Effect of Different Diffusion Strategies on Extraction of Sugar from Sweet Sorghum

Abstract

Many studies have been reported suggesting sweet sorghum as an attractive feedstock for production of bio fuels. Sugar from sweet sorghum is generally extracted using a roller press but roller mills require high capital and operational cost and hence may not be economically viable for small scale industries. Diffusion processes could be used for multiple feedstocks, and may be an alternative method of sugar extraction for versatile small scale processes with multiple feedstocks.Several diffusion techniques for extraction of free sugar from sweet sorghum were studied. Batch diffusion, fed batch diffusion, and counter current diffusion were evaluated for sugar extraction efficiencies from sweet sorghum. The effects of different parameters such as liquid to solid ratio (1.5, 3 and 4.5), contact time between solids and liquid (10 minutes, 15 minutes and 45 minutes) and temperature (60˚ C and 70˚C) during the diffusion process were evaluated. The effect of shaking (120 r.p.m) on batch and fed batch diffusion processes was also studied. Results showed that liquid to solid ratio and temperature did not significantly impact sugar extraction during batch diffusion. Longer contact time between solids and liquid and shaking yielded significantly higher sugar during batch diffusion. Liquid to solid ratio, time, and temperature significantly affected fed batch and counter current diffusion processes. The highest yield of sugar, 70.81% maximum theoretical yield (MTY) was obtained at 70˚ C, 45 minute contact time and liquid to solid ratio of 3 during fed batch diffusion with shaking.