The bacterial cultures grow best at temperatures between 100-130 degrees. Your yogurt wasn't warm enough.

Try warming your mixture on a heating pad or in a cooler filled with 120 degree water and leave it undisturbed for another 4 to 6 hours (or until it is the thickness you want).

Malna - thanks. I picked the Claudia recipe because it's a traditional no-thermometer method. She says to boil the milk, let it simmer for 2 minutes and cool util it's possible to leave a finger in it and count to 10! I kept checking with my finger and added the yogurt - I think - when the milk was stil VERY hot but I did manage to count to 10.

But you may be right. Maybe the finger test is too subjective.

I'll warm the mixture when I get home. Hope it works.

I wonder if you are confusing making kefir and making yogurt.... The method you describe is how I make kefir.

There are three stages, or what is called the 3 T's, to making perfect yogurt.

1. Temperature for heating the milk, or milk mixture (add-ins like gelatin powder, dry milk powder, sweetener, flavoring, etc.).

Bring the milk to 190-210-degrees F (just under boiling). It will be covered with tiny bubbles under the protein film that develops on the top of the milk. This temperature destroys "bad" bacteria. "Bad" bacteria can prevent curds from forming. Heating the milk also prepares it for rapid fermentation.

2. Temperature for cooling. Cool milk to 110-115-degrees F. This is the ideal temperature for for adding the culture/starter. If you don't have a thermometer for checking the temperature, use this old-time method. Dip your finger into the warm milk and count to 20. If you can stand the heat, the milk is ready. If you are going to make a lot of yogurt, I'd suggest getting an instant read thermometer.

At this point, your starter is at room temperature in a small bowl, and you add about 1/3 c. of the warm milk to the starter and mix together. Then you add the milk/starter mixture to the rest of the warm milk and mix well so the starter is thoroughly mixed into the milk.

Note: The temperature window for adding the starter/culture is between 110-115-degrees F. If you add the starter at the cooler end of the temperature window, the yogurt will have a mild flavor. Adding it at the upper (warmer) temperature, the yogurt will be more tart. This a good thing to remember for different uses. Children tend to prefer mild yogurt, or if you are going to use it in a dessert, you may like mild yogurt better. If you are going to drain the yogurt and use it as yogurt cheese or in a dip, tart yogurt may be your preference.

3. Temperature for incubating. As malna pointed out, there is a range of temperatures. Below 105-degrees F the "good" bacteria in the starter become less active and take longer to grow. Over 120-degrees F will destroy the bacteria. Try to maintain a temperature around 110-degrees. You'll also get better results if the temperature is constant.

--One tablespoon of yogurt may not be enough to ferment 3 cups of milk - it depends on how active the cultures are and how old the yogurt is. I usually use 3 T. per quart of milk. I also like to use Stonyfield Farm plain yogurt because it has 6 live cultures while other brands of yogurt only have 2 cultures. You can freeze your starter yogurt in portions (I freeze it 1 T. per cube in an ice cube tray and pop them out when frozen and store in the freezer. Thaw in the refrigerator, and bring to room temperature just before using it for making yogurt.)

These days I prefer making kefir because it's not as temperature sensitive as making yogurt, and it's better for you than yogurt. Using real kefir grains, all you do is add them to milk - cold from the refrigerator (I also make coconut milk kefir). Allow it to sit at room temperature (away from sunlight) to ferment anywhere from 12-24-hours. I've included a link to Dom's Kefir Insite if you are interested in fermenting kefir. The biggest challenge making kefir is finding a source for real kefir grains. Kefir grains last forever. They continue to grow and make more.

-Grainlady

Here is a link that might be useful: Dom's Kefir Insite

I also think you have a problem with temperature. If it's too hot, the yogurt won't thicken well either, it kills the beneficial bacteria which pretty much negates the reason I eat and make yogurt.

I put mine in my dehydrator, easy to keep the temperature steady, but Elery did his in a small cooler with warm water and then wrapped in a towel and it worked fine.

I start the next batch with the end of my current batch and find that as time passes my yogurt becomes less thick and more sour.

Yogurt has pretty much reached its maximum thickness after 10 hours, so it won't thicken further by leaving it on the counter, at least not appreciably.

Use that batch for baking and try again, after a couple of successful batches you'll be more comfortable with temperatures. Maybe you could freeze it in portions and use it in smoothies.....

Mine is thick enough to mound up on a spoon, but it took a few tries to get there.

Annie

Yogurt tends to be a fickle beast for me. I can follow the same process and sometimes it sets in four hours and sometimes it doesn't set in 12 hours. But, I agree that the temperature is key. It does need to stay around 100 degrees once you've let it cool down.

My 'failed' yogurt goes into smoothies, so it's not a total waste.

If you want thicker homemade yogurt:

--Longer Initial Heating. Bring to 200-degrees F. and hold for 20-minutes or longer.

--Let ferment longer - around 7-hours.

--Strain (drain) it for Greek-Style yogurt. A good yogurt cheese maker is a good tool to have if you like to drain yogurt, and a good alternative is a 4-cup permanent coffee basket filter or cone-shaped permanent coffee filter.

--Add 1/2 c. non-fat dry powdered milk per quart. Mix in just before heating it. This is especially helpful if using low-fat or fat-free milk.

--Add 1 t. unflavored gelatin powder per 1-quart of milk.

Odds and ends....

1. When you drain yogurt, the greatest proportion of whey drains off in the first hour. If you can only drain your yogurt for 5-10 minutes, you will be surprised how it will improve your finished product.

2. A cup of yogurt gives up 25% of its volume in 5-minutes - a pint gives up 18% - and a quart only 12%.

3. Definitions:
-Drained Yogurt. Yogurt that has drained for about 10-minutes.

-Thick Yogurt. Drained for at least 30-minutes.

-Yogurt Cheese. Drained for 8-hours or longer. It is the consistency of cream cheese and will hold its shape.

-Yogurt Cream. Heavy cream made into yogurt by the addition of 1-teaspoon of yogurt to 1/2 pint of cream. Good substitute for creme fraiche.

-One quart of yogurt will yield approximately 1-1/3 c. of yogurt cheese (about 2 c. of whey is drained off). One quart of yogurt will yield about 2-1/2 c. of thick yogurt (about 1-1/4 c. of whey is drained off.)

4. If you add too much yogurt/starter to the milk, it may result in sour, watery yogurt.

5. After fermentation begins, don't move or bump the yogurt because it can destroy the curd.

6. What to do with the whey....
-add it to soup
-mix with vegetable or fruit juice
-mix with water (or coconut water), lemon juice and some chia seeds for a healthy replacement for a "sports" drink

7. Better Jell-O....
Mix one small box of Jell-O (sugar or sugar-free) with 1-cup hot water. Mix until it's dissolved. Add 1 c. yogurt. Stir until mixed. Chill.

If you aren't a fan of Jell-O, make a mixture using 100% fruit juice + unflavored gelatin to equal 1-cup, add 1 c. yogurt.

-Grainlady

Grainlady and Annie - thank you so much for the detailed info and tips. I've printed it all and will try again. I'm very keen on making yogurt at home and your posts are a tremendous help to me.

Sorry for my belated reply. The weekend here in Israel starts Friday and I have a computer only at work, so didn't see your posts till now. Sunday is the beginning of the work week here. It was great seeing your posts first thing in the morning :)