How to make Yogurt

Yogurt is very healthy, especially if made with live cultures. It assist in keeping the digestive system healthy, reduces urinary tract infections, increases calcium uptake and stimulates the immune system. Yogurt is an essential part of my daily breakfast. Unfortunately I am one of the increasing number of people who are allergic to cows' milk. I can use goats' milk though and therefore decided to start making my own goats' milk yoghurt. For those who are allergic to any kind of lactose: you should give it a try with coconut milk.

What you need

1. Fresh cows', goat or sheep milk.
2. Live yoghurt cultures (100 ml plain yogurt or 1 pack of powdered culture per liter milk)
3. Thermometer that can measure to at least 50*C
4. Clean stainless steel pot with a heavy "sandwich" bottom
5. Whisk
6. Oven or other source of heat that can keep the yogurt warm for several hours
7. Yogurt containers (glass or food quality plastic)
8. Refrigerator

The Why....

Use only fresh milk to avoid infection with other bacteria. Also don't use longlife milk as it is basically "dead" and will be diffcult to activate.

You need live yogurt culture that can multiply in the milk and turn the milk into yogurt by turning milk sugar (lactose) into lactic acid. The lactic acid makes milk products more easible digestible, which is important as the stomach of adults doesn't provide for milk digestion any more (unlike the stomach of an infant). This live culture can be bought as a powder or in form of a live yogurt. I have tried the Togg's plain goatmilk yogurt and it works.

Yogurt Culture

Yogurt cultures are most active at a temperature of 44*C. Therefore the milk must be heated to and kept at this temperature for several hours. Overheating would kill the yogurt culture and lower temperatures would inhibit the process. Normal fever thermometers only measure up to 42*C, therefore it is necessary to obtain a food thermometer. I prefer a digital one as it doesn't break as easily as a glass thermometer and also allows instant temperature readings.

Digital Food Thermometer

When making yogurt you have to be very hygienic to avoid infection of the milk with foreign bacteria. Always wash your hands and equipment thoroughly. Equipment should always be rinsed with cold water first and then washed with hot water afterwards. Equipment can also be desinfected with a little JIK in the water. Avoid contact of the milk with strong smelling liquids or smoke as that will change the taste of the milk. The pot should have a thick bottom as milk will burn very easily in thin pots/sufurias. If milk burns the protein in the milk crumbles and the texture of the milk becomes unpleasant. It will also take on a burnt taste. 
After the yogurt is cultured (turned sour) it will still be quite liquid. It needs to set first. For this it needs to be cooled for several hours, best overnight. This will also stop the culturing process.

The How...

Delicious & healthy homemade yogurt

The milk at boiling point

Step 1: Boil the milk

I boil my milk to kill any unwanted bacteria as it comes from some neighbours cow in various containers and I can't be sure it isn't "a little bit dirty". If the milk comes from your own cow and you use it immediately and you are also sure about your hygiene standards, it is also fine to make raw milk joghurt. 

Step 2: Let the milk cool down to 44*C

Use a thermometer to ensure you introduce the culture at the right temperature. If you are using yogurt instead of powdered culture add it to the milk at a slightly higher temperature as it will cool the milk down.

The sensor inserted into the milk

The digital thermometr showing 44*C

Step 3: Add the culture

Use a whisk to stir in the powdered culture or the plain live yogurt.

On he left: Adding live yogurt culture

Above: Stirring it into the milk with a whisk

Step 4: Pour the cultured yogurt into glass or plastic containers

The yogurt sets better if left to set in small containers than in one big bowl. I use small food-quality plastic containers with a screw lid. But you can use even used and washed yogurt pots or drinking glasses.

Step 5: Close the containers and place them in a dish with warm water

The containers with the yoghurt should have a lid to avoid infection with bacteria and smells. The containers are then placed in a shallow dish holding warm water. It should be just enough water to reach up to where the yogurt is filed in the containers. This will help to keep the temperature stable and avoid burning.

Fill the dish with warm water

Above: The yogurt pots are closed with lids and placed in the dish filled with warm water so that the water reaches about the same level as the yogurt in the pots

Step 6: Keep the yogurt warm

Leave the yogurt in the oven for 1 - 4 hours at about 50*C until it is well cultured and has reached the taste you like. It will still be a bit too liquid at this state. It only sets properly after a few hours in the refrigerator.

If you don't have an oven wrap the yogurt container in some thick towles or keep it inside a styroform container or even a small cooler box (add warm water). This will maintain the temperature for long enough to culture the yogurt.

Left: the water-filled dish with the ogurt pots in the oven.
Above: Keep the temperature at around 40*-50*C. The temperature does not have to be exact, as long as it does not get over 50*C or cools too much

Step 7: Cool the yogurt overnight

For the yogurt to properly set (get thick and stiff) it needs to be cooled. This will also stop the culturing process so that the yogurt does not continue to get more and more sour. For this a refrigerator is needed.

The yogurt in the fridge

Step 8: Flavouring the yogurt

To add flavour you can stir in vanilla sugar (to make vanilla yogurt) or any fruit concentrate, like the passionfruit concentrate (check out my older posts). You can also use a tablespoon of your favourite jam or even honey. I personally just eat the plain yogurt with some fresh fruits.

Extra Hint...

Greek yogurt is mild, extra thick and creamy yogurt made from ewes' milk. Ewes' milk is richer than cows' milk and gives Greek yogurt it's wonderful texture. To make a yogurt similar to Greek yogurt you can let the yogurt culture at 44*C for a few more hours, but this will produce not only a thicker but also more sour yogurt. To make a thick and mild yogurt you have to add powdered milk to the fresh milk before boiling it. For 1 liter of milk you should add about 250g of powdered milk. Stir it in well so it dissolves completely, then continue as usual.