Dear Mr. Wizard,
I have been wondering about the effects of falling temperatures during mashing. If I have a single infusion mash that starts high at 155 ºF (68 ºC) (alpha amylase range), and slowly cools back down to 148 ºF (64 ºC) (back into beta amylase range), do the beta enzymes “reactivate” or do the high temperatures cause them to remain denatured?
North Bend, Washington
The Wizard Replies:
Denature is one of those words that is often thrown around with little explanation. An enzyme, by definition, is a protein that catalyzes a biochemical reaction. The amylase enzymes catalyze the degradation of starch into smaller molecules.
Enzyme activity is affected by temperature and the rate of a specific reaction increases until the temperature causes the enzyme to denature. In simple terms, the protein or proteins that comprise an active enzyme irreversibly uncoil when they denature. Common examples of denatured protein are found in the refrigerator and kitchen. The cheese making process begins by denaturing milk proteins to form curd. Once milk is converted to curds and whey there is no turning back. Another example of denatured protein is a cooked egg. The solid white material in any cooked egg is denatured egg white. Whether the denatured egg protein is found in meringue, fried, poached or hard-boiled eggs, the native (not denatured) egg white cannot be restored.
Enzymes may be in their native states without being active and environmental factors such as pH, mineral co-factors and substrate concentration do affect enzyme activity. The amylase enzymes active in a mash are most effective around pH 5.2. If the mash pH were increased to say 7 pH by adding a strong base-like sodium hydroxide the activity of the amylase enzymes would dramatically reduce and become inactive. If the pH was then reduced to 5.2 pH by adding a strong acid, the enzymes would again become active. This is because pH affects the electrical charge on the various ionizable groups associated with proteins. These groups include carboxylic acid and amino “functionalities,” to use the scientific language. The charge on a functional group is affected by pH and this has a profound affect on enzyme activity, but pH changes do not necessarily cause an enzyme to denature (although radical changes in pH can cause an enzyme to denature).
The practical message is to be careful with your mash. When in doubt it is always safest to start off a bit cooler than desired and to move the temperature up to the target. Enzyme denaturation does not occur instantaneously and if you intend on mashing in at 140 ºF (60 ºC), for example, and accidentally come in at 162 ºF (72 ºC) you can quickly add cool water and retain the activity of some beta-amylase molecules that have yet to be “cooked” by the high temperature. Happy mashing!
Dear Mr. Wizard,
Hello and HELP! Every batch of I.P.A. or other highly hopped ale that I have brewed has a distinct iced tea flavor. I have looked and looked but can’t seem to find any advice to remedy this. I talked to the staff at my local homebrew shop and they told me that the flavor came from the hops and that I would come to appreciate it. Could it be from dry-hopping? I know that iced tea tends to be high in tannins, so could this be the cause? Could Polyclar help remove the tannin? I have tried to adjust my brewing techniques (lowering the temperature of the steeping and sparge water, increasing boil times, etc.), but still have this flavor. I have brewed an oatmeal stout and a Belgian that came out fine. I am a partial extract brewer using specialty grains.
Mr. Wizard Replies:
I partially agree with the information your homebrew shop provided and that is that hoppy beers often have a bite from the tannins in the hops. This is similar to the astringency of strong tea and young red wines. However, I strongly disagree with the notion that hoppy beers are all overly astringent and that the true hop connoisseur will come to appreciate the flavor in time. To me that is a defeatist attitude. To tackle the problem a brewer should consider what is happening in the mouth and then work backwards to conquer! The source of the iced tea flavor in hoppy beers is obviously the hops. Hops contain bittering acids, aromatic oils and plant matter. It is the plant matter that imparts this potentially unpleasant flavor. If the quantity of plant matter added to the beer is reduced, so is the astringency in the finished product. One could conclude that I am suggesting that you avoid brewing hoppy beers - but that’s not my point.
The “classic” ideas about hopping are really quite limited when brewing some of the aggressively hopped beer styles found on the market. The basic notion is that high alpha hops are used early in the boil for bitterness and that any hop used for imparting aroma is a lower alpha variety. The problem with this rule of thumb is that the aromatic oils in hops are produced in the same place (the lupulin gland) that the bittering acids are produced meaning that the concentration of aromatic oils typically decreases somewhat proportionally with alpha acids.
Using high oil hops is one way of adding a good deal of hop oil while minimizing the addition of the hop plant matter. The notion that high alpha hops in general have poor aroma is totally false. Anyone who has ever rummaged around in the hop room of a brewery that uses whole hops has likely smelled many nice high alpha varieties. Historically, the alpha acids had a value that simply could not be “wasted” and any hop varieties with appreciable alpha were used for bittering. In fact, most beer brewed in the world has little hop aroma and the vast quantity of hops grown in the world are produced for alpha acids. In fact, most statistics on hop production equate yields in terms of metric tons of alpha produced because that remains the most important stat to the commercial brewer.
Another way of minimizing the plant material added to the brew is through hop pellet selection. Two types of hop pellets are produced by hop processors: the type 90 and the type 45. A type 90 pellet contains 90% of the weight of unprocessed hops. This means that 100 pounds of raw cone hops yield 90 pounds of pellets. The missing 10 pounds is from stems, strigs and the like. Type 45 pellets are made by separating much of the leafy matter from the lupulin glands that contain the stuff brewers want from hops. 100 pounds of hops yield 45 pounds of type 45 pellets. Using type 45 pellets for aroma will reduce the amount of plant material added to your beer by 50%. Let’s go a step further and essentially eliminate plant material from the equation and use a liquid hop preparation - not sexy, but functional. Hop extracts that contain both bittering acids and oils and are available in fractions of particular compounds. If you want hop aroma without bittering acids and plant material there are hop oil extracts available. There are even hop tablets that are kind of like Alka-Seltzer tablets infused with hop oils that make measuring a no-brainer.
On another note, I personally have never used a fining, such as Polyclar, to remove astringency from beer but the idea has merit. The reason tea drinkers add milk to hot tea is to bind tannins and mellow the tea. Astringency is a sensation and occurs when tannins from food or drink bind with proteins in the mouth. If the tannins are already bound to a protein then they are not available to the palate. Polyclar resembles protein and reacts with tannins in solution. Some winemakers use egg whites to fine their wines and I suppose one could do the same with beer. The bottom line is that you can have in-your-face aroma sans astringency!