Transmission Zero

Introduction

Yoghurt is healthy, tasty, and is easy to make without the need for any fancy or expensive devices. This method uses only a vacuum flask, thermometer, and standard equipment which can be found in any kitchen. It will give you a delicious and thick plain yoghurt.

Required Equipment

The following equipment is required in order to make the yoghurt.

• Microwaveable measuring jug
• Kitchen scales (preferably electronic)
• Microwave
• 500 ml Thermos® or similar brand vacuum flask (ideally with a wide neck)
• Kitchen thermometer
• Funnel (optional)
• Sieve (optional)

You can use a stove to heat the milk instead of a microwave, but you will need to adapt the instructions a little.

Ingredients

The following ingredients are required in order to make approximately 520 g of yoghurt.

Normally the tablespoon of yoghurt would come from your previous batch, but of course this is not possible when you are making yoghurt for the first time. For your initial batch you can use yoghurt from your local shop, but it’s important to use a live bio yoghurt as these contain the necessary bacteria to turn the milk into yoghurt. Failure to get the right starter yoghurt will result in lukewarm milk rather than yoghurt! Always check the label to ensure it contains live cultures, for example Bifidobacterium longum, Streptococcus thermophilus, and either Lactobacillus bulgaricus or Lactobacillus acidophilus. If in doubt, Yeo Valley Natural yoghurt is a good choice and can be purchased in 150 g pots.

The milk can be whatever kind of cow milk you normally drink. Whether you use skimmed milk or whole milk, you’ll still end up with an excellent batch of yoghurt. It’s also possible to substitute cow milk for goat milk if you prefer. Note however that this recipe is not suitable for milk such as soya milk, almond milk, and lactose free animal milk.

If you want to change the size of the batch, you can scale the ingredients up or down as appropriate.

Preparation

Before getting started, ensure all of your equipment is clean by scalding it in hot water. Failure to do so could introduce other bacteria into the mix which will compete with the good bacteria in the yoghurt, potentially causing the yoghurt making process to fail.

Making the Yoghurt

Making yoghurt is a simple case of heating milk to denature the milk proteins and kill any bad bacteria, adding powdered milk to give it more strength, letting it cool down to the temperature required by the good bacteria, adding some live yoghurt, and then keeping the temperature constant for an extended period. The only complicated parts are ensuring you don’t overheat the milk (it will boil and get a skin), letting it cool sufficiently (to avoid killing the good bacteria you are about to add), and at the same time not allowing it to cool too much (the good bacteria won’t work efficiently).

Once in the flask, the process takes 6 to 8 hours. For this reason you may find it most convenient to prepare the yoghurt just before you go to bed, and put it into the fridge when you wake up (it won’t be cool enough to eat at this point). The longer you leave the yoghurt in the flask, the more the bacteria will turn lactose into lactic acid, and the more sour the yoghurt will taste. How long you decide to leave it is down to personal taste and experimentation.

Here are the steps to follow:

1. Pour 450 ml of milk into a microwaveable measuring jug.
2. Heat on full power for two minutes.
3. Stir the milk whilst adding 30 g of skimmed milk powder. Ensure all of the milk powder has dissolved properly.
4. Continue heating in the microwave, stirring it and taking the temperature every 30 to 90 seconds. Stop when the temperature reaches 82°C. Do not allow it to boil.
5. Cover the jug with e.g. cling film to keep dust out and prevent evaporation. Stir and check the temperature periodically until it has cooled to 42°C. This will typically take around an hour, but you could put the jug in a bath of cold water to speed the process up if you prefer. If the milk cools too much, gently heat it in the microwave again until it reaches 42°C.
6. Add the tablespoon of yoghurt and stir it in until it is well mixed with the milk.
7. Pour the mixture into a vacuum flask and put the lid on securely. You can optionally pour it through a sieve and funnel to ensure there are no lumps of undissolved milk powder.
8. Put the flask somewhere where it won’t be disturbed and leave it there for 6 to 8 hours.
9. The yoghurt should now have the consistency of jelly. If it is still runny, it probably isn’t ready yet.
10. Pour the yoghurt into a container. It may take a little encouragement to get it out of the flask, particularly if it doesn’t have a wide neck, but resist the temptation to poke around the flask with a metal spoon or anything which might damage the flask. The yoghurt may be a bit lumpy when it comes out of the flask, and may have some liquid (whey). This is perfectly normal and does not indicate how the final product will turn out.
11. Stir the yoghurt until it is smooth and creamy, then refrigerate it.

You can eat the yoghurt as soon as it’s cool enough to eat. It will last for several days in the fridge before the level of lactic acid reaches the point where it’s too sour to eat.

Flavouring the Yoghurt

I prefer the flavour of plain yoghurt, and like to mix it with cereal or seeds. You can of course flavour it with fruit, cinnamon, honey, or anything else you like. Just be sure to put some unflavoured yoghurt to one side if you intend to make another batch from it.

Straining the Yoghurt

If you like a really thick yoghurt which has a consistency similar to that of cream cheese, you can strain the yoghurt. If you pour the yoghurt into some muslin cloth and sit it above a container, the liquid whey will drip into the container leaving you with some very thick yoghurt.

Making More Yoghurt

Now you have made yoghurt, you can use it to make future batches of yoghurt rather than buying a starter from the shops. As long as you keep your equipment clean and don’t let the yoghurt become too sour, you can keep using a tablespoon of your previous batch (unflavoured) to make the next batch. If you want to wait longer before making your next batch, you can freeze the yoghurt until you need it. I’ve not frozen my starter for extended periods, but I’ve heard it will still be good for a month or so. Just be sure to let it defrost before using it.

If the yoghurt fails to thicken or tastes strange, it’s best to just throw it away and buy some new yoghurt to start your next batch off.

Nutritional Information

This is the nutritional information for 100 g of the yoghurt made with cow milk of varying fat content. It is based on the assumption that the weight of the whole batch is 520 g.