Dear Mr. Wizard:

Recently,I was making a batch of Scotch ale. The recipe called for wheat DME as a priming sugar. Obviously I can experiment with anything I want in my homebrew, but I was wondering if I really needed to use wheat DME or if I could have used the amber DME I had already? Depending on the recipe, it will call for different types of DME as a priming sugar, for example, wheat, light or amber. To what extent does the use of various DME as priming sugars contribute to the flavor or color of the beer? Also, could you could explain the pros and cons of using DME vs. corn sugar to carbonate beer? What does DME do for beer that priming sugar doesn’t?

Dave Ross
Philadelphia, PA

Mr. Wizard replies:

This is a question I often ask myself when reading recipes. It seems to me that using DME or saving wort for priming is a pain in the neck. The contribution of color or flavor to beer from priming sugar is insignificant compared to the flavor and color present in wort before fermentation. Even if the priming sugar added some flavor, an argument could be made for adding it before wort boiling, for example, brown sugar.

I think the best sugar to use for priming is either corn or invert sugar because they are both 100% fermentable and easy to handle. The problem with using wort or DME for priming is the inconsistent fermentability of wort. If you use DME with an unknown fermentability for priming, then it’s impossible to control the carbonation level. Commercial brewers who prime with wort measure wort fermentability before priming and base the amount of primings on this measured number.

The main difference between beers primed with DME or wort versus those primed with corn sugar is that the beers primed with corn sugar are not in compliance with the Reinheitsgebot.

Invert sugar consists of equal parts glucose and fructose. When fructose is transported into the yeast, it’s converted to glucose and enters the glycolytic pathway where it’s used as cellular fuel and ends up as alcohol and carbon dioxide. When maltose from wort is transported into the yeast cell, it’s first converted to two molecules of glucose and then follows the same biochemical pathway as the glucose from corn sugar. The only difference between wort and a corn sugar solution are the non-fermentable sugars, proteins and color compounds present in wort. These compounds are present in much higher concentrations in the original wort.

I expect to hear some strong opposition to these views, but that is the way I see it. This would be a good question to put up to an experiment followed by a blind tasting to determine what effect, if any, can be quantified by using different types of priming solutions.

Dear Mr. Wizard:

I’m planning to brew some smaller (1 and 3 gallon) experimental batches and wanted to know if I should still boil these batches the standard 60 to 90 minutes. Or should I set the boil time in relation to the amount of wort (1 gallon = 12 minutes, for example)? Would using Wyeast (with a starter) or White Labs yeast vials cause me to over-pitch these smaller batches? I also wanted to know if you have ever used pure oxygen in your homebrewing wort before you pitched your yeast and if it made a dramatic improvement in the taste of your finished beer.

Jim Albrecht
Naperville, Illinois

Mr. Wizard replies:

Brewing small experimental batches is a good way to determine the effect of a particular brewing variable. By changing one variable at a time, you can see how yeast strain, hop variety and fermentation temperature affect beer flavor.

Homebrewing techniques are really not much different than those used by very large brewers. The main difference is the batch size. A large commercial brew kettle may contain 30,000 gallons of wort, but the timing of hop additions and length of boil are the same as for smaller batches. The duration of boiling affects chemical reactions, like hop acid isomerization, protein precipitation and destruction of microorganisms. These reactions are dependent on time and are not a function of wort volume. In other words, don’t reduce your boil time in relation to batch size.

When it’s time to add yeast, you should scale down the amount of yeast added to the smaller batch just like you scale down the malt, hops and water. If you don’t scale down you will over-pitch the wort and the results of your experiment may be difficult to interpret. The most accurate language used to discuss pitching rates is “yeast cells per milliliter” of wort. This language is not practical for homebrewers because most of us don’t have a microscope lying around the house.

A good rule of thumb for dried yeast is 0.5 grams of yeast per liter of wort. This translates to about 10 grams (about 1/3 ounce) of dried yeast for a 5-gallon batch. Liquid yeast is a bit trickier because cell density varies more in liquid yeast suspensions. When I’m growing yeast for pitching, I use a 10X factor. For example, if I want to brew 5 gallons of beer I will use a 0.5-gallon starter culture. Usually, I will let the starter complete its fermentation and discard the liquid above the yeast to reduce the volume of propagation liquid added to the wort. If you choose to re-use yeast from a previous fermentation, use about 1 cup of thick yeast slurry per 5 gallons of wort.

I have used both pure oxygen and air for aeration and have had good results with both. The greatest advantage of oxygen over air is that wort will hold more oxygen when the gas source is pure oxygen as opposed to air. The only time this really makes much difference is when you are brewing high gravity beers. Another advantage of oxygen is that you don’t have to worry much about contaminating your wort with bottled oxygen. With that said, I typically use air that is run through a sterile filter before it’s injected into the wort stream. Good luck with your experiment.

For more of Mr. Wizard’s wisdom, pick up the latest issue of Brew Your Own at better homebrew shops and bookstores.

Do you have a question for Mr. Wizard? Write to him c/o Brew Your Own, 5053 Main Street, Suite A, Manchester Center, Vermont 05255. Or send e-mail to wiz@byo.com.