EVALUATION and COMPARISON of SIMPLE METHODS FOR pH MEASUREMENT of REDUCED-MOISTURE SOLID SYSTEMS

It is desirable to quickly and accurately determine the pH of reduced-moisture solid food systems. Several techniques of pH determination were evaluated on such systems. Methods involving the addition of water yielded pH values higher than actually existed based on pH-dependent chemical reactions. the Ultra M® micro electrode had problems with reproducibility and stability in the reduced-moisture systems as well as the buffer solutions used for calibration. the Horiba Cardy pH meter and the surface pH electrode used directly on the surface of the reduced-moisture solid system yielded pH values similar to those determined using pH-dependent chemical reaction markers. the ability to measure the actual pH of reduced-moisture solid systems would enable better understanding of potential modifications in product formulation needed to retard microbial growth and limit chemical reactions responsible for loss of shelf-life.