Use of inverse gas chromatography with humidity control of the carrier gas to characterise aroma–starch interactions

The interactions between aroma compounds and native corn starch were studied by inverse gas chromatography (IGC). A system of humidification of the carrier gas has been set up and generated a fixed and stable relative humidity of 56±3%. The IGC system worked under pressure (2.1 bars), using starch as stationary phase without any support. This technique allowed to maintain the starch matrix with a constant water content of 10%. The specific retention volumes of volatiles (1-hexanol, 2-hexanol, octanal, ethyl hexanoate and d-limonene) were measured under dry and humid conditions. Retention was higher under humid conditions, especially for 1-hexanol. Retention indices of volatiles with various functions and carbon chain lengths were determined on starch and compared to RI on Carbowax. RI on starch increased with the carbon chain length, like on Carbowax. Retention on starch and Carbowax followed the same general order, relative to the functional group.