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United States Department of Agriculture

Agricultural Research Service

Research Project: Postharvest Quality and Processing of Sugarcane and Sweet Sorghum for Sugar and Ethanol Production Title: A new look at starch in the sugarcane factory and refinery: The presence of soluble and insoluble starch

Authors
item Eggleston, Gillian
item Cole, Marsha
item Gilbert, Audrey -
item Rose, Ingrid -
item Andrzejewski, Brett
item St Cyr, Eldwin
item Stewart, David -

Submitted to: Sugar Industry Technologists Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 17, 2013
Publication Date: September 1, 2013
Citation: Eggleston, G., Cole, M., Gilbert, A., Rose, I., Andrzejewski, B., St Cyr, E., Stewart, D. 2013. A new look at starch in the sugarcane factory and refinery: The presence of soluble and insoluble starch. In: Proceedings of the Sugar Industry Technologists. 72(1066):326-339.

Interpretive Summary: In recent years, starch impurity concentrations in U.S. raw sugars manufactured from sugarcane have generally increased. Most starch occurs in the molasses around the raw sugar crystal and not inside the crystal. Thus special attention needs to be applied to the centrifugation process in the factory and refinery to minimize the starch in sugars. Despite the increases in starch concentrations, the retention times across factories have not changed, which has caused considerable insoluble (granular) starch to be found in syrups and in some raw sugars. As insoluble starch detrimentally affects enzyme applications and viscosity, we are currently developing a method to accurately measure both insoluble and soluble starch in factory sugar products.

Technical Abstract: Starch impurity concentrations in sugarcane are country dependent and, in recent years there has been a general world-wide increase. This has occurred mostly because of one or a combination of the following: (i) increased mechanical processing of unburnt (green) sugarcane; (ii) varying environmental conditions; and (iii) the introduction of new sugarcane varieties with higher starch content. Approximately 18% starch was found to partition into an A-raw sugar and 82% into an A-molasses. By developing a new method to accurately remove the surface molasses layer from raw sugar crystals we were able to calculate that the true starch partition coefficient is approximately 7%. Thus, most starch occurs in the molasses around the crystal and not inside the crystal. Special attention needs to be applied to the centrifugation process in the factory and refinery to minimize the starch in sugars. Despite the increases in starch concentrations delivered to sugarcane factories, the retention times across factories have not changed. As a result, considerable insoluble (granular) starch has been observed using both microscopic and chemical techniques, in syrups and in some raw sugars, particularly those with high soluble starch content. Approximately 2.7 ppm/Brix starch was solubilized per min using syrup pan boiling. This warrants further investigations on the effect of raw sugars on the filtration system associated with carbonatation refineries to determine if it is soluble starch, insoluble starch granules, or both that are detrimental to the filtering process. Current iodometric starch methods in the sugar industry mostly measure soluble starch and do not take into account all the insoluble starch present. As the insoluble starch detrimentally affects amylase applications and viscosity, we are currently developing a method to accurately measure both insoluble and soluble starch in raw and affined sugars, as well as other sugar products.

Last Modified: 11/21/2014
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