Analysis of Changes in Bioactive Compounds Profile in Onions Under Different Sulfur, Calcium and Magnesium Supplementation on Different Agri-Climates in Kenya

Onion (Allium cepa) is a vital crop both as a dietary staple and a source of bioactive compounds with significant health benefits. However, its potential as a functional food is limited due to low bioactive compounds, thereby reducing its nutrition. Therefore, this research aimed to investigate effects of sulfur (S), calcium (Ca) and magnesium (Mg) supplementation on enhancement of onion bioactive compounds for increased nutrition. RCBD was adopted across major onion production areas in Kenya: Kisaju-Kajiado and Koma-Machakos. Experimental treatments included varying levels and combinations of S, Ca and Mg supplementation, and effects evaluated towards the bioactive compounds concentration. Preliminary tests including Levene’s, Kolmogorov-Smirnov, Durbin-Watson and Shapiro-Wilk test, Cox and Snell, Nagelkerke and McFadden tests for normality, linear and multinominal regression, including collinearity were performed using SPSS software and the data was found to be parametric. Analysis of Variance (ANOVA) tests analysis was further performed and where significant differences were found, Post Hoc test was performed and results displayed. Treatment supplement of S, Ca and Mg at 60 kg/ha significantly proved the highest bioactive compounds with means of 243.33 QE/kg TFC levels, 1024 GAE/kg TPC levels on “White Lisbon” and 9 mg anthocyanin levels, 39 mg quercetin levels and 3.9 S/kg DM organosulfur levels on “Red Creole” variety. This research is therefore recommended to farmers intending to enhance their onion nutrition by increasing the bioactive compounds during production for increased marketability. Therefore, this study concluded that, S, Ca and Mg supplements significantly enhance onion bioactive compounds therefore significantly increases onion nutrition through increased bioactive compounds for increased marketability as well. Keywords: Bioactive compounds, Nutrition, Supplement, Enhance, Marketability.