Mad about Science: Gelatin

By Brenden Bobby
Reader Columnist

A jiggling bowl of Jell-O during a hot summer barbecue really hits the spot. But have you ever wondered how we make the stuff? One minute it’s a powder, the next it’s a liquid; a little chill later, and it becomes a weird cherry-flavored quivering mess. How does it do that?

It all begins with gelatin, which is a compound derived from collagen harvested from animal parts — particularly the skin, bones and tendons of pigs and cattle. 

Harvesting collagen to create gelatin is a surprisingly old practice. It begins by boiling the bits unfit for human consumption. These parts are treated with compounds that alter the pH, then grinding it into powder.

Gelatin transforming into jelly is interesting when viewed at a molecular level. The powder absorbs water and is then dissolved by the application of heat. As the mixture cools, the collagen reforms the molecular bonds to create a matrix that traps water within the strands. At a macro level, this creates the wobbly jelly we all know and love. Heat it up again, and the process repeats. Scientific magic!

Culinarians have known about gelatin for at least a thousand years, and likely longer. It was first written down in an Arabic text called Kitab al-Tabikh (The Book of Dishes) from the 10th century. The author of the cookbook recommended suspending fish heads in a gelatin mixture to create a dish called “qaris.” Fish-flavored Jell-O sounds terrible, but it was a medieval staple that was portable and made a watertight seal around food that rotted quickly.

Noticeably absent from The Lord of the Rings movies were hobbits eating fishy Jell-O, despite it being thematically accurate for the time periods they were portraying.

Though we don’t have a written record of it, it’s believed that some form of gelatin was used by the Romans to create thick and jelly-like broths. It was likely similar to some “kitchen-sink” style congee dishes from East Asia. It is not uncommon to cook the porridge with the bones and residual bits of a butchered animal to give it a little more nutrition.

It is likely that the Roman thermopolium, which was essentially an ancient fast-food restaurant, accidentally created some kind of gelatin compound by allowing meat and bits to boil for hours or perhaps days on end. The texture and taste was likely masked by garum, which some people refer to as “Roman ketchup.” Garum was a serving sauce made from fermented fish guts and blood, which probably tastes awful when poured over a hot dog.

It wasn’t until the 17th century that the importance of gelatin became front and center in the eyes of culinarians, particularly in France. It is understood that fancy aspic dishes were commonly enjoyed by the aristocracy. Aspic is an evolution of the fish-flavored Jell-O we explored earlier. Chefs would create a savory broth with gelatin and entomb within it meats, vegetables and eggs. Aspic has fallen out of favor, but it had a major resurgence in the United States during the 1950s and ’60s.

It’s likely the explosion of popularity of aspic and Jell-O was because of World War II. Gelatin was a staple in battlefield food because it was lightweight, held lots of protein, and was easy to transport and mix with other rations. Soldiers returning home after the war took comfort in one of the few pleasures available to them on the battlefield, and a booming postwar economy led to the exploration of more culinary and pharmaceutical uses for gelatin.

Medications and supplements are frequently mixed with gelatin to create gel tabs, or gelatin tablets. The medication is suspended within the water that is trapped by the gelatin matrices, which breaks down at our internal body temperature and allows rapid dispersal of the meds into our bloodstream.

Gelatin production at an industrial scale is a bit of a horrifying prospect. After pigs and cattle have been processed for meat, the bones and skin are shipped in refrigerated trucks to the processing plant that will produce gelatin. The skins are separated and washed in a gigantic vat, then flushed down a line where they are cut into thin strips. The skin is smashed together and stored at a cool temperature to create big blocks of flesh that are then crushed in order to extract the collagen. 

Pig skins are immersed in an acid bath to break down the collagen bonds and make them soluble. Cow bits require an alkali bath that can take weeks to convert the pieces into raw collagen. To convert collagen into gelatin, the mixture is precisely controlled in huge stills where they are subjected to heat and water — up to 90 degrees Celsius (almost 200 degrees Fahrenheit).

The extracted material needs to be put through heavy filtration to remove any residual solids. The liquid is passed through a number of metal and fabric meshes to remove the larger impurities. The final step of filtration passes the liquid gelatin through carbon filters to achieve total purity. Excess water is then evaporated off to create a syrup-like consistency, and then the gelatin is forced through an extruder that creates long ropes that look like spaghetti noodles. Once it is dried, it is often crushed into powder for larger-scale applications, or converted into gelatin sheets for home cooks and pastry chefs.

Stay curious, 7B.