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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: Seasonal variations of sugarcane stalk and extraneous matter on pH, color and ash as they affect the production of high quality raw sugars (Part II)

Authors
item Eggleston, Gillian
item Viator, Ryan
item Gateuil, Audrey -
item Fenger, Julie-Anne -
item White, Paul
item Jackson, Windell -
item Waguespack, JR., Herman -

Submitted to: International Sugar Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2013
Publication Date: September 1, 2013
Citation: Eggleston, G., Viator, R., Gateuil, A, Fenger, J., White, P., Jackson, W., Waguespack, Jr., H. 2013. Seasonal variations of sugarcane stalk and extraneous matter on pH, color and ash as they affect the production of high quality raw sugars (Part II). International Sugar Journal. 117:646-653.

Interpretive Summary: There is presently a trend to manufacture high quality raw sugars for supply to refineries, as well as a trend to use sugarcane leaves and tops for biomass. Strategies to improve the quality of raw sugar will require attention to cane quality factors as well as process manipulations. This study was undertaken to ascertain seasonal cane supply variations in juice quality parameters that affect raw sugar manufacture across the Louisiana 3-month processing season. As the sugarcane matured across the season there was a tendency for the pH of the tissue juices to became more acidic, which is most likely detrimental to sucrose losses in the factory. Except for stalk juice, the harvest date had a strong affect on tissue juice color, and sugarcane variety also affected the juice color. Juice color at pH 8.5 accentuated varietal differences in juice more than at color at pH 7.0. For pH, color and ash quality parameters studied the type of tissue had the strongest effect, followed by variety, then date of harvest; the varietal effect was greatest in the stalk than other tissues.

Technical Abstract: There is a trend in the U.S. and world-wide to produce very high pol (VHP) and very low color (VLC) raw sugars for new refineries. In Louisiana (LA), a new refinery is requesting VHP/VLC sugar with lower ash concentrations for liquid sugar manufacture and short, medium, and long-term refinery strategies. Great variations in the quality of raw and VHP/VLC sugars exist mostly because of the range in quality of the seasonal cane supply. Strategies to improve the quality of raw sugars will require attention to cane quality factors as well as process manipulations. This study was undertaken to ascertain the variations in juice quality parameters, known to affect VHP/VLC sugar manufacture and refining, across the LA 3-month processing season (late Sept to Dec) in 2009 and 2010. Juice was extracted from separated stalk (S), growing point region (GPR or immature apical internodes), green leaf (GL), and brown leaf (BL) tissues of three popular sugarcane varieties (HoCP 96-540, L 99-226 and L 99-233), five to six times between Sept and Dec. Except for the GPR tissue, as the sugarcane matured across the season there was a tendency for the pH of the tissue juices to became more acidic (P<.05), which is most likely detrimental to sucrose losses in late season. At some U.S. refineries, premiums for low color in sugar are paid on color measured at pH 8.5 whereas the rest of the world measures ICUMSA (International Commission for Uniform Methods in Sugar Analysis) color at pH 7.0. Except for stalk juice, the harvest date had a strong (P<.05) affect on tissue juice color measured at pH 8.5, and sugarcane variety also (P<.05) affected the juice color. For both seasons, juice color at pH 8.5 accentuated varietal differences in juice more than at color at pH 7.0 and was also more sensitive to GL colorants that contribute to the color of raw, VHP/VLC, and affined sugars. The highest per cent increase in color measured at pH 8.5 over color at pH 7.0 was observed for GL (av. 94.9 ± 0.3% std. dev.) and the lowest for BL (23.6 ± 3.1%); the values for GPR and stalk (S) tissue were 44.8 ± 3.2% and 64.3 ± 17.7, respectively. In those areas of the world where color (ICU) is measured at pH 7.0, the color of raw sugar may not always indicate all the colorants delivered to the refinery in raw sugar and which need to be removed during the refining process. Conductivity ash was highest in all tissues at the beginning of the season, decreased in the middle of the season then increased again to the end of the season.

Last Modified: 10/26/2014
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