Homemade Yogurt

Yogurt is one of many foods which seems fairly innocuous when you first encounter it, but which becomes stranger and stranger the more that you consider it. First off, this thick and creamy snack is the mammary secretion of another animal. This liquid is then fermented (which is to say, rotted under controlled conditions) in order to foster a swarming colony of bacteria, which we humans then eat. This is very strange, no matter how you try to think about it.

I have been making homemade yogurt for around ten years now. In that time, I have learned that the health benefits of homemade probiotic yogurt are not over-hyped. Eating probiotic yogurt can help you burn fat 1), recover from diarrhea after a course of anti-biotics 2), improve digestion 3) and generally help your overall levels of health 4).

I am certainly not claiming that homemade yogurt is any kind of miracle cure, as it is not. However, it packs a surprising nutritional punch and is extremely inexpensive, especially in comparison with the commercially produced variety. Although I may be getting ahead of myself.

Yogurt – An Examination

First, let’s talk about what yogurt actually -is-. Yogurt is milk, which is simple enough. Yogurt can be cow milk, sheep milk, goat milk – arguably, it could even be human milk. In some weird way, the idea of consuming human milk as an adult seems so much more bizarre than making yogurt from the milk of some other species entirely… and there simply isn’t enough space here for me to indulge in a lengthy examination of the cultural reasons for that. At any rate, yogurt is made from milk. The is generally pasteurized to kill all common bacteria, and then it is cooled to around the temperature of the human body before being inoculated with the specific strains of desirable bacteria that make yogurt what it is. The temperature is then maintained at this ideal temperature for the breeding of bacteria. In this time, the bacteria consume the lactose in the milk and excrete lactic acid, thickening the yogurt and giving it its distinctive tart flavour. It is because of this consumption process that even lactose intolerant people can generally eat homemade probiotic yogurt.

Once the fermentation process has completed, the entire batch can be placed somewhere cool like a refrigerator in order to stop the fermentation process. This cool temperature causes the bacteria to go into a dormant state, but not to die. Then, when you eat the yogurt later, you are enlisting legions of friendly bacteria to your cause, fighting the digestive battle that happens daily in your gut. I know, I’m getting carried away my descriptions - I'll try to keep it in check.

Yogurt As Opposed to “Dairy Product”

Most commercial yogurts not listed as being “probiotic” have no active bacteria in them. Before the cooling step described above, they are pasteurized again to kill all bacteria, both beneficial and detrimental, and then they are cooled. At this point, they may have gelatin, sweeteners and various flavours added in. In a literal sense, these are not yogurt – they are simply yogurt-style dairy products. The allowable legal descriptions vary, but in most areas you will see a name that says “yogurt dair snack” in the same way that “peanut spread” is peanut butter cut with oil and icing sugar. It’s delicious, but it isn’t quite what most people think they’re buying when they pick up the tin.

Without a doubt, these little tubs of sweetened thickened dairy product make a delicious treat and they are generally relatively high in both calcium and protein. But if you’re looking for the benefit of probiotics or the helpful bacteria that improve your digestion and potentially grant all the benefits referenced above, then the major commercial brands generally won’t offer you that. Even some of the probiotic brands have uncertain quantities of actual living bacteria in them, which means that it’s tough to say what kind of a benefit you’ll actually receive from consuming them. These considerations led me to start making my own.

