Fresh Homemade Yogurt

Finished Yogurt

Yogurt is an amazing food—it’s delicious, good for you, and a great ingredient with tons of applications.  The fact is that when you make it at home it tastes better, is even better for you, and you’ll use it more (because you have it).  I first made yogurt following David Fankhauser’s directions and I recommend that you check them out, but I’ve adapted the process as I’ll describe below.

The idea behind yogurt is controlled bacterial fermentation.  If you just leave your milk out on the counter, chances are that you’ll be infiltrated with bacteria that won’t be nice to your milk and they’ll crowd out any good bacteria.  So the trick here is to eliminate the bad bacteria and to give the good bacteria an environment in which to thrive.  The key to pulling that off is good sanitation of your equipment, heating the milk to kill the bacteria present, and then holding the milk at a temperature at which yogurt making bacteria thrive.

First gather all your equipment.  I use 4 quart -size mason jars (along with a 1 cup jar for starting my next batch) and make a gallon of yogurt at a time, but you could do this for a single quart (4 cups).  You’ll also want a pyrex liquid measuring cup (at least 2 cups), a spoon for stirring, a wisk, an a nonreactive pot with a thick bottom (if you don’t trust your pot to distribute your stoves heat evenly and gently then you’ll want to use a double boiler), and a candy thermometer (sensitive from 0 to 225° F [-10 to 110 C]).  Sterilize your jars, lids, and any metal or glass utensils by boiling them in a large pot with about an inch of water for five minutes with the lid on.  You can do this in batches if it won’t all fit.  Plastic utensils can be sterilized using antibacterial dish soap, or better yet with a soak in water with a splash of chlorine bleach followed by a thorough rinse.


The ingredients are easy: milk and plain yogurt with live active cultures listed on the ingredients.  Concensus on the web supports using Dannon plain yogurt as a starter, but feel free to experiment with what is available to you.  The best yogurt will list only milk and cultures as ingredients.  I used Mountain High yogurt which makes a fairly thick and creamy yogurt.  You’ll find that the types of bacteria from different yogurts will bring about subtly different results.  As far as the milk goes, I highly recommend that you use whole milk and not less than 2%.  The fat helps make a creamier yogurt and when it drops below 2% it will be grainy.  It should go without saying that you want the freshest milk and yogurt possible—don’t even open the containers until just before you are ready to measure them out.

Measure out your milk into your pot, attach your thermometer, and slowly heat over low to medium until the milk reaches 185-195°F.  Be sure to stir regularly to ensure that the milk does not burn and stick to the bottom of the pot. What you are doing here is scalding the milk, which kills any bad bacteria that might be present in the milk, improves the flavor of the finished product, and makes for a thicker yogurt.  I’ve skipped this step before and ended up with a tasty, but runnier yogurt that was less successful at propogating subsequent batches.  Be careful not to let the milk exceed 195º because if it boils it will make a mess and your yogurt will have a “cooked” flavor.  As you begin heating the milk, turn your oven on to 200°.

 Heating Milk

From here you want to cool down the milk to the temperature at which you are going to incubate the yogurt.  Do this by creating an ice water bath in your sink or a large container and set the pot in.  Stirring the milk and stirring the ice water will lead to faster heat transfer and cool the milk faster.  The yogurt bacteria die at temperatures over 130° F and aren’t very active below 98° F.  I recommend cooling just to 130° F because the milk will continue to drop a few degrees after you remove the pot from the water.  We’re shooting for incubation at 122° F. 

 Cooling Milk

Once you hit 130° F, take the pot out and set it on the counter.  Pour 1 cup of the milk into a 2 cup Pyrex measuring cup and then add your yogurt to fill it to the 2 cup mark.  (This additional cup of volume goes into the 1 cup jar as a starter for the next batch)  Blend the yogurt with the milk in the cup with the wisk and then pour this into the pot of milk, stirring it thoroughly throughout the milk with the wisk.  Working quickly, pour the innoculated milk into your jars and put the lids on immediately.  Turn off the oven, place the jars in the oven, close the door, and turn on the oven light.  What you are looking for is to maintain the heat around the yogurt close to 122° F without exceeding 130° F. 

I find that by switching out my oven light with a 40 watt bulb and doing a preheat at 200° F it works out just right.  If you have a gas oven, the pilot light may complicate things.  You can test your oven by placing a jar filled with water in the oven and measuring the temperature of the water each hour for several hours (a remote probe thermometer is handy here).  Alternatively, you can follow Fankhauser’s method of putting the jars in a cooler and filling it to 3/4 the height of the jars with water heated to 122° F, checking occasionally and adding hot water as needed.  Absent these resources, wrap your jars in towels or blankets to insulate their current temperature.

Now you wait.  The bacteria are reproducing, consuming the milk sugars, and producing acid.  After 3-4 hours the yogurt should have gelled.  If it hasn’t, let it sit longer, up to 12 hours.  The longer the yogurt incubates the more tart it will taste.  The photo below is of yogurt incubated for 4 hours.  At this stage it is thick and creamy with just a hint of tartness.  The milk flavor really shines through.  6 hours takes you to the typical tartness you find in grocery store yogurt (but with superior overall flavor).  If I’m making it just for me, I usually go for 8-10 hours, but my wife likes it less tart.

 Finished Yogurt

It’s not a bad idea to let the yogurt sit on the counter to cool for about an hour before you put it in the refrigerator, since the jars would heat up everything in the refrigerator initially.  Remember that the bacteria will still be working during that time, so factor it in as you consider your preferred tartness.  Once the yogurt is fully chilled in the refrigerator it is ready to eat.

I highly recommend that you try it plain.  Discover what yogurt really tastes like when it is not turned into candy.  I’ve learned to love plain yogurt.  As you develop a taste for real yogurt, you will have a better gauge of how much fruit and sweetener you might add when you do use them.  A spoonful of jam is an easy way to do fruit and sugar thing.  A better way is to add your favorite fresh fruit and honey or agave nectar to taste.  I once added the juice and zest of an orange along with a teaspoon of honey to a bowl of yogurt and had one of the most sublime breakfasts in recent memory.

Later this week I’ll post how to make greek style yogurt, along with several other ways of using your yogurt.