## 3 Results and Discussion
### Differential Scanning Calorimetry--Phase Transitions and Crystallisation Curves
Based on the shapes of the milk-fat peaks in the DSC curves, it can be concluded that the milk fat has undergone transitions compared to the milk fat in the fresh mixtures (Figure 14). [PERSON] et al. [47] studied milk powders with different fat contents. After a six-month storage period, they indicated that the fat content had not changed significantly. However, the melting characteristics of the milk fat changed after storage. Fatty acid preparations n-3 and n-6 were added to all the mixtures. The DSC curves of these mixtures were characterised by three exothermic crystallisation peaks of n-3 and n-6 fatty acids (Figure 16). The maximum temperature range for the first small, weak exothermic peaks was from \(-\)18 to \(-\)22 \({}^{\circ}\)C. The temperature was not significantly different from that of the temperature for the fresh mixtures (Figures 14 and 16). The presence of this type of peak indicated the crystallisation of \(\alpha\)-linolenic fatty acid from the n-3 group. The temperature of the second weak exothermic peak ranged from \(-\)29 to \(-\)31 \({}^{\circ}\)C. This peak concerned the presence of \(\gamma\)-linolenic acid from the n-6 group. The peak characterised by a temperature of \(-\)29.47 \({}^{\circ}\)C in the DSC diagram of the M2 mixture was the most distinct. Even though the addition of n-6 acid preparations was also high in the M3 mixture, the peak was not as distinct (Figure 16). The greatest differentiation in the maximum temperature was observed for the third peak, which indicated the presence of docosahexaenoicenoic acid from the n-3 group. For the M1 mixture, this temperature was approximately \(-\)41.86 \({}^{\circ}\)C, and for the M2 and M3 mixtures, it was approximately \(-\)47.24 \({}^{\circ}\)C (Figure 16). Docosahexaenoicenoic acid hassix double bonds in its molecule; the period of storage and environmental factors could reduce the number of bonds and change the properties of this acid [59]. In the DSC cooling diagram of the M2 mixture, a small exothermic peak was observed at a temperature of approximately \(-81.09\)\({}^{\circ}\)C (Figure 16). The DSC cooling diagram of the A1 agglomerate was characterised by a sharp, distinct, exothermic peak at a temperature of about \(9.28\)\({}^{\circ}\)C and three small peaks. The DSC cooling curve of the M1 mixture was characterised by a broad, exothermic peak with three single peaks and an additional three small peaks (Figure 16). The greatest differences were observed for the third small peak; its temperature in the DSC curve of