Ed­i­ble Earth­worms

North & South - - Good Times -

Sci­en­tific prin­ci­ple: Crosslink­ing Time re­quired: 45 min­utes, plus 4 hours of set­ting time

In­tro­duc­tion

Us­ing the power of crosslink­ing, these re­al­is­tic-look­ing worms not only look amaz­ingly dis­gust­ing, but they also taste great!

Equip­ment

• 50 plas­tic bendy straws

• Rub­ber band

(or length of string)

• Jug

• Tall con­tainer

• Plate

In­gre­di­ents

• 375ml (1½ cups) boil­ing wa­ter

• 2 boxes straw­berry or rasp­berry jelly crys­tals

• 10g (1 Tbsp) pow­dered gelatin

• 125ml (½ cup) cream

• Green food colour­ing

In­struc­tions

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!

Ex­plore fur­ther

• 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?

Ed­i­ble Earth­worms

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