Get Nerdy With a Goose Island Innovation Brewer

Posted on Tuesday, November 10, 2015 by Tim Faith - Innovation

Hi, my name is Tim Faith. My role as Innovation Brewer for Goose Island is to cultivate creativity amongst our brewing team and bring new ideas to fruition. I run the pilot system as well as a variety of alternative wood projects and aid in blending of large batch specialty beers. 

These write-ups are part of our brewer education program. We are given questions and asked to give an in-depth summary of the findings and how they may be applicable to our brewery and the overall production of beer. These may cover areas we may or may not be familiar with, or have daily interactions with, so more often than not they kindle growth for both writer and reader. The first question asks specifically about yeast mutation on a more subtle level than massive genetic chromosomal drift – this is an area of interest as we begin to map the origins of our current yeast. The second question ask about malt modification (or malting/kilning) process’ and how it effects our beer. This is important to us as we explore new malts both from macro-malting companies, but also the growing number of small maltsters, and how quality is a crucial aspect to the resultant beer.

Question 1

Discuss modification in malting, include the difference between degrees of modification, chemically and practically in the brewing process and how the resulting malt(s) can affect beer and fermentation.


Malt modification has been a crucial topic of discussion among brewers over the last 20 years. More specifically, over the last half century large breweries have had their malt fashioned to their systems and process' in order to maximize efficiency. Malts were highly modified, representative chemically of having high diastatic power, high protein content/modification, higher FAN content, increased mineral content and physically higher Friability. All these factors culminated to boost efficiency and maximized extract when brewed with adjuncts. By having higher diastatic power, this provided the necessary enzymes for conversion that were otherwise lacking in Corn or Rice adjuncts. Similarly, the Amino Acids and Peptides, often grouped together into the term “Free Amino Nitrogen” or FAN, is crucial to yeast health and performance, and is likewise not often found in adjuncts.

But what does this all mean to craft brewers? As the tendency shifted from adjunct brewing to all malt brewing there was a paralleled change in malt type and thus a required understanding of its parameters, performance and effects to finished beer. Because many of the large breweries relied on their own in-house malts, smaller malt companies and changes in climate created some degree of variance in malt modification (Brewers Association 2014). Knowing these parameters and acknowledging the methods that have been used to show modification, it can help us produce the utmost quality beer. Thus, in its most general definition, malt modification can be defined by the process in which the composition of the barley endosperm is degraded through enzymatic action during malting (Wentz 2004).

Apart from the key characteristics noted above, a few more factors have been measured to convey degrees of malt modification. Rheology, the study of the internal friction of a fluid or its tendency to resist flow, or Viscosity; this can give us incite into grain quality and its performance through the brewhouse and through fermentation. Malt modification and mash performance are highly dependent. If malt comes into the brewery under-modified, one could expect to find more steely malt, which would be composed of smaller starch granules, a higher degree of beta-glucans (carbohydrate modification) and un-hydrolized proteins – all to which have influence on higher viscosity, increase time and temp required for gelatinization (Declan 2005). This can ultimately reduce filterability of wort and hurt expected brewhouse yields. Corrective measures can be implemented by imparting a step mash program beginning with protein rests. At a temperature of 122, under modified malt is hydrated which activates glucanolytic, proteolytic and pentosan enzymes, thus aiding in both protein and beta-glucan solubilization and starch conversion. This rest specifically takes what malt that was under modified and finishes the necessary step of conversion of both carbohydrate and protein modification, in house – a  tool that can in the end allow better wort filtration and extract. If protein rests were used for already fully modified malts, this could affect body, leaving the resulting beer thin and watery.

Mineral content of malt and its concentration in wort are often overlooked because they don't affect yield or mash/lauter performance. However they do have profound effects on yeast performance and fermentation. Many brewers may not have the necessary tools to convey this information. Today, most malt is fully modified and delivers an adequate concentration for cellular metabolism. “[Specific] minerals activate or inhibit enzymes and influence the transport of carbohydrate and amino acids into cell[s]” (Holzmann 1976). Some metals in malt effect finished beer, leading to gushing, or oxidation catalysts in the case of Copper and Iron. It was discovered that many of these minerals and metals have a direct relationship with FAN levels (Holzmann 1976). Protein precipitation also leads to metal and minerals to fall out of suspension leaving little for the yeast in fermentation. Thus, FAN carry-over and mineral content of wort is highly dependent on malt protein modification.

Craft brewers need to continue to be conscious of these factors when constructing new recipes or trouble shooting current beers. It isn't always the case that internal factors such as human error or pitching inconsistency produce variability, but could also be seasonal or yearly fluctuation in malt composition and modification. Record keeping of both brewhouse and fermentation process indicators and interlocks can show the first signs that malts may have changed. Best recognized in frequently brewed flagships, if one sees RDF abruptly change from one week to another, this could be a sign that the enzymatic content or diastatic power of the malt too, changed.

Being aware that all these factors are a result of modification can help brewers improve all aspects of the beers. From mash times to lauter filtration and protein precipitation, on through fermentation, yeast health and performance and finishing beer, malt is the foundation of all beers, and should never be a subject be taken for granted. Control of malt composition along with communication from malt suppliers will better prepare brewers and their beer as new varietals are released, new brands are used and incremental climate affects crops.



Under Modification

Over Modification

Soluble Carbohydrate (Extract)



Soluble Protein (S/T Ratio)



Wort Viscosity (Beta Glucans)












Diastaic Power




Low (Steely)

High (Mealy)

Mineral content



Acrospire Length (During Malting)



Table 1.0 Characteristics of malt modification

[i] Brewers Association. “Malting Barley Characteristics for Craft Brewers.

[ii] MJ Wentz, RD Horsley, PB Schwarz “Relationships Among Common Malt Quality and Modification Parameters.” Department of Plant Sciences. Fargo University, 2004.

[iii] Declan L. Goose, Lisa Rapp et al. “Development of a New Rheological Laboratory Method for Mash Systems – Its Application in the Characterization of Grain Modification Levels.” Department of Food and Nutritional Sciences, University of Cork, Ireland and The American Society of Brewing Chemists. 2005.

[iv] Holzmann, A. Piendl, A. “Malt modification and Mashing Conditions as Factors Influencing the Minerals of Wort.” Institut Fuer Brauereitechnologie. Universitaet Muenchen, Germany. 1976

Question 2

Define/discuss petite mutants and their effect on yeast performance and beer flavor.


Domestic selection has been practiced with numerous organisms. It has lead to human control of live-stock, the selective breeding of dogs based on purpose or aesthetic, and most importantly, it has brought about a wide variety of culturally distinguishable malt based beverages, beer. Until Pasteur, beer was typically given “boil” or fermentation by continued use of the same vessel, equipment, or by mixing in already finished beer – this went unknown to the brewers of the time. The beverage was dictated primarily by local taste, which favored sweetness in environments where sugar was scarce. These yeast cultures were sporadic, contaminated and uncontrolled. With the advent of microbiology, and the isolation of the first pure yeast cultures in 1883 by Hansen, we were able to hone in on yeast culture purity, viability, vitality, metabolism, growth and genetic and phenotypic qualities. (Boulton 2015)

Like all living things, yeast is susceptible to mutation and at a great rate unless kept in check. This is why it has been so important to the study of genetics, as it was the first Eukaryote to have its genome fully sequenced. These mutations lead to the selection of certain qualities desired by the brewer, termed evolutionary engineering, a form of domestic selection (Boulton 2015). Over time, the population of the selected traits in yeast would drift favorably in a preferred direction. However, much of this selection was done on a chromosomal level, which was portrayed phenotypically in beer character. Together with cone cropping, cleaning, sanitation and microbiology, we no longer have to rely on continuous propagation and risking unchecked genetic mutational drift.

However, genetic mutation can also occur within Mitochondria, which was first identified by Ephrussi in 1949 (Barnett 2011). This came to be known as 'petite' mutations, which are representative of DNA mutations within Mitochondria. These mutations lead to the impaired ability of the Mitochondria to synthesize certain proteins, inhibited ATP transport in and out the Mitochondria, and the cells had deficient respiration on media lacking a carbon source (Boulton 2001) Morphologically, these colonies would generally be smaller in size, too – Thus the name “petite” (Stewart 1998).

On a macro level, this has several implications to the brewer. Fermentation trends exhibiting the petite mutation were more susceptible to stress, had a tendency to produce a flavor profile inconsistent with the brand (diacetyl production, acetaldehyde, and skewed flavor) and perform metabolically insufficient (Boulton 2001). On top of this, flocculation impairment was another common characteristic

Methods to control these petite mutations are similar to chromosomal. Banking yeast provides a sustainable source of a snap-shot culture. Regenerating cultures every several generations can help prevent any mutation development, as well as limiting storage time. (MBAA Conference 2014). Aiming for consistency in pitching techniques has also been found to lead to less variation, stress and thus mutation (MBAA Conference 2014).

What implications does this have for us? Indeed, one could argue that over the years our house stain could have certainly well developed to some degree these mutations. Specifically, our yeast is highly flocculative in nature. The fact that it falls from suspension so quickly, may account for stalled fermentation and residual diacetyl production. However, petite mutation could also account for these factors individually. Ideally we would be able to type this yeast against a culture that was pre-banked. Discovering the original source of this yeast could further the potential in reviving, and, perhaps correcting any mutations that may have arisen over the years.


MBAA Conference: Achieving Beer Characteristics Through Yeast. Parker, N. Ryder, D.S. Smart, KA: 06/06/2014

Boulton, C. Quain, D. “Brewing Yeast and Fermentation.” Blackwell Science. 2001.

Stewart, G.G. Russel, I. “An Introduction to Brewing Science and Technology: Series III, Brewer's Yeast. Institute of Brewing (IBD). 1998.