Characterisation of the variation in the physical properties of commercial creams using thermogravimetric analysis and rheology

Abstract

A study was conducted to compare the physical properties of Aqueous Cream BP obtained from different manufacturers. The samples were studied using thermogravimetric analysis (TGA) and stress scan rheology as complimentary techniques. TGA studies showed two main peaks in the first derivative curves, corresponding to free and lamellar water. The profiles for creams obtained from different manufacturers showed marked variations between the samples, although the total water content was similar in all cases. Similarly, stress scans also showed marked differences between the creams, although no clear correlation between the thermogravimetric and rheological data was observed under the conditions used in the study. Three batches of cream from one manufacturer were then examined. Differences in the rheological properties were again observed, but less marked differences were seen in the TGA profiles. The study indicates that while the chemical composition of commercial aqueous cream may be controlled, considerable variations in the physical properties of these systems may be observed, both between different manufacturers and between batches from the same manufacturer. The implications of the poor correlation between stress scan rheological and thermogravimetric analysis data are discussed in terms of the use of these two methods in the quality control of creams.