Sodium citrate is an emulsifying salt that's often used in the dairy industry to improve cheese texture and reduce the amount of separation that occurs. So how does it work? To understand the mechanism, we need to get into a little biochemistry. Casein is the primary protein component of milk and cheese. Biochemically, it is rather hydrophobic and likes to join up with other casein proteins to form micelles, single layer spherical membranes with hydrophilic portions of the protein pointed outwards and hydrophilic portions pointed inwards towards a non-polar core (in this case, milk fat). When rennet or acids are added to milk, the hydrophilic ends are lopped off or denatured, making the casein very hydrophobic. The now extra hydrophobic casein proteins begin associating with each other due to hydrophobic interactions and make curds and eventually cheese.
In cheese, the casein proteins are tightly bound with each other and each protein contains and inorganic calcium component. Sodium citrate sequesters the calcium from casein and replaces it with sodium, making the protein slightly less hydrophobic and more hydrophilic. This causes the proteins to interact more readily with water and weaken their association with each other, allowing for a looser protein framework. This loosened framework translates to a smooth and silkier cheese sauce.
Ultimately, by using this one ingredient, making mac & cheese from scratch becomes a whole lot easier.
Mac & cheese
265 g or 265 mL/1 1/8 cups water or milk
11 g Sodium citrate
285 g or 4 cups Cheddar cheese
Water as needed to cook pasta
240 g or 2 cups dry macaroni
Salt to taste
1. Combine water/milk with the sodium citrate in a pot, whisk to dissolve, and bring to a simmer over medium heat.
2. Add cheese into simmering liquid gradually until melted
3. Bring a large pot of water to boil for the pasta and cook al dente according to the package directions, 5-6 minutes.
4. Drain pasta but do not rinse it.
5. Stir in warm cheese sauce, and fold any accompaniments you wish to add.
6. Season mac and cheese with salt, and serve immediately.
For our mac & cheese, we served it with sauteed spinach and mushrooms, roasted tomatoes, chicken sausage, and garnished with chives. Celantani pasta also works well in lieu of macaroni.