Carbonic Maceration

[Bacchus82]

Hello all,

I am an aspiring sommelier and new to eGullet. I have been studying a lot lately, preparing for my career. My main study guide right now is the Wine Bible by Karen MacNeil. I was curious if anyone knew much about carbonic maceration. I know that it is the fermentation process used with Gamay grapes and that the entire fermentation process takes place entirely within the grape. Thats where I am confused. The process of fermentation as I come to understand it is the grapes are crushed and yeast is added which converts the sugar to alcohol. This may be a stupid question, but how do you add yeast to Gamay grapes while they are still whole? Mrs. MacNeil doesn't go into detail about how this is done. Any input on the process would be greatly appreciated.

[cdh]

Wild yeasts are everywhere. Particularly on fruit skins. Break the skins and the wild yeast will go to town on the sweet stuff inside. No need to add yeast to fruit unless you want to make absolutely certain which exact yeast is doing the fermenting.

[Florida Jim]

I know that it is the fermentation process used with Gamay grapes and that the entire fermentation process takes place entirely within the grape.

Not entirely.

Intracellular fermentation is only the first step, as the whole grapes are left in the fermentor (which has been flushed of all oxygen by carbon dioxide gas) and the initial part of the fermentation takes place without the involvement of yeast. Rather, in the absence of oxygen the grapes start to die and their own enzymes attack them turning some of the sugar to alcohol (usually about 3% alcohol). This usually takes 5-15 days and his done at elevated temps.

The second part of the fermentation is when any juice in the fermentor is removed, the grapes are pressed off, the press and free run juice are combined and the fermentation is allowed to finish extracellular. Usually, this fermentation is done at much cooler temps.

There is also a semi maceration carbonique in use in Beaujolais (mainly) where vats are filled with whole grapes without the vats having been flushed with CO2. Those at the bottom are crushed by the weight of those at the top and an ordinary fermentation begins due to the wild yeasts on the grape skins. This causes CO2 to rise to the top of the vat and seals out oxygen thus promoting intracellular fermentation in the grapes that are still whole. Of course, with this method, the amount of each fermentation in the mix is unknown.

FWIW, I sometimes wonder if folks who do a "cold soak" actually understand that, by throwing dry ice in on top of their grapes, they are not only holding off primary fermentation but also encouraging intracellular fermentation. Although, many do punch-downs during the cold soak so perhaps the degree of intracellular fermentation is less than with the semi-carbonic maceration technique.

Best, Jim