I’ll be brief and minimally graphic in this introduction. A waterborne illness infected my body in Africa and wrought havoc on my digestive tract and consequently my immune system for 16 months. My doctor was astounded I hadn’t taken any antibiotics because she found alarmingly low levels of the required microbes in my intestinal tract. She recommended nearly unfathomable amounts of probiotics, incorporating fermented foods into my diet and feeding those microbes with vegetable based fiber. Unpasteurized full fat yogurt, VSL #3 (affiliate link) and farmers market sauerkraut (and recently I have added kombucha) were the factors that brought my recovery at long last. Since all of these are very expensive or simply unavailable except seasonally, I decided to try and make my own family of inexpensive probiotic foods. Surprisingly, my first attempt yielded the most amazingly rich and tart yogurt I have ever had!

Tools Required:

1. Slow-cooker, preferably with a warm setting. Mine is a staple of my kitchen and stays warm for 6 hours after cooking (affiliate link)
2. Pot if you are going to use the double boiler method. Otherwise just use the ceramic crock pot!
3. Half Gallon of high fat milk
4. Whisk or fork
5. Tightly woven fabric for straining if thicker or greek style yogurt is prefered. Cheesecloth is too open, so use muslin or similar fabric (affiliate link)
6. Stove to heat pot
7. Thermometer (affiliate link)

Materials Required

1. Time: 1.5 hours active, 15 hours passive
2. High Fat Milk
3. Yogurt culture: either biologically active commercial yogurt (check label for microbes) or probiotics (affiliate link)

Procedure

1. Pour a half cup or so of milk into a bowl and stir in your starter culture (material #3)
2. Pour the rest of the milk into the pot and slowly heat it up to 180-200 degrees (82-93 C).
   1. Some literature says this alters the protein structure so the milk sets rather than separating into curds and whey.
   2. Heat slowly and stir often to ensure milk does not scorch or burn on the bottom
3. When the milk reaches 180-200 degrees, add a few cups (not so much that it overflows your yogurt pot) of cold tap water to the crockpot then transfer to the pot with the hot milk to the crockpot. Add more cold water if there is room.
   1. Somehow, without any further action the temperature of the milk/water in the crock pot equalized after 10 minutes perfectly at 110, the desired temperature!
4. Cool the hot milk to 110 degrees (43 C) then stir in the starter culture from step 1
5. Keep the temperature at 110 for 2-4 hours
   1. I turn the crockpot on warm for 30 minutes, off until the temperature drops to 100. Then repeat as necessary.
6. After ensuring the milk is at 110, wrap the entire ceramic part of the crockpot with a towel or blanket for insulation, then transfer to the oven for another 6-10 hours.
   1. The oven simply provides insulation so turn the light on if you have one. Alternatively you can use a cooler or a pile of blankets or towels.
7. Check the yogurt to see if it has set properly and to the desired extent. If not, just let it keep fermenting and warm it up if you can.
8. If the yogurt has set, transfer to your desired storage containers and refrigerate.
   1. The rest of the steps are optional!
9. If you like your yogurt more tart, let it keep fermenting and taste test until it gets there
10. If you like thicker yogurt or greek yogurt, straining is required. Either:
    1. Line a colander with the straining fabric
    2. Hang the linked yogurt bag above a 2 quart bowl
       1. Using this method yields 17 oz. (weight) of yogurt and about 30 oz (fluid) of whey per half gallon of milk, or 4 234 calorie servings.

Some pictures of the process

Basic process. Note the most important step: take a bit of the milk for a white russian!

While coffee is being brewed, the yogurt is strained into greek style after a night of sleep allowed it to ferment and set.

I like really thick yogurt. Ok ok, my preferred product resembles yogurt cheese more than Greek yogurt!

Whey

After straining to thicken or make greek yogurt, about half of the volume of milk will remain in the form of whey. Whey is incredibly nutritious: packed with enzymes, probiotics and protein but also contains a concentrated amount of the substances that cause lactose and dairy allergies/intolerances. I’ll write a piece dedicated to whey in the future. For now, you can drink it as a probiotic, inoculate fermenting veggies, substitute it for water in recipes like bread or stock/broth for a protein (and calorie!) boost, spray it on plants to mitigate powdery mildew, add it to soil/compost as an acidifying fertilizer, or feed it to livestock or pets!

Final thoughts

Preface:

As this was my first attempt, I made a small batch in case I failed. This allowed me to use my crockpot and a soup pot as a double boiler. No incubator or specialized equipment was necessary. There is a lot of time required, but it is mostly passive. In the future, I’ll be upping the batch to 1 gallon of milk or more.

Secondly, our bodies are designed to digest fat as a primary food source while carbs cause the inflammation that was originally attributed to cholesterol and fats (and heart disease, high blood pressure). In fact, the human body produces cholesterol to repair the inflammation caused by carbs so high cholesterol is an indicator of a problem, not the problem itself (202 kB PDF Meta-analysis of 76+ studies). More fat in the milk correlates with more yogurt or cheese can be extracted. So don’t fear consuming fat, and use high fat milk for this process!

Lastly, yogurt doesn’t really “go bad” per se. Instead the tartness increases until it reaches vinegar levels. The fermentation acts as a preservative which is why we can leave it unrefrigerated, even more so warmed to the ideal growth temperature for spoilage microbes, for so long with no ill effects. The same can actually be said for milk which turns into yogurt, cheese or any of the fermented products that form staple foods in the Middle East (eg: kefir, laban) and Asia. Although when uncontrolled, potentially harmful microbe colonies can outcompete the desired ones. So as long as a reasonable amount of time has passed while the yogurt was refrigerated and there is no fuzzy discoloration, the yogurt is likely to reach an unpalatable tartness before it actually expires!