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Carbonic Maceration

PressuredLeaf

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Somebody explain carbonic maceration. If the juice ferments inside the fruit, then there is no yeast and it is akin to a metabolic process, no? orrrrr.... um, overwhelmed with CO2, the sugars magically convert to ethanol?

There are many many microorganisms on the skins of grapes, most of them being yeasts and various fungi. This includes sacharomyces, pichia, etc. By excluding oxygen, coupled with the high specific gravity of the grape juices, fermentation quickly favors the more robust organisms (like sacharomyces) who can tolerate the high gravity juice.

So, excluding O2 makes the conditions favorable and selective for strongly fermenting organisms. I’m not positive, but I’m guessing the softer/ milder tannins from these type of wines occur because there is less physical rupturing of the skins.
 

ChinaVoodoo

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There are many many microorganisms on the skins of grapes, most of them being yeasts and various fungi. This includes sacharomyces, pichia, etc. By excluding oxygen, coupled with the high specific gravity of the grape juices, fermentation quickly favors the more robust organisms (like sacharomyces) who can tolerate the high gravity juice.

So, excluding O2 makes the conditions favorable and selective for strongly fermenting organisms. I’m not positive, but I’m guessing the softer/ milder tannins from these type of wines occur because there is less physical rupturing of the skins.
I imagine an anaerobic fermentation of crushed grapes would include many of these organisms. In this case, because the insides of the grapes ought to be sterile, I'm leaning towards the fermentation being metabolic as per Bob's last post.
 

PressuredLeaf

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I imagine an anaerobic fermentation of crushed grapes would include many of these organisms. In this case, because the insides of the grapes ought to be sterile, I'm leaning towards the fermentation being metabolic as per Bob's last post.
Yup, Bob is correct. I should have done a better literature search! Maceration appears to be mostly enzymatic (accounting for 1-2% ethanol production) followed by a secondary pressing and fermentation to finish off the juice. I am honestly surprised they claim 1-2% ethanol from enzymatic processes alone, I wouldn't think the intracellular concentrations of NAD+ would be high enough to get up to 2% ethanol. I still imagine the organisms on the skin contribute in some fashion. While a fresh berry may be "sterile" so to speak. Many of the organisms on the skin are capable of forming digestive extracellular enzymes and others are filamentous as well.

 
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