Editor's Note: Fractional Freezing is currently an illegal process for homebrewing scale productions. This piece is meant to inform the author and the audience about the interesting aspects of the chemical process not promote home use. Please follow all local/federal laws when it comes to alcohol production.
I love my drinks cold. Wicked cold. It doesn't matter if it is water, milk, or cider; it is perfect when frost is starting to form on the top. I'll even expedite this process by placing the beverage in the freezer for 5-10 minutes. Sometimes though I'll forget it is in there for a day or two, and when I return the drink is transformed.
While the bottom of the mixture still is liquid, the top is frozen solid! A few minutes out on the counter remedies this but just what is going on? What I stumbled upon is actually the first step in a process called Fractional Freezing.
Frozen grapes used to make Ice Wine. Photo taken by Dominic Rivard from Bangkok, Thailand.
This process can happen in two ways. With ice wine the freezing happens before the fruit is harvested, leading to concentrated sugar to begin the process. These grapes are then used normally to make wine. However the higher sugar content makes for a higher alcohol content, without sacrificing the taste. The result is (supposedly) exceptionally wonderful but often over $100 per bottle.
With beer and cider the fractional freezing happens after the product is already made. Let's say you put your five gallons of finished cider outside on a cold, February day. After coming back to it you notice that there is a thin layer of ice on top. That ice is the water separating from the alcohol mixture. If you kept removing layer after layer, day after day, you would eventually get a gallon of wine with the same amount of alcohol that comes in five!
It is illegal in the US to do any form of home distilling (and I would not recommend "just leaving" your brew outside with no intention of doing this) but back in colonial times "jacked" cider was used as currency in New Jersey.
So even though I won't be able to use fractional freezing with my own brewing, I can now enjoy those ice-wines knowing just a bit about the process.