June 2, 2008 Potatoes are a valuable source of mineral nutrients that provide high levels of potassium. Individuals with compromised kidney function, however, must minimize their potassium intake. A new study in the Journal of Food Science explored the effects of leaching and boiling on levels of potassium and other minerals in potatoes and found that boiling cubed or shredded samples reduced potassium levels by 50 percent and 75 percent, respectively.
Shelley Jansky, PhD, and Paul Bethke, PhD, both of the United States Department of Agriculture – Agricultural Research Service and University of Wisconsin-Madison Department of Horticulture, utilized samples of potatoes that had been shredded as well as potatoes that had been diced into 1 cm cubes. The samples were then leached or boiled, two treatments that are most likely to have an impact on the mineral content of a consumed product.
The mineral content of the potatoes was drastically reduced by either cubing or shredding them and then boiling. Boiling shredded potatoes reduced levels of zinc, manganese, magnesium, and sulfur by 50 percent. Boiled potato cubes lost 35 percent of their total magnesium and zinc.
Leaching, which refers to soaking food in water before cooking, had little effect on the mineral levels of the samples. Because leaching alone was an ineffective method for reducing potassium content, there exists little benefit for renal failure patients trying to reduce potassium consumption by leaching potatoes.
Those with compromised kidney function can decrease their mineral intake while still taking advantage of the other nutritional qualities of potatoes by boiling them, thinly sliced. This method will remove a large quantity of many minerals, including potassium. It is not necessary to complicate the process by leaching potato slices before boiling them.
“Our study offers information about the nutritional quality of potatoes and the effects of cooking on the contents of mineral nutrients,” the authors conclude. “It will likely result in changes in recommendations by medical staff working with patients who have compromised kidney function.”
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- Bethke et al. The Effects of Boiling and Leaching on the Content of Potassium and Other Minerals in Potatoes. Journal of Food Science, 2008; 0 (0): 080528102909257 DOI: 10.1111/j.1750-3841.2008.00782.x
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