SODIUM TRIPOLYPHOSPHATE

Found this ingredient on the label for Kraft Macaroni and Cheese: The Cheesiest, following four other ingredients (at least).

Here is the basic rundown, via Wikipedia:

• Often referred to as STPP, sometimes STP or sodium triphosphate or TPP.
• The formula is: Na₅P₃O_10.
• This is basically a salt. It is actually the sodium salt of triphosphoric acid (a condensed form of phosphoric acid). Keep in mind that phosphoric acid is often used for rust removal and food-grade phosphoric acid is linked to lower bone density (imagine food-grade phosphoric acid shaving calcium off your bones as it would remove rust from metal).
  
• _{Mostly used as a preservative for seafood, meats, poultry and pet food. Also can be used in toothpaste and as a builder in soaps and detergents, improving their cleansing ability.}
• _{Morover, according to Wikipedia: "}STPP is a solid inorganic compound used in a large variety of household cleaning products, mainly as a builder, but also in human foodstuffs, animal feed, industrial cleaning processes andceramics manufacture. STPP is widely used in regular and compact laundry detergents and automatic dishwashing detergents (in powder, liquid, gel and/or tablet form), toilet cleaners, surface cleaners, and coffee urn cleaners. It also provides a number of chemical functions including: sequestration of "water hardness," enabling surfectants to function effectively; pH buffering; dirt emulsification and prevention of deposition; hydrolysis of grease; and dissolving-dispersing dirt particles."
• Also: "In foods, STPP is used to retain moisture. Many governments regulate the quantities allowed in foods, as it can substantially increase the sale weight of seafood in particular. Many people find STPP to add an unpleasant taste to food, particularly delicate seafood. The taste tends to be slightly sharp and soapy and is particularly detectable in mild-tasting foods. The increased water holding properties can also lead to a more diluted flavor in the food." Great. Adds to the consumer's final cost and makes the final product taste watery, soapy and diluted.
• Since STPP is widely used in regular and compact laundry detergents, it has raised concerns due to its tendency to "irritate skin and mucous membranes and cause vomiting. Is easily absorbed through the skin from clothes."
  

So, this is a salt, commonly used as a preservative and moisture retainer for human foodstuffs. Also, sodium tripolyphosphate is often used in laundry detergents and other cleaning agents. Seems mild enough but has been earmarked as an irritant, which is easily absorbed through the skin....

The questions is: do we really need this stuff in macaroni and cheese? I imagine that its role in the Kraft Mac and Cheese is to retain moisture for the "cheese sauce" mixture. Do my conscientious readers have any good guesses?