Custard curdling, then becomes creamy as it continues cooking?

[Cahoot]

Recently I made a batch of pastéis de nata, and when I pulled it out of the oven, let cool, then bit into it, realized that the pastry was a bit underdone, but the custard filling had curdled with the oil having separated from it. Since I figured there was nothing to lose, I put the batch back in the oven to at least fully cook the pastry, but to my surprise when I tried it after it cooled again, the custard was creamy and fully emulsified. Is there a scientific explanation for how a custard can become curdled during baking (which I presume would only happen because of overbaking), but then become creamy again after continued baking?

 

[Norcalbaker59]

Recently I made a batch of pastéis de nata, and when I pulled it out of the oven, let cool, then bit into it, realized that the pastry was a bit underdone, but the custard filling had curdled with the oil having separated from it. Since I figured there was nothing to lose, I put the batch back in the oven to at least fully cook the pastry, but to my surprise when I tried it after it cooled again, the custard was creamy and fully emulsified. Is there a scientific explanation for how a custard can become curdled during baking (which I presume would only happen because of overbaking), but then become creamy again after continued baking?

If it was undercooked, then most likely, it was not curdled at all. Rather, it was in the process of cooking, and what you saw as a partially cooked custard when you removed it from the oven. A curdled custard will look very lumpy. When it is very curdled, it will look like cottage cheese.

 

[Cahoot]

If it was undercooked, then most likely, it was not curdled at all. Rather, it was in the process of cooking, and what you saw as a partially cooked custard when you removed it from the oven. A curdled custard will look very lumpy. When it is very curdled, it will look like cottage cheese.

It's entirely possible that I visually misidentified it, I remember that the fat had separated (you could literally dab the oil off the custard with a paper towel), but I can't 100% say if it was lumpy or not. I think it was lumpy, but could be misremembering. However, I actually baked another batch yesterday where it was overbaked and curdled, and I feel like it had the same texture.

In fact the batch which I made yesterday was entirely a different problem. I used this recipe, but while the recipe calls for baking at 240°F (465°F) for 15-20 minutes, I baked at 475°F for 30 minutes, and even then the top wasn't very well browned - I had to turn the broiler on and leave the pan under the preheating broiler for 1.5 minutes to get it more satisfactorily browned. Since in the batch I talked about in the original post I baked for well beyond the specified time and still ended up with a creamy filling, I hoped it would turn out okay even with the extra cooking.

The two differences from the recipe was that I baked in disposable aluminum molds and I used regular puff pastry instead of the special pastéis de nata puff pastry (the entire reason why I make these are to get rid of excess puff pastry lol), but I don't think either of those would have an effect on how the top colours. I think my oven only heats from the bottom and that may be the cause, but in previous batches where I used higher heat and/or baked on a higher rack, I had issues with the crust edges completely burning before the bottom/sides of the pastry were even cooked.

 

[Norcalbaker59]

@Cahoot. 475°F is pretty high for most pastry. Even for a regular pie that’s pretty high. I emailed you a recipe that bakes I think it was 420°F. Something like that.

yes when a custard curdles it is unmistakable because it looks very lumpy and feels very gritty.

Getting the caramelization without causing curdling is difficult. The amount of sugar in the custard is key. The sugar will trigger the Maillard effect.