Check this out from the Wall Street Journal (which, though it has a conservative bent that I largely disagree with, I find the WSJ has done some really, really good health reporting, and so I follow their leads):
Instead, working with scientists at about a dozen academic institutions and companies in Europe and the U.S., PepsiCo studied different shapes of salt crystals to try to find one that would dissolve more efficiently on the tongue. Normally, only about 20% of the salt on a chip actually dissolves on the tongue before the chip is chewed and swallowed, and the remaining 80% is swallowed without contributing to the taste, said Dr. Khan, who oversees PepsiCo's long-term research.
PepsiCo wanted a salt that would replicate the traditional "salt curve," delivering an initial spike of saltiness, then a body of flavor and lingering sensation, said Dr. Yep, who joined the company in June 2009 from Swiss flavor company Givaudan SA.
"We have to think of the whole eating experience—not just the physical product, but what's actually happening when the consumer eats the product," Dr. Yep explained.
read more here.