Reader Belinda wants to know why pastry cream and most other custards are thickened with starch while another similar cream, Bavarian cream, is thickened with gelatin. I didn’t see that one coming this morning, Belinda! That’s a great question. Let’s see if I can answer it. You make pastry cream by creating a thin custard, then adding starch and heating it to the boil — done! With Bavarian cream you again prepare a thin custard, melt gelatin into it while it’s still warm, allow it to cool somewhat, then fold in whipped cream.
Of the two, Bavarian cream tends to be both lighter and firmer. It’s frequently molded, which means it needs a strong gel under the hood. My feeling is that it would take an awful lot of flour to create a starch gel of an equivalent strength, and that would affect the Bavarian cream’s flavor as well its texture.
Another factor is surely heat. You need very little heat to melt gelatin and setting it requires no heat at all. It simply needs to cool. As it does so, you can confidently fold something like whipped cream into it without fear of the heat melting the butterfat and collapsing the foam. The gelatin simply disperses into the whipped cream, then sets. You couldn’t do the same thing with a hot starch custard and whipped cream.
Certainly you can fold a chilled starch custard like pastry cream into whipped cream — and I often do, the result is diplomat cream. Diplomat cream has a lightness comparable to Bavarian cream, though it’s far looser, more flowing. It could never stand up on its own. So I guess that’s why you use gelatin instead of starch in a Bavarian cream: when you need a gel that is extremely light but also very strong.
But I’m going to noodle that some more today, Belinda. You really got me thinking…and it’s giving me a headache. Thanks…I think.