Prediction of dry mass glass transition temperature and the spray drying behaviour of a concentrate using a desorption method

A predictive tool (SD2P®) based on a drying by desorption method was recently developed in order to determine the key process parameters values prior to spray drying. However, the SD2P® software cannot currently take into account the risk of stickiness during the process. In the study reported here, new standardized desorption method was tested and with this new method an equation was proposed to evaluate the dry glass transition temperature (Tg) of a concentrate according to its total solid content, its viscosity and its average evaporation rate. The concentrate’s behaviour during spray drying could then be predicted on the basis of the Tg. Four validation experiments were performed using different infant formula samples; the concentrates prepared from the four infant formula powders were then spray dried using a one-stage pilot dryer. The drying parameters were predicted using the SD2P® software. The results showed that the Tg predicted using this method were 18–30 °C higher than Tg measured by DSC (Differential Scanning Calorimetry). The drying temperatures predicted by SD2P® corresponded well to the values measured and this new method can correctly predict the behaviour of a concentrate with regard to spray drying. The advantage of the method presented here is that it can easily and quickly evaluate a concentrate’s Tg range and spray drying behaviour by direct analysis of the fresh concentrate sample.