Mocha porter

[benji]

I wonder how much caffeine is extracted with a cold brew

[dcalnan]

It depends on a few factors, higher temperatures more dissolve into solution than at cold temperatures, but with cold brew you tend to have double the amount of coffee to water, and then have a higher concentration of caffeine to water ratio.

[beerfly]

Yea not sure myself but I would be leaning towards the colder the temp the less caffeine extracted.
Grounds from an espresso machine are good fertiliser but caffeine kills plants, so at high temps all the caffeine is extracted. (i know there is a pressure variable)
So I would go with there is some but not a lot + for really good flavour you should go with whole beans and not crush them so less surface area.

[helmet]

Nibs and cold brewed is the way to go then? How much of each for a 1 gallon brew do yis reckon?

[dcalnan]

A figure I've seen for adding nibs is 4oz per 5 gallons, I'm presuming that's american gallons so that works out at around 35g for a uk gallon. As for coffee I'm not sure I've only added ground beans to the fermenter, one thing you could do to avoid caffeine is use decaf beans, but make sure it's swiss water decaf, and not the chemically treated decaf.

[helmet]

Nice one, thanks!

[dcalnan]

So I was doing some reading into this today and discovered a method of using cocoa bean husks in the mash. They use the husks for tea aa well so there's a few methods you could use them, I'm going to contact the chocolate makers I got my nibs from and see if they can source some husks for me.