Gc 200

Differential scanning calorimetry (DSC) measurements of crystallized lactose samples were performed using a DSC instrument (DSC 1 STARe System, gas controller, GC 200, Mettler-Toledo, Columbus, OH) as previously explained (Wijayasinghe et al., 2015; (link)Chandrapala et al., 2016) (link) with slight modifications. Crystal samples were scanned at a heating rate of 10°C/min starting from 50°C and ending at 250°C. The STARe thermal analysis software (v. 15.00, Mettler-Toledo, Schwerzenbach, Switzerland) provided relevant information including the on-set, mid-point, and end-set temperatures and enthalpies of lactose crystal samples.

Concentrated lactose and lactose + lactic acid solutions were transferred into preweighed differential scanning calorimetry (DSC) aluminum pans (40 μL; ME-26763, Mettler Toledo, Schwerzenbach, Switzerland) and the pans were hermitically sealed. Subsequently samples were transferred into a DSC (DSC 1 STAR e System, gas controller, GC 200, Mettler Toledo). An empty pan was used as a reference. The DSC was calibrated using indium (melting point, 156.6°C and ΔH m , 28.45 J•g -1 ). All samples were scanned with a starting temperature of 25°C and end temperature of 280°C at a heating rate of 5°C•min -1 , which was a modified version of the method described by Haque and Roos (2006) . Onset and end-set temperatures of water evaporation and related enthalpies (area under the curves) were analyzed using STAR e thermal analysis software, 12.1 (Mettler Toledo).
Freeze-dried samples were also subjected to the same program with slight modifications in which samples were scanned to 120°C at a heating rate of 10°C•min -1 , then cooled at 5°C•min -1 to 25°C, followed by a second heating scan at 10°C•min -1 to 200°C. The scans were normalized by the system according to the sample mass, and the integrated peak energies were used to compare the differing degrees of crystallinity.