What Are Fermentable Sugars?

Fermentable sugars are those that yeast can break down into alcohol and CO2. These sugars are typically simple or di- and trisaccharides, easily metabolized by common brewing strains of Saccharomyces cerevisiae.

Common fermentable sugars in brewing include:

• Glucose (dextrose): Simple monosaccharide, highly fermentable. Found in small quantities in malt and commonly added as priming sugar.
• Fructose: Naturally present in some adjuncts (fruits). Also, fully fermentable.
• Sucrose (table sugar): A disaccharide made of glucose and fructose. Easily fermentable but can thin out beer if overused.
• Maltose: The primary sugar in wort, derived from malted barley. Readily fermentable and crucial for achieving balanced attenuation.
• Maltotriose: A trisaccharide that is fermentable but at a slower rate. Not all yeast strains can fully utilize it.

What Are Non-Fermentable Sugars?

Non-fermentable sugars are more complex and are not metabolized by standard brewing yeast. These sugars remain in the final beer, contributing to residual sweetness, mouthfeel, and body.

Common non-fermentable or poorly fermentable sugars include:

• Dextrins: Large, complex carbohydrates formed during mashing. They’re key to body and perceived fullness.
• Lactose: A milk sugar used primarily in milk stouts. Brewing yeast cannot ferment it, resulting in lingering sweetness.
• Pentoses (like arabinose, xylose): Found in small quantities in some grains and adjuncts, but not typically a major factor in traditional beer styles.

Impact on Final Gravity, Body, and Sweetness

• Final Gravity (FG): The more fermentable sugars in the wort, the lower your FG. A low FG usually means a drier beer with higher alcohol content. High FG indicates more residual sugars, contributing to sweetness and body.
• Body: Dextrins and unfermented sugars increase the body of the beer. A pale ale with too few dextrins might taste thin, while a stout with good dextrin content will feel creamy and full.
• Sweetness: While sweetness is partially influenced by FG, perception is also impacted by the type of residual sugars, alcohol content, and even carbonation.

Brewing Practices to Control Sugar Profiles

• Mash Temperature: A higher mash temp (~68-70°C) favors alpha-amylase activity, resulting in more dextrins and less fermentable sugars. Lower mash temps (~63-65°C) yield more fermentable wort.
• Grain Bill Design: Choose malts and adjuncts based on their sugar contributions. Caramel malts add dextrins and sweetness, while base malts provide fermentables.
• Yeast Selection: Some yeast strains are highly attenuative (e.g., Champagne yeasts), while others leave more residual sugar. Always match your strain to the beer style.
• Adjunct Use: Adding lactose, fruit purees, or honey alters the sugar profile. Be mindful of which sugars these adjuncts contribute.

Why Testing Matters

Consistent results come from data. You can’t manage what you don’t measure.

Fermentable sugars testing let’s you know how much sugar is available for conversion. Residual sugar analysis tells you what’s left behind, helping you fine-tune recipes for flavor and mouthfeel.

Using lab tools or sending samples to specialized labs is one option. But many small breweries lack the time for frequent lab analysis.

How Beer-o-Meter can help in your brewery

The Beer-o-Meter is a practical solution for brewers who want real data without a full lab setup.

What it offers in this context:

• Accurate measurement of residual sugars in beer.
• Insight into fermentability potential of your wort before pitching yeast.
• Helps optimize beer sweetness control by tracking sugar breakdown over time.
• Tracks sugar curves to better predict and control brewing final gravity.

For any brewer aiming to balance sweetness, body, and alcohol levels with precision – not guesswork – the Beer-o-Meter bridges the gap between old-school craftsmanship and modern data.

Because after thirty years, I can tell you: precision isn’t just for the lab. It belongs in every brewhouse.