Study of three drying methods in production of nutritious flours from the fermentation slurry of orange‐fleshed sweet potato

Abstract

When producing ethanol from sweet potatoes, the fermentation generates slurry with nutritional content but underutilized for human consumption. Therefore, the nutritional properties of the flours obtained from the fermentation slurry of orange-fleshed sweet potato (rich in carotenoids) was investigated. Three drying methods were carried out to produce slurry flours: convective using a hot-air (60°C), microwave, and lyophilization. For carotenoids determination, were applied a conventional method and the Raman spectroscopy, a modern and alternative technique. Regarding the drying methods, the microwave was the most promising since it produced flour presenting higher levels of carotenoids (β-carotene 849.7 µg/g and lycopene 548.4 µg/g). Also, the microwave drying time was 15 min, being much faster than the other methods. In the centesimal analysis of macronutrients, the slurry flours presented high fiber content, around 55 g/100 g. Finally, biscuits containing parcels of the flours demonstrated potential acceptability, by sensory analysis evaluating aroma and appearance. Practical applications Since ethanol is a product of worldwide importance, and it is produced mainly from corn and sugar cane, the production from sweet potatoes as an alternative raw material has interested researchers from different countries. Knowing that the ethanol production from sweet potato generates a residual slurry, this study focuses on adding value to this slurry, producing a nutritious flour. The potential for industrial application is promising, assuming it is a residue of an industrial infrastructure already installed. For the industry, obtaining more than one product in the same process represents a financial advantage and resource optimization.