Sodium Citrate is sometimes used as an emulsifier for oils when making cheese. Sodium citrate allows the cheeses to melt without becoming greasy. Consider the following quote from modernist cuisine:
The modernist version of mac and cheese owes its chemistry to James L. Kraft, who in 1916 patented the first American cheese slice. He showed that sodium phosphate keeps the water and fat droplets mixed when the cheese is melted. We use sodium citrate, which has the same effect and is easier to find. The resulting texture is as smooth as melted American cheese, but as complex and intense in flavor as any of your favorite cheeses.
Add 132 g cold water (or milk) a pot and add 5.5 g sodium citrate. Bring to a simmer while mixing with a whisk. Now add 132 g grated cheddar cheese, in 3-4 parts while emulisifying with a immersion blender (Bamix) after each addition of cheese. Remove from heat.
Use as a hot cheese dip or cool and use as a cold cheese dip base to add to. Perfect for a mac’n’ cheese sauce.