There have been brewing projects discussed in the past that might have useful info.
http://www.google.com/search?ie=UTF-8&oe=UTF-8&q=brewing&domains=http%3A%2F%2Fwww.arduino.cc&sitesearch=http%3A%2F%2Fwww.arduino.cc%2Fcgi-bin%2Fyabb2%2F