Wednesday, October 15, 2008

Experiments in the theatre of Ice Cream....

Physics, chemistry and cream.

To egg or not to egg. That is the question.

Heres the short version. For some of the science see below.....

Lessons learned....

Custard based creams are definitely smoother.

Strain the custard, gently.
Small containers are best.
Watch the custard like the family priest at a kindergarten.
Stir the custard, stir the mix.
Powerfreeze is the boss. Minus 25. Minus 18 is the bare minimum.
Pre chill the made mix in the refrigerator.

A quick flick through Harold McGee (On Food and Cooking) clears up some of the science.

The basic elements

Ice Crystals, Air, Concentrated Cream.

In this post

Ice crystals.....

Absolutely necessary for the structure of the ice cream, but also a common issue if they become too big. The addition of eggs slow down ice crystallisation. They make for a smoother ice cream, without the gritty texture you get from large, clumped together ice crystals (unless you scramble them). This is also the idea behind freezing the ice cream as quickly as you can. The faster you freeze it, the more even the ice crystal formation, and the smaller they are.

The aim is to make them so small they are imperceptible. It's also the reason behind not thawing and refreezing. Stirring helps with this, as does prechilling the mix in the fridge. Stirring breaks up ice crystals, spreads them out, encouraging the creation of many more but smaller crystals, and also helps introduce air into the mix. A final help is freezing the mix in several containers, giving a larger surface area exposed to freezing temperatures, and speeding up the freezing.

This is the recipe I used (available in full on their website), taken from the Murphy's Ice-Cream recipe book (the Book of Sweet things). The addition of egg yolks (taken fresh from the chickens out back) to the mix made it especially creamy and velvety - as did freezing it in smaller containers. The texture was far superior to the Tessa Kiros Caramel Ice Cream of last week.

One addition I would make to the recipe - when the custard thickens, chill it in an ice bath immediately, stirring all the time. It scrambles like a bastard.

Below....the best ice cream I have ever made.

Finally, Kitchen Chemistry with the bould Heston Blumenthal - the Ice Cream episode....

1 comment:

Snag Breac said...

You are fantastic. Keep making ice-cream.