Selective Adsorption of Essential Oil Compounds by Waxy/Amylose Extender (wx/ae) Double-Mutant Rice Starch Revealed by Gas Chromatography

The present study describes how waxy/amylose extender (wx/ae) double mutant and waxy (wx) single mutant rice starches adsorb many kinds of chemical compounds in essential oils using dynamic adsorption and gas chromatography. Selectivity in the dynamic adsorption is determined by the functional groups of chemical compounds. Compounds with a hydroxyl group (- (-OH) are easily adsorbed. Compounds with aldehyde (- (-CHO) and ketone (- (-C(=)O)-) groups, or with ester bonds (- (-C-O-C-)-O-) are also adsorbed if they had a cyclic structure or carbon double bond. Compounds with an ether bond (- C-O-C-) are adsorbed if they had a carbon double bond. The dynamic adsorption process may be driven mainly by forming hydrogen bonds between hydroxyl groups of starch and these proton acceptor groups of chemical compounds in essential oils. The authors also analyzed the adsorption capacity of the wx/ae and wx starches for several compounds which are adsorbed to these starches in a dynamic process, by static adsorption. The wx/ae starch has greater capacity than wx starch to adsorb chemical compounds, due to its larger surface area and surface pore volume. The adsorption capacity of starch for chemical compounds is also affected by the structural features of the chemical compounds.