Use of the alditol acetate derivatisation for the analysis of reducing sugars in potato tubers

The alditol acetate derivatisation for determining levels of reducing sugars in ethanolic extracts from potato tubers by gas chromatography was investigated. Standard curves for alditol acetate derivatives of aqueous solutions of allose, glucose and fructose were of acceptable linearity over the concentration range of interest (R² = 0.9933, 0.9992 and 0.9997, respectively). Reproducibility of replicate derivatisation of the standards was also acceptable [mean relative standard deviation (RSD) was 5.16%]. Fructose was converted to mannitol and glucitol hexa-acetate in a fixed proportion (mean mannitol:glucitol ratio was 0.67) over the concentration range applicable to potatoes. This ratio was used to calculate reducing sugar levels in ethanolic extracts from five varieties of potatoes using allose as an internal standard. Reproducibility for replicate analyses of reducing sugars in potatoes was acceptable (Mean RSD = 6.65%) and values were within the range of those reported previously.