Determination of saccharides in fruit juices by capillary electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A fast method for the detection of cheap sweeteners is presented. Detecting the adulteration of foods rich in carbohydrates is complicated by the presence of variety of commercial sweeteners that are designed to match exactly the major carbohydrate profiles of these foods. Electrophoretic and mass spectrometric assays for the determination of fruit juice authenticity were developed. Capillary zone electrophoresis with indirect detection was employed to detect adulteration of juices demonstrated by the ratio of the concentrations of major low molecular mass saccharides (glucose, fructose and sucrose). Traces of oligosaccharides, which are not present in the sugar profiles of citrus fruits but are present in inexpensive sweeteners, were evaluated as the other group of target compounds. The fast determination of oligomeric starch hydrolysates in a complex matrix was tested by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and applied to orange juice. MALDI-TOFMS was shown to be a suitable method for the identification of adulteration of fruit juices by starch hydrolysates. The effects of the presence of salts and low molecular mass saccharides on the detection of oligosaccharides by MALDI-TOFMS were studied. Low molecular mass saccharides and organic acids decrease the detectability of oligosaccharides by MALDI-TOFMS, but the concentration of maltooligosaccharides present in juices sweetened with starch hydrolysates is high enough to be detected with good sensitivity.