PLANO, Texas—Later this month, at a pilot manufacturing plant here, PepsiCo Inc. plans to start churning out batches of a secret new ingredient to make its Lay's potato chips healthier.

The ingredient is a new "designer salt" whose crystals are shaped and sized in a way that reduces the amount of sodium consumers ingest when they munch. PepsiCo hopes the powdery salt, which it is still studying and testing with consumers, will cut sodium levels 25% in its Lay's Classic potato chips. The new salt could help reduce...