Yesterday my daughter Amanda suggested that we make yogurt since she has been eating a lot of it. I found a recipe in the NY Times Cooking App and read the comments on the recipe. This turns out to be a very easy food to make, which should not be a surprise since in the past the average family in many countries made yogurt daily as a way of preserving milk. One key step is to have a way to keep the milk at the optimal temperature of 110 degrees while the yogurt cultures do their thing. Since I have a sous vide rig, this turned out to be a very easy way to keep the milk at the target temperature. Other tricks are to put the milk in an oven with the light on or on top of a refrigerator or other appliance which is generating some heat. Here is how I made the yogurt:
½ gallon good quality whole milk
¼ cup yogurt with live cultures
2 quart mason jars
Candy thermometer
Sous vide rig
Put the milk in a large pot and over medium heat warm the milk to ~185 degrees, stirring occasionally to ensure that there is no scorching on the bottom of the pan. Remove the pan from the heat and cool the milk to 110 degrees. I filled a sink with cold water and put the pan in this cold water bath to accelerate the process. Put the ¼ cup of yogurt and about ½ cup of the warm milk into a bowl, mix together well, and then mix the yogurt/milk mixture into the rest of the warm milk. Ladle the milk into mason jars using a funnel. There will be a little wastage of milk which will not fit into the jars. Cover the jars with a square of plastic wrap and the screw lid and put into the sous vide container. Fill the sous vide container with water until it comes ¾ of the way up the jars. Set the sous vide machine to 110 degrees and 12 hours and just let it run. This is a good thing to do right before going to bed.
In the morning, check to see that the milk has thickened into yogurt. If you want milder yogurt, ferment it a shorter time, and if you want a more tart yogurt, ferment it a longer time. This batch fermented about 10 hours.
Chill the bottles to room temperature in a water bath in a plugged sink, and then put them into a refrigerator to chill and to continue to thicken. Amanda had her first sample after it had chilled about an hour and thought it was very good.