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American Sugar Cane League-funded proposal for the 2008 grinding season.
Report on Production and Storage of VHP (very high pol) and VLC (very low color) sugar
Lead PI- Dr. Vadim Kochergin, Audubon Sugar Institute, LSU AgCenter
The following tasks have been performed during 2007-08 grinding seasons (November 2007 through December 2008).
- Two sugar mills with various boiling house configurations produced improved-quality sugar using enhanced washing procedures. Lafourche mill that utilizes conventional three-boiling scheme produced 10 million pounds of VHP and VLC sugar. The St. Mary mill with “double magma” crystallization configuration produced two 600, 000-pound piles of VHP-VLC and conventional sugars next to each other in the same warehouse.
- Quality of stored sugar has been evaluated by periodically analyzing composite samples over 300 days.
- About 15 million pounds of VHP and VLC sugar (raw color of about 1,200 ICUMSA and 99. 3 % pol) have been produced at St. Mary sugar mill in November 2008. Temperature and relative humidity sensors have been installed to monitor conditions at various depth inside the sugar pile (up to 50 ft. deep).
- Method of sampling was altered compared to previous season. Five six-foot-deep core samples are obtained by using a gas-powered auger. Samples were analyzed for purity, ash, invert content, color and moisture.
- Initial tests have been carried out on evaluation of sugar cooling in slingers and belt conveyors.
(See related files below for Raw Sugar Color Graph)
Discussion of the Results
- Changes in sugar color measured at pH 8.5 over 300 days of storage are reported in the graph below. Most data represent sugar quality at 1- to 1.5-f00t depth below the surface. One data set represents the samples taken from 5 ft. deep from the pile. Sugar quality in a larger pile at Lafourche sugar mill (conventional three-boiling scheme) shows some fluctuation but not a significant increase in storage. The VHP sugar from St. Mary pile did not show any changes during the entire storage period. Conventional sugar stored in the adjacent pile show about 25 % increases in color. Sugar color in production samples (as shipped) show significant deterioration towards the end of the storage period. It is difficult to conclude at this point of time if the difference is due to better storage of VHP sugar or it is related to the sampling depth. The core of the sugar piles is typically more colored compared to the top layer.
- The top crust consisting partly from fine dust particles is typically ¼ to ½ inch thick. It has been deteriorated dramatically mostly during the last 100 days of storage. Significant increase in reducing sugars and corresponding decrease in pol and increase in color and moisture were observed. The crust appears to serve as a protective coating to the rest of sugar in the pile.
- A certain decrease in sugar pol has been observed in all samples. This was accompanied by pH decrease, which may be an indication of sucrose inversion. The level of invert sugars did not change significantly in most samples but the top crust.
- Sugar directly under the top crust does not differ in quality compared to the sugar located deeper inside the pile (1-1.5 ft.).
- Temperature and relative humidity probes were placed outside the sugar pile at Lafourche sugar mill and 5 ft. deep inside the pile, respectively. The temperature data inside the pile show that the top several feet of sugar act as an “insulation” layer, protecting sugar from sudden temperature swings. Generally temperature inside the pile follows the temperature trend outside. During the first two months of storage, sugar cooled to about 70oF, but later into storage its temperature has never risen above 82 oF even when the outside temperature increase up to 90-95oF.
- Sugar moisture remained virtually unchanged over entire storage period.
- Color measured by ICUMSA methods (at pH 7) is about 50-60% of that measured at pH 8.5.
- VHP and VLC sugar was produced mostly by increase of washing time. It is presently unclear how much additional sugar is melted to obtain incremental decrease in sugar color. This needs to be clarified in the future studies.