Pastry Cream Conundrum

Reader Helen writes with a very interesting problem:

I’ve had a pastry cream disaster that remains a mystery to me. I’ve been making it with no problems for a long time. Just made 4 batches 2 weeks ago. Today, I tried it 3 times and every time it curdled as soon as it came to a simmer. I’ve never had this problem before and usually simmer it for 1-2 minutes to make sure to kill the enzyme in the yolks that thins out the starch as the cream sits. The only thing I did differently today was use all new ingredients (milk, cream, and eggs). I tasted milk and cream and they didn’t taste spoiled. I noticed that my corn starch expired 2 years ago, but it worked fine 2 weeks ago, so I can’t imagine it went bad all of a sudden. Here is my recipe and procedure: http://www.beyondsalmon.com/2014/07/pastry-cream.html

It’s pretty standard stuff. When the cream curdled, it looked like broken mayo with fat oozing out. The only thing I can think of as a bit unusual is that my eggs were very fresh from a local farm. I know that would be terrible for hard boiled purposes, but I’ve never heard of the age of the egg effecting pastry cream. Any ideas where I might have gone wrong?

Very interesting problem you have there, Helen. Any time there’s curdling of any kind I always think about heat first. Could the heat have been higher than normal? If so it’s possible that the cream on the bottom or sides of the pan might have been hotter than normal even though the whole mass hadn’t simmered yet. Whisking might not have helped much in that case. That’s the simplest explanation.

Still, from your description it sounds more like a broken emulsion than a curdled custard (cooked egg proteins usually form small grains). You see this with buttercreams when there’s a temperature disparity between the butter and the meringue. I see from your formula that you like to add butter to finish your pastry cream. Had you added it by this point? And if so might you have added faster than normal? Or might it have been colder than normal? That’s another possibility.

Barring those two possible causes the eggs are the next most likely suspect. Custard, like hollandaise and mayonnaise, relies on the emulsifiers found in egg yolks to remain stable. The main emulsifier in egg yolks is lecithin, a fatty substance (a so-called phospholipid) that’s responsible for keeping the oil-in-water custard emulsion smooth and even. The thing is, lecithin levels aren’t necessarily constant from egg to egg. They can fluctuate depending on the diet of the chicken. Some very interesting recent research from Israel (where researchers have been working to develop a low-cholesterol egg) has demonstrated that dramatic changes in egg fat levels can be achieved with relatively minor adjustments to chicken feed. Those studies were focused specifically on cholesterol, though it wouldn’t surprise me a bit if a similar principle applied to a fatty compound like lecithin. That said, my suggestion is to go back to grocery store eggs which come from chickens that have a more consistent diet.

Those are my best ideas, Helen. Anyone else have any theories?

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8 Responses to Pastry Cream Conundrum

  1. Helen Rennie says:

    Hi Joe,

    I don’t know how to thank you. Problem solved. I went out and bought all new ingredients and still had the same problem. Then it occurred to me that I was only making half of the batch. I’ve done that once in the past without trouble and assumed it would be ok. I must have gotten lucky. I make a full batch and it came out fine. I am guessing the sides of the pan must have been overheating when I was doing half the batch.

    If you don’t mind, a few more follow up questions. I make my pastry cream in a 2 quart saucier (a saucepan with sloped sides). This avoids the cream sitting in corners inaccessible to the whisk. Is that the best pan for pastry cream or does the one with straight sides work better? I’ve never seen a recipe specify what kind of pan they want you to use? Do they expect you to get into the corners with a rubber spatula once in a while when using a pan with straight sides or does it somehow work out fine with just whisking?

    Thank you so much for turning me into a better baker :)

    Cheers,
    -Helen

    • joepastry says:

      And here I was getting all fancy on you…just goes to show the most direct solutions are always the best! Regarding the pan, the sloped sides are intended to speed evaporation and make sauce reduction easier — but they do help you reach the corners of the pan as well. They aren’t essential for something like pastry cream, but I’d call them a nice-to-have!

      Cheers,

      - Joe

  2. Great advice. I have found that fresh eggs are best and have noticed a difference when they are older.

  3. Kathleen says:

    Dear Joe,
    I made “too much” pastry cream 7 days ago, and would like to use the rest of it to fill some eclairs in two days. Assuming pastry cream was properly boiled and stored, how long will it last? Have you ever re-boiled pastry cream to kill the microbes?
    Much thanks,
    Kathleen

    • joepastry says:

      Hey Kathleen!

      7 days is the max for keeping food if it hasn’t been reheated (to the boil) according to commercial sanitation rules. Which is not to say that the leftover pastry cream isn’t edible in your case, but you’ll definitely want to make sure it looks and smells OK before you eat it. Sadly re-boiling it isn’t possible…or well it is possible but the boiling will probably cause the starch gel to fail to a large extent. But there’s no harm in trying in this case, is there? What is there to lose? Assuming you can bring it back to a steady boil for a minute or so, it will be usable for several more days. Let me know what happens if you decide to try!

      - Joe

      • Kathleen says:

        Hey Joe,

        I did try it, and it ruined the texture. I did not attempt to re-thicken it by adding anything. I just pitched it and made more. Ah well!
        Thanks,
        Kathleen

        • joepastry says:

          Yeah I figured. It was worth a shot if it was headed to the trash anyway. Thanks for reporting back, Kathleen!

          - Joe

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