Eleusine coracana (Finger millet, ragi) is one of the cereals which can cultivate in higher altitudes. This study analysed the effects of various drying techniques such as spray, tray and freeze drying on the retention of micronutrients and structural changes in ragi. Minerals, such as iron and calcium were determined using atomic absorption spectroscopy (AAS) and water-soluble vitamins, such as vitamin B1, B2 and B3 were determined by high-performance liquid chromatography (HPLC). The micronutrient content of freeze-dried ragi powder was observed to be 349.6 ± 0.6 mg/100 g of calcium, 0.550 ± 0.1 mg/100 g of iron, 0.421 ± 0.01 mg/100 g of vitamin B1, 0.193 ± 0.05 mg/100 g of vitamin B1 and 1.103 ± 0.05 mg/100 g of vitamin B3. Along with micronutrients analyses, proximate and various important physiochemical properties were also analysed. Structure analysis of dried ragi using scanning electron microscopy (SEM) indicated that both tray and spray dried ragi show variations in their structure when compared to freeze-dried porridge powder. Crystallisation of starch during drying was determined using Fourier transform infrared (FTIR) spectroscopy. Selected physiochemical properties were also analysed for all dried samples. The results of this study showed that freeze-drying to be the best technique to preserve nutrients over spray and tray drying methods.
Keywords: Drying techniques; Finger millet; Freeze-drying; Micronutrients; Proximate composition.
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