The kidneys play an important role in maintaining potassium balance in a body. Patients with chronic kidney disease (CKD) are at increased risk of developing hyperkalaemia and should limit dietary sources of potassium. Good dietary sources of potassium are foods from the fruit and vegetable group. By restricting these foods, patients move away from healthy eating guidelines. We can influence the leaching of potassium from foods through appropriate food preparation methods, where ultrasound is one of the options for potassium leaching. In the master thesis, we used the chemical analysis to investigate how the contents of potassium, sodium, zinc, iron, dry matter and ash vary with the type of soaking (water or ultrasonic), heat-treatment, soaking time and size of food pieces for 6 types of fruit and vegetables. Based on the trends, we conclude that to reduce the potassium content to the appropriate level (200 mg/100 g), a 180-minute soaking in ultrasound is more suitable than in water, and the leaching is notably influenced by heat and mechanical treatment. Most heat-treated subsamples had lower final potassium contents compared to non-heat-treated subsamples. In broccoli and carrot samples, potassium content was reduced to an adequate level only by soaking and heat treatment. In potatoes samples, potassium contents decreased below the threshold value only after a longer soaking time (180 minutes) and heat treatment. In peach samples, 30 minutes of soaking in ultrasound was sufficient to reduce the potassium content below the limit value. In the case of pear and blueberries, the potassium levels in the untreated raw subsample were already low enough for patients to include in their diet. We also found that carrot and potato subsamples in smaller pieces also had lower final potassium contents compared to subsamples in larger pieces.
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