Hordeins in Barley and Wheat

Image Credit: (ResearchGate, 2019)

In this continuation of The Ultimate Guide to Proteins in Beer Brewing, we expand on what we learned about proline and move onto hordeins, which are the main storage proteins in barley. Why did we learn about proline before this? Because hordeins contain A LOT of proline, which is both beneficial and problematic depending on what aspect of brewing you are looking at.

If you haven’t, check out Part I: The Ultimate Guide to Proteins in Beer Brewing – Part I – Iconoclast Brewing

Table of Contents

Now that we have an understanding of proline, it’s time to tackle the different major proteins in barley and wheat.

There are several major players in proteins within beer making:

1. Hordeins
2. Albumins and Globulins
3. Lipid transfer Proteins
4. Protein Z
5. β-Glucanases
6. Proteases
7. Amylases
8. Cysteine-Rich Proteins
9. Hevein-Like Proteins

This article will focus on hordeins. But don’t worry, we’ll have an article for each of the types of proteins found in malt!

Hordeins

First up, are Hordeins.

Hordeins are the primary storage proteins in barley and are categorized into four different groups classified based on their solubility and molecular weight:

1. B-hordeins
2. C-hordeins
3. D-hordeins
4. γ-hordeins

B-hordeins are the most abundant of all hordeins in barley. B-hordeins have a major impact on the clarity, foam stability and mouthfeel of a finished brew. Due to having a vast amount of proline, they can interact with polyphenols to create chill haze.

Just use some Clarity Ferm, you’ll be golden!

Note that some barley has been genetically modified to prevent or significantly decrease the accumulation of B-hordeins:

• Lys3a Barley Mutant (Mascher et al., 2019)
• Risø 56 (Cameron-Mills & Brandt, 1988)
• Risø 1508 (Cameron-Mills & Brandt, 1988)
• Ethiopian R118 (Cameron-Mills & Brandt, 1988)

C-hordeins are next up. They have a lower molecular weight than B-hordeins as well as being sulfur-rich as opposed to being proline and glutamine-rich. These hordeins are also less prevalent than the B-hordein counterparts.

So how do they affect beer making? C-hordeins play a large role in beer’s flavor, mouthfeel, appearance and clarity! It is also worth noting these hordeins are also responsible for triggering sensitive individuals with Celiac or gluten-intolerance disorders.

Let’s start with C-hordeins role in malting. As we know the process of malting involves soaking barley in water, allowing them to germinate and then kiln-drying, this activates enzymes that will later break down starches and proteins into simpler compounds when mashing.

During that malting process, C-hordeins are partially degraded, which leads to the production of polypeptides (much like a peptide, but a much longer chain of amino acids. If you’re wondering why this isn’t simply called a protein, that’s because proteins are typically made up of one or more polypeptide chains that have folded into a specific three-dimensional shape, allowing the chain to perform a specific function.) In short, a polypeptide could be a part of a functional protein, but without being folded into a 3D shape through complex interactions with amino acids, it by itself is not a protein.

Some of the peptides resulting from C-hordein degradation contributes to the flavor profile of the finished beer. We mentioned this in Part I, but what does this look like when we examine peptides?

• Bitterness: Some peptides affect bitterness of beer. This is especially true when they are released during a protein rest (aka proteolytic breakdown of larger proteins). The bitterness is said to be different from that which is contributed by the isomerization of alpha acids.
• Mouthfeel: Some peptides will give beer a smoother texture, whereas others can add astringency. Let’s add some practicality to this: If you are targeting a smoother mouthfeel, target the lower range of a protein rest at 113F to 122F. This range breaks down chill hazing inducing proteins while preserving some of the proteins that cause smoother mouthfeel. If you want a more astringent mouthfeel, aim for the higher end of the temperature range, about 122F to 131F but be aware that if you stay too long at this temperature you will end up with a thin bodied beer. This occurs because at the 122F to 131F range, peptidases become more active. Peptidases are great at reducing chill haze causing proteins, but also are exceptional at further breaking down medium-chain peptides, resulting in a thin body. I never go over 15 – 20 minutes at this range.
• Stability: Peptides play a big role in foam stability. Again, similar to mouthfeel forward peptides, stay in the lower end of the protein rest range between 113F to 122F to gain lots of foam stability without compromising the fuller mouthfeel. You can consider using under-modified malts and other malts with a high concentration of proteins to enhance this effect. Avoid a vigorous boil, which can cause coagulation and subsequent removal of beneficial proteins and instead opt for finings like whirlfloc or irish moss to remove particulate matter.
• Reactivity: Peptides can react with amino acids to produces melanoidins through Maillard Reactions, what you would normally be aiming for when performing a decoction mash. This results in a perceptibly sweeter beer. Peptides can be broken down by yeast several times over until they become small molecules like esters, higher alcohols and sulfur compounds. This includes the dreaded fusel-alcohol or solvent like flavors These chains also have the ability to chelate metal ions, which has an influence on oxidative stability. They will actually bind metal ions, and reduce the risk of oxidative reactions that would otherwise cause off-flavors.

D-hordeins

These are the least studied hordeins among all the hordein groups. However, we do know that they are sulfur-rich, like C-hordeins, are water-soluble (unlike B and C-hordeins which are alcohol soluble). Their impacts on a beer’s characteristics are not well-defined like B-hordeins and C-hordeins.

γ-hordeins

Finally, we come to γ-hordeins, which are intermediate in abundance when compared to the other hordeins. They are alcohol-soluble, play a distinct role in foam stability, mouthfeel and haze formation in beer and have a unique amino acid composition. This composition is balanced between sulfur-rich and sulfur-poor amino acid types.

γ-hordeins are different in the nature of peptides they produce, with many of these peptides being of intermediate molecular weight. While they are not as resistant to breakdown as B-hordeins, γ-hordeins still contribute a more consistent foam stability due to that molecular weight.

Conclusion

From the primary storage proteins in barley, the hordeins, to the soluble proteins like albumins and globulins, each plays a unique role in shaping the beer’s character. As we’ve delved into the specifics of hordeins, it’s evident that these proteins, especially B-hordeins and C-hordeins, have profound effects on beer’s clarity, foam stability, mouthfeel, and even its flavor profile. The lesser-known D-hordeins and γ-hordeins, though not as extensively studied, still hold their significance in the brewing process.

Understanding these proteins and their behavior during malting and brewing is crucial for brewers aiming to perfect their craft. Whether it’s manipulating the mashing temperature to achieve a desired mouthfeel or using specific malts to enhance foam stability, knowledge of these proteins provides brewers with the tools to fine-tune their brews. As we continue this series, we’ll explore the other proteins in malt, shedding light on their roles and impacts on the final beer product.

In the next article of this series, we’ll look at yeast’s preferred sources of nitrogen and why it is important in the context of proteins and beer making!

References

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Boulton, C., & Quain, D. (2001). Brewing yeast and fermentation. Blackwell Science Ltd.

Cameron-Mills, V., & Brandt, A. (1988). Expression of a Hordein Gene Family. Plant Molecular Biology, 11(5), 491-502.

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ResearchGate. (2019). SDS-PAGE for a barley grain and a barley malt sample after extraction of the hordein [Image]. https://www.researchgate.net/publication/336804156/figure/fig1/AS:962745428107264@1606547805071/SDS-PAGE-for-a-barley-grain-and-a-barley-malt-sample-after-extraction-of-the-hordein.png

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