Twice I have tried to make a fresh mint liqueur (flavored vodka), and both times it has turned a very unpleasant brown/black color. I'd like to figure out how to do this while keeping the nice bright green color, or even no color. The discoloration is also associated with a change in smell - not completely unpleasant, but not the same mint.
The method I tried is just the standard that you read on the first 10 google hits, or the question found on seasoned advice. Wash the mint leaves, put in alcohol, let sit, add sugar syrup, possibly glycerin, and enjoy.
The first time I did this, I left the stems in the mix out of laziness. I let it steep for a week or two, and it was completely brown/black.
This second time I removed the stems, and I also only steeped the leaves for 24 hours. I also used a glass weight to keep the leaves completely submerged. After the 24 hours, I strained the flavored vodka into a clean jar and put it in the cupboard. The mint vodka was always kept in the dark cupboard, at room temperature. 24 hours later, the top half of the vodka had already discolored, and an additional 24 hours later, all of the vodka had browned.
I had hoped that the discoloration was due to something in the leaves oxidizing(?), and that by removing the leaves after a short time, I'd remove what was causing the browning. Sadly, the alcohol appears to have extracted whatever is browning. Note: the leaves themselves also browned in a similar timeframe, and from the top down (they were compacted in the original jar).
The mint is a spearmint variety, for what that's worth. I've not tried it on a different mint, b/c the variety I used is my favorite.
Any ideas on how to prevent the discoloration?