How can I get homemade yoghurt to thicken properly?

Question

Pretty much always when I make yoghurt myself, the homemade version comes out much thinner, much more liquid, than the store-bought yoghurt that is used to produce my yoghurt. How can I make it thicker? Should I increase/decrease the temperature? Add other ingredients (I just heat milk, add yoghurt, stir it, and then put it away in a closed container for 10 hours or so)?

Any general ideas on how to make yoghurt thicker?

Edit

Current Procedure:

• I take the milk from the fridge and I start heating this directly.
• Right from the start, I also add the yoghurt, straight from the fridge as well.
• I'll continuously (slowly) stir the milk
• Once it reaches about 40 degrees Centigrade I'll take it off (but perhaps my rustic measure with the temperature is off)
• I then put the lid on the pan I used to heat the milk, wrap this in blankets, and put it away overnight.
• Next morning, yoghurt is ready - but quite liquid.

Answer 1

Your method is wrong. Look at this site.

1. Avoid UHT (Ultra Hight Temperature) pasteurized milk.
2. Heat the milk without the yogurt. You want the milk to reach about 90ºC for pasteurization.
3. Keep it at 90ºC for 20 minutes.
4. Let the milk cool down to around 40ºC before adding the yogurt.

The site has more info.

The reason your method isn't working is that you heat the milk together with the yogurt. Heating will create hot spots where the temperature can become really hot (killing the yogurt ferments). By letting the milk cool down to the desired temperature, there will be no hot spots, and all the yogurt ferments will be happily alive.

Answer 2

You have milk based yougurt. Try this:

INGREDIENTS:

Whole milk, double-cream both in measure 50/50 1L/1L (use non UHT the best you can get)

your yogurt starter (buy best pure yogurt you can get, one 150-200ml is sufficient)

METHOD:

Bring mixture of milk/cream to boil and leave to cool down to 53-54 degrees celsius Add your yogurt and mix well (whisk is here great tool)

You can transfer it from the pot into termo-botles or just leave it in room temperature. It's bacteria and will work in lower temperatures, will just take longer (room temperature) Keep it away from drafts and dramatic temperature changes. (Kitchen next to central heating is good, or pre-heat oven over night to 50 or less degrees celsius, just for an hour and switch off and leave your yogurt pot in the oven).

So if you start morning, the next day morning your yogurt should be done. Yo can just use same pot and help them to stay warmer by wrapping it in cloths or blankets.

Than put your yogurt into a sterile glass jars and for at least 2 days leave it to carry on in fermenting slowly in the fridge.

PRECAUTIONS:

Hygiene (everything needs to be clean but no residual cleaning products)

Temperature (54-55 should be the maximum while adding your starter, you can pour a bit of mixture into bowl and whisk that small amount with starter and than add it into your pot)

Answer 3

Very simple, wrap it in a few layers of muslin cloth (aka cheese cloth) and hang it suspended over a bowl in the fridge for a day or two.

Answer 4

There are many myths surrounding yogurt making:

• UHT milk is bad. This is simply not true. I have made yogurt with whole fat UHT milk for years and it comes out nice and thick. In fact even a high quality whole milk powder will also make a lovely, thick yogurt.
• Store bought yogurt will always be thicker because of additives. Also not true. My yogurt is as thick as a high fat sour cream and contains no added milk powder, gelatine, etc.
• You need many hours of 'fermentation' to make yogurt. Again I don't agree. My yogurt sets in 3-4 hours, after which it goes in the fridge to cool and finish the culturing process.
• The milk must be exactly x temperature when you add the starter. This is only somewhat true. As long as the milk is at or below 45°C it is fine. If you can stand the temperature, so can the bacteria—ie, if you can hold a finger in it for ~10 sec, it's ok. The temperature will stabilize during the incubation period, so even if it's too low, it won't matter.
• Everything must be sterile. This is only somewhat true. Clean everything carefully, of course, but you are adding a starter with billions of cultivated bacteria into an ideal environment for it to grow. It will easily dominate other bacteria that happen to get in. That said, an over-long incubation will give other bacteria a chance to express themselves, so best to avoid that.

The keys to making good thick yogurt are:

• Protein. The milk becomes solid because of a protein in the milk, and for that to happen, the protein must first be heated to above 70°C. I heat it to 75-80°C for just a few minutes and it still turns out very thick. A milk with high quality protein will make a great yogurt.
• Incubation temperature. If you want to make good yogurt in 3-4 hours, it must be incubated at a steady 40-45°C. A lower temperature might also produce yogurt, but you are in a race with other bacteria, so the quicker it's done the better. Buy a 75 cent indoor thermometer and start looking for ways to create the right temperature environment.
• Generation time. Try to bake a new batch every 4-5 days. After a week in the fridge the bacteria are starting to suffer and will not be as strong and active when introduced into the next batch. A short generation cycle will let you go on making yogurt with the same culture for dozens of generations.
• Sugar quantity. This is my own personal guess based on bread making, etc. A little sugar will boost the bacteria, but too much will slow it down. I use 2 tbsp per litre of milk and it works very well. Tart with a hint of sweet. Up to double this amount should be fine but more could affect it. Like I say I'm guessing here but it seems to make sense.

Two final notes.

• The "water" that separates out of the yogurt is whey protein—generally seen as a very healthy thing to eat. A firm yogurt will let you pour it or spoon it off if you don't like it, but there's no reason not to just scoop it out with the rest and stir it back in.
• Fat content is important, but the milk protein is what will make or break the yogurt. I have made a very thick yogurt with skim milk powder or skim milk with added skim milk powder. It's all about milk solids. Of course a 3.x% whole fat milk will produce a tastier yogurt, because milk fat is oh so tasty!

Answer 5

Besides fixing the process by not heating the yogurt, i suggest a cheat: add 2 tablespoons of powdered milk for each liter of milk.