Specific natural isotope profile studied by isotope ratio mass spectrometry (SNIP-IRMS): C-13/C-12 ratios of fructose, glucose, and sucrose for improved detection of sugar addition to pineapple juices and concentrates

The delta(13)C values of fructose, glucose, and sucrose have been determine d in authentic pineapple juices. The sugar fraction is separated from the o rganic acids by an anionic exchange process. Then the individual components (fructose, glucose, and sucrose) are isolated on a preparative HPLC device using a NH2-type column. It is demonstrated that no significant isotope fr actionation occurs when close to 100% of material is recovered and when the hydrolysis of sucrose is avoided. The control of the recovery rates and of the sucrose hydrolysis rate after purification is recommended for a reliab le interpretation of the results. Correlations between the delta(13)C value s of fructose (delta(13)Cf), glucose (delta(13)Cg), and sucrose (delta(13)C su) can be characterized by systematic differences between these values. Fo r the set of measurements on authentic pineapple juices and concentrates, t he mean and the standard deviation of the differences are delta(13)Cf - del ta(13)Cg = -0.6 +/- 0.6 parts per thousand, delta(13)Cf - delta(13)Csu = -1 .3 +/- 0.6 parts per thousand, and delta(13)Cf - delta(13)Csu = -0.7 +/- 0. 5 parts per thousand. The determinations of the C-13 content of fructose, g lucose, and sucrose enable a refinement of the detection of added sugars in fruit juices, re-enforcing the SNIP-IRMS method.