Making Yogurt


When I first began to make yogurt, the question that I received most often was “You can DO that?”. Most people genuinely believed that in order to produce yogurt, a factory with a bazillion dollars’ worth of capital equipment was required. Many people think the same thing about homebrewing beer, which is a surprisingly similar undertaking which also does not require a factory or massive amounts of capital equipment. Here’s what you do need for a roughly 2-Litre or half gallon batch of homemade yogurt:

  • A large pot
  • A container large enough to empty the pot into
  • A spoon or other utensil for stirring the milk
  • A thermometer which can read from 100F – 200F or around 37C to 100C
  • A mesh strainer or basket to pour the milk through after pasteurizing
  • A kettle or second pot to boil water in order to pasteurize everything that goes near the milk
  • Containers to store the yogurt while it ferments (I use thermos vacuum flasks)
  • Glass or plastic containers to store the yogurt after it has finished fermenting
  • A yogurt starter culture.
    • This can be purpose-made freeze-dried stuff, it can be some of your last batch of yogurt, or it can be a high quality probiotic yogurt you bought somewhere else.
    • If using freeze dried culture, follow their instructions per volume of milk.
    • If using existing yogurt, I use around 1 cup per 2-3L batch – so 10% yogurt relative to milk by volume.
  • 2-3 Litres of milk, preferably a milk that you like.
    • I generally go with full-fat cow milk, because in the words of the immortal Ron Swanson, “There's only one thing I hate more than lying: skim milk, which is water that's lying about being milk.” 5)
  • Some method of keeping the fermenting yogurt at a steady temperature around 110F / 43C.
    • Some ovens have a light bulb which keeps them warm enough if left on.
    • There are also dedicated yogurt making machines.
    • Food dehydrators typically have a “yogurt” temperature setting.

For fermenting, I prefer to put the milk in Thermos type vacuum flasks. You simply fill them with boiling water while the milk is heating in the pot, and dump the boiling water out just before you add the milk to them. This warms the vacuum flasks and then keeps the milk at a steady temperature the entire time it ferments, without requiring electricity or supervision.

The Process

  1. Pasteurize the containers, mesh basket, any spoons you’re going to need, any measuring cups, so on.
    1. Pasteurize everything with boiling water before you put it anywhere near the milk. This is the critical part. We are destroying all competing bacteria so that our friends the yogurt bacteria can conquer and thrive.
  2. Pasteurize the milk.
    1. This is just heating the milk to a temperature at which all common bacteria are mercilessly slaughtered. In practical terms, that is around 182 Fahrenheit or 83.5 Celsius – higher is better, but milk will definitely scald above 182 or so. You’ll need to stir it regularly as it heats in order to keep it from burning or clumping, and even so there will likely be some chunks of burned or congealed milk. We’ll deal with that later.
  3. Cool the milk.
    1. Let it sit on the counter, dunk the pot in cold water, put the lid on and set it in a snowbank, whatever you have available.
    2. Bring the temperature down to 110-115 as quickly as possible.
  4. Did you pasteurize the mesh strainer? Good, now strain the milk through the strainer. Look at all the chunks and that weird skinlike stuff that congeals on the milk when you boil it.
    1. Throw away all the stuff you strained out of the milk and keep the milk (which is hopefully sitting around 112F / 44C).
  5. Inoculate the milk with starter culture. Whatever starter culture you are using, make sure that it is thoroughly and uniformly mixed together with the milk.
  6. Pour or ladle the inoculated milk into the jars or vacuum flasks, seal them up, and put them someplace where they will stay at around 110 degrees Fahrenheit for between six and twenty-four hours, depending on how tart and strong you like your yogurt.

The hard work is now done. Write down the time you started fermenting, and set yourself an alarm for 6, 8, 12, or 24 hours later if you like extremely strong and tart yogurt. Experiment to see what you like best and stick with the process that gets you the best results.

That’s it! You’ve made yogurt. Once the batch is done, you can put it into other fridge-safe containers and cool them in the refrigerator. If using jars just put them directly into your refrigerator to stop the fermentation. If you reserve around 400-500mL of your yogurt in a freshly pasteurized glass jar, you will have enough starter culture for two more batches using your own yogurt to inoculate.

In general, you will be able to make a batch this size (half gallon) for approximately the same price as a 500g / 1L container of commercially-produced yogurt. You will have complete control over the ingredients, and after the fermentation is complete you can add sugar, fruit, chocolate, vanilla or any other flavouring you like.


Health | Food

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