Analysis of Food Carbohydrates

Abstract

Earlier methods employing polarimetric, colorimetric, or enzymic determinations are generally not applicable for complex mixture of sugars which are often present in food matrices; therefore, food carbohydrates, such as sugars, starches, and dietary fiber polysaccharides have not been analyzed routinely in the same foods until the advent of chromatographic techniques. Since the mid 1960s, methods employing gas-liquid chromatography (GLC) have appeared in many reports1--4. One major disadvantage of GLC methods for sugar analysis arises from the need to convert sugars to their volatile derivatives. Consequently, high-performance liquid chromatography (HPLC) has become the technique of choice for many analysts5--8. For a number of years, the only detector available for HPLC sugar determination was the non-specific refractive index detector, which lacks the sensitivity of the flame ionization detector used with GLC. With the development of anion-exchange resin columns and pulsed amperometric detector with gold electrode specifically for carbohydrate analysis, simple and complex sugar mixtures can now be separated and quantified on the same HPLC column using different eluants9,10. In an effort to simplify and consolidate various independent procedures for determining different fractions of food carbohydrates, we developed a scheme11 by which sugars, starches, and dietary fiber polysaccharides can be sequentially fractionated from the same half-gram freeze-dried portions of a food as shown in Fig. 1. High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was used for quantification of various sugars in different fractions.