Effect of soaking, boiling and frying on selenium content of major African fresh foods

Selenium is an essential trace element that is crucial for normal functioning of human body systems and it is obtained from diet or dietary supplements. The concentration of selenium (Se) varies from soil-to-soil and therefore in various food types. We profiled the selenium concentration in the major African fresh foods and studied the effect of boiling, frying and overnight soaking on their selenium content. The foods were taken to the chemistry laboratory, processed for determining selenium concentration in the fresh foods and then subjected to the various treatments before determining their Se concentration using an atomic absorption spectrometer. Among the fresh foods studied, pumpkin seeds were found to have the highest Se concentration (109.25 ± 0.125 parts per billion (ppb)), while Irish potatoes had the lowest (16.25 ± 0.125 ppb). In most fresh foods studied, boiling and frying had the effect of reducing the Se concentration, except in yams that showed an increased concentration after frying. Overnight soaking of matooke (plantain bananas) and beans showed an effect of causing a considerable reduction in the Se concentration from 36.375 ± 0.281 ppb and 59.125 ± 0.031 ppb to 14.03 ± 0.441 ppb and 24.375 ± 0.281 ppb, respectively. Boiling and frying cause a significant reduction in Se concentration of most African fresh foods. Overnight soaking of matooke and beans caused further reduction in the selenium concentration of the fresh foods. This implies that people who pre-soak their food before cooking it are likely to lose more selenium than those who do not soak and may be more likely to suffer from Se deficiencies.