Lifecycle of an Enzyme: Synthesis and active formation of the aleurone layer

Lifecycle of an Enzyme: Synthesis and active formation of the aleurone layer

Enzymes are an essential part of life. They are also an essential part of beer. As a reaction catalyst, they make things happen quickly. Sometimes too quickly. By controlling the use of these very specific and very powerful chemical tools, it is possible to engineer desired results. Each individual protein matrix has a tightly regulated set of actions, based solely on its physical configuration and electro-chemical charge. When it comes to brewing, several important enzymes are developed for processing, but where does it all start?

In the life cycle of barley, a seed is planted, the seed grows, then it flowers. Once that happens, self-pollination occurs, then a new seed is formed and the process can begin again. This cycle can be broken at any point, but a “pause” can only really occur at the seed stage. Here the enzymatic activity and chemical reactions are at their slowest, preserving energy for survival. If kept in ideal conditions, a barley seed kernel may last several years. On the other hand, if it is subjected to extreme conditions, it may become non-viable in as little as a few weeks.

For most types, barley has a preferred temperature and moisture to initiate seed growth. Until those needs are met, the contents of the kernel remain tightly locked. A hardened seed coat offers protection from the elements, and a temporary rain jacket to shed light hydration. Evolution has enabled most seeds to endure long periods of privation, but some limits do apply. Starting the embryonic growth of a seed is a one-way ticket. If the process is stopped for any reason, the plant is going to die.

The aleurone layer contains most of the genes for enzyme synthesis, but it must be activated to begin production. Barley needs a relative humidity of about 97.7% to germinate, and this can be from moist air or hydrated soil, but quantity is key. When water hydrates the kernel to approximately 35-45% of its weight, then hydrolysis allows for existing enzymes to begin starch breakdown. This “first-step” provides the fuel for further reactions, including the enzymes necessary for the breakdown of more starch.

Seeds react to hormone levels, and two specifically influence germination: Gibberellins (GA) and Abscisic acid (ABA). As the first increases and the latter decreases, the seed can move from a state of relative dormancy to seed germination. GA is known to incite a gene response producing alpha amylase in the aleurone layer, while ABA is known to suppress it. This amylase production is responsible for the release of stored seed energy, and should be sufficient for conversion of the entirety of the starch reserves. In fact, it can even convert more starch, like adjuncts, if the synthesis is optimized.

Other enzymes are synthesized in the aleurone layer of the kernel as well. Proteases, xylanases, and the all-important β-glucanases are all exponentially compounded in the early stages of seed growth. This is manipulated by maltsters and brewers alike. For those interested, check out another post for details on how a Maltster like Sugar Creek Malt manipulates the process. 
 

Proteases are responsible for breaking down proteins and peptides, freeing the simple amino acids necessary for Malliard reactions. This is essential to provide nutrients during fermentation. It also provides foam positive protein formations. Care must be taken, as certain proteases and extended resting times can destroy foam positive proteins, resulting in a less than appealing appearance. Go even further, and the resultant beer can be watery and thin. No proteases? Yeast will not receive essential nutrients for cell division and fermentative reactions. Stressed fermentations are known to give unpleasant flavors and aromas.

Xylanases are a specific set of enzymes that specifically work on arabinoxylans. Arabinoxylans are non-starch polysaccharides that are partially water soluble. Due to this solubility, they contribute significantly to mouth feel. Why avoid huge amounts of arabinoxylans? Well, they are known to cause extraction and filtration issues. The polymeric structure causes compound blockage of small pores, leading to large frustrations. When this happens, the only recourse is to free the blockage and try to keep the xylans in a loose liquid matrix until the very end of transfer. Xylanases break down this problematic structure to aid in filtration and extraction while providing substance.

One of the more well-known enzymes in brewing is β-glucanase. These enzymes are responsible for similar actions as xylanases, however they act upon different substrates, fibers in the cell wall. β-glucans are freed from the structure causing benefits or problems down the line.  

β-glucanase is synthesized in the aleurone layer during seed germination. For the growth cycle, it offers a “key” to unlock bound starch reserves. β-glucans act as a “net” or “screen” holding back the access to starch granules. In the malting procedure, the β-glucanase is developed to an appropriate degree. Without some β-glucan present mouthfeel and viscosity will suffer, so again, balance is key. 

Procedures for mashing can be adjusted to compensate for poorly modified malt, but only to a degree. Keeping a low rest temperature in the mash will allow higher activity, even if the overall enzyme content is lower. The risk is that other enzymes may “over-act” at these same resting temperatures, causing more harm than good. As an alternative option, exogenous enzymes typically derived from fungi, can be added to the mash. A nice blend of enzymes, such as Ultraflo® Max, can work quickly to achieve multiple goals at once. This will boost glucan reduction without the need for increased resting times.

Once enzymes are synthesized in the aleurone layer, they can begin to digest links between molecules. The maltster will select a very specific set of procedures, tailored to the development and interaction of these enzymes. After “half” of the work is done, the seed has released most of its development, and the activity is halted. Kilning, or low temp drying add flavor/aroma, and hold the seed in a steady state. From here, any brewer can blend into their grain bill and create a uniquely distinct barley offering!

 

Meet the Author

J.D. Angell

Meet the Author

J.D. Angell

After several years of providing hazardous materials training and maintenance for the world's largest brewing facility, JD began home brewing countless varieties of craft beer. Some early success and a detour with industrial scientific research engaged his interests in industrial equipment and complex science, while working at a liquid yeast supplier pointed him specifically towards enzymes. Currently heading Bircus Brewing Company in Ludlow, KY, JD blends contemporary flavors with traditional science and innovative techniques. With over a decade of operational brewing and independent contracting experience across 5 time zones, he has amassed a plethora of knowledge to share with fellow brewers. 

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