This week I’m going to attempt to talk about a very complicated subject in an approachable way. This subject is intriguing me more and more as we dive deeper into the rabbit hole through our classes in Brewing Technology, Microbiology, and Biochemistry. The subject is biotransformation during fermentation, and today I will attempt to demystify the processes of fermentation that take place on a molecular level.
Photo Cred: thebrewingnetwork.com
For years I have explained fermentation at my beer tastings and workshops as the simple process of brewer’s yeast converting sugar into alcohol and carbon dioxide. I, myself, believed in the simplicity of this explanation. But in recent days, I have come to realize that my understanding of the transformation that occurs during fermentation to be incomplete. Well, the beginning and end points were mostly correct. Fermentation does indeed begin with sugar and some of the many byproducts of fermentation are indeed alcohol and carbon dioxide. But, I was missing an entire microscopic world in between the lines.
You see, fermentation produces other by-products besides just alcohol and carbon dioxide. These can show up as flavor enhancing by-products or as off-flavors in our final product. Some examples would be phenols, esters, diacetyl, and terpenes- to name a few.
What I've learned most recently is the world that exists in between the microbiological lines. What actually happens to a sugar molecule that comes into contact with a yeast organism is that the chemical properties go through something called a metabolic pathway. This is a journey that the sugar molecule must make on a microscopic level, during which it is transformed through the addition or removal of different atoms. And because we have different types of sugars like maltose, maltotriose, fructose and dextrins in beer, each sugar is subject to a different metabolic pathway. To take it one step further, each pathway offers several different possibilities of diversion. In other words, one sugar could produce many different outcomes based on fermentation conditions. Sometimes the pathways subject the original sugar molecule to as many as 15 transformations before reaching the molecule’s final form in beer.
I must admit to you that the existence of these pathways blew my mind. And not just in regard to beer. As I've learned about this tiny world in which yeast and sugar molecules interact in an extremely busy fashion, I’ve gained a new appreciation for some of my other favorite fermented foods. I mean, this is what happens in a loaf of bread? Yogurt has all of this going on? You mean to tell me that plain looking sauerkraut is actually a hub of microbiological activity? And yes, this is what is so intriguing about the process of fermentation.
Photo Cred: goop.com/wellness
As I continue to dive deeper into my understanding of fermentation and its by-products, the intrigue grows. And this, of course, is the joy of reaching a new level of understanding about something that you thought you already knew. What you find out is that your knowledge just barely scratched the surface and that there was always still so much more to learn. It makes me wonder, what else do I think I know but perhaps I really have no idea about what is actually happening between the lines?