Here is a question from a cruiser and one that I have had long discussions about:
I was looking for an easy way to make yogurt without having to buy a ‘yogurt maker’. I found several suggestions on the internet, including using a heating pad, or a slow cooker (e.g., turn on low for 10 minutes every hour), etc., but they just seemed complicated. The one most appealing was to simply pour the heated milk and yogurt culture into a pre-warmed wide mouth thermos and let it sit for 6-8 hours. This works GREAT! The hardest part for me was finding a wide mouth thermos that held at least 4 cups. (I didn’t have any wide mouth at all and wanted this size instead of the more common 16 oz. versions.)
I found several descriptions on the internet for making the yogurt but they are all pretty much the same. Heat the milk to just below boiling (a thermometer really helps) and keep it there for 5-10 minutes, stirring constantly. Then let it cool down to ‘warm’ (I use 110 degrees). Then mix a few tablespoons of yogurt with active cultures with a cup of the warm milk and mix well. Then pour this back into the larger portion of the warm milk and then pour into the thermos.
Next, I’m going to be trying some of the dry yogurt culture just in case we run out and can’t find any active yogurts wherever we travel.