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Top 10 Reasons For Fermentation Failure

By Ed Kraus

Reason #7
Fermentation Has Already Completed:

In a twisted way, you may not be getting a fermentation because the fermentation has already completed. Many ask, "how could this be?" It's almost like experiencing an unbelievable magic trick. "How did my wine do that?" But, after checking the wine with a hydrometer, the truth becomes clear. The juice fermented, and you didn't even know it.

Wine Hydrometers from EC KrausRelax, its really not your fault. And, there's really no problem, anyway. Most wine making directions you run across will lead you to believe that all fermentations will take anywhere from 4 to 6 weeks. But in reality, if the conditions are right, a fermentation can complete in as little as seven days. Yes, that's right "seven days." We have personally experienced fermentations that have completed in as little as five days, but this is far more rare.

The only real way to know where you stand with your fermentation's progress is to take a hydrometer reading. The hydrometer has the final say as to what has actually happened. If you take a hydrometer reading and you discover that the Specific Gravity is 0.998 or less, well then, yes, the wine is done fermenting. If this is the case, there is really nothing else for you to do other than continue on with rest of the directions ahead of schedule.

Many first-time winemakers will get the notion that they should add more sugar if there fermentation completes quickly. If you have added the correct amount of sugar at the beginning of fermentation, this would not be the right thing to do.

Just because a fermentation only lasted a week or so, does not mean the wine has any less alcohol than a fermentation that took 2 months. Time does not control the amount of alcohol made, the amount of sugar available to the wine yeast does. Adding more sugar at this point will only complicate the situation.

For example, if your starting hydrometer reading indicates that you have enough sugar in the must to produce 12 percent alcohol, you will have 12 percent alcohol once all those sugars are fermented, regardless of the amount of time it takes. And, you will know when all those sugars have been fermented by the fact that the hydrometer reads 0.998 or less on the Specific Gravity Scale.

Many ask, "why does this happen?" The fact of the matter is, there are many reasons why a fermentation might go fast or slow. There are an endless number of variables that can come into play when dealing with Mother Nature. But having said this, a large percentage of the time it is temperature related.

All things being the same, musts that are 75 degrees F. or higher will ferment much, much faster than a must that is 70 degrees F. or less. The amount of wine yeast that is pitched into the must can make a difference. Two packs of wine yeast will ferment the same juice, not twice as fast, but faster that one pack of yeast will.

If the yeast is pre-started ahead of time, this can influence the rate of fermentation as well. Not only does pre-starting the wine yeast allow the yeast cells to hit the juice with their feet running, so to speak, but it also allows the yeast to multiply in number, ahead of time, which could contribute to having an explosive fermentation.

Having a fast fermentation is neither a good thing or bad thing. But the reasons that caused it to ferment fast may be bad. For example, if you had a fast fermentation that was caused by warmer temperatures, this could be bad. Having too warm of fermenting temperature will also facilitate the growth of unwanted micro-organisms, which may give the wine an off-flavor. But, if you had a fast fermentation because you pre-started your wine yeast, then no harm is done.

Having said this, there is really no advantages to having a fast fermentation in of itself. Of course you get to bottle your wine sooner with a faster fermentation, but I know of no studies that have indicate "fast" is better or worse than "slow."

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Related Articles:
"Hydrometer Scales And What They Mean"
"Using Yeast Starters For Improved Fermentation"


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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.