I love yogurt and I eat a lot of it. I have been making my own yogurt for a while. Not only it is healthier, because I do not add any sugar and you don't know what else is added to commercial yogurt, but I feel it is very cost effective.
Fresh milk is very easy to come by in the UK and is a relatively cheap staple. Yogurts are often more expensive by the same volume. The price difference between milk and yogurt seems greater if they are organic.
For example:
1kg of Yeo Valley Organic Yogurt is £2.75.
2.2 litre of organic milk will cost you £1.85, and will make about 2kg of organic yogurt.
I'll let you do the maths and compare.
At some supermarkets, I often see unsold organic milk that is very close to the expiry day reduced in priced to as low as £0.10 for a litre. They are still the same quality milk and you are going to heat treat it anyway to make my yogurt. In this case, the savings are even greater.
You do need a small batch of plain unflavoured natural live yogurt as a starter culture. 150g of Yeo Valley Organic Yogurt costs £0.55, and has enough to make your first 3-4 litres of yogurt. Some of the new yogurt can be saved to be used as a starter for the making the next batch of yogurt. So as long as every time you are sucessful, you may not need to buy yogurt again.
To convert milk to yogurt, you do need to spend the extra time and energy. If you have a yogurt maker, you are already sorted. But if you don't have such an expensive kit and you do have a lot of time, you can make it using simple appliances, like a saucepan, a kitchen hob, a sterilised container with lid, and sterilised thermometer.
Remember to keep your tools and containers sterile to minimise the introduction of unknown foreign bacteria to the fermentation process. I often find that is enough to give a good clean then sterilise by running it through or immerse in boiling water or very hot steam.
Method:
I have adapted the various methods i have found online:
- If using fresh milk, first heat the milk very slowly to 85 deg C (185 deg F), without burning it. If you don't have a thermometer, you can tell if it has reached temperature with some experience by the way it starts to bubble and steam up. This will kill off any unwanted bacteria and denature the proteins for a good consistency. If using UHT milk, this step is done for you. Fresh milk is only pasteurised at 60 something deg C, which does not seem enough.
- Pour the heated milk in a sterilised container. This step is needed in case some milk has stuck at the bottom of the saucepan and you don't want to ferment in the same pan. Allow it to cool to 38-40 deg C (102 deg F). If using UHT milk, you just need to warm up to 38-40 deg C.
- Once the temperature is 38-40 deg C, add and mix the starter yogurt culture from existing yogurt to the milk. Generally, I find that 75g is enough to ferment 2 litres. If you do not have a thermometer and your container is metal, you can tell if the temperature is right when you can hold on to the container for 10 seconds without feeling it is too warm to have to let go.
- Keep warm with something insulating. I have a 3 litre food flask to keep it warm, but if you don't have one you can wrap it with foam wrap/towels/paper, and place in a cardboard box. Careful not to spill if your lid does not seal.
- Depending on the temperature and the amount of starting culture, it will take 3-6 hours to ferment. I often get away with leaving it overnight for 8 hours while I sleep, as my rig will only keep it at the optimum temperature for 3-4 hours anyway.
- You will know it is ready when the milk is no longer runny. Scoop a portion in a sterilized jar and seal to use as a starter for your next batch. Put them in the fridge to chill before enjoying.
The taste is optimum once cooled.
The yogurt once made can keep for 1-2 weeks if stored properly in the fridge. If you see solid and watery whey separation, not to worry. You can stir it back in, or pour the whey out to for thicker greek style yogurt. If removing the whey, it does not need to be wasted as you can drink it or use it in bread making for example.
My result, very smooth and tasty:
Enjoy it plain, or with your favourite filling, be it jam, granola, honey or whatever you fancy. You can even use it in curries and smoothies. Chop up some mint, herbs and throw it in some yogurt with a pinch of salt, mix and then you have an awesome sauce that go well with BBQs and kebabs.
There was one time I failed, the yogurt turned out to be grainy and lumpy in texture because I added the starter while the milk was too warm.
The resulting taste and texture will really depend of the culture. It will often taste the same as the original natural live starter yogurt in its plain state. Avoid using yogurts that has flavouring or other fillings in as a start. Stick to something plain but quality for your starter, something that will likely result in great tasting yogurt that you enjoy, without having to restructure the texture and taste with additives like what some cheap commercial yogurt makers have to do. I say this because I once tried using a cheap brand of natural yogurt as a starter, and the end result was palettable, but had a consistency of runny mucus, nothing like as smooth and delicate as the picture above.
Some probiotic cultures from the likes of Actimel and Yakult often produce a more cheesy tasting kind of yogurt, especially if you ferment it too long. You then see why they have to mask the flavour with a lot of sweeteners. Tip: if your yogurt over-ferment and it gets too cheesy, it's not the end of the world: drain the whey through a cheese cloth, and you will end of with amazing spreadable soft cheese. Optionally add some salt for taste. Nothing goes to waste.
The more you make, the more experience you get, the easier it becomes and the more efficient you will be at making the best yogurt and fitting it in around your lifestyle. An alarmed digital thermometer will allow you to do other things while the milk is heating or cooling and then sound when temperature is ready. This will save you from constantly checking. So sure if such invention exists. But if you are using the same heater, volume and cooling method every time, then time it takes to heat and cool to temperature should be consistent enough every time so you can just set a timer once you have worked out the timings. The total active time you need to spend tending the yogurt making process can be as low as 30 mins including the cleaning, and everything else is just waiting time.
In the long run, if you eat a lot of yogurt like me and my family, as well as cost benefit, there is an environmental benefit too in terms of the number of yogurt pots you saved from using. Also every time you successfully make a something of your own, you get a great sense of achievement.