Orange Curd Using Confectioner's Sugar
I'm a huge citrus fan, love lemon curd. I'm thinking of trying orange curd. I've read that due to less acidity, orange curd needs a spritz of lemon in order to "curdle" (thicken up) properly. But I like the idea of making a truly orangey orange curd. I'll look around for blood oranges and Sevilles, which I've read have the proper amount of acidity.
But - what about substituting confectioner's sugar for the granulated? I guess there is only one way to find out - do it myself, but before I do, I was just wondering if anyone here has tried this.
(By the way, I picked up from Julia Child a kind of contempt for confectioner's sugar in icings due to the cornstarch, but that would be cooked off during the cooking process of making the curd. I think that's the reason I feel guilty enough to ask about using confectioner's sugar. I really admire Julia, and she seemed to have a special dislike of this 'convenience food.')
I do a lot of curd making at work, always starting with the same lemon curd recipe. With orange I sub half the lemon juice for orange concentrate, all the lemon zest for orange. If it still isn't tart enough for you, add a bit of citric acid towards the end of cooking. I strain mine to get the zest out for a silky smooth texture. It often isn't orange-colored (the yellow of lemon curd comes from egg yolks, not lemon) so I add a tiny bit of red color to help the eye know it's orange-flavored.
I've never noticed a difference in thickness between the different curds (lemon, key lime, orange, passion fruit) I do mine in a bain marie, put all the ingredients (eggs, yolks, juice, zest, sugar, butter) in the bowl, cook over med low heat for a long time (several hours, but I'm usually making gallons at a time) stirring every so often to keep it from making a skin on the top.
I don't actually have it in percentages, I just make the same size, a half size, or a double size. I'll give you an 8th size and the full size.
3 whole large eggs
6 egg yolks (this should be 6 1/2 and 2 1/2, but 6 and 3 should be fine)
6 oz sugar
4 oz lemon juice
3 oz butter
3 T lemon zest
20 whole eggs
3 # sugar
2 # juice
1 1/2 # butter
2/3 cups zest (about, I use a frozen zest with lemon oil added and use a disher to measure, but the disher is about 1/3 cup and I use 2 scoops)
Put everything in a metal/heatproof bowl, set over pot of simmering water. Cook until thick, whisking occasionally (with a full batch I do every 10-20 minutes, with a small batch, every 2-3 would probably be better)
You might need to add more water to the pot. When it's thick (like thick sour cream) remove from heat and strain. Put plastic wrap on the surface to avoid a skin as it cools. Store in the fridge, or freeze for long term storage.
re: Hank Hanover
Actually, I've been reading up about this - curd is an emulsion, and I wonder whether the acidity really matters so much after all. Perhaps it is how the butter is added. Some say that you should beat in the butter after the sugar-citrus-yolk mix has been sufficiently heated. Rather like a sweet mayo. It makes sense to me but as they say - there is only one way to find out.
I didn't know that about the acidity of oranges. I've made orange curd from (I think) valensia oranges and it curdled just fine.
I don't think it would matter whether you use granulated or powdered sugar sine it all melts anyway. I've only ever used granulated though. If there's cornstarch in your sugar that would thicken the curd somewhat when it cooks.
According to Beranbaum (and others), the acidity affects the thickness of the curd. I looked around and found this:
" In addition, the citric acid in the lemon juice denatures proteins, providing the typical texture and mouth feel characteristics of the lemon curd (Schmidt, 1983). By denaturing the protein, the emulsion stability of the lemon curd is increased."
Perhaps Valencias have enough acid. Also, some curd recipes use only egg yolks and some use the whole egg. I wondered about that. Maybe the egg white helps to make a firmer curd.
No reason to use confectioners' sugar, unless, of course, you want to. Pay the cornstarch addition no mind, it's a very small amount, 2% of the total product, IIRC.
As far as wanting the most orangey of orange curds, throw in a bit of sour orange juice, which will work to raise acidity instead of lemon. Oranges vary in acidic content, as do lemons. You can find sour oranges in markets now. I assume you're also adding zest?