They all go into Banana Bread!
But, what do they all have to do with mead? That might not be so obvious.
A long time ago – over a year which is tantamount to infinity in internet terms – we had an article about choosing yeast strains. In this article we said that the primary function of yeast in mead was to turn sugar into alcohol.
This is basically true; without yeast, honey and water would never become the transcendent tipple known as mead. But we want the full picture: What else is going on in that tiny little factory known as Saccharomyces cerevisiae?
[Warning, what follows is pretty geeky and technical.]
In fermentation it is important to know three things:
- Strain Traits
- Primary Metabolites
- Secondary Metabolites
1. Strain traits are easy to understand and most of what we covered in the aforementioned article. Basically, it’s the list of known characteristics of a particular strain of yeast.
- How warm should the yeast be? (Temperature Range)
- How much alcohol will kill (or deactivate) the yeast? (Alcohol Tolerance)
- What percentage of the sugar will it eat? (Attenuation)
- Will it settle out of solution, or will my beverage be hazy? (Flocculation)
2. Primary metabolites are the chemicals that a cell makes in a process which is essential to its life-cycle. For yeast it looks like this:
C6H12O6 → 2 C2H5OH + 2 CO2
All that means is that yeast takes a sugar (in this case a glucose molecule) and turns it into two ethanol molecules and two carbon dioxide molecules, aka alcohol and bubbles.
This is significantly less efficient than aerobic respiration, making only a tiny fraction of energy by comparison. This is because so much of the energy potential remains in the form of alcohol.
Well, their loss is our gain!
For more on the aerobic and anaerobic stages of yeast, MoreBeer! has a great article here.
3. And now we come to the answer to our riddle. What do bananas, cloves, and eggs have to do with mead? Their flavor compounds are secondary metabolites of yeast!
If yeast encounters ferulic acid (found in grain and some honey) it will, under the right circumstances, convert it into 4-vinyl guaiacol or a whole set of aldehydes. Don’t like the sound of eating 4-vinyl guaiacol or aldehydes? Well, they're also known as cloves and vanilla respectively.
It is well known that we are huge advocates of sanitization at Groennfell Meadery. The reason is that if Brettanomyces gets into your mead instead of the strain of yeast you want, the ferulic acid will be metabolized into 4-Ethylphenol instead of 4-vinyl guaiacol. The difference? Instead of cloves, your mead will smell like the south side of a horse blanket.
Esters, phenols, aldehydes, hydrogen sulfide (egg smell), and a million other compounds are secondary metabolites of fermentation.
While often overlooked, secondary metabolites represent a huge amount of a beverage's “character.” A skilled brewer, vintner, or meadmaker can take a yeast strain, play around with the fermentation environment, and produce a huge variety of flavors with the exact same ingredients.
Pretty cool, right?
 We are well aware that most banana bread is made with baking soda and not yeast, but some are yeast breads and it makes for a better title.