Tempering egg yolks - why?

Rickard_Modig_19323

Hey! I'm learning more about pastry and tempering egg yolks is something that really confuses me.

The process is described as - if you want to mix e.g. boiled cream and milk for an anglaise - you would stir a bit of the milk into the egg yolks while stirring, then after the temperature of the egg mixture rises you would mix it all back into the hot milk. The purpose would be to reduce the risk of curdling the eggs.

I have two theories about why this process is used and I'd love to have them either validated or busted!

My first theory is that if the difference in temperature of the mixtures is greater, the heat flows more quickly into the cold eggs and they may denature before they disperse, sorta like you want to disperse corn starch in cold water so it doesn't hydrate before it's spread out evenly in the mixture. At this point I'd like to mention that while I did take thermodynamics in college, I got a D. So this may be well off.

My other theory is that while you want to bring for example an anglaise to about 82 degrees centigrade, egg yolks start to denature around 62 or so. Maybe you want them to be spread out evenly through the whole thing before the mixture reaches even that temperature.

If the cream/milk is below 62 (or whatever the exact temperature is) when you mix the two, you should be able to just dump the eggs into the warm milk and it shouldn't make a difference. This is actually how a colleague told me he makes crème brûlée.

I also don't see why this procedure should at all be necessary if you're making anglaise, and why you wouldn't just mix eggs, sugar and milk/cream and heat it while whisking - unless you want to boil the milk to steep e.g. vanilla.

Basically a lot of recipes I find are different in this regard and I keep getting frustrated because I don't see why. Would love to be enlightened.

Chris_Young_80640

Yes, I think most recipes are artifacts of how they got made in a really busy kitchen where folks are impatient. You are correct that simply mixing everything together and then heating makes life much easier. This is definitely the way to do things when adapting a recipe to sous vide cooking.

I basically believe your first theory is the more correct explanation of the problem. Essentially, reduce the delta T between the eggs and the cream to reduce the rate of heat transfer to avoid local hot spots of curdled proteins.