It’s not a secret that tetrapacked milk practically doesn’t go sour. It is pasteurised (as minimum) and it doesn’t have any bacterial culture in it. Many people (including my parents) buy special culture to make home-made yogurt. I was wandering if I could make yogurt with some natural fermenting agents, as our grandmothers did it: old school. For my experiment I used local dairy products you can find in any Quebec supermarket: 2% plane unsweetened yogurt, kefir from organic section (it’s a Russian originated yogurt type fermented drink, check out Wikipedia article on kefir), 2% and 3% milk and 0.25% buttermilk. I already knew that this tetrapacked milk doesn’t go sour by itself, but I was told by a friend that the buttermilk does.
Two days ago I set an experiment. In well-washed (but not sterilised) glass jars I mixed:
1) milk with buttermilk
2) milk with kefir
3) milk with plane yogurt
and 4) in the last milk jar I just throw one raspberry
My father told me to try raspberry. He said that raspberries, the same way as grapes do, provide a fine environment for "good" bacteria culture. This is why they can make raspberry wine (not my family, but other - qualified - people). I honestly didn’t believe in magic raspberry, but I have tones of milk, so I decided what the heck. I left the jars on my kitchen counter, covered with a cotton dishcloth for two days. And now I am happy to present the results.
1) Tetrapacked milk, mixed with buttermilk went sour and turned into a nice, but very low-fat clabber
2) Kefir successfully turned milk into itself – as predicted
3) Plane yogurt, that claimed having “active acidophilus, bifidus and L.casei cultures” hasn’t done flying squat! Milk didn’t curd at all
4) But the most spectacular result gave the raspberry. I used 3% milk for that jar and I made a yammy creamy very thick clabber! That was quite a surprise. Raspberry does work!
Conclusions. Don’t just believe what a package tells you. If you really want to eat dairy with active beneficent bacterial cultures – do a test. They can write whatever they want on the yogurt cup – but it is not necessarily true. You could easily be eating yogurt with long-dead cultures and wonder why it doesn’t work as promised. It’s that easy: wash a jar, mix a teaspoon of yogurt with pasteurised milk and see if your yogurt is actually alive.
Disclaimer: I am not responsible for anything you manage to grow in your kitchen. Please be advised that home-based uncontrolled bacteriological experiments could produced unwanted and potentially harmful result. You can accidentally grow "bad" bacteria (or fungus), so please be smart and don't drink anything that doesn't look or smell right to you.