Sign Up for Brew Your Own’s Free E-Newsletter
Story Index Techniques Upping IBU'S, Stopping Enzymes: Mr. Wizard
| Upping IBU'S, Stopping Enzymes: Mr. Wizard |
| Ashton Lewis | |
| October 2007 | |
Upping IBUsI have been planning on making an extract oatmeal stout, but after entering all my ingredients into a recipe calculator I am concerned with my hop utilization. I boil my wort in about two gallons (8 L) of water and have noticed, through the recipe calculator, that as I add more sugars the hop utilization goes down. I plan on using six pounds of liquid malt extract and a pound or two of honey. If I add just the malt, it shows that I will have around 20 IBUs but if I were to add the honey to the boil that would lower it to about 16 IBUs. I have heard of brewers boiling their hops in plain water and adding the malt and sugars after they have boiled the hops for a while. Could you explain how I would go about getting better hop utilization without buying new equipment? Adam Boyle
On the surface this may seem like an easy question. Since hop utilization decreases as wort gravity increases it seems logical that one solution to the dilemma faced by extract brewers who boil concentrated wort is to boil the hops separately. This may sound attractive but one downside to this is that the quality of the bitterness and the extraction of plant substances from the hops are reportedly different when hops are boiled in water compared to boiling in wort, and the differences are not for the better. The difference between an expected bitterness of 16 versus 20 indicates a reduction in bitterness by 20%, meaning that one way to combat the issue is to increase the weight of bittering hops added to the boil by 24% (the additional hop addition also has a reduced utilization, so the increase to the recipe needs to be 24%). This will minimally increase the cost, maybe by a buck or so, of your ingredients. If you really want to keep your ingredient efficiency in line with all-grain brewing you still have a couple of other options. The first option is to boil the hops in wort with a specific gravity in the neighborhood of 1.048, which is similar to the average gravity for a full-volume wort boil. You do not have to dilute all of your extract to this strength, just enough to give a decent ratio of wort to hops. I suggest using at least one gallon of wort per half ounce of hops because the solubility of iso-alpha acids in wort is limited and if the ratio is too low then your hop yield will suffer. You should boil the first hop addition for at least 60 minutes to get the best isomerization and during this time you don’t want to evaporate much more than about 10% of the wort volume. When using malt extracts, the time required to boil the wort is not nearly as critical as with all-grain brewing because the wort has already been boiled during the production of the malt extract. You really only need about 20 minutes to make sure you kill anything that might be in the extract, meaning that you could add your extract to the boiling wort and hops towards the end of the 60 minute boil. If you do this you want to make sure the wort gravity is not excessively high. You could mix the bulk of your extract with water, get it boiling and then add the contents of your hop boil to it to make things flow easily. Remember that hops added late in the boil are primarily for aroma. Since isomerization is not required for extracting aroma this method should not reduce the contribution of late hops as compared to a full-volume wort boil. In essence this method is nearly identical to the method you proposed, except the hops are being boiled in wort as opposed to water. Another method is to use two kettles to do a full-volume wort boil by splitting the volume into two easier to handle kettles. This will require more equipment (a second kettle) and allows you to easily boil the two pots on your kitchen stove. The beer in question contains a couple of pounds of honey and in this particular example you could hold off on adding the honey to the end of the boil. So you have a few options to address your dilemma without having to risk potential off-flavors associated from boiling hops in water! Ending enzyme activityI brewed a Belgian clone with an OG of 1.091. Not knowing Laaglander Extra Light DME had such a high percentage of unfermentables, the wort got down to 1.042 and stopped completely. Adding fresh yeast, keeping the temperatures right and rousing the yeast regularly did nothing, of course, since the problem was the high percentage of starches in the wort. I didn’t want to bottle at 1.042 so I dissolved one teaspoon of amylase enzyme (and three teaspoons of yeast nutrient) into about 3?4 cup of boiled and cooled-to-lukewarm water and dumped it into the carboy. Within 24 hours, activity and bubbling started back up and a bubble was escaping the airlock every ten seconds or less, so the enzyme must have been doing its work despite being added at fermentation temperatures instead of mashing temperatures. Is there any way to stop the enzymatic activity when the gravity gets down to a reasonable level? Or will it just keep going until all the starches are broken down? I really don’t want to turn this batch into Belgian rocket fuel! Have I created a monster? Kevin Huddleston
I am not sure you have created a monster but you may have a runaway train on your hands! There are only two ways to stop an enzymatic reaction. You can destroy the enzyme or wait until there is no more substrate for the enzyme to act upon. Enzymes are easily destroyed when heated to the point where the enzyme denatures. If you had a way to pasteurize your beer you could easily halt this reaction. You probably don’t have a convenient way to denature the enzyme and by the time this answer is published the enzyme you added will have run its course. When an enzyme runs out of substrate the action ends and in non-living systems where enzymes are added to perform a function this is often how the reaction ends. It is difficult to know if this is likely to be a happy or tragic ending without knowing what type of amylase you added. If you added a mixture of alpha and beta amylases, the result would most likely be a pretty dry beer with residual sugars that yeast cannot ferment. Adding alpha and beta amylase would be akin to extending your mash profile to produce a dry beer, but even with these beers there are some unfermentable sugars. If you used the ultimate amylase enzyme in your brew and blasted it with a de-branching enzyme like amyloglucosidase (AMG) you may end up with an extremely dry and high alcohol beer. Some brewers use AMG to brew low calorie and low carbohydrate beers with a lesser alcohol content. A couple of years ago I wrote an article intended as a joke about using Beano® at home to brew light beers and some homebrewers began using it. Beano® contains alpha-galactosidase but achieves a similar outcome as AMG. If you added a tablet or two of this stuff, I predict that the end result may be pretty disappointing for the style of beer you brewed. There is a solution to your problem that falls into the band-aid category. You could halt fermentation and greatly slow the action of the enzyme you added by cooling the beer down near freezing. This would give you enough time to rack into a keg, carbonate it and drink it before much happens. The worst thing that could happen is that the enzyme activity continues and you have an over-carbonated keg. Or the enzyme produces some sugar from the residuals in the beer but there is no yeast activity, resulting in some added sweetness. I do not suggest using this band-aid fix if you do not have a keg because if there is yeast and enzyme activity still going on you could have a bunch of bottle bombs sitting around. | |
