What is jelly made of?
- Water – Jelly is mainly water
- Gelatin – comes from boiling animal bones and skin, which extracts an animal protein called collagen
- Preservatives – citric acid, acidity regulator (sodium citrate),acetic acid
Why does jelly set?
- The key to jelly setting is down to the protein collagen! Collagen as seen under a scanning electron microscope:
- About 25% of the protein in your body is collagen which is made of three protein fibres twisted round each other – triple helix
- Collagen in animal skin and bones is broken down by heat and treatment with acids and alkalis. Bonds between collagen molecules (intermolecular bonds), bonds in the molecules (intramolecular bonds) and hydrogen bonds are broken down, making gelatin.
- When protein loses its shape it denatures.
- When the gelatin is heated and mixed with water the protein fibres come apart and unravel. As it cools they coil up again and intertwine trapping the water molecules between them. This mixture of water molecules spread evenly in a collagen matrix is known as a hydrocolloid.
- The concentration of gelatin needs to be about 1% to form jelly
- The strength of a gelatin-based gel is its bloom strength and can be measured with a penetrometer or gelometer.
- Bloom strength even has its own formula (for those who think it isn’t science without a formula) for different types of gelatin;
C1(B1)½÷(B2)½ = C2
C = Concentration (g/ml)
B = Bloom strength
- Jelly has a melting temperature below 35°C. Our body has a temperature around 37°C.