Detecting adulterated commercial sweet sorghum syrups with ion chromatography oligosaccharide fingerprint profiles

Abstract

Some commercial sweet sorghum syrups can be fraudulently or accidently adulterated with inexpensive sugar syrups, particularly high fructose corn syrup (HFCS) or corn syrup, and sold at a relatively low market price or even mis-branded. This undermines the economic stability of the current small-scale producers of food-grade sweet sorghum syrup as well as the developing large-scale bioproduct industry. An analytical method is urgently needed to evaluate adulterated commercial sweet sorghum syrups. Ion chromatography with integrated pulsed amperometric detection (IC-IPAD) has been previously used to differentiate white, refined sugars manufactured from sugarcane and sugar beet. By applying a strong IC-IPAD NaOH/NaOAc gradient method over 45 min, monosaccharides, oligosaccharides and oligosaccharide isomers of at least 2 to 12 dp, as well as sugar alcohols can be detected in multiple commercial sweet sorghum and other sugar syrups. Fingerprint IC oligosaccharide profiles are extremely selective, sensitive, and reliable. By using five characteristic marker chromatography peaks of high fructose corn syrup (HFCS), including isomaltose, maltose and maltotriose, in combination with a low sucrose peak, adulterated and mis-branded syrups were identified. The analysis of 7.0 Brix blind syrup samples, marker peaks allowed the detection of as low as 10% HFCS adulteration, which is within the lower limit of adulteration before action is taken.