Science Experiments: Jelly Liquidiser

This Christmas science experiment video is part of the National Science Learning Centre's iTunes U collection. https://itunes.apple.com/gb/institution/national-science-learning/id580170047

Science Experiment: The power of enzymes to break down protein

Equipment used: Jelly (made up and set), bowl for jelly, fresh pineapple

Procedure:

Make up some jelly (the best one for this experiment is the packet stuff made from animal protein) and put in bowl (leave it to set)

Take some fresh pineapple, (tinned pineapple won't work) and place on top of the jelly.

Sit back and watch, occasionally stirring, and see what happens.

Explanation

Jelly is made from gelatine which is a processed form of collagen, an animal protein found in connective tissue, bones and hooves. This protein gives body parts strength and flexibility, and in the jelly it creates a protein mesh which traps the water and holds it in place.

The pineapple contains an enzyme called bromelain which breaks down the collagen releasing the water and turning the jelly to mush. In nature the pineapple plant's sap contains much more bromelain to deter animals from eating the plant, as when eaten the bromelain in the sap starts to break down the surface layers in the mouth causing pain to the animal eating it. You may have noticed this yourself with very fresh pineapple.

Science Curriculum use:

Primary science ideas:

- Solids, liquids and gels
- Food in science terms
- Observing and questioning.

Secondary science ideas:

- Is this a chemical or physical change?
- Scientific enquiry -- use this experiment for proposing and testing explanations
- Include in a 'circus' of other enzyme demonstrations e.g. milk powder and protease; egg white and trypsin

Extension:

Does the enzyme activity of pineapple vary?
- How could you measure it?
- What factors might affect it -- and do they?
- Suggest how bromelain production in pineapples might have evolved.