Evaluation of Activated Carbon Treatment in the Decolourization of Starch Hydrolysates

Abstract

Starch hydrolysates, typically produced by enzymatic hydrolysis of starch from different raw materials, are presented as glucose syrups with a brownish colour due to colour compounds formed during the processing. The colour must be removed for further commercial use, usually done by activated carbon (AC) downstream treatment. This research studied the decolourization of starch hydrolysates with AC to evaluate better optimum process conditions, thus help reducing resource consumption and waste generation in the actual downstream systems. Adsorption by powdered NORIT GBSP AC was carried out in a lab-scale batch process at a constant temperature (70 °C) for different contact times in a range of 5 to 90 minutes, AC dosages from 0.1 to 0.8 g / 100 ml solution and sugar concentrations of 16, 20, 30, and 40 Brix. The results showed that the adsorption time to reach equilibrium decreases with higher dilution (10, 20, 30 and 60 min for 16, 20, 30 and 40 Brix solution). All dilutions achieved decolourization from 85 % to 90 %, with colour reduced to nearly 50 ICUMSA Units. Regarding the obtained product sugar, a lower amount of AC is required for higher sugar concentration (0.020, 0.021, 0.021, and 0.010 g AC per g decolourised sugar for 16, 20, 30, and 40 Brix). For better determination of best decolourization conditions, further investigation of the correlation between faster adsorption with higher water and energy consumption and lower dilution for less required AC is required. Additional studies in other separation techniques are proposed, especially membranes, showing high AC waste reduction potential.