How hydrogen bonding plays a key role in making treats like Jello and panna cotta and how the source of gelatin may surprise you.
When I was 6 years old, my easy, go-to summer dessert was the red Jello. Today, my easy, go-to summer dessert is homemade panna cotta, the Italian classic. Nothing beats this cool, creamy, and deceptively easy treat!
What do these 2 desserts have in common? The key ingredient - gelatin.
To make panna cotta, milk, sugar, and a pack of unflavored gelatin are heated on the stove, poured into a container, and chilled. The hardest part is waiting for the panne cotta to set into its final state: a chilled custard, similar to flan or the creme in creme brulee. I like it topped with berries.
How does a packet of gelatin powder turn milk into a jiggly custard and plain water into a jiggly childhood favorite?
The answer is literally right under your nose...kinda sorta. You see, gelatin is made of the same material that keeps skin texture firm - collagen. Collagen is an abundant connective tissue protein that is important to the structural integrity of muscles, tendons, skin, and bones of mammals.
Most gelatin we eat is derived from pig tissue and bones. Pig parts are boiled down and filtered, which transform the pig’s collagen into gelatin through a process called hydrogenation. Hydrogenation breaks down collagen proteins into shorter protein chains with more hydrogen atoms poking out like little arms. These little arms will later play an important role in causing liquids to gel or firm up. The shortened proteins are then extracted, processed, and dried into sheets or powder. Gelatin is a funky protein. Heated up, it is a liquid. Cooled down, it is solid.
To understand how heating and cooling of gelatin transforms its physical state, we must first understand hydrogen bonding. The name “hydrogen bond” is a misnomer. Hydrogen bonds are not chemical bonds, but rather a weak electrostatic attraction between two atoms. Hydrogen bonds are not exclusive to gelatin; they also hold DNA and water molecules together.
The little hydrogen “arms” that were made during the hydrogenation process of gelatin have an affinity to water molecules. At sufficiently low temperatures, the arms will form hydrogen bonds with water molecules. If enough gelatin is added, a complex matrix of hydrogen-bonded water and collagen protein strings creates a semi-solid gel that jiggles!
A small amount of gelatin can hold a lot of water because of the many hydrogen “arms” it has. If you heat this gel up, the energy will easily disrupt the weak hydrogen bonds, unraveling the protein and detaching water molecules from it. This is the liquid form of gelatin and water. Let the mixture cool again, and the hydrogen bonds will reestablish.
I found this wonderful, easy recipe for panna cotta from natashaskitchen.com. I've made this multiple times and it is a family favorite! Hope you enjoy it!
Panna Cotta Recipe
1 cup whole milk
1 (0.25 oz) envelope unflavored gelatin
2 cups heavy whipping cream
½ cup sugar
pinch of salt
1 teaspoons vanilla extract
1 cup sour cream
Your favorite toppings - berries, whipped cream, chocolate, etc.
1. Off the heat, place whole milk in a medium sauce pan and sprinkle the top with 1 packet gelatin. Let stand 3-5 min or until gelatin is softened. Place pan over medium/low heat and stir until gelatin dissolves and mixture is steaming, about 4-5 min (do not boil).
2. Add heavy whipping cream, sugar, vanilla extract, and salt. Continue stirring about 5 min until sugar is fully dissolved and mixture is steaming (do not boil). Remove from heat and let cool 5 minutes.
3. Place sour cream in a medium bowl with a pouring lip. Whisking constantly, gradually add warm cream. Once the mixture is completely smooth, divide it into 6 wine glasses or 8 ramekins. Refrigerate until fully set; 4 to 6 hours.
4. Add toppings and enjoy!
If you have time and are feeling fancy, you can make a berry sauce as your topping.
Berry Sauce
2 cups berries (strawberries, raspberries, blueberries)
3 tablespoons granulated sugar
1/2 tablespoon lemon juice
1. In a small sauce pan, combine half the berries, lemon juice and sugar. Bring to a low boil and cook 4-5 min or until syrupy.
2. Stir in remaining berries and remove from heat. When syrup is at room temp or just barely warm, spoon it over the top of chilled panna cottas.
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