The science behind Jell-O 

Jell-O is a popular gelatine-based dessert that’s loved worldwide. The generic name for such food products is jelly cups. Jell-O is one such brand, with the name trademarked to Kraft Heinz. And because it’s so popular, Jell-O has become a colloquial name for all jelly cups — just like Xerox has become shorthand for photocopiers and Jeep for off-road SUVs.

What makes jelly cups so jiggly and wobbly?

The science

The texture and properties of jelly cups come from gelatine, a protein derived from collagen. 

Collagen is a structural protein found in animal connective tissues, like bones and cartilage. It is composed of three polypeptide chains wound together in a triple helical structure. To extract gelatine, collagen is treated with a limited amount of water (usually warm) to break down the long protein chains. The resulting gelatine is purified, dried, and ground into a powder for various applications — including to make jelly cups by mixing it with flavours and sweeteners. Today, there are plant-based versions of gelatine as well.

Some fruits, including pineapple, have enzymes that can break down gelatine and make it watery, which is why fruit-based additives should be chosen with care.

Gelatine is a biopolymer. The powder readily dissolves in water warmer than 40 degrees C. The gelatine has separate chains of amino acids held together by weak bonds. When warm water is added to gelatine powder, these chains unwind and separate, dissolving the gelatine in water. 

When cooled, the molecules in gelatine come together and reassociate, but this time, water molecules are trapped in between. With water, gelatine resembles a solid substance but is not really solid in nature — hence the jiggly consistency. Random protein coils in gelatine can also rearrange into triple helices like in collagen, creating a continuous 3D network structure. These regions are called junction zones — and this is how jelly cups are made.

Properties

The network of molecules in gelatine is flexible, giving a jelly cup its elasticity and the characteristic wobble. Gelatine is also thermo-reversible in nature, meaning it can be reheated and cooled again to its original state.  

A higher concentration of gelatine molecules will result in a firmer final product; a lower concentration will produce softer gels that may not hold their shape and collapse when demoulded. 

The final consistency of a set jelly cup is also affected by the rate of cooling. If it is cooled slowly, larger junction zones form, resulting in a firmer product. Rapid cooling does not allow for enough renaturation, resulting in something softer.

From The Science pages

Question Corner

Flora and fauna