Brewing beer involves microbial activity at every stage. This starts with raw material production and malting, through to ensuring the final product (the bottle of beer) remains stable.
In some cases, microbiology contributes to the formation of the beer through traditional food fermentation; in other cases, microbiological awareness is necessary to protect the quality of the end product. Chemical and microbial analysis is a daily task of maltsters and brewers globally.
With the beer production process, the fermentation of cereal extracts by the yeast Saccharomyces is the most important microbial process. The yeast produces ethanol as a fermentation end product. The final alcohol content is determined by comparing the initial and final specific gravities.
While all yeasts make ethanol, different yeast types are used to create different beers, mostly notably the separation between ale and lager yeasts (Digital Journal showed how these differences lead to varied tastes in the article “The evolution of lager yeast charted.”) The type of yeast used affects the temperature at which the beer is fermented. Ales are fermented at warmer temperatures (55 to 70 degrees Fahrenheit; whereas lagers are fermented at cooler temperatures (38 to 50 degrees Fahrenheit). Importantly, beers may be made from corn, wheat, rice, and barley; however, they are classified by the type of yeast used in their production: for ale or lager.
Brewing begins with a simple cereal grain such as barley.
It is malted, sprouted, dried and stored for around four weeks.
Then it is ground, mixed with water and mashed.
The mashed barley is boiled with hops.
The mash is then cooled and fermented with yeast.
The product – beer – is then filtered, matures and packaged.
With protecting the beer as it is processed and bottled, a succession of microbial constituents that dramatically influence the final product. These include beer spoilage bacteria, which can give the beer a sour taste.
Moving to craft beers, the growing variety of beers of different flavours has increased in recent years, matching consumer tastes and a move away from bland tasting lagers. The consumer demand is, in turn, fuelling the quest for new types of beer. To assist with this process, breweries are linking up with scientists.
This is where chemistry becomes involved. Breweries are using spectrophotometric technology to provide rapid and precise measurements. A recent variant is a technology called UV-Vis spectrophotometry.
This is, as the name suggests, spectroscopy in the ultraviolet-visible spectral region. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. The method allows different compounds to be visualized. Breweries are using this to note color, protein, polyphenols, ethanol, iodine, sulfites, hops, and total carbohydrate.
UV-Vis instruments provide the brewery full detail on each of the essential aspects of a beer that contribute to its taste, color and aroma. By building up libraries, improvements can be put in place and new craft beers developed. In a sense a “fingerprint” is produced for each beer. Color, for instance, is a key measure of batch quality.
The full list of compounds that UV-Vis can detect in relation to brewing is:
Absorbance Integral
α-and β-Acids in Hops
Anthocyanogene
Bitterness/Bitter Substances
Color
Diacetyl Content/Vicinale Diketone
Ethanol (Ethyl Alcohol)
Free Amino Nitrogen (FAN)
Iodine
Protein
Sulfite
Total Carbohydrates
Total Polyphenols
Isohumulones
Isohumulones, for example, are extracted out of the hop cones during brewing. These provide the bitter flavour, which may or may not be wanted depending on the beer type. These are usually measured in International Bitterness Units (IBU).
Speaking with Laboratory Roots magazine, Rick Blankemeyer, who is the quality assurance analyst at Stone Brewing Company (Escondido, CA), enthused: “We use the UV-spec to monitor multiple aspects of the brewing process to ensure we are producing consistent beer across our many styles.”
Recently, major regulatory groups such as the American Society of Brewing Chemists (ASBC), European Brewery Convention (EBC), and the Association of Official Analytical Chemists (AOAC) have come to recognize UV-VIS spectroscopy as a reliable analytical method for testing beer.
In addition, via a recent webinar, Blankemeyer noted that UV-Vis spectrophotometry is a cheaper option for most small- to mid-sized craft brewers for effectively for quantifying the range of analytes found throughout the brewing process. This is one part of the process for craft brewers to improve and to compete with the major players.
In addition, having such information on hand allows producers to compare their product to quantitative standards and adjust accordingly.
This article is part of Digital Journal’s regular Essential Science columns. Each week we explore a topical and important scientific issue. Last week we learnt how clues about the nature of water are helping scientists to design different coatings and conserve energy. The week before we outlined the latest research into dissolvable medical devices.
