Comparison of various methods for determination of water in white yoghurts

Water content was determined in 11 samples of white yoghurts. Several techniques, namely Karl Fischer (KF) volumetric titration, near and middle infrared spectroscopy (MIR), oven drying and moisture analyser were used. Optimisations of solvent, titration temperature and extraction time were carried out for the KF titration. Methanol at room temperature with 5 min extraction period was used as final conditions. For the infrared spectroscopy (FTIR) the suitable solvent and the appropriate wavenumbers for water analysis were chosen. The measurement in the near infrared (NIR) region at the wavenumber 10270 cm⁻¹ using acetonitrile as solvent and transmission method was evaluated as the best of the FTIR methods. Based on the comparison of individual methods the oven drying at 105 °C seems to be the most suitable, but it is the most time consuming. However, KF volumetric titration and especially FTIR methods appear to be good alternatives to the drying methods.