Friday, December 17, 2010

Petri Dish

People have been making yoghurt for centuries. The process of its creation is more like a science project than it is cooking. Think of milk as containing sugar (giving it sweetness), protein (for structure) and water (making it a liquid).

Basically, bacterial culture is allowed to multiply in milk and ultimately ferment it. The bacteria feeds off of the lactose (the sugar found in milk) and produces lactic acid.

In science, when an acid is mixed with a protein, the protein denatures (i.e. changes form, coagulates, or curdles). Now that lactic acid is present in the liquid, the protein in the milk changes form to produce the solid-like texture of yoghurt.

Here is how it works practically. Begin with a quantity of milk. You want to make the milk into a suitable environment for the bacteria to grow. Bacteria are living organisms, and like humans, they require a certain temperature to live. Too hot, and the bacteria will die. Too cold, and the bacteria will not thrive.

Warm your milk until it becomes frothy on the sides. Set the milk aside and let it cool to the approximate temperature of your body. This should take only about 10 to 15 minutes. The most simple way to test if the milk is the right temperature is by sticking your finger in it. You should be able to hold your finger in the liquid comfortably for a few seconds. You shouldn't be able to feel a difference between your temperature and the temperature of the milk.

Now it's time to introduce the bacteria. Bacteria starters can be readily found and bought over the Internet. However, the easiest starter to use, is...wait for it...yoghurt. That's right! We already know that yoghurt contains active bacteria. So, you can use a spoon full of yoghurt that you have left over or a store-bought yoghurt as an effective starter.

Note: You only want to use a plain yoghurt as your starter. Do not use flavoured or fruit yoghurt for this purpose.

As a general rule, you only require one dessert spoon (a heaping tablespoon) of yoghurt per litre of milk.

Mix the yoghurt into the milk well and place it in a container. You may cover the top of the container with cellophane wrap, if you wish.

Now, you want to leave the mixture in an environment where it will be kept still and is a little warm. I have learned that the perfect place to make yoghurt is in an oven. To provide the little warmth the bacteria needs to multiply, simply keep the oven light on.

Your yoghurt will be ready between 4 and 12 hours. The longer you leave your yoghurt, the more tangy it will become.

Try the following suggestions:
- save money and make your own pro-biotic yoghurt by using store-bought pro-biotic yoghurt as your starter culture
- create your own flavoured yoghurt by mixing in fresh/dried fruit or jam/jelly
- sweeten your yoghurt with a little honey and have it as a healthy snack
- use the yoghurt to make a refreshing smoothie
- make cream cheese by straining the yoghurt (click here for my entry on making your own cream cheese)
- make goat milk yoghurt/goat cream cheese by using goat's milk instead of cow's milk
- use your homemade yoghurt in recipes for cakes, cookies, muffins, pancakes, dips, marinades, etc.

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