The effect of the salt content on the crystallization behaviour and sorption fingerprints of spray-dried lactose

Different types of salts in various proportions affect lactose crystallization. In this study, two common monovalent salts, NaCl and KCl, were used at lactose:salt ratios of 5:2 and 5:1 (w/w) to observe the change in crystallization behaviour of the mixtures compared with that of pure lactose obtained from spray drying. The same operating conditions (170 °C inlet air temperature, 38 m3/h main air flow rate, feed pump rate 11 ml/min, nozzle air flow rate of 473 L/h) were maintained for each run in a Buchi (B-290) Mini Spray Dryer to compare the behaviour of different feed compositions. To analyse the crystallization behaviour of each spray-dried product, Moisture Sorption Characteristic diagrams and Moisture Sorption Finger-prints were used, and Scanning Electron Microscopy (SEM) micrographs of the samples have also been carried out. The results show that, at lower salt contents (lactose:salt = 5:1), both lactose/salt mixtures showed the highest change in moisture content, but there was significant difference in sorption behaviour at higher salt contents for both salts. Among all the lactose/salt powders, the lactose:NaCl mixture at a ratio of 5:2 was found to be the most crystalline product in nature.