Crème patissière: pleasure and pain of those days when I was learning to master the basic recipes of patisserie. Let’s be honest: I started well. I succeeded with crème patissière right away, at the first shot. The first thing I made out of that was a wonderful pie with raspberries. It was Ferragosto, and there was the usual family reunion lunch. My grandparents had prepared their most acclaimed cake: a sponge cake filled with custard and covered with baked meringue. Beautiful and decadent. It was their strong suit and it was very much appreciated among family members (and not only them). But that day of my adolescence something was going to change. I just had the idea of preparing that raspberry pie, who knows why. Maybe it was just an experiment to test the raspberries of the garden. It was a simple pie: base of shortcrust pastry, crème patissière and raspberries. Despite its simplicity, it was very well appreciated, much more than my grandparents’ cake, I must say. My grandpa didn’t bat an eye, but my grandma got almost offended that her masterpiece was overshadowed by a simple pie.
But after that first, unexpected success, crème patissière started to give me some annoyances. Precisely, it broke down: lumps formed and the liquid phase separated from the rest. Since that, our relationship was a kind of on-off: sometimes I succeeded with my crème, sometimes not. It was a grief for me and it made me anxious each and every time I had to prepare a crème. My grandma said it was because of my mood: you can’t make a good crème if you are sad! But my rationale mind was telling me that probably I wasn’t using the right method. Long story short: I was doing something wrong.
Thanks to my University studies, I understood more about emulsions. Since that, I started to prepare my crème more pedantically, but still I felt far from the infallible recipe. After a few researches and some reading, I understood a few key concepts…let me share them with you, please…
How do you make a crème patissière?
Crème patissière is an O/W (oil in water) emulsion. In order to make it, you need:
· Eggs: they act as emulsifier thanks to the presence of proteins and phospholipids. They contain also the fats forming the emulsion.
· Milk: it contains both water and fats forming the emulsion.
· Starch: it gelatinizes determining the thickening of the crème.
· Sugar: it serves only as sweetener.
Those are the basic ingredients, but we can add also other favours as vanilla, for example.
Whole eggs or just yolks?
Eggs act as emulsifier thanks to the presence of proteins and lecithin (a mix of phospholipids). Actually, lecithin is not a great emulsifier (proteins work much better in that sense), I tested it by myself, unfortunately…but it is a long story that will be told in another post :) When you warm up your crème, the proteins lose their globular structure, or to use a biochemist term, they denature. The native protein can be represented by a ball of wool, while the denatured one has a looser structure:
The denaturation allows hydrophilic groups to take contact with water, while the hydrophobic ones with fats. The proteins of albumen (ovalbumin and ovotransferrin, the most abundant, although we find also ovomucoid) coagulate at different temperatures. Specifically: ovalbumin around 85 C, while ovotranserrin around 61 C. Yolk coagulates around 68 C.
So, whole eggs or yolks? This was the question tormenting myself for a while. I’ll be honest: I have often used whole eggs. In this case, you will get a clearer crème patissière. Actually, most of the recipes require just yolks. Compared to egg white, yolk contains more proteins. Furthermore, it contains fats and pigments as carotenoids and lutein that act as coloring agents. Therefore, using just yolks allows obtaining a richer and thicker crème, with a darker yellow color. The amount of yolks varies a lot: from 2 to 8-9 per liter of milk.
Starch is a polymer made by units of glucose linked to each other. Depending on the type of bond between the glucose monomers, we have amylose (1→4 bond, linear polymer) or amylopectin (1→6 bond, branched polymer). The presence of starch is a difference between crème patissière and English custard, where starch is not included. Several types of starches can be actually used: regular flour, e.g., or corn starch, but also other types of starches. Their function is always the same: absorbing liquid, gelatinizing and making crème patissière thicker. Each starch has a different jellifying temperature. For corn starch is 75-80 C, while for regular flour you have to go up to 80-85 C.
How to avoid lumps?
When preparing a crème patissière, we start making a batter with egg yolk, sugar and starch. During this process, the starch grains get dispersed, namely they are separated into smaller grains. Starches are not soluble in cold liquids, but they gelatinize in hot ones around specific temperatures. When hot milk is added to the batter, the external part of the starch grains gelatinizes and the liquid diffuses slower to the core, which remains powdery and raw (here the lump formation). On the other hand, adding some cold milk to the batter, as suggested by Bressanini and This, will help the dispersion of the grains, which will reduce their diameter. Now, if we add the hot milk, the grain diameter is so small that the starch homogeneously gelatinizes. Long story short: no lumps ;)
To boil or not to boil?
You can bring crème patissière to boil. Actually, it is highly recommended in many pastry books. However, Di Carlo suggests to do not bring the temperature higher than 85 C, when the starch of flour gelatinizes. This precaution avoids that your crème patissière will get the unpleasant taste of fried egg. According to Pedrolli, boiling the crème allows inactivation of amylase, an enzyme present in the egg that hydrolyses starch and, consequently, determines the softening of the crème. So, just to be sure, I bring the crème patissière to boil and then I remove it immediately from the stove. If the crème keeps boiling, the coagulated proteins start to associate with each other into lumps: your crème patissière has just broken down. You can “save” it, by blending it, e.g. with an immersion blender. However, you won’t avoid the unpleasant taste of fried egg.
Still there? :) Great!
In the next post, I will give you the recipe for a good crème patissière. I wanted to do it today, but I think we covered enough. That’s all for today, I wish you a great week end! :)
Hervé This, Pentole e Provette, 106-108, Ed. Gambero Rosso
Hervé This, La scienza in cucina. Piccolo trattato di gastronomia molecolare, 69, Ed. Dedalo
Stryer, Biochemistry, 342, Ed. Freeman
Leonardo di Carlo, Tradizione in evoluzione, 278-281, Ed. Chiriotti
Dario Bressanini, Sui grumi della farina e dell'amido
Gaia Pedrolli, Problemi di crema