yoghurt - do you have to heat pasteurised milk so high?

[tootiemoonie]

all instructions for yoghurt making start with heating the milk to near boiling point, Why is this necessary when using pasteurised milk/ (or is it?)

[BBWCHATT]

Tootie -
I found this for you on the internet:

http://www.parentcentre.org.uk/learnjourn/inde x_ks2.cfm?ver=graph&subject=sc&subpage=teach&t ip=2

How to make yoghurt

You will need:

half a litre of milk
two tablespoons of plain yoghurt.
Start by heating the milk until it boils, then leave it to cool. (Boiling the milk kills any unwanted bacteria that might interfere with the yoghurt-making process.)
After about an hour and a half, when the milk is only just warm, pour it into a glass bowl. Add the yoghurt, whisking gently with a fork. The yoghurt contains the useful bacteria, and they now need comfortable conditions to breed and multiply. Cover the bowl with a plate and wrap a teatowel around it. Put the bowl in a cold oven and leave overnight.

The temperature inside the oven - normally just above room temperature - will give the microbes the right conditions to multiply.

In the morning, put the bowl in the fridge until the yoghurt is chilled and ready to eat. Now get your child to flavour the yoghurt by adding fruit, jam or honey.

Can your child explain why we need to kill the bacteria in the milk first, and what the useful bacteria eat?

If the unwanted bacteria stayed alive in the milk, they would eat it, but wouldn't turn it into yoghurt , and might be dangerous. When they are killed, the useful bacteria can then eat the milk and multiply. As they do so, they turn the milk into yoghurt.