Wednesday, June 16, 2010

DIY yoghurt

We really like yoghurt. Until I started making it myself, plastic yoghurt containers would account for at least half of the contents of our recycle bin, and I'd often wonder how 1L of yoghurt could cost about $5, when I could buy 1L of milk for about $1.20.

A while back I bought an EasiYo yoghurt maker. It really does live up to its name - just put cold water and the contents of an EasiYo packet (containing powdered milk and yoghurt culture) into the 1L plastic jar and shake. Fill the incubator flask with boiling water up to the indicator line, place the jar onto the baffle in the incubator, put on the lid and wait 8 hours. That's it. The varieties I tried tasted pretty good too. However, the packets of powder are not much cheaper than ordinary supermarket yoghurt, there still is packaging, and I imagine it takes a lot of energy to turn fresh milk into powdered milk.

Time for some DIY experimenting with making yoghurt from scratch using ordinary milk and yoghurt culture, I thought!

First I tried extrapolating from the EasiYo incubation method. I heated the milk first and put it in the EasiYo jar, then cooled it to roughly the temperature of cold water. I then added in starter culture (a few spoons of commercial natural yoghurt). Then I copied the EasiYo incubation method - boiling water up to the indicator line in the incubator, with the jar sitting on the baffle so that only the bottom 2-3cm of the jar was sitting in the water. Don't do that! The result tasted alright, but the consistency failed badly (it was drinking consistency). I still don't understand why the EasiYo incubation method works perfectly with their powder, but fails with ordinary milk and culture. Both essentially have the same ingredients and cultures, so I would have thought the same incubation environment/temperature would work for both.

In any case, after a bit of experimenting, I've now discovered what does work well. I'm still using the EasiYo 1L jar and the incubator flask, but I don't use their baffle in the incubator and I use cooler deeper water for the incubation. (Of course you don't need the EasiYo incubator flask and jar. Any sort of small esky or similar can be used for incubation, and the yoghurt itself can be in any sort of container that has a well-fitting lid.) The entire process takes around 30 minutes, but most of that is waiting time (while the milk heats and then cools). Hands-on time is maybe 5 minutes. I usually do the dishes at the same time so I am "there" in the kitchen to keep an eye on the milk temperatures. Obviously this method is not quite as quick or easy as making EasiYo yoghurt, but now that I've streamlined the process I find this almost as easy...and I prefer the more natural taste of my DIY yoghurt!

How it is done...

Preparation: Remove the starter culture from the fridge and set aside to warm a little by the time you will need it. Place the incubator in an out-of-the-way corner so that it won't be moved at all for 10 hours or so. Put on the kettle - you'll need about 1.5L of boiling water. If you are using an EasiYo flask as your incubator, remove the baffle (the red plastic part closest to the window in the picture below) and instead place something about 6cm high (I use the small heatproof dish seen in the picture below) in the bottom of the incubator so that the top of your jar will end up roughly near the incubator top.

Killing bacteria: Place the jar and lid on the sink, put your thermometer (to be used later) in the jar, and fill the jar and lid to overflowing with boiling water.

Heating the milk: Pour some boiling water into one saucepan and place another saucepan on top to mimic a double-boiler. Pour about 930ml of milk (assuming you will be using a 1L jar) into the top pan. Use a medium heat to keep the water boiling slowly.

After about 8 minutes, the milk will develop a subtle cooked milk smell and small bubbles will form around the wall of the saucepan. At that point, stir it with and ordinary clean spoon (the hot milk will kill any bacteria). If you can feel that milk solids are starting to stick to the bottom of the pan, and if stirring the milk makes it look frothy all over (as in the picture below), then the milk is hot enough.

Cooling the milk: Pour the hot water out of the jar that the yoghurt will be made in and just shake out the drops (don't dry it). The water will still be rather hot, so its easiest to use two hands, but you don't want to contaminate the thermometer by putting it down anywhere. I sit the thermometer in the saucepan of hot milk simply as a place to put it temporarily. Pour about half the water into the incubator ready for later, and discard the rest (I use it to top up my washing up water).

Pour the hot milk into the jar and put the thermometer in the milk. Then, put the jar in a container of cold water - you can apply permaculture-like principles and use the saucepan you used to heat the milk as the cold water container (to soak it to facilitate washing it). Add a large handful of ice (if you have it) to the cold water, and periodically swirl the jar around in the water and stir the cooling milk with the thermometer. Once the ice has melted I start checking the thermometer every minute or so - I'm always amazed at how quickly the milk goes from too hot to too cold at this stage! I aim for 46C (115F), but usually overshoot the mark and end up with the milk being cooler. I've had successful batches of yoghurt with the milk temperature at this stage being anywhere between 46C (115F) and 43C (110F). (I've not tested outside that range.) The milk temperature at this stage is only one factor that affects the consistency of the final product, but I think I've had my best consistencies when this temperature was about 44C. Last time I timed it, the cooling process took 16 minutes.

Making the yoghurt: Remove the thermometer from the milk, wash it, and place it in the hot water in the incubator. Remove the jar of milk from the cold water and tip in roughly 2 dessert-spoons of starter. (You don't need to measure it, but sterilize and cool your measuring spoon first if you do.) Tip the boiling water (that was) out of the jar lid, and screw it on tightly. Shake the jar well.

Check the water temperature in the incubator and add cold water to adjust it to about 46C (115F). This does not have to be too precise - I've had successful yoghurt with temperatures a degree or two higher and lower than this.

Place the jar in the incubator, adjusting the water level so that it is just below the lid of the jar.

Put the lid on the incubator and leave it undisturbed for somewhere between 8 and 24 hours. The longer you leave it, the more tart the yoghurt will become. (I like it best at around the 10 hour mark.) After the yoghurt has incubated, remove the jar from the incubator and place it in the fridge.

Yoghurt and dishes all done!!

Saving starter for next time: Always save some starter as soon as you first open a new jar of yoghurt. Place a small clean jar and its lid on the sink, put a spoon in the jar, and fill the jar and lid to overflowing with boiling water. Let sit for a few minutes, then pour out the hot water and shake out the drops (drying these items would risk contamination). Allow to cool to roughly room temperature. Then spoon several table-spoons of the new yoghurt into the jar, attach the lid, and keep in the fridge ready for next time you make yoghurt. I believe the culture can be stored for up to a week in a fridge, but since I make yoghurt every 2-3 days, I've never tested keeping it that long.

Other starter options: If you've not made yoghurt before, or if you've not made it for a while, you'll obviously need to use something other than yoghurt from your previous batch as starter culture. You can buy a small container of commercial natural yoghurt (unsweetened and unflavoured) and use some of that as starter. Again, make sure you remove the portion you will use as starter as soon as you open the container. Or, if you happen to have the EasiYo kit, you can make up one of their unsweetened and unflavoured varieties in their usual way, and use a little of that as your starter. (I've made successful batches of yoghurt using Farmer's Union European style natural yoghurt, and also using the EasiYo Greek style yoghurt.)


  1. I have recently bought the Easiyo Yogurt Maker and made my first batch with their flavoured yogurt powder, loved it!
    Now i'm trying to make another batch with soy milk and a bit of starter from my first batch, hope it works!

    1. I've not tried making yogurt with soy milk. Please do let us know how it goes!