PREDICTION OF WATER ACTIVITY LOWERING ABILITY OF FOOD HUMECTANTS AT HIGH a w

Equations for prediction of the a w lowering effect of humectants in a complex IMF food system were investigated in the range 0.98–0.81 water activity. Three equations have previously been used to predict a w lowering effect of simple solutes in solution, but have never been tested in an IMF system. In addition, two equations were derived, a linear slope method and a graphical procedure. Four commonly used food humectants were incorporated into a model IMF system and the resulting a w 's measured. The measured results were compared to the predicted values of these equations. The linear slope method was shown to be the most accurate of the five equations studied. It is simple and requires only the initial a w and moisture content of the system along with a predetermined slope value for the moisture sorption isotherm for each humectant. The Ross derivation also provides a relatively accurate method of predetermining the final a, in this range.