Estimation of water activity from pH and °Brix values of some food products

In this study, a predictive model for the estimation of water activity (a(w)(25 degrees C)) as a function of pH (1.00-8.00) and degrees Brix (0-82.00) values of simulated food solutions (SFS) was developed, through response surface methodology. Response fit analyses resulted in a highly sigW nificant (pH < 0.0001) square root polynomial model that can predict a(w)(25 degrees C) of SFS in terms of pH and degrees Brix values within the defined variable ranges. The linear, quadratic and interactive influences of pH and degrees Brix on a(w)(25 degrees C) were all significant (pH < 0.0001). Model validations in SFS and in a number of actual food systems showed that the model had acceptable predictive performance, as indicated by the calculated accuracy and bias indices. (C) 2007 Elsevier Ltd. All rights reserved.