How Brewers Lower Carbs in Beer with Enzymes and Ingredients

November 13, 2025 •

4 min read

The low-carb beer trend, originally sparked by diets like Atkins, has become a multi-million dollar industry. But how do they lower carbs in beer while still retaining flavor? The answer lies in a combination of carefully controlled brewing techniques and the use of specialized enzymes.

Quick Summary

Brewers use enzymes, specific yeast strains, and controlled mashing temperatures to break down complex starches into simple, fermentable sugars, leaving fewer residual carbohydrates in the final product. Techniques also include using adjuncts like rice and corn or diluting the beer after fermentation.

Key Points

Enzyme Use: Brewers add enzymes like amyloglucosidase (AMG) during fermentation to break down complex, unfermentable starches (dextrins) into simple sugars that yeast can consume.
Low Mash Temperature: Mashing at a lower temperature (e.g., 145–148°F) favors beta-amylase activity, producing more fermentable sugars and leaving fewer residual carbs in the final beer.
High-Attenuation Yeast: Choosing specific yeast strains that are highly efficient at consuming sugars ensures a thorough fermentation, resulting in a drier beer with less residual sweetness.
Ingredient Selection: Opting for a higher proportion of light base malts and adjuncts like rice or corn provides a cleaner, more fermentable sugar base, minimizing unfermentable compounds.
Extended Fermentation: Allowing the beer to ferment for a longer duration gives the yeast more time to process all the available sugars, further reducing the final carbohydrate count.
Post-Fermentation Dilution: Some large-scale breweries lower both the alcohol and carbohydrate content by diluting a higher-gravity, fully-fermented beer with water.
Flavor Compensation: To combat the thin mouthfeel often associated with low-carb beers, brewers may use non-caloric flavor additions like dry hopping or spices.

The Science Behind Low-Carb Brewing

At its core, brewing beer involves converting the starches from malted grains into fermentable sugars, which yeast then consumes to produce alcohol and carbon dioxide. The key to making low-carb beer is to ensure the yeast consumes as much of the available sugar as possible, leaving behind minimal residual carbohydrates.

The Role of Enzymes

Enzymes are the primary tool brewers use to control the amount of residual carbohydrates. Naturally present in malted barley, these proteins act as catalysts during the mashing process, breaking down starches. Brewers can use native malt enzymes or add exogenous (external) enzymes to increase their efficiency.

Native Malt Enzymes: Different temperatures favor different enzymes. Beta-amylase is most active at lower mash temperatures (around 145–148°F / 63–65°C) and breaks down starches into highly fermentable maltose. Alpha-amylase is more active at higher temperatures (above 152°F / 67°C) and produces more complex, unfermentable sugars called dextrins, resulting in a fuller-bodied beer. For low-carb beers, brewers focus on a longer, lower-temperature mash to maximize beta-amylase activity and create a more fermentable wort.
Exogenous Enzymes: To achieve an even drier, lower-carb beer, brewers often add supplementary enzymes like amyloglucosidase (AMG), also known by commercial names like Ultra-Ferm. This powerful enzyme can break down the complex dextrins that native malt enzymes leave behind, making them available for the yeast to consume. The use of AMG is a game-changer for producing very dry, crisp beers with minimal residual carbs.

Specialized Yeast Strains

The type of yeast used is another critical factor. High-attenuating yeast strains are known for their ability to ferment a higher percentage of the available sugars, leading to a drier finish. These yeast strains are particularly effective when combined with an enhanced mashing regimen or added enzymes. For instance, combining high-attenuating yeast with amyloglucosidase ensures that virtually all fermentable sugars are converted, leaving a very low carbohydrate count.

Adjusting the Grain Bill and Ingredients

Brewers can also manipulate the initial ingredients to reduce the potential for residual carbohydrates. Using a higher proportion of lightly-kilned malts, such as Pilsner or 2-row, provides fermentable sugars without introducing the heavier residual carbohydrates found in darker or specialty malts. Additionally, incorporating adjunct grains like corn or rice can increase the fermentable sugar content without adding complex carbohydrates that would remain in the finished beer.

Other Techniques

Extended Fermentation: Allowing fermentation to continue for a longer period gives the yeast extra time to work through all the available sugars, resulting in a lower final gravity and fewer residual carbs.
Post-Fermentation Dilution: For some light lagers, brewers produce a higher-gravity wort, ferment it, and then dilute the final product with water to reduce both the alcohol and carbohydrate content. This method is less common for craft breweries focused on flavor intensity but is a standard practice for many mass-produced light beers.
Sensory Enhancements: Low-carb beers can sometimes lack body and flavor due to the high attenuation. Brewers may compensate by using non-caloric additives for flavor and aroma, such as citrus peel, specific spices, or dry-hopping with aromatic hops. Some might also adjust water chemistry with minerals like chloride to enhance perceived mouthfeel.

Low-Carb Brewing Method Comparison Table


Method	Primary Action	Impact on Carbs	Impact on Flavor/Body	Common Use Case
Enzyme Addition (e.g., AMG)	Breaks down complex starches (dextrins) into simple sugars.	Highly effective; can reduce carbs significantly.	Creates a drier, crisper finish; can reduce mouthfeel.	Used for achieving very low-carb profiles, like Brut IPAs.
Low Mash Temperature	Favors beta-amylase, producing highly fermentable maltose.	Effective; reduces dextrins, leading to a lower final gravity.	Creates a drier character while retaining more flavor than with added enzymes alone.	Standard practice for all-grain brewers seeking a drier beer.
High-Attenuating Yeast	Consumes a higher percentage of available sugars.	Effective; directly reduces residual sugar content.	Results in a drier finish; can be combined with other methods.	Used with various methods to ensure a thorough fermentation.
Adjunct Grains (Rice/Corn)	Provides simple, highly fermentable sugars.	Effective; replaces complex carbs from malt with fermentable sugars.	Creates a lighter, often less complex flavor profile.	Common in mass-produced low-carb light lagers.
Post-Fermentation Dilution	Adds water to reduce carb and alcohol concentration.	Effective; lowers concentration of all components.	Thins the body and potentially mutes flavors.	Primarily used by large breweries for light beer production.

Conclusion

Brewers employ a multi-faceted approach to reduce carbohydrates in beer, primarily focusing on maximizing the conversion of starches into fermentable sugars. Through careful control of mash temperatures, the strategic addition of specialized enzymes like amyloglucosidase, and the selection of high-attenuating yeast and specific ingredients, it is possible to produce flavorful beer with significantly reduced carbohydrate content. These techniques allow for a wider range of brewing possibilities, catering to the growing consumer demand for lower-carb beverage options.

Optional Outbound Link Example: For those interested in the history of low-carb dieting and its influence on the beverage market, a look at the Atkins diet phenomenon provides excellent context.

Frequently Asked Questions

The primary method is to use enzymes like amyloglucosidase to break down complex, unfermentable starches into simpler sugars that the yeast can fully ferment into alcohol and carbon dioxide.

Yes, low-carb beer often has a drier, lighter, and crisper taste with a thinner mouthfeel, as the high level of fermentation removes most of the residual sugars that contribute to body and sweetness.

Yes, low-carb homebrewing is possible and similar to standard brewing. Brewers can add a special dry enzyme to the fermenter along with high-attenuating yeast to break down and ferment more sugars.

Holding the mash at a lower temperature (around 145–148°F) promotes the activity of beta-amylase, which creates more fermentable sugars. Conversely, higher mash temperatures produce more unfermentable dextrins.

Specialized high-attenuation yeast strains are more efficient at converting sugars to alcohol, leaving less residual sugar and therefore fewer carbohydrates in the final product.

Not necessarily. Many low-carb beers have an alcohol by volume (ABV) comparable to standard beers, as the brewers intentionally convert more carbohydrates into alcohol instead of leaving them as residual sugar.

Brewers use highly fermentable grains like rice or corn, and may add non-caloric flavorings such as aromatic hops, citrus peel, or spices to enhance the taste without adding carbohydrates or sweetness.