An exploration of Yeast and the sugar they consume.

I am here to talk about a subject I saw brought up in a Daily Questions Thread in early March. It was regarding using table sugar in yeast starters instead of the home brew standard of Dried Malt Extract(DME). It was explained to me that using sugar in a starter could harm my yeast, preventing them from consuming sugar properly during fermentation. It could also mess with the actual growth of yeast, since there are no nutrients for the yeast in sugar. I was curious to see the actual effect simple sugar could have on yeast health and finished beers.

I devised an experiment where I would use yeast propagated differently to see what would happen when we changed the starter sugars. After the first portion of the experiment I will ferment a basic wheat beer recipe (I have been itching to brew a Weissbier for a long time now). I will begin with two starters, both 1600 ml, and propagated for 48 hours:

A. Regular Pilsen Light DME and di-ammonium phosphate (a yeast nutrient)

This is my control group. My ideal propagation conditions are here: simple and complex sugar, and plenty of nutrients for the yeast to be happy.

B. Plain old table sugar (sucrose)

The starter using only sucrose is intended to see how the lack of nutrients and complex sugars is handled by the yeast.

My hypothesis is that the sugar starter batch will finish with a slightly higher gravity with a lot more off flavors because of the stressed yeast. From what I have read on forums and blog posts the yeast will stop producing the enzymes to break down maltose if they consistently consume sucrose or glucose. This change is supposed to be genetic in nature, so using sugar can essentially stunt your growth. I had a quick message with u/chino_brews on reddit and he gave me a very detailed explanation on the subject. I’ll be honest: I did not follow. I love the science of brewing but when it comes to gene expression I lose it. So good on chino_brews on being much more knowledgeable on said subject!

Now I understand that this experiment is a bit shortsighted in that the yeast health will only be measured by one batch of beer. Those who harvest their yeast want the absolute best in terms of yeast health, so I assume that they will only use DME and nutrient. This test is designed for a brewer that might have forgotten DME the last time they went to the store, or only has half the amount of DME required. I want to see how much a one time substitute will affect a beer.

This article is merely trying to delve into how yeast works, and I don’t feel like getting a Bachelor’s in microbiology to understand it when I can brew a few batches of beer and drink them. I am not trying to draw any sweeping conclusions from this or trying to challenge the long standing traditions of beer brewing. I’m just a guy with too much time on my hands.

Now, in my preliminary research into this subject I found John Palmer’s discussion of the topic in How to Brew :

“Yeast cannot live on sugar alone. Yeast also need nitrogen, and amino and fatty acids to enable them to live and grow. The primary source for these building blocks is the free amino nitrogen (FAN) and lipids from the malted barley. Refined sugars like table sugar, corn sugar or candy sugar do not contain any of these nutrients.”

I figure that because I am still fermenting in healthy wort, the yeast will end up getting plenty of the nutrients while making beer.

I set out to the brew store and picked up 10 pounds of malted white wheat and WLP320, an American Hefe yeast. I chose this for its cleaner profile, so any off flavors or changes would be easier to discern. I have to admit, though, I felt so wrong making these yeast starters.

This is my sacrilegious attempt to try to grow yeast. I did two 800 ml starters for the sugar, and a 1600 ml starter for the regular DME. I planned on brewing the next day, but it didn’t pan out, so these sat and were shaken regularly for about 72 hours.

One thing I noticed right off the bat was that the sugar starters lacked any krausen, which was starting to form on my standard starter around 8 hours after pitch. Even after 30+ hours no krausen is formed, or bubbles made when shaken. However, when I do shake them, there is a lot of gas released, so I know the yeast is doing its thing. This is most likely caused by the lack of proteins, so there is nothing to capture the CO2 on its way out of the mixture.

I was off to brew my first solo 10 gallon batch!

A very full mash tun.

My first time “fly sparging.” I added water to it as it

drained, seemed to work. I reached ~78% efficiency.

Thunderdog breeze blockers – patent pending.

Now, I prefer fermenting in buckets. I know a lot of brewers like seeing their beers ferment, and that fine and dandy. I enjoy the pragmatism of a bucket. I don’t have to get a special harness just to lift the damn thing, and if i drop it or mess up, I don’t look like this(warning: carboy injuries). The only drawback in this case is that I can not show you in that much detail what is going on in the buckets. I can show you the krausen though!

DME on the left, sugar on the right.

The levels of krausen are almost exactly the same.

The sugar starter beer had some major activity,

it left hop gunk all over my lid. The other was spotless.

(Sugar on the Left___________DME on the Right)

I was quite surprised when I saw the physical differences of the beer. They both finished at 1.011, but DME was brighter and darker. I used Pilsen DME to make the starter, so I guess this is a testament to the Maillard Effect.

As I sipped on the finished beers I realized something I am sure the advanced homebrewers already have: hefeweizen yeast tastes really fucking good if its stressed. I realized only then that I probably chose the worst style to test stressed yeast profiles. Whatever. I’ll have to brew another ten gallons!

My impressions on the beer:

DME: Light, cloudy, thick heading starting out that falls over time, leaving a finger width lasting head. I taste very light hints of orange and clove spiciness. Bubblegum flavors come through as the beer warms in the glass. Overall pretty good, not groundbreaking but definitely something I am going to share with friends.

Sugar: Wow. This one hit my nostrils first. Very pronounced orange/lemon flavors and the thick white head lasts a while. Cloudier but lighter in color than the DME batch. I was very surprised to see the 2 inch head last until the bottom of my nonic pint. I tasted a layered yeast flavor that came off quite pleasant when it mixed with the wheat spiciness and mouthfeel.

I invited some friends over and had them try it. Everyone was easily able to tell them apart, as the head retention on the Sugar beer lasted longer and had a much lighter color, along with the significantly more lemon like flavor and smell.

I wouldn’t say that one was better than the other, because the DME beer had an attractive orange-yellow color to it, and had a bit more of a “clean” taste. The Sugar beer was over all pretty good too, but I am assuming that this is probably because I chose such a forgiving yeast.

I would not recommend to anyone to use sugar in their yeast starters. I merely got bored one day and felt like brewing some beer. I might do it again, if I were using the same yeast (which I probably won’t, because the same orange/lemon flavors can be achieved with different yeasts and better harvesting methods). I enjoyed both beers equally, but I think I need more beer to test and make a decision on whether or not sugar starters are fine for home brewing.

If you have any recommendations on what style I should try next it would be appreciated. I am trying to find a style that doesn’t take well to being stressed by the yeast.