So we bought a slow cooker! Yay! And since I love eating yogurt–we have even experimented with making our own it in the past in jars–we decided to give it a try in the slow cooker.
Yogurt, is just milk fermented by a culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus bacteria. It must be added into the hot milk and be alive in the finished product.
It is one of the many types of fermented milk foods that we as a civilization have come to enjoy, introduced by the Seljuk Turks from the beginning of the 11th century throughout the Middle East and then to the Balkans by the Ottomans as early as the 14th century. While it would be an understatement to say that it is very popular, many people enjoy making homemade yogurt even though it can be readily purchased in stores. Its standardization and industrial production in the second half of the 20th century made it a consumer product in many countries of the world.
Well here we are: first here are the ingredients of a typical random off the shelf yogurt: milk, active bacterial culture, milk and whey protein, modified corn starch, gelatin, natural and artificial aromas, citric acid, pectin, sodium citrate, caroube gum, concentrated fruit juice, sucralose, guar gum, calcium monophosphate, carboxymethylcellulose, potassium sorbate, vitamin A palmitate, vitamin D3, dye.
Incredible!
Especially when you think that making your own yogurt requires ingredients: milk and a source of bacterial culture, and f you like your choice of sweeteners to taste. Powdered milk can also be added to thicken it but, seriously not needed. In short: about four ingredients total.
Secondly: If you consume a lot (4-5 times a week at least) it becomes advantageous because it takes the cost down by half the price of buying it.
Third: It's a fun scientific experiment (that you can also eat)!
This is basically the basic universal method that has been used for hundreds of years and now I will detail my method that uses a slow cooker as an incubator. (A thermometer is essential!)
Heat milk slowly to 180° without boiling (this "sterilizes" bad milk bacteria);
- Cool milk to about 110°;
- Take a cup of milk and mix it with the source of bacterial culture (i.e.: a little plain yogurt) and add it to the rest of the milk;
- Leave the milk alone (without stirring) for several hours at a constant temperature of 110F until it is set;
- Refrigerate for a few hours.
Now here's how to make the most of that beautiful slow cooker you didn't know what to do with. We picked ours up from Walmart and the recipe including quantities and time (important: you have to adjust the quantities and times indicated according to the size of your slow cooker! I think at least. Your first tests will be educational at least):
- 8 cups (about 2/3 of a gallon) 2% milk (or 3.25% – preferably normal milk, not skim)
- 1 small container of plain yogurt containing an active bacterial culture, this should be shown on the packaging
- 1/3 cup skimmed milk powder (optional, but this is what gives you a really thick texture when you make homemade plain yogurt, which will be a little more liquid than that found in the dairy aisle
- your flavors (honey, sugar, jam, compotes, pie filling, dried fruit, lark… to be added only at the end of the process.)
Put the milk mixed with the powdered milk in the slow cooker, cover and put at LOW for 2 hours. At the end of this time check the temperature of the milk with a thermometer. If it is at 180° turn off the slow cooker and let it cool for 2 hours. If it's not yet at 180° let the slow cooker work a little longer. At the end of the cooling time: re-check the temperature and bring it backup to about 110° (105 or 115° is okay too..) if you need to. If it's not ready yet at this point let it cool again. Take a cup of cooled milk and mix it (in a small separate bowl) with plain yogurt. Pour this into the slow cooker and mix well with the rest of the milk. Make sure that the cooker does not get too cool. Leave it on the counter in a place away from minimum drafts for 5 hours or overnight.
If the heat remains constant at 110° during all this time (halfway through the incubation you can put the slow cooker back on to warm it up for 10 minutes if you are not sure. I ended up doing this the first time we made yogurt to ensure that it was growing. Avoid stirring to check there is definitely a safe smell for yogurt, not the curd smell!
When it is done you can let it cool back off and then, when cooled, put the removable part of the slow cooker in the fridge for a few hours to complete the process before.