Thermodynamics rocks

8 Jul

Wanna make homemade frozen yoghurt but you don’t have a ice cream machine? No problem, just turn to science!

Would you believe that making a batch of frozen yoghurt (or ice cream if you like) is faster if you do it by hand, the old fashioned way, than with an ice cream maker? Seriously!

Ice and salt. That’s your Ice cream maker right there! Here’s how it works:

When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment. By adding salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder and that is how your ice cream freezes. Using rock salt is better as it takes longer to dissolve in the water, allowing more time for your yoghurt to freeze. Read more about this HERE.

I could not believe how easy it was. I had to try it.

First, you have to use greek yoghurt simply because it’s nice and thick and rich. It costs a bomb: about RM14 to 18 a small tub. What? Well, make some yourself. How? Pour a tub of regular yoghurt (about RM4 for 150g) onto a cheese cloth; wrap it into a ball and allow to drip, in the fridge (you need a tall container to collect the whey) for about 6 hours.

Done? Unwrap the cheese cloth and you will see a wonderful smooth ball of rich yoghurt. Oh my. The texture is slightly cheesy and the consistency is thick. Oh my.

Next. Mix sugar or honey or as I did, maple syrup to the yoghurt: to your taste. And, if you like, vanilla extract (just a drop).

Transfer the yoghurt into a ziploc bag and seal tight. Put the bag in another ziploc bag and seal tight.

Put enough ice to fill a huge saucepan. Cover the ice with salt (about 1/2 cup). Place the bag of bagged yoghurt in the ice (surround it with salted ice as much as possible) and cover the container. Shake, shake and shake so the yoghurt is kneaded by the ice. Shake for about 10 mins and leave the yoghurt to sit in the ice a further 15 mins or so. More if you like it really frozen solid. I liked mine frozen but not hard (kinda like how I like my martinis shaken, and not stirred) so I didn’t let it sit longer. NOTE: It took me some time to get this shot — I shot it outdoors under the morning sun so the yoghurt melted a wee bit 🙂

REMEMBER your zip lock bag has to be really sealed tight so the salt does not seap through.

Is that it? You betcha. Scoop out your yoghurt and eat it immediately. You will, like me, probably wanna lick the zip lock bag … not one bit should be wasted! Only hitch is you can’t make a huge batch at one go. Unless you have gallon-sized zipper bags and a huge stock pot. You can make enough for a party of four or five. Or four or five servings just for you 🙂

Isn’t science just delicious?

Veggie Chick


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