To maximize gelatin extraction when making stock, use bones rich in collagen like knuckles and feet, and simmer the stock for a long time (12-24 hours) at a low temperature with a slightly acidic environment.
Gelatin, derived from collagen, is what gives stock its rich body and mouthfeel. Here's how to maximize its extraction:
Choose the Right Bones: Bones with a high proportion of cartilage and connective tissue are key. Knuckle bones, feet (chicken or beef), and necks are excellent choices. These contain a lot of collagen.
Roast the Bones (Optional): Roasting the bones before simmering adds depth of flavor to the stock. Roast them at around 400°F (200°C) until they are nicely browned, but not burnt.
Acidic Environment: Adding a splash of vinegar or lemon juice to the stockpot helps break down the collagen. About 1-2 tablespoons of vinegar per gallon of water is sufficient.
Low and Slow Simmer: A long, slow simmer is crucial. Aim for 12-24 hours. The low temperature allows the collagen to gently break down into gelatin without scorching the stock. Avoid a rolling boil, which can emulsify fats and make the stock cloudy.
Water Level: Ensure the bones are fully submerged in water throughout the simmering process. Add more water as needed to maintain the level.
Skim the Impurities: During the first few hours of simmering, skim off any foam or impurities that rise to the surface. This will result in a clearer stock.
Cool and Strain: Once the stock has simmered for the desired time, let it cool slightly before straining it through a fine-mesh sieve lined with cheesecloth. This removes any remaining solids.
Don't add salt to the stock while it's simmering. Salt can inhibit the breakdown of collagen. Season the stock to taste after it's finished and reduced.