Up in the Air: Cakes and Chemistry (CBS 2018)

Public summary: 

This is a CBS talk by Dave and Rosy Ansell from CBS 2018 and is transcribed from their notes.

Useful information
Kit List: 

Butter, flour, sugar, eggs, baking powder, bicarb, .... (cake ingredients)
Selection of cupcakes made with different ingredients (e.g. no raising agent)
Hot air ballons experiment
Vacuum pump
Yeast and bread-making experiment.


Intro - who ami I? I'm a chemist and cakes are about chemistry!
Thought it would be fun to talk about what makes a great cake.
Set out to make some example cakes to show you what I mean... I got some suprises, turns out 'what my gran used to say' is not totally accurate! This is more like a real reaserch talk than I expected.
What ingredients do I need for a cake? Audience Question. Get things out.
Butter, flour sugar, eggs.
disapointing cake, what went wrong? didn't rise. Cakes are simple... but aparently tempremental.
Obviously it's a huge subject, people make hours and hours of TV about how to make the very best most beautiful cake and I've only got 1/2 an hour. Stick to why cakes rise.
talking about gases... where are gases important? everywhere! gasses all around you. Are gases stuff? waving hands.
What's missing from this cake? Bubbles! (Show cake on the visulizer to the audience) What are bubbles made of? Air (or gasses).
Gasses are 'stuff' (waving hands), think of wind where air bashing into your face, squishing balloon, pushing air in from mouth, blow up balloon, fire piston.
Okay, so where can we make some bubbles? Audience ideas:
yeast - it's biology so it's a bit slow, leave this yeast bottle here.
bicarb/baking powder - prompt with people who've been into CBS and seen mini explosions
electrolysis - metal bad for you all the bubbles in one place.
So maybe we can use bicarb... cake with bicarb and water not very good, hot some gas escapes
bubbles when we add bicarb and what? vinegar fizz demo, we can show this gas isn't air, fire extinguishers demo.
vinegar in cake? eugh!
Not enough lemon juice either.
Cream of tartar. add to water, nothing. water+bicarb, nothing. Mix the two, fizz.... Gas released is carbon dioxide, can extinguish candle (again).
Mixing biccarb and cream of tartar gives baking powder. Cream of tartar is powdered acid, add water wet cake mix.

response of yeast bottles.
but i found out when I was doing the baking for this show that what my gran told me when I was little isn't really true...
Some baking is made with yeast, yeast is alive, that's biology isn't it?
more suprisingly... I've been a bit careful what I say so far... because it turned out when I was baking the cakes for this show that there's something else at least as important to how cakes rise and it's not chemistry at all. Dave's going to look smug now. It's physics.

cakes -gases bubbles are essential. What happens to cake in the oven? It gets hot! we can look at what happens when air gets hot. toaster/bottle demo (hot air balloons) Why? (demo I can't read looks like 'Sinnal ctun')

Baking powder cakes without beating
but what suprised me last night was if you beat the batter with no biccarb or baking powder or yeast this is what you get. It turns out the beating is hugely important. Beating bubbles in, can''t really see the bubbles like this but if we take the air out from around a bubble (or balloon) like this we can see it gets bigger (vacuum pump demo)
fact is mixed is better. Put batter in plastic cups in vacuum pump to see how much they rise up due to bubbles expanding.
What if we beat the batter with baking powder?
This looks like a convincing cake. Gas expands when you heat it (hot air baloons demo) but what happens when it cools down again? sinks. Is that what cakes do? sometimes...
However we hope that the batter reacts to heat and goes solid. Back to chemistry again!
Today we've seen bits of chemistry, biology and physics....
I hope lots of you will go home and play with things you're doing.

Risk Assessment
Risk Assessment: 

Josh Garfinkel should have a copy as he was in charge of CBS that year.