Ask Mr. Wizard

The Effects Of Cold-Water Extraction

TroubleShooting

Royce Faina — Philadelphia, Pennsylvania asks,
Q

I’ve been contemplating brewing a table beer and was reading up on BYO.com about it. I was wondering if after a cold-steep mash can those grains be mashed at typical saccharification rest for use in a second beer or does the cold-steep rob the grain’s enzymes? Would a decoction mash of those grains be useful if the diastatic power is now lower?

A

Homebrewers are always pushing the envelope for cool ideas and this one is certainly doable. Let’s start with a quick review of what happens in a cold mash. When milled grains, be they unmalted or malted, are mixed with ambient water, soluble carbohydrates, proteins, and enzymes are brought into solution. Although malt certificates of analyses (COAs) outside of the U.K. don’t report cold water extract (CWE), this value is a handy index of modification. As malt modification increases, so does the solubility of extract in ambient water. The majority of CWE is carbohydrate, but soluble protein is also part of the equation.

In a typical hot mash, the extractables represented by CWE are almost immediately brought into solution, followed by gelatinized starch, then by fermentable sugars and dextrins that come from amylolytic activity during the mash. So-called cold mashes are relatively new to brewing and can be conducted over a range of temperatures and times. The commonality among these mashes is that very little amylase activity occurs; what is extracted is color and flavor, especially from specialty malts.

Because CWE values from paler malts are typically around 20%, compared to about 80% for hot water extract (HWE) values, there is a lot of stuff remaining in malt following cold-steep extraction. Specialty malts have a wider range of CWE values, but the values are rarely reported because specialty malt COAs are usually limited to color, HWE, and moisture.

Assuming that the cold-steep method is being used to extract rich malt flavors to present a different flavor-profile in the finished beer, using hot sparge water or mashing the drained grains into a hot mash would defeat the purpose of the cold mash. One strategy to maximize the goods in the cold steep would be draining the wort for use in a cold-steeped beer, and then using the “spent grains” as a component for a second brew. Yes, enzymes are extracted in the cold-steep method, but if the spent grains are used as a component in the grist bill for a second brew you don’t need to worry much about enzymes because more malt will be added. You could use infusion, step, or decoction mashing methods for the second brew, but if you are not using undermodified malt in the cold-steep mash, an infusion mash will work well for the majority of modern malts.

Response by Ashton Lewis.