Can Yeast Use Sucrose for Fermentation

Questions abound about the fermentation process, and much of them have to do with the relationship between yeast and sugar. The question “can yeast use sucrose for fermentation?” rests firmly in this territory and requires a relatively intimate familiarity with the nature of yeast and its role in fermentation.

Yeast

First, it is helpful to understand that yeast is a living organism.

It is likely billions of years old, as it is a relative of the fungi family, and fungi were the first living organisms on earth.

We know that yeast is single celled and can reproduce either sexually or asexually.

During sexual reproduction, a yeast cell will attract another yeast cell and those two haploid cells will “mate” to form a new cell, called a diploid cell.

During asexual reproduction, a yeast cell, also a haploid, referred to as the mother cell, will simply create a daughter cell from her own body, which will be attached to the mother cell as it grows, until has reached more than 50% of the volume of the mother cell, at which point it will detach and live on its own.

Yeast can also reproduce with or without oxygen; indeed, yeast can perform miraculously well in the short term without oxygen, though it prefers to use oxygen. Lack of oxygen ultimately leads to stress, dormancy, and death.

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But what it absolutely needs to survive, thrive, and continue to reproduce in any of those ways is sugar.

Sugar

Sugar is basically just a carbohydrate, and a carbohydrate is just energy.

Sugar is made up of glucose and fructose, and in its most basic form, we call sugar sucrose.

Glucose is an important energy source found in living organisms and a component of many carbohydrates, and fructose is a monosaccharide, or a single sugar found naturally in plants like fruits and vegetables.

Also read: Why does yeast ferment glucose faster than fructose?

Yeast and Sugar

For some mysterious reason known only to the fermentation gods, yeast and sugar evolved together to create fermentation.

Fermentation is something that happens completely naturally without any need for human involvement whatsoever.

Long before humans came along, fruit grew naturally on vines, yeast was attracted to its natural food source (the sugars in fruit), and it would settle in and get to fermenting.

Before we were humans, while we were still our apelike ancestors, we were likely picking that fermented fruit from the forest floor and enjoying a nice gentle weekend buzz.

It is such a natural process, fermentation, that humans have been making wine for thousands of years, and beer for at least half that time.

All we had to do was crush fruit and leave it out for a few weeks to come back and find wine.

Same goes for beer.

Once the agricultural revolution settled in and people began domesticating animals, irrigating, and growing crops, they started toasting their cereal grains and making oatmeals and meads.

Leave those out long enough, and yeast will settle right in and get to fermenting.

Now you have beer.

The Fermentation Process

The fermentation process is basic and can be followed with pretty much any fermentable sugar to make any form of alcohol.

With foods like grains and even corn, it often helps to roast the grains first as that process converts the starches inside the grain into sugars, which attracts even more yeast to do even more fermenting.

But at its simplest, the fermentation merely requires sugar.

In wine, the sugar comes from the grapes.

When it comes to beer, the sugar comes from the grains.

It also comes from the grains in bread.

In bioethanol, the kind used to make alternate fuel sources, the sugar comes from the corn.

In every instance, yeast is attracted to the sugar, and it consumes as much as it can take, converting all the sugar into ethanol (alcohol) and carbon dioxide as well as hundreds of other micronutrients and secondary metabolites.

That, in a nutshell, is fermentation.

Which Type of Sugar is Best for Fermentation?

Remember, virtually any sugar with glucose or fructose in it will ferment.

One of the most easily fermentable sugars is table sugar, with brown sugar coming in just ahead of it, because it contributes 100% of its weight as a fermentable extract, unlike other naturally occurring sugars like fructose which have hundreds of other byproducts.

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Table sugar is a product of sucrose, and is like the distilled version of naturally occurring sugars. It is the purest form available.

Which is why not only can yeast use sucrose for fermentation, but it prefers it. And it is why many brewers and vintners, not to mention ethanol producers, will add table sugar, the most common form of sucrose, to their batches of wort or must before adding yeast to increase both alcohol and carbon dioxide levels.

So yes, sucrose is absolutely a fermentable sugar, along with any form of glucose, fructose, or maltose, which is a disaccharide formed from glucose.

High fructose corn syrup is another highly fermentable sugar, which is why bioethanol producers are so fond of using corn as an alternate fuel source.

What yeast will not abide is sugar substitutes like stevia, xylitol, erythritol, and splenda, all of which are devoid of fructose or glucose, and while they may offer a sweet adjacent flavor, do not produce their own sugar alcohols.

Interestingly enough, some brewers and vintners have turned to those nonfermentable sweeteners for added sweetness after fermentation has ended to ensure only the sweetness is added with no additional alcohol or carbon dioxide.

Adding a fermentable sugar, even after primary or secondary fermentation, would run the risk of any residual yeast activating and agitating once more and creating more alcohol, which would require a change to the ABV %, and the carbonation, which could potentially cause bottles to explode.

And no one wants that.

Cheers!

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