But yoghurt IS acidic - @ least compared to milk or cream.
& I thought yoghurt sauces need to be kept @ a low temp. to prevent curdling...?

Okay, that is already far more than I knew about the subject. So high temp curdles yoghurt? The simmering chicken stock wasn't more than 210F or so.

I've had scalloped potatoes curdle a number of times. Thankfully I wasn't serving it to anyone else but hubby and me.

Add a little corn starch, cook and blend with a hand blender. That should "cure" some curdling.

A high power ultrasonic transducer can emulsify some curdling, if you have one. :-)

dcarch

My recipe for Hungarian goulash recommends tempering the sour cream with a tablespoon of flour before adding to the hot stew, to prevent curdling. I would imagine the same would help yoghurt.

You asked about other sauces as well. They can break from too much heat also. In fact, too much heat or too rapid a heat change is the main reason sauces break. They can also break if they're left unattended for too long, possibly because of a heat differential between the bottom and top when they're not stirred.

I make béchamels with low fat milk or nonfat condensed and they work fine. I've read that it's the protein that's important, not the fat.

1. Most of these sauces are actually emulsions. Stirring a lot can help more than anything, especially if you're adding with something acidic like wine.

2. Put the milk/cream next to the stove to warm up while you're starting the base, so that it's not as big a temperature difference.

3. Don't put in a lot of cold at once. You're trying to maintain a steady temperature, so don't chill it. Start with a good dollop, stir, and when it's well incorporated add more.

4. Keep the temperature down. Don't let it bubble.

Exception: if you're making a cheese sauce, turn it down right when you see the first bubble and add the cheese right away. I forget why. Something changes in the milk, I think.

I've always thought that you add cream/yogurt at the very last minute - you don't "cook" it.

Another recipe that is famous for curdling is homemade tomato soup. These are some notes I've compiled in my "Book of Odd Knowledge" over the years on the subject.

-Add tomatoes to milk, rather than milk to tomatoes.

-Have both milk and tomatoes hot when they are combined.

-Don't "hold" the soup --- serve it as soon as ready.

-Thicken either the tomato juice or the milk before they are combined.

-Evaporated milk is the least likely milk product to curdle; non-fat dry milk is the most likely to curdle.

I'll add that I've made homemade ricotta using whole milk + lemon juice or citric acid - acid most definitely causes milk protein to separate from the whey & adding an acid is often the first step in cheese-making...

Yes....I would have waited until the thighs were done simmering in the sauce to add the yogurt and I might have blended in some flour into the yogurt before adding it to the dish with the heat off.

Teresa

This post was edited by teresa_nc7 on Tue, Jan 20, 15 at 8:35

John, I had a similar experience just the other day however I couldn't have waxed so eloquently about it then, or now. Your post is such a sad tale that I almost feel guilty that it made me smile.

So the main takeaway I'm getting is to have the dairy at room temp, add it gradually, and for extra anti-curdle precaution mix in some starch (flour, corn starch etc) and/or temper before adding. Basic idea is to reduce temperature shock and further bind the protein/fat with starch.

And have a high power ultrasonic whatchamacallit at the ready.

I usually simmer the sauce after adding the dairy (yoghurt etc) to develop and meld flavors before serving. But I suppose I could try marinating the meat in the dairy before cooking it.

Marinating chicken in milk is a classic. :)

Another classic is chicken marinated in yogurt!

I gather that enzymes in yoghurt make meat more tender. Not that chicken really needs tenderizing, but can't hurt.

>>Not that chicken really needs tenderizing, but can't hurt.>>

Well, that depends. I got a 6-lb fryer last week for roasting, and that chicken must have been on a treadmill, or maybe it ran marathons during the day when nobody was looking!

I even checked the package to make sure I hadn't bought a "free-range" bird by mistake, because those are often more muscular. But nope, it was a plain ole assembly line chicken.

I always brine my chickens, but this particular clucker would have been MUCH better if I'd slathered it with a yoghurt marinade!

I'll never forget my first curdling. I was in my mid 20's and after a brooklyn stoop chat with an elder neighbor, i decided to make his verbal recipe that his grandmother and mother had made. (he had never made it or cooked at all)...thick pork chops, single layer, seared, covered with onion, then braised in milk to cover. Two hours (ish)...then a can of whole tomatoes, squeezed in hand and the stem butt removed...(some cussing always when the careful squeezing always hit the wall a bit)...another hour or two and it was done.
It was a time before i attempted it. Then, with 6 thick pork chops to fit our pan i seared, added onion, then milk, ...checked it and it was a curdled mess after just a few minutes. Horrified i was wanting to toss it out. DH said not so fast..."lets call Mom". MIL being a brilliant cook just laughed and said to simmer and reduce the liquids and caramelize the onions. The milk solids will firm and become nutty and said, "i gave you Marcella's books. Read her recipe for pork braised in milk!".
....I thought the milk was soured and bad. Old. I still find it odd but having made cheese i understand now.
(I had wanted to give a meal of my neighbors recipe to him since i made more than for the two of us but did not)
It was good, with reservations, at the time).
...i still thought we were eating spoiled milk, : )

Marcella Hazan's recipe is amazing.

"By the time the loin is cooked the milk should have coagulated into small nut-brown clusters on the bottom of the pan. (If it is still pale remove the loin, uncover the pot, raise the heat and cook briskly until the milk bits darken.)"

Adding tomato was just another element and we have made it many times since. Usually a frozen garden tomato or two.

Here is a link that might be useful: pork loin braised in milk