|GILBERT, AUDREY - Agro Paris Tech|
Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2015
Publication Date: 1/1/2016
Citation: Cole, M.R., Eggleston, G., Gilbert, A., Chung, Y.J. 2016. Development of an analytical method to measure insoluble and soluble starch in sugarcane and sweet sorghum products. Food Chemistry. 190:50-59.
Interpretive Summary: Existing starch methods for the sugarcane and sweet sorghum industries are extensive but limited to measuring mostly soluble starch with little impact in solubilizing the granular (insoluble) starch content. The purpose of this study was to develop a research method to 1) measure total starch, 2) determine the concentration of insoluble and soluble starch in various sugar products containing a broad range of insoluble starch, and 3) underpin the development of a factory starch method. The USDA research method uses a combination of microwaving and probe ultrasonication to rapidly and selectively solubilize granular starch with high precision and accuracy. This method also uses corn starch as a reference, incorporates a color blank, and removes unwanted particle contribution from sample results. To the best of our knowledge, this is the first report of the use of microwave-assisted probe ultrasonication to totally solubilize the insoluble starch content in various sugarcane and sweet sorghum factory and refinery products and allows for soluble and insoluble starch concentrations to be determined.
Technical Abstract: A rapid, quantitative research method using microwave-assisted probe ultrasonication was developed to facilitate the determination of total insoluble, and soluble starch in various sugar crop products. Several variables that affect starch solubilization were evaluated, 1) conductive boiling time, 2) microwave boiling time, 3) probe ultrasonication time, 4) water loss, 5) concentration, 6) sample color, and 7) sample. The optimized method solubilizes <40,000 ppm insoluble starch with microwave-assisted sonication in 6 min, has acceptable precision (<6% CV), accuracy (=95%), uses a corn starch reference, and incorporates a color blank to remove contribution from natural colorants found in industrial samples. This method was validated using factory samples and found applicable to sugarcane and sweet sorghum bagasse (3% CV), mixed juices (2%), massecuites (4%), molasses (7%), and raw sugars (12%), 100% satisfactory performance z-scores were also obtained. Total starch values obtained with this method were significantly higher than those measured using other methods presently accepted by the sugar industry.