Analysis of the moisture content in tomato paste: Photopyroelectric approach versus conventional thermogravimetry

Water, the most common substance in foods, is of importance to food quality in terms of adequate storability, taste etc. Therefore both maximal or minimal amount of weater in foods is specified by the legislation. At present the most widely spread reference method for assessment of moisture is thermogravimetry (TMG) that makes combined use of a balance and drying oven. A few hours long period required to complete the analysis constitutes the major drawback of TMG. On the other hand, the pyroelectric (PPE) method, one among the photothermal (PT) techniques, that by the virtue of its operational principle allows for a relatively simple direct measurement of thermal diffusivity   and thermal effusivity e (both of these thermophysical parameters depend on the sample´s composition) might prove a candidate method for assessment of moisture without the need for use of drying oven. Potential of the PPE method for direct moisture analysis was explored using a number of tomato pastes (characterised by a varying amount of dry matter) as test samples. The outcome suggests a good agreement between results of the initial PPE experiments with those acquired by the traditional TMG.