Potassium-containing polyphosphate glasses having a relatively high amount of potassium and a relatively low level of insoluble material (e.g., less than about 10% by weight), and a method for their production that includes using a boron-containing glass-former additive. More specifically, these polyphosphate glasses may be described according to the formula M.sub.(n+2)O(PO.sub.3).sub.n, where M is at least K or K+Na and the glasses have a mole % M-as-K that is about 33 to 100. These polyphosphate glasses may be used in reduced sodium foods (e.g., beverages and meat products).