Scientific principle: Crosslinking Time required: 45 minutes, plus 4 hours of setting time
Using the power of crosslinking, these realistic-looking worms not only look amazingly disgusting, but they also taste great!
• 50 plastic bendy straws
• Rubber band
(or length of string)
• Tall container
• 375ml (1½ cups) boiling water
• 2 boxes strawberry or raspberry jelly crystals
• 10g (1 Tbsp) powdered gelatin
• 125ml (½ cup) cream
• Green food colouring
1. Carefully pour the boiling water into a large jug and add the jelly crystals and gelatin, stirring until dissolved. 2. Add the cream and whisk until fully mixed. 3. Stir in 3 drops of green food colouring. 4. Stretch out the flexible part of the straws so they are fully extended. 5. Gather the straws together and use a rubber band or string to hold them together. 6. Place the straws upright in a tall, tight-fitting container or jar. 7. Carefully pour over the mixture to fill each straw. Refrigerate for 4 hours. 8. If the straws start to float, place a weight on top to hold them down. 9. Once set, rinse the outside of the straws in lukewarm water to loosen the worms. 10. Starting at the top, gently squeeze each straw together with your fingers (or the back of a blunt knife) and slide down the length of the straw to push the worms out onto a plate. 11. To make the worms look as though they are in soil, crush dark- chocolate cookies and lay them on the plate as a base for the worms to sit on.
The Science Behind Edible Worms
Jelly wobbles because it contains gelatin, a coiled-up protein chain that unravels and floats around as strands when hot water is added. As the water cools down, the gelatin strands coil back up and become tangled with each other, trapping the fluid they are in and transforming the liquid into a solid structure.
This process of gelatin strands becoming tangled with each other is called crosslinking. Because the worms have a high aspect ratio – meaning they are long and thin – they need to be stiffened to help them keep their shape.
Adding the extra gelatin causes more crosslinking to occur, with the chains making the structure firmer and stiffer when set. Jelly is usually transparent – or see-through – but the additional protein and fat molecules from the cream deflect and scatter the light so that the worms become opaque.
Mixing red jelly and green food colouring make the worms a “realistic” brown colour – but you can, of course, make them any colour you like!
• What happens if you change the amount of gelatin in the worm mixture? Why do you think this is?
• Do the worms look different if you do not add the cream to the mixture?
• What happens if you do not rinse the straws in warm water before squeezing out the worms?
• Why do you think the warm water helps?