The science of ice-cream (video)

Posted Aug 23, 2014 by Tim Sandle
Ever wondered about the science behind ice-cream? The American Chemical Society has issued a interesting video, and one appropriate for the summer months.
Mexican Neapolitan ice cream at Michoacana Ice Cream shop in Sonoma is a delicious variation on the ...
Mexican Neapolitan ice cream at Michoacana Ice Cream shop in Sonoma is a delicious variation on the traditional standard. Spices and that little something extra with a Mexican flavor makes it extraordinary than the usual vanilla, strawberry and chocolate combination.
The summer weather continues and at this time of year ice-cream is a popular treat. The American Chemical Society's latest Reactions video looks at the science of ice-cream.
In the video American University Assistant Professor Matt Hartings, Ph.D., breaks down the chemistry of this favorite frozen treat, including what makes ice cream creamy or crunchy, and why it is so sweet.
For those more interested in making ice-cream at home rather than understanding the chemistry, The Independent recently ran a feature on the subject. Interestingly, the meaning of the phrase "ice cream" varies from one country to another. Phrases such as "frozen custard", "frozen yogurt", "sorbet", "gelato" and others are used to distinguish different varieties and styles.
The core ingredients of ice-cream are cream, sugar and egg yolks. One recommended preparation method, based on BBC's Good Food, is:
Make sure that you have plenty of room spare in the freezer. First, separate the eggs, placing the yolks in a large bowl. (You will not need the whites for this recipe. You can use them to make meringues.)
Add the sugar to the egg yolks and whisk until pale and thick.
Add the cornflour (if using) and whisk well to incorporate into the egg yolks.
Put the cream and milk into a medium saucepan.
Cut the vanilla pod open lengthways and scrape out the seeds with the back of a knife, then add to the cream and milk.
Heat the cream and milk until just below boiling. Slowly pour the hot cream and milk onto the eggs and sugar, whisking as you go.
Sieve the custard into a clean pan, and set it over a very low heat. Stir the custard constantly with a wooden spoon, paying special attention to the corners of the pan, until it is steaming and has thickened slightly. The custard is ready when you can draw a clear line through it on the back of the wooden spoon. This can take up to 10 minutes.
Tip the custard into a large, shallow, freezer-proof container, and allow to cool to room temperature (you can speed this up by sitting the tub of custard in a large bowl of iced water).
Once at room temperature, place a lid on the custard and chill in the fridge overnight.
Once chilled, transfer the custard to the freezer and take it out every hour, for three hours, to whisk it with an electric handheld whisk. This will disperse the ice crystals and keep it smooth.
Then leave the ice-cream in the freezer for a final freeze, until it is solid.
Remove the ice cream from the freezer 10 minutes before serving, so that it’s easy to scoop.