed by cutting malt kernels in half using a special tool called a farinator or by carefully bisecting kernels with a razor blade; the appearance of the endosperm is transformed from “mealy” to “glassy” during crystal malt production. The objective is to have 100% of crystal malt kernels appear glassy when visually evaluated after bisection, and this metric is reported by maltsters who produce crystal malts.

A farinator is a tool that maltsters can utilize to analyze the extent of crystallization that occurs during roasting. This kiln-roasted caramel malt has some percentage mealy (seen with white cross-section) and some percentage glassy (see with a dark cross-section). Photo courtesy of Briess Malt and Ingredients Co.

So what does the production process and glassiness have to do with wort fermentability? MRPs are not fermentable, and malt starches and dextrins that can be converted into fermentable sugars during mashing in the mash tun decrease as glassiness increases. This means if you are using crystal malts with a relatively high proportion of mealy kernels that you should expect these malts to yield fermentable sugars when mashed. Crystal malts are primarily used for flavor and color at usage rates that are usually less than 10% and normally in the 5% range, so the contribution of extract is relatively low. This is a good malt to tweak in recipes by noting its influence on beer flavor.

Response by Ashton Lewis.