It is a sodium salts of phosphoric acid, 
AKA 'Cold phophate uses as pH control agent, water hardness precipitation,phosphatizing 
reagent. Mostly used in meat curing and sausage making to maintain moist (jucier),
tender and flvourful of meat and cheeses in shop display cases for longer.

Also used in dry or slurry form into all meat emulsions, 

Usage: 1/2 tsp/lb of meat (max 0.5% by weight.
Often used as emulsifiers (as in processed cheese), thickening, and leavening agent for
baked goods and to modify textures and  surface tension in liquids like evaporated milk.