Dear Mr. Wizard:
Could you please explain Carapils to me? What does this brand-name malt do in a mash, and how does it work? One of my homebrewing pals and I had a recent disagreement about this. He seems to believe Carapils works by leaving behind unconverted starches that the yeast cannot ferment, leading to greater body, mouthfeel and foam stability. I remember reading from various sources that starches are bad in beer, because yeast can't eat them but bacteria can, and so this leads to infections. I believe there should be no starches in finished beer and that starch is not what contributes to improved body, mouthfeel and foam.
Carapils is also called "dextrin malt." I know there are also other "cara" malts, such as cara-Munich, cara-Vienne and carastan. Can you sort out this whole cara-issue? Thanks for your sagely advice, Sir Wizard. It is always much appreciated.
Mr. Wizard replies:
Caramel, cara or crystal malts are synonymous terms describing a large family of malts that are made by changing the kilning process. All malts are kiln-dried to arrest germination. To make caramel malts, the maltster adds a key step, known as "stewing" or saccharification, before drying. The "stewing" step heats moist, unkilned malt (or re-hydrated kilned malt) to about 158° F. The malt is held at this temperature for 1 to 2 hours with minimal ventilation to minimize drying.
Most caramel malts are made in roasting drums where ventilation and temperature are easily controlled. Stewing allows the starch inside of the malt kernel to convert to sugar, just like mashing. After the stewing step, the malt is then dried and roasted at various temperatures and times.
Caramel malts contain high concentrations of Maillard reaction products ("MRPs"). The Maillard reaction is a complex series of chemical reactions initiated when "reducing sugars" react with free amino nitrogen. This occurs in hot, moist environments. Reducing sugars include sugars like glucose and maltose that are formed when starch is broken down by amylase enzymes. The stewing step drastically increases the concentration of reducing sugars inside of the malt kernel. Free amino nitrogen refers to the nitrogen end of a protein or polypeptide not chemically tied up in a peptide bond (the bond between two amino acids in a protein or polypeptide chain).
The concentration of free amino nitrogen increases when barley is converted to malt. Well-modified malts have a higher concentration of free amino nitrogen (frequently called FAN) than poorly modified malts. When sugars participate in the Maillard reaction they become unfermentable; that's why using a high proportion of crystal malt increases the final gravity of beer.
The Maillard reaction is responsible for the formation of a wide array of aromas including toffee, caramel, toasty, nutty, raisin-like and sherry. The reaction is also responsible for an increase in color.
Toasted bread is a classic example of the Maillard reaction and can be used to illustrate how the reaction can progress from subtle to very pronounced colors and flavors. Some crystal malts are very light in color and flavor and are made using kilning regimens (after stewing) similar to pale malts. Darker crystal malts are kilned at higher temperatures for longer periods of time after stewing. Maillard reaction products are also widely believed to improve mouthfeel as well as beer foam stability.
All the malts you name in your questions are different types of crystal malt. Carapils is produced by Briess in Chilton, Wisconsin and is a very pale crystal malt. Other maltsters make similar products and sometimes use names like dextrin, dextrin or cara-pils to describe their products.
A dextrin is an unfermentable carbohydrate chain that is not large enough to be considered starch because it does not turn iodine black in the iodine reaction. This can be confusing because dextrins don't have much to do with why these malts react the way they do! Cara-Vienne and Cara-Munich are darker in color than these lightly colored caramel malts.
As far as your friendly debate is concerned, you and your pal are both correct! You are correct in saying that starch is unwanted in beer and that caramel malts do not leave starch in the finished beer. And your friend is correct when he says that caramel malts do improve mouthfeel, body and foam stability! I hope this settles your homebrewing disagreement.
Mr. Wizard, BYO's resident expert, is a leading authority in homebrewing whose identity, like the identity of all superheroes, must be kept confidential. To see more of Mr. Wizard, check out the latest issue of Brew Your Own at better homebrew shops and newsstand locations.