- Fresh Whole milk (preferably raw, never ultrapasteurized)
- A good organic plain commercial yogurt with live cultures (7 Stars, Stonyfield, Brown Cow)
- Glass Jars (wide-mouth quart mason jars work very well)
- Stainless steel or glass pot large enough to hold all of the milk
- Candy thermometer (needs to reach to 150 degrees F and down to 80 degrees)
- Pour milk into the pot and turn on medium heat, stirring occasionally to prevent burning or sticking.
- Gently heat the milk to 105-110 degrees if raw or 130-150 degrees if pasteurized.
- Remove the pot from heat and allow to cool to between 95-105 degrees (placing the pot into an ice water bath greatly speeds this process)
Keeping the milk warm:
- The next part depends on your method of keeping the milk warm. You can get creative here. You will need to keep the milk warm for at least 24 hours to break down all lactose.
- Warm water bath method:
- Place 1 tablespoon of commercial yogurt into each quart mason jar.
- Pour warm milk into each jar and stir well.
- Run warm water into a crock pot monitoring the temperature to reach 95-100 degrees.
- Plug in the crock pot and turn it to its lowest setting possible.
- Place the sealed mason jars into the water bath.
- Monitor the temperature of the water and adjust the heat setting as necessary (if you cannot get the temp low enough, your crock pot will not work).
- Food Dehydrator – same as above except place mason jars into dehydrator set at the desired temperature for 24 hours.
- Warm oven – put a thermometer in the oven and see what temperature the oven reaches when the oven light is on or with a lamp in the oven. If you can find a way to keep the oven between 95-105, then proceed as in the dehydrator method.
- Bread warmer or other warm heating pad:
- Leave the milk in the pot in which you heated it.
- Add 1 tablespoon of yogurt for every quart of milk and stir well.
- Place the pot onto the warm surface and monitor until you are sure the milk will stabilize at the correct temperature. Layers of towel between the warmer and pot can reduce the temperature if needed.
- Cover and let sit for 24 hours.
- Yogurt maker – follow the company’s directions but allow to sit for 24 hours.
- Warm water bath method:
- After staying warm for 24 hours, place the yogurt into jars if it is not already in them and store them in the fridge. Yogurt will stay good for quite a while (a few weeks). It also thickens and tastes better chilled.
- This yogurt will be much thinner than commercial yogurt as there are no thickeners added. It may also taste a little sourer than you are used to—this is what real yogurt should taste like and it becomes quite pleasurable when you get used to it.
- Do not heat the yogurt over 110 degrees or you will kill the bacterial cultures and denature important enzymes.
- The 24-hour fermentation gives the bacterial culture plenty of time to break down all of the lactose in the yogurt making this type of yogurt appropriate for those intolerant to lactose. Note that commercial yogurt is only fermented for 8 hours.
This process takes some getting used to and requires a little experimentation to get it right. All of my batches have been delicious, though, and continue to improve with experience.
Note that using older milk will often result in the milk totally separating into curds and whey. If this happens, strain the curds (solid part) out of the whey and soak up excess moisture with a clean towel. You now have yogurt cheese which you can use like sour cream. Keep the whey in the fridge for making other fermented treats such as sauerkraut or kimchi or for preserving home-made mayonnaise (see Nourishing Traditions by Sally Fallon for recipes).