WATER SORPTION BY WHEAT ANS SOY FLOUR - COMPARISON OF 3 METHODS

The water sorption isotherms of wheat and soy flour were constructed at 30°C using the gravimetric (static), inverse gas chromatographic (IGC) and computerised inverse gas chromatographic (CIGC) techniques. The times required for the construction of a single sorption isotherm by these methods were approximately 3 weeks, 2 days and 3 hours, respectively. Good agreement was observed between sorption isotherms for wheat and soy flour obtained with the IGC and static methods. Differences between the two methods were in the order of 7·5% for wheat flour and 12% for soy flour. The respective differences between the static and CIGC methods were in the order of 18·5% for wheat flour and 12% for soy flour. The experimental data were fitted successfully to both the BET and GAB model equations, and monolayer (Vm) and sorption constant (C) values were calculated for all three methods. It is proposed that both the IGC and GIGC techniques may be used reliably as alternatives to the static method industrial applications involving flour-based products where time is a critical factor. © 1994 Academic Press Limited.