An Experiment to Visualize and Probe the Relationship between Polysaccharide Structure and a Glycemic Index Proxy

An experiment was developed for a first year food chemistry laboratory course that demonstrates the influence of several aspects of polysacharide structure on the rate of amylase catalyzed hydrolysis. The experiment would be particularly well-suited to a first year chemistry course that was targeted at nonchemistry majors, such as health related disciplines. The experiment illustrates numerous chemical concepts from the a versus [beta] glycosidic bonds to branched versus linear polymers to spectroscopy versus RGB color space. There are several general concepts related to analytical chemistry and enzymatic catalysis that are relevant to health and nutrition with regards to the glycemic index, resistant starches, and dietary fiber. Students use their camera phone and image analysis to quantify polysacharide hydrolysis based on reaction with the chromophore dinitrosalicylic acid. The experiment provides a strong visual and quantitative tool showing how a proxy for the glycemic index is influenced by the amylose to amylopectin ratio of a starch and the influence of having an a or [beta] glycosidic bond. A motivating factor for developing the experiment was studies showing tools that assist people's understanding of the glycemic index have beneficial health outcomes.