Fishbone Principles

Fishbone Principle #1: "Use bifocals when viewing and interpreting data."

Looking back, I realize that one of my weakest skills at the start of my journey was truly understanding at a gut level the importance of gauge repeatability and reproducibility (R&R). Fortunately, active participation in ASBC over the past 20 years has provided me with the skills required to address this shortcoming. Once I "got it," the application of this knowledge has played a critical role in my career. If there is only one piece of advice I can offer the young reader, it is to always interpret data through two filters, namely "process" and "measurement"!

What do I mean by this? Well, early in my career I generally assumed all data was essentially "infallible" and as such provided an accurate assessment of the pertinent attribute at the point in the brewing process the sample was taken. For example, I have seen situations in which the "data" indicated DMS levels in product exiting a brewhouse were essentially zero. Likewise, at several other breweries, DMS data from daily sampling in fermenting revealed wild up and down swings, leveling out to more stable determinations only when aging was reached.

On the surface, the data in the first example "logically" leads to the conclusion that DMS in packaged product must be coming from yeast reduction of DMSO to DMS. In the second situation, the data indicates some pretty crazy things must be going on during fermentation, given the "non-biological" pattern observed. In both scenarios, however, fundamental gauge R&R issues were subsequently identified, leading to erroneous process conclusions including sampling errors, matrix effects (especially the constantly changing water/ethanol matrices during fermentation), the fundamental flaw of assuming uniformity of matrix within a fermenter (especially the first several days of fermentation-thank you, Chris Boulton!), the error of assuming that beer:headspace equilibration for DMS either during fermentation or at bunging occurs rapidly (likewise influenced by the erroneous paradigm of vessel homogeneity throughout fermentation), bunged vs. open vessels, calibration/standardization protocols, and test method differences. Once these gauge R&R issues were identified and addressed and the brewing process surveyed once again, the "picture" provided in each of these breweries changed radically! Once the picture became clearer and reflective of what was actually occurring in situ, the subsequent approaches taken and strategies employed to gain process control for DMS likewise changed radically-as illustrated in Fishbone Principle #2.

Fishbone Principle #2: "When practice and theory disagree, practice prevails."

Mentors have played a crucial role in my professional development in the brewing industry. The above quote is one I first heard expressed by Dr. Morten Meilgaard of The Stroh Brewery Company, and the spirit of this foundational principle permeates the fishbones!

A classic case in point is the set of fishbones dealing with DMS control in brewing. "Dogma" for this effect, then and still today, is the published literature indicating that the majority of DMS in beer originates from yeast's reduction of DMSO during fermentation. Yours truly assumed this gestalt several employers ago when troubleshooting for the first time in my career deteriorations in beer quality linked to elevated levels of DMS. Indeed, literature proving beyond any doubt that yeast has the metabolic ability to reduce DMSO to DMS in a glucose-salts medium played a key role in initially focusing efforts on yeast. Likewise, it has been clearly demonstrated that yeast mutants lacking the enzyme methionine sulphoxide reductase cannot produce DMS. However, believing in the extrapolations and paradigms by widely-published author(s) that these in vitro observations are relevant to in vivo, a prolonged and fruitless period subsequently followed in trying to regain process control for packaged beer DMS.

Fortunately, as a result of collaborations with key mentors in my career, namely Steve Anderson and Joe Hertrich, "practice" soon demonstrated the primary critical control points for DMS in the production of approximately 150,000,000 barrels of American lager beer to be brewhouse practices and material specifications for malt and recovered CO2-regardless of the yeast strain used.

While I appreciate the controversial nature of dismissing yeast as the primary source of DMS in U.S. lagers (I feel a little like the apostle Peter, or even perhaps Judas, given my love of yeast!), I simply cannot stress enough to the reader-especially readers just starting their journey in brewing-the importance of the foundational principle "When practice and theory disagree, practice prevails!" In retrospect, my initial willingness to assume that research findings in a laboratory setting are directly applicable to production brewing was flawed. Since then, I have always critiqued basic research vis-a-vis the ranges of process variables and beer constituents explored relative to practical brewing conditions. As a result, I have learned basic research employing ranges of processing parameters and/or wort or beer constituents exceeding production ranges or levels by 10-, 100-, or even a 1,000-fold may lead to conclusions with little practical application or relevance.

Since then, personal experiences with multiple brewers in achieving and maintaining process control for DMS have consistently shown yeast to be a "non-issue". Indeed, next to process control for oxidation, the most frequently observed challenge I have had as a brewer is to maintain process control for DMS! As the examination of fishbones in series XV dealing with process control for DMS reveals, there is an astonishing plethora of ways process control can be lost-and regained-for DMS control. Indeed, but for carbon dioxide recovery processes, in every case the assignable causes were determined to reside upstream of fermentation in the supply chain. Frankly, had I stuck with dogma, I doubt very much I would still be employed in the brewing industry today, given that the most critical mission of support functions is to enable sustainable process control in operations! It will be left to the users of these fishbones to determine whether like Hamlet, this viewpoint is "a tale told by an idiot, signifying nothing" or if it leads to improved process control for DMS in their breweries-or for that matter any effect covered in the scope of these fishbones!

A second, but latter, example demonstrating Principle #1 is reflected in fishbone series XXII dealing with the root causes for phenolic off-flavors in beer. Fortunately, this issue arose after the first two principles had been painfully learned as a result of troubleshooting losses of process control for DMS. Rather than assuming the paradigm of phenolic off-flavors being a result of wild yeast infections (and therefore focusing efforts on yeast-management practices), I directed that a process survey be conducted of the causative compound, 4-vinyl guaiacol (4-VG). While not a popular approach to some, to everyone's surprise (and mine, too!) it became quickly apparent that levels of 4-VG cooled wort exiting the brewhouse exceeded the reported flavor threshold by three- to fourfold! As this process step was clearly prior to fermentation and yeast contributions, in this site the brewhouse was identified as a critical control point for 4-VG control! As a result, we were able to zero in on the mashing processing parameters responsible for the high levels of 4-VG and implement effective and sustainable source corrective actions-all in a fraction of the time needed previously to resolve DMS issues. From reviewing the relevant fishbones, it should become clear to the reader what these actions were!

Given my belief in practice over theory when it comes to process control for DMS or phenolic off-flavors, why then do the fishbones on these topics include statements indicating yeast to be the primary source of DMS and wild yeast for 4-VG? Retaining these observations is consistent with the next fishbone principle, namely, "Don't play favorites."

Fishbone Principle #3: "Don't play favorites!"

Principle #3 requires that no effort has been made to selectively screen, critique, edit, or choose the content included in the fishbones. Hence, whenever I read or hear information in direct conflict with an already stated cause or my personal paradigms, I nevertheless readily add it to the pertinent fishbone. For example, when the observation that levels of DMS in bottled ale containing yeast remains unchanged over six months is interpreted as providing evidence that yeast is capable of producing DMS, that is how it was entered into fishbone XVf. As no brewer or brewing scientist (including yours truly) is immune from what I refer to as "gestalt gout", it is left to each user of these fishbones to determine whether or not a fishbone observation is applicable in his or her brewery. I decided very early on to adopt this approach in large part because of the next fishbone principle, namely, "Vive la difference!"

Fishbone Principle #4: "Vive la difference!"

The beauty of a career in the brewing industry encompassing several employers is realizing that no two brewers or breweries are alike, eh?! Differences among brewers across the supply chain abound for the type and age of brewing technology employed, product design, brewing processing parameters, cultural and technical paradigms, yeast strains, training and education programs, brewing materials-you name it! As a result, some fishbone "causes" are specific to only a single brewer, while others are generally applicable across the global brewing community. Therefore, should any reader choose to apply any of the observations contained in these fishbones, it is important to always keep in mind the next two principles, namely:

Fishbone Principle #5: "What's good for the goose is not necessarily good for the gander."


Fishbone Principle #6: "Beware of the law of unintended consequences!"

In applying information contained in these fishbones, it is critical to remember that as a brewer or brewing scientist no "effect" should be considered in a vacuum! This reality is a "good news, bad news" Catch-22. The good news is that because of the highly interactive relationship between controllable brewing processing parameters and product quality, there exists a need in the first place for brewers and brewing scientists alike! The bad news is that because of this, no process change-whether accidental or directed-impacts only a single product quality attribute or process parameter. Fishbone Principles 5 and 6 are perhaps best illustrated by examples:
1. While reduced kettle boil times improve foam stability (XXVI series), reduced boil times diminish process control for DMS (XV series) and physical stability (XXXII series).
2. While increased levels of wort oxygen improve yeast vitality and viability (I series), this can diminish beer flavor stability resulting from decreased levels of SO2 by "happy yeast" (XVI series) and as measured by ESR lag time (X series). Likewise, this also impacts relative levels of esters, higher alcohols, VDK, acetaldehyde, and sulfur compounds (XI-XIV series) in beer-some directly (e.g., higher alcohols) and some inversely (e.g., sulfur)! Whew! What tweaking one little process parameter can do vis-a-vis impacting process control for a wide array of critical processing and product quality parameters!

These examples illustrate the degree to which each controllable process parameter in brewing can simultaneously impact a plethora of different attributes. Many of the fishbones are populated with painful lessons arising from the violation of these principles. The reader of these fishbones is therefore cautioned to pay careful attention to Principles 5 and 6! Each brewer will need to decide when making a process change which "effect" is the most critical relative to the business needs of the time. Likewise, consideration will need to be given to determining, and monitoring, the degree of "process play" available relative to other simultaneously impacted attributes. This reality is best expressed in the seventh and last principle.

Fishbone Principle #7: "Every well-intentioned process change implemented to improve one process or product attribute comes with a price for other(s)!"