Electrochemical and Chemometrics-Based Methods to Evaluate the Quality Traits of Sweet Sorghum Stalk Juice Bioenergy Feedstock.

Sweet sorghum is a promising fermentable sugar feedstock for renewable fuels and biobased products. Inexpensive yet accurate methods are on demand as a part of breeding strategy to evaluate the stalk juice quality. Of complex juice constituents, reductants and chelators especially flavonoids, alkaloids, cyanogenic glycosides, and aconitic acid putatively contribute to its pest resistance. This study developed new cyclic voltammetry (CV) and bulk electrolysis methods combined with chemometrics to classify the sorghum phenotypes for important quality traits including the pest resistance. For sweet sorghum juice, the peak anodic potential (E_pa in volts) of derivative CV (pH 5, 0.1 M KCl) overlapped with quercetin and tannic acid model reductants. Fluorescent porphyrin/chlorophyll-like condensed aromatic structure correlated (Pearson’s) with the electroactive species in stalk juice samples. While aconitic and other aliphatic carboxylates could be electroactive, condensed aromatic structures were determined to be the primary electron donor in the sweet sorghum juice that required sufficiently high potential to oxidize (resulting in more positive E_pa), and donated the largest number of electrons (highest CV peak areas).