Cooking with Buttermilk - guh!
Quick food science question, and yes, I *did* poke around a little before posting I promise. I had a clean out the fridge dinner-for-one last night and wanted to throw together a sauce for some frozen tortellinis. I had some fresh mushrooms and frozen peas/carrots etc.. so went "cream sauce" route rather than "red sauce" route. Alas... no cream! No half and half! So I could make a milk based bechamel foundation.. maybe go overboard on the butter component.. but HEY.. LOOOK! A fresh pint of buttermilk I hadn't used... and a hunk of Maytag blue cheese to melt into it! That's going to be tangy, creamy goodness!
Technique: Olive oil... saute some prosciutto scraps... add some garlic... then mushrooms and saute until they give off their liquid and the sauce tightens back up... then I add the frozen peas/carrots and get this warmed up...<smugly feel proud of my skillz> and here comes the buttermilk... and then... YUCK!! It separates immediately! The milk solids curdle up and I have a soupy, murky, gross looking mess. I try to re-constitute it with the blue cheese chunks melting in but it's a lost cause. It didn't taste much better than it looked.
So I assume that the acidic properties of the buttermilk caused the separation / curdling (anyone who has ever added cream to a wine-based sauce too aggressively knows what I'm talking about) but why is buttermilk "stable" in the fridge and yet separates with a bit of heat? If I had brought it to a boil, etc... I wouldn't question.. but this was immediate upon pouring into the pot.
Hopefully someone learns from my mistake!
Just like yogurt, buttermilk will separate at the drop of a hat (or heat). It's not a stable product where heat is concerned. While I know that adding cornstarch to yogurt will stave off curdling for a bit, I've never heard it used as far as buttermilk is concerned. I'm thinking there's simply not a reason for stabilizing buttermilk since there are other options.
I'd simply consider this a learning experience.
I do use Buttermilk every so often, but the application is somewhat different - I "soak" sometimes a Venison roast ( to tenderize) or a Beef roast ( for a milder version of Sauerbraten) overnight fully submerged in Buttermilk in the refrigerator. This Buttermilk ( or fresh Buttermilk/finishing a carton perhaps) is added to the liquid covering the meat during the simmering process, after it is seared in usual fashion. I still will thicken the sauce with a bit of flour at the end, and I have never seen the sauce curdling, when Buttermilk is used that way.
No roux or starch? Buttermilk, while thick, is usually nonfat. In a sense you added sour nonfat milk to your dish. However Indian cooks often add yogurt to their sauces. I don't recall the details on how to minimize separation with yogurt. In some cases they go ahead and let it separate.
While I've used buttermilk in baked goods, and added a few splashes to a dressing, I've never tried to cook with it.
Yeah, I think it's the acid as well and you are right on the money. It's the same thing that happens when the half & half (or milk, cream, whatever) is slightly starting to get old in the coffee shop and the acid levels build up and it curdles immediately when you pour it into your hot coffee.
Ironically, if you had indeed gone the bechamel route with the flour/roux as a binder your buttermilk would probably have held together.
I'm absolutely NOT a food scientist, but I would guess that the acid is part of it -- and the fact that with the fermentation of the buttermilk, there's something with the proteins that would cause them to bind immediately. (I believe they're already starting to bind with the fermentation...)
not sure -- but the more I think about it, I can't think of ever having seen a warm buttermilk sauce of any kind -- plenty of cold sauces and dressings, but never a warm one.
thank you for all the replies. I think the key learning I picked up was Sunshine842's comment that the proteins "bound" in the heat and acidity. I'm still not understanding it end-to-end (as in- why is cream stable.. what causes the curdling) but I think I can see an approximate root cause.