The Effect of Vitamin C on Yeast Fermentation
If you’ve been hearing about the possible effect of vitamin C on yeast fermentation and wondering if it might be right for you in making wine or brewing beer, you are definitely on to something. Vitamin C has become more of a wonder vitamin than many originally thought, and while it has saved human lives for thousands of years, it apparently can also save a great wine or beer as it ferments. How? Let’s look.
Yeast Fermentation
When making wine or beer, fermentation is the most important step, without a doubt. In early times, meaning 10,000 years ago, and up to only about a few hundred years ago, humans did not have to trouble themselves over fermentation. They set up the ideal circumstances – crushing grapes or grinding and boiling grains – and then they simply let nature take its course.
Wild yeast would settle in and ferment.
The problem was, and still is for many who enjoy working with wild yeast, that wild yeast is, well… wild. It is difficult to control and almost impossible to predict.
Furthermore, many winemakers and brewers are finding that even when they think they are working with wild yeast from the plant, say the grape or the grain, they are also usually working with environmental yeast from the brewhouse or the winery.
An abundance of evidence has shown that the yeasts found on plants like grapes and grains are highly unlikely to provide an ABV above 5%. Once that alcohol level is reached, those plant based yeast strains will simply go dormant, flocculating on the surface or at the bottom of the vessel, ready to be sifted out and reused another day.
It is typically Saccharomyces cerevisiae that will produce those higher ABVs, and that yeast is honestly usually found on countertops, on equipment, or on the clothes or skin of the brewer or vintner.
Thus, whether we realize it or not, we are almost always working with Saccharomyces cerevisiae in one strain or another, so we need to pay close attention to how this primary yeast behaves during fermentation, and one of those critical behaviors is stress.
Stresses Yeast Experience During Fermentation
That’s right. Stress.
Yeast can get stressed out, and those tiny living organism can get stressed out for a number of reasons.
Osmotic Pressure
Osmotic pressure occurs in brewing or winemaking as concentrations of the liquid changes or as one liquid is added to another. If you combine two different beers or wines, or if you pitch a new yeast starter into an existing must or wort, the yeast in the existing liquid can get stressed out by the sudden change in those liquids and the resulting changes in concentrations of salts or other solutes. The pressure on the cell membranes of the yeast can become overwhelming and cause the yeast to become stresses and either die or grow sluggish.
Ethanol Concentration
As briefly touched on above, as the alcohol levels increase in beer or wine, yeast that cannot tolerate those high levels will lie dormant or die off. When a wine or beer is fortified with liquor or a wine or beer with a much higher ABV, the yeast will almost always die off immediately, becoming useless for further fermentation.
Low pH
When bacteria get into a batch of wine or beer during fermentation, either on purpose or by accident, that bacteria can produce lactic acid, which will create a more acidic environment. Typically, when this happens, the right balance will allow either good bacteria to fight off bad bacteria and raise the lower pH or a strong enough yeast strain can fight off the bacteria and prevent the creation of that acidic environment. However, if the bacteria is allowed to proliferate, the environment in the must or wort can become so acidic that it lowers the pH and creates a hostile environment for yeast, forcing it to grow sluggish or die.
Limited Nutrition
Yeast need sugar! We know that, but additional nutrients come along with the sugar, namely thiamine, nitrogen, and mineral salts. If the must or wort does not have enough sugar, vitamins, and minerals, it will simply slow down and stop doing its job. After all, it is seeking an energy source, and if the food it is surrounded by does not produce energy, well then the yeast will not have energy to ferment.
Starvation
Forget nutrients. Sometimes the wort or must simply does not have enough food! If you pitch too much yeast into a batch with not enough food, the yeast will go into stress mode, eat any dead yeast cells in the batch, and often cause off flavors by fermenting too fast.
Effect of Vitamin C on Yeast Fermentation
The nice thing is that vitamin C can solve pretty much all of the above problems. Adding vitamin C, or asorbic acid, to your must or wort prior to adding your yeast will essentially fortify the yeast. It will feed the yeast, which can then produce its own vitamin C and become highly resistance to stress.
Thus, studies have shown that vitamin C makes yeast resilient and able to handle stress without further interference from the brewer or winemaker.
Indeed, even in bread vitamin C has been shown to help yeast produce more carbon dioxide gas, allowing for a better rise, a closer crumb, and a softer bread.
In the end, while vitamin C may not act as a preservative for wine, beer, or bread, it will help your yeast function at higher levels with less stress, allowing you to have a better, less stressful fermentation yourself.
The one downside to adding vitamin C is that, depending on the source you use, you may end up with a beverage that is slightly tart, which is not necessarily a bad thing.
Cheers!
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