What Are Fermentable Sugars in Beer And Why They Matter

Brewing is an art of sugar management. When you brew beer, sugar isn’t just about sweetness, it’s what feeds your yeast and turns wort into alcohol. But not all sugars are the same. Some can be fully fermented into alcohol and CO₂. Others stick around and make your beer taste sweeter or feel fuller.

That’s why understanding and measuring fermentable sugars is key to brewing beers that hit the right flavor, body, and alcohol level.

What Are Fermentable Sugars?

Fermentable sugars are simple sugars that yeast can digest and convert into alcohol and CO₂ during fermentation. The main ones in wort are:

Glucose – fast and easy for yeast to consume
Fructose – similar to glucose, quickly fermented (very small concentration in natural malt, often ignored),
Sucrose – breaks down into glucose and fructose (very small concentration in natural malt)
Maltose – the most common sugar in wort
Maltotriose – more complex, slower to ferment

Yeast loves these sugars. They provide the energy needed for growth, reproduction, and alcohol production.

What About Non-Fermentable Sugars?

Some sugars in wort can’t be fermented easily:

Dextrins – longer-chain carbohydrates
Lactose – unfermentable by most brewer’s yeast
Other polysaccharides – too complex for standard yeast

These sugars stay in the beer and add:

Body
Mouthfeel
Sweetness

Why Fermentable Sugar Levels Matter

The balance of fermentable and non-fermentable sugars affects:

Factor	Impact of Sugar Profile
ABV (Alcohol %)	More fermentables = more alcohol
Final Gravity (FG)	Fewer fermentables = higher FG
Sweetness	More non-fermentables = sweeter beer
Mouthfeel	Dextrins give body and fullness
Attenuation	Tells you how much sugar was fermented

Getting your sugar profile right is critical, especially for styles like:

Lagers (clean, dry finish)
IPAs (crisp but not thin)
Stouts (full-bodied with residual sweetness)
Sours (dry and acidic)
NA Beers (where leftover sugars can skew flavor)

Target Sugar Levels in Wort

While values vary, here’s a rough idea of what a typical wort might contain:

Sugar Type	% of Total Sugar (approx.)
Glucose	10–15%
Fructose	1-2%
Sucrose	2-5%
Maltose	40–60%
Maltotriose	10–15%
Dextrins (non-fermentable)	10–20%

How to Adjust Sugar Profile

Want a drier or sweeter beer? Here’s how to adjust fermentability:

Mash temperature
- Lower mash temps (62–64°C) → more fermentable wort
- Higher mash temps (68–70°C) → more dextrins, less fermentability
Enzyme additions
- Use glucoamylase or amyloglucosidase to break down complex sugars (e.g. Brut IPA style)
Adjunct choice
- Corn sugar or dextrose = fully fermentable
- Oats, wheat, and lactose = increase non-fermentables
Yeast strain
- Some yeast strains can ferment maltotriose and higher sugars better than others

Why You Should Lab-Test Fermentable Sugars

Estimating fermentable sugar levels based on OG and FG is helpful — but it doesn’t tell you which sugars are present, or in what amounts.

At testmybeer.com, we measure actual sugar concentrations using EBC-compliant enzymatic methods. We break it down by type:

Sugar Measured	What It Tells You
Glucose, Fructose, Sucrose	Simple sugars → early fermentation
Maltose + Maltotriose	Backbone of alcohol production, Ferments slowly, depending on yeast

Total Fermentables	What your yeast can turn into alcohol

Knowing these levels helps you:

Troubleshoot stuck fermentations
Fine-tune mouthfeel
Compare different mash programs
Design low-alcohol or high-attenuation beers
Ensure consistency across batches

How to Interpret Sugar Test Results

Sugar Level	Interpretation
High glucose	Early in fermentation or added sugars present
High maltose	Good fermentability, normal for wort
High maltotriose	May require yeast strain with higher attenuation
Low fermentables	Risk of stuck fermentation or low ABV
High non-fermentables	Full body, residual sweetness, may affect stability

Final Thoughts

Fermentable sugars are the fuel that powers your beer. Knowing exactly what sugars are in your wort and how much of each gives you real control over the final result.

From designing recipes to hitting target ABV or mouthfeel, sugar testing is the foundation of better brewing.

Want to know what’s really in your wort or beer?

Send us a sample and let testmybeer.com show you your sugar profile — so you can brew smarter, cleaner, and more consistent beer.