Why did my yogurt turn out weird?
I made yogurt yesterday. Just like I do on a regular basis, but it turned out weird. And I just cannot figure out why.
Brought 36 ounces of organic 1% milk to almost boiling. Let it cool down (maybe not enough) and whisked in a 6oz container of stoneyfield non-fat plain yogurt.
I put it in a large pyrex bowl and put it in the incubator. Bowl fits perfectly and there is no outside air getting in.
I left the yogurt to set for about 13hours. It set and had a pretty thick texture (maybe a little grainy) but it is not tart like yogurt AT ALL. It is very smooth and creamy tasting.
I like tart yogurt! It tastes like yogurt. This does not taste like yogurt, but does have the texture.
What happened? Is it safe to eat?
Do you always use Stonyfield as your starter? I find that when I make yogurt, the final product tastes like whatever I used for my starter, so if you like tangy yogurt, you need to use a tangy yogurt for a starter. Fage makes a good starter and gives a nice, tangy finished product.
As you stated, you may not have allowed the milk to cool long enough before adding your Stoneyfield yogurt starter. If it thickened up, then there were probably still enough bacteria to ferment, so not all of the bacteria were killed off by the heat, but enough to slow the fermentation process down.
If you keep the yogurt it in your incubator for a few more hours (up to 24 hours total), you will probably get the tartness that you are looking for.
The lactic acid produced by the bacteria are what thicken and coagulate the milk proteins. After thickening, more lactic acid is produced as the bacteria continue to metabolize the lactose. So in the future if it is thick, but not tart, then leave it longer.
You probably managed to maintain a few live bacteria because you were using a large ratio of yogurt starter to milk. For 36oz of milk, you should only need 2-3 Tablespoons of yogurt starter (or roughly 2oz of Stoneyfield yogurt from a 6oz container).
Generally, Stoneyfield and Danon are good options for store-bought yogurt starters as long as they are used well before their expiration date.
In regard to using a tarter yogurt to make tart yogurt, this is not necessary. Different commercially available yogurts will have slightly different combinations of live active bacteria, but the main two that all will have are Lactobacillus bulgaricus and Streptococcus thermophilus. Those, and time, are all you need to make a thick and tart yogurt. I've forgotten about yogurt in my incubator for longer than 24 hours and it gets super tart.
If you do want a tarter and thicker yogurt like Fage or Chobani, once you finish fermenting a batch of yogurt, strain it through a fine weave cheesecloth or thin fabric for a few hours and you will have a thicker and tarter greek yogurt.
This is a good analysis. To it, I'll add:
1. Looks like you heated your milk too high. Up to 180-185 F but no higher.
2. Your organic milk --was it pasteurized using UHT? Try to find organic milk pasteurized at a lower heat method.
3. Too much starter, I think. About 2 T. would have been right.
4. Heated milk should cool down to 110 F before adding starter.
5. Check temp of incubator -- too hot or too low?
6. A longer incubation time will increase tartness.
Good luck. You can read more here:
We made successful yogurt every other day for years using UHT milk. What made it work so well, was that we wouldn't reheat the milk. It is the lack of shelf stable UHT milk in the USA that has forced us to buy our yogurt. We'd take the milk straight from the pantry, a spoon full of dried milk powder and a scrape of the the previous days yogurt. When scraping the previous day's yogurt, we'd get sampling of top of the container, middle of the container and bottom of the container. If we'd didnt get several strata samples, it wouldnt work as well, for as long. We'd maybe have to buy a yogurt starter once every 2 months, and that would be from a Turkish or Indian yogurt.
In one flat, our kitchen was poorly insulated, and on cold winter nights, we'd find that yogurt didnt set properly.
For more yogurt wisdom: find sam's posts on the subject. He trouble shot many people's yogurt problems successfully.
It's fascinating that you had such good success with UHP/UHT milk but I guess it makes sense considering you were using dry milk powder to thicken the yogurt. My general understanding of UHP milk is that it is hard to coagulate because the long and high temperatures alter the proteins beyond the point of no return.
Like you, I generally do not heat pasteurized milk but I also do not add dry milk powder because I like a good drinkable yogurt. It still thickens, but not as much as heating it up.
I've gotten away from having to buy yogurt starter cultures regularly by using an heirloom Bulgarian yogurt that should last indefinitely if properly cared for.
Yes, the high temperatures of UHT changes the protein structure so much it results in poor coagulation.
But...the other issue is flavor. UHT kills flavor, kills the milk's flavor complexity -- one of the more ironic things since we purchase organic milk for its additional flavor complexity. All for naught when the organic milk is pasteurized via UHT.
You want to purchase milk that has been as gently pasteurized as possible for the most flavor.
re: maria lorraine
I think there might be something to this uht milk issue. I have never used organic milk before this batch. I made a second batch last night using the same milk and noticed it was ultra pasteurized. I used a few tbs of fage as the starter this time and let it set for about 20 hours in my incubator. It still had a very very mild flavor, but is a bit more tart. Thanks for all of the input.