What is Fermentation?
When you think of fermentation, you probably think more about the result than you do the process. Fermentation is the conversion of sugar, by the interaction of yeasts into alcohol with a by-product of carbon dioxide (CO2) gas. Since wines get their flavor from the grape skin, most red wines are fermented with natural yeasts that grow on the grape skins. the crushed grapes ferment or soak with their skins, often at varying temperatures, until the yeasts have converted the sugar to alcohol.
Requirements for proper fermentation process includes suppression of the growth of undesirable microorganisms, presence of adequate numbers of desirable yeasts, proper nutrition for yeast growth, temperature control for prevention of excessive heat and prevention of oxidation.
- Temperature - Temperature plays an extremely vital role in the fermentation process. The optimum temperature for a fermentation is 72 degrees, but anywhere from 70-75 degrees will do just fine. If the temperature is too cool, the yeast may not be invigorated enough to ferment. Whereas if the temperature is too warm, the yeast may ferment fine, but the flavor of the wine will usually suffer. This is due to the increased production of unwanted enzymes by the yeast and the possible growth of micro-organisms that thrive in warmer temperatures.
- Prevention of Oxidation - Contact with air must be restricted to prevent oxidation during fermentation. In very large containers, the volume of carbon dioxide given off is suffient to prevent air entry. However, with smaller fermentations, traps are inserted to prevent entry of air while still allowing the carbon dioxide to exit. Following fermentation, small amounts of sulfur dioxide are added to help prevent oxidation.
Wine fermentation has two distinct stages: primary and secondary, which are sometimes described as aerobic and anaerobic fermentations:
- Primary Fermentation - This stage will typically last 3-5 days. On average, 70% of the fermentation process will occur during this stage. In most cases, you will notice considerable foaming during this time of rapid fermentation. The primary stage is also known as aerobic fermentation because the fermentation vessel is allowed to be opened to the air. This air plays an important roll in the multiplication of yeast cells. This is why it is important that you do not use an air-lock during these first few days of fermentation. While alcohol is being produced, a significant portion of the yeast's energy is devoted to reproducing itself.
- Secondary Fermentation - This stage is when the remaining 30% of fermentation activity will occur and usually lasts anywhere from 1-2 weeks depending on the amount of nutrient and sugars still available. The secondary fermentation gets slower and slower each day with less activity occurring at any given time. This stage is also known as anaerobic fermentation, which means that the air exposure is to be kept to a minimum. This can easily be accomplished by attaching an air-lock to the fermentation vessel. It is the reduction in air exposure that entices the yeast to forget about multiplying and start using all of its energy to making alcohol.
Now that you understand how the fermentation process works, it's time to enjoy a glass of your favorite wine. Maybe you're not ready to start making wine on your own, but that's what Seven Springs Winery is here for. Stop by the best winery at the Lake of the Ozarks and grab yourself a glass of our Missouri wine today!
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