Changes in potassium content of different potato varieties after cooking

We sought to determine analytically the potassium content of different varieties of raw potatoes, and to estimate the amount of potassium that can be extracted or leached from raw potatoes by cooking.

Six different varieties of fresh potatoes were obtained from the Whole Foods Market in Manhasset, New York. Two different cooking methods (normal cooking [NC] and double cooking [DC]) were applied to each potato. Potassium was extracted from the ash of dried samples. The potassium content of aqueous extractions was ascertained by atomic absorption spectrophotometry.

Mean potassium content was highest in the purple Viking potato (448.1 +/- 60.5 mg [11.5 +/- 1.6 mEq]/100 g [values are mean +/- SD unless otherwise noted]), and lowest in the Idaho potato (295 +/- 15.7 mg [7.6 +/- 0.4 mEq]/100 g). All raw potatoes had a mean potassium content of about 300 mg (7.7 mEq)/100 g or greater. The DC method resulted in a greater reduction in potassium from raw potatoes than the NC method. All potatoes retained a mean potassium content greater than 200 mg (5.1 mEq)/100 g, using the NC versus the DC method.

The potassium content of the raw potatoes studied varied considerably, with most tubers retaining a moderate amount of potassium after leaching. This study showed that the DC method appears to be more effective than the NC method in leaching potassium from the potatoes studied. Our findings provide useful information for dietitians involved in menu planning for people on potassium-restricted diets.