Effect of Sun and Solar Drying on the Proximate Composition and Mineral Properties of Zobo Leaves

<b><sc>Abstract.</sc></b> Hibiscus sabdariffa known as roselle, is one of the underexploited food crops with nutritional and food industry processing potential. Thus, this study was undertaken to determine and compare the effects of sun-drying method and solar drying method on the proximate composition and mineral properties (Fat, Protein, Carbohydrate, Crude fibre, ash content). The zobo leaves used for the experiment were obtained from Zobo Project Demonstration farm at the Department of Agricultural and Food Engineering, University of Uyo. The zobo leaves were thoroughly cleaned and sorted to remove debris and dust. Samples were kept in a Zip-locked bag to avoid any form of contamination and moisture absorption. The experiments were carried out in triplicates, at Food Engineering Laboratory of the University. Known quantity of the zobo leaves were dried in the sun on pavement and in the solar dryer. Solar-dried and sun-dried zobo leaves show that the ash content for sun-dried samples was found to be slightly higher (0.97%) than all other samples (0.85%, for solar samples and 0.74% for fresh samples). Crude fibre content in the sample was found to be low for all the samples (3.54% fresh, 6.78% solar and 2.06% sun). However, the fresh sample contained the highest amount of protein. Crude Protein content in the sample was found to be low for all moisture levels (5.02% fresh,6.78% solar and 4.72% sun). However, the solar-dried sample contained the highest amount of protein. Fat content in the sample was found to be low for all moisture levels (0.96% fresh,0.83% solar and 0.61% sun). However, the fresh sample contained the most amount of fat. Carbohydrate content in the product for fresh, solar-dried and sun-dried samples was found to range from (6.82%,5.65%, and 4.39%) for all moisture content levels. The values for the carbohydrate content advocated that the fresh and dried zobo leaves can be a good source of energy giving, and the results for the mineral composition (Iron, Zinc, Sodium, Calcium, and Magnesium) for the fresh, solar-dried and sun-dried samples of zobo leaves shows that the most abundant mineral is calcium and magnesium (between 41.95 to 43.20) and (349 to 360) respectively, while the least is sodium (5.9 to 6.5). These minerals did have significant differences between their means; hence, sun drying and solar drying had significant effects on the mineral composition of the zobo leaves for both fresh and dried samples.