Schools’ giant jellies set for Norwich
17th September 2014
The Institute of Food Research is issuing its annual challenge to schools to see who can use their food physics skills to best effect, in constructing the tallest possible jelly. This isn’t as easy as it sounds, as most jellies struggle to top 10cm. The pupils must use food science, experimentation and ingenuity to try and tower above the competition, maybe even breaking the metre barrier this year.
It’s not just height that will see a school victorious in this quivering quest. The teams will have to keep a workbook showing how they have applied scientific thinking and experimental techniques to their final creations. These will be judged at the grand unveiling, which will take place at 11:00am on Friday 26th September, at The Forum Norwich, as part of the Norfolk & Drink Food Festival.
Head judge is Terrance Isaac-Griffiths, Commercial Director from Norse Commercial Services. “This competition is proof that food is something we can have lots of fun with! Jelly is a really popular dessert in our School dining rooms and I am really looking forward to judging these fantastical jelly creations.”
Dr Phil Smith MBE, coordinator of the Teacher Scientist Network will also be judging the pupils’ efforts.
Food scientists have to take into account the way foods and ingredients change their properties during cooking, freezing, dissolving and all manner of processes to produce the highest quality finished product that looks and taste great. Building a tall jelly is a simplified, and somewhat messier, version of the sort of challenges facing food scientists.
So why is it so difficult to make tall jellies?
The answers lie in the molecular structure of gelatin, the protein jelly is made from. If you looked at gelatin on the molecular scale, you would see it was made up of long thin strands, with each molecule made of three individual strands wound around each other. This is similar to the double helix structure of DNA, but in gelatin there are three strands – a triple helix.
The strands are held together by weak bonds, and if they are heated up these bonds break. For jelly you buy in the supermarket, this happens by adding boiling water. When proteins lose their shape like this it is called denaturing. As the jelly cools, or as you add cold water, the molecules start to come together again, this time trapping water molecules between the tangle of molecular chains. This mixture of water molecules spread evenly in a matrix of gelatin proteins is known as a hydrocolloid.
When the jelly completely cools, and sets, the water between the tangled molecules makes the structure less strong, so that it can’t even support its own weight. So the molecular structure they form when they set stops jellies getting very tall, but it does give them their familiar wobble. This molecular structure has a melting point of about 35°C. This is just below our own body temperature, and this gives jelly its ability to melt in the mouth.
Jellies must be made from a standard jelly pack and made up following the instructions on the pack. Using less water and more gelatin is against the rules.
The schools are allowed to use any other edible materials to support their jellies. But all jellies must be freestanding, and the jelly builders must be willing to eat anything added to the jelly. Freezing a jelly is also against the rules, as although this temporarily strengthens the structure through freezing the water trapped in it, when it defrosts the water is lost and the structure collapses completely.
Experimentation, testing out and ideas beforehand and trial and error are crucial; don’t forget to record what works and what doesn’t work in the workbook as this will be judged as well.
Using other foods to strengthen the structure, but there are some foods that need to be avoided if you want to avoid a jelly disaster. Pineapple is a top jelly no-no, as anyone who’s been tempted to add fresh pineapple to a jelly would find out. This is because pineapple contains proteins called proteases, whose sole job is to chop up other proteins. So in a jelly, the proteases attack the long gelatin molecules, breaking them down and preventing the jelly from setting at all. If you hold pineapple in your mouth for a while, you might feel a tingling sensation, which are the pineapple proteases at work on the proteins in your skin. Kiwi fruit, mango and papaya also have proteases, and so should also be avoided when jelly making.