Wednesday, 14 March 2012

Bloggers Scream for Ice Cream Challenge: Coke Float and a Science Lesson

I'm not very good at making ice cream. I don't have an ice cream maker and when I make it in a tub in the freezer it usually goes all grainy or too hard and brittle and loses its creaminess. So when Kavey announced that the March Bloggers Scream for Ice Cream challenge was to recreate an ice cream-themed memory or experience from our childhood, I was thrilled. And to be honest, there was only one contender: The Coke Float.




I was born in the late 1970s and my fondest childhood memories are from growing up near Southampton in the mid-1980s. I used to sing True Blue with my friends in the playground at school, wear chiffon scarves in my hair and lace fingerless gloves with cut off jeans at the weekends. And I remember going out with my sister for the entire day during school holidays and weekends: from about 8.30 in the morning, returning home at about 5pm for dinner. And if we turned up any earlier at our doorstep, with muddy knees and thirsty from bike riding, we'd be lucky if we got one of these to drink on the porch.


I don't know how it started. I think my sister had been given a Coke float by a friend's Mum and then she asked ours to make it one day for us. You just pour Coke into a long glass, and top with a scoop of vanilla ice cream. You can use lemonade or cream soda instead, if you prefer. Just leave a bit of room at the top of the glass, because it fizzes and spews out these creamy bubbles. The bubbles themselves are fizzy, which makes it fun to eat. And if you push the ice cream down into the glass, it will froth and fizz and probably spill all over the worktop. So eat it gently, with a spoon and then drink what's left in the glass.

And if you're wondering about why it turns frothy, I asked food science blogger Alex from the Procrastibaking blog to explain. "So, ice cream, if made properly, is based on milk and eggs." He continued: "Those two ingredients are filled with proteins which are whisked, churned and frozen. This allows the formation of a stabilised protein structure with pockets of air from the churning (so ice cream isn't just a solid block of...well...cream). It's sort of like an amalgamation of lots of layered nets."

The ice cream is colder than the cola, the cola is carbonated and it also contains Aspartame. "When you drop your ice cream into the glass of cola, the ice cream begins to melt, forming a layer atop the cola. The net like structure of the protein is still present and it waits to capture anything that tries to cross it. The addition of the ice cream causes a set of complicated reactions that lead to the carbon dioxide being released and travelling upwards, they get caught in the layer of melted ice cream. This entrapment is what is seen as foam: CO2 gas trapped in a protein structure.
The aspartame acts as a surfactant, which decreases the surface tension of the bubbles in the cola's surface, leading to more bubbles trapped in the foamy net. This is why certain drinks produce more foam - they have more ingredients which act as surfactants."

Got that? 

Enjoy!



Do you have any childhood ice cream memories?