Quality control in brewery industry: understanding yeast and sugar interplay in the mash phase

The brewer's needs start with the determination of the wort’s state: in the mashing stage, starch is converted to fermentable sugars by specific enzymes (amylase) present in malt. The conversion stage can be assessed by measuring the residual starch in the wort, ensuring that subsequent operations can proceed. Usually values below 1 g/L of residual starch are considered acceptable while higher values require attention as the risk of contamination by undesirable microorganisms capable of using starch may arise. 

As we mentioned before, starch’s conversion releases about 70-80% of fermentable sugars which are divided in maltose (60-65%), maltotriose (15-20%), glucose (10-15%) and the remaining 20-30% of non-fermentable sugars (dextrines); in addition to that we have a small percentage of fructose and sucrose, with a slight bigger amount of sucrose. 

The mashing phase represents one of the core steps in beer production where it is evident the symbiotic relation between fermentable sugars and yeast: yeast cleaves fermentable sugars producing alcohol and CO2, turning wort in beer. Yeast divides sequentially fermentable sugars starting from simpler sugars to more complex ones.

Table 1 Wort theoretical composition at 12 °P

As seen in Table 1, maltose and maltotriose are the most abundant in wort, so their utilization by yeast significantly influences fermentation efficiency and the final product characteristics.

Most yeasts can metabolize maltotriose but this process starts only after all the more easily absorbed sugars (glucose and maltose) have already been consumed. The use of maltotriose also varies in different strains of yeast: depending on the type of strain used, it will be possible to have different residual sugar on the finished product. Approximately 20% of the wort consists of dextrins which are non-fermentable polysaccharides for standard brewery strains that contribute to the flavor of beer by imparting fullness. 

You can metabolize dextrins, for example, by introducing appropriate enzymes (dextrinases) or by using yeasts such as Saccharomyces diastaticus known for its ability to metabolize dextrins. Sucrose is a sugar found in low percentages in wort, but its concentration can increase significantly in the case of dextrose/sucrose additions in wort for the production of high alcohol beers (high gravity wort). On the other hand, when producing non-alcoholic beer with maltose-negative yeast strains, the approach used is completely opposite: the mesh composition has 70% of non-fermentable sugars while the remaining 20-30% is composed by fermentable ones. In this case, only the small fraction of glucose, fructose and sucrose present will undergo fermentation, resulting in a small percentage of residual alcohol.

The Importance of Wort Composition Analysis

In essence, the study of wort composition is the key to defining numerous aspects of both the brewing process and its product: it is possible to assess the effective efficiency of mash and fermentation, to compare different yeasts’ fermentative capabilities and to better understand finished product’s characteristics.

Limitations of Density Measurements

In practice, brewers usually prefer to measure density to characterize the wort, rather than a detailed analysis of its composition. Employing density measurement as the only parameter can lead to misleading results, so the study of fermentable sugars at the beginning and end of fermentation provides essential information: two different worts may have the same density but very different fermentability.

How CDR BeerLab® Supports Brewers

In this perspective, CDR BeerLab® can provide strong support in determining the profile of fermentable sugars throughout the fermentation process with quick and easy analysis. Another advantage of the system is its ability to combine the determination of starch and fermentable sugars in a single analysis session, saving time during production and collecting more information than a simple densimeter.

The flexibility of the system allows the analysis routine to be adapted not only to classical procedures but also to different production practices as in the case of dry-hopping. Taking the measurement of fermentable sugars as an example, it is good practice to measure their content both before and after the addition of hop: in this case fermentable sugars may increase after the hop addition (hop creep) and their determination may influence the finished product causing more carbonation.

• Analyzing the composition of fermentable and non-fermentable sugars in wort is crucial for optimizing mash efficiency, understanding yeast performance, and ensuring consistent beer quality.
• Sugar profiling provides essential insights beyond density measurements, helping brewers address challenges such as fermentation variability, contamination risks, and specific requirements for high-alcohol or non-alcoholic beers.
• CDR BeerLab® offers a fast and integrated solution for analyzing starch and fermentable sugars, supporting brewers with reliable data to improve production efficiency and adapt to modern brewing practices like dry-hopping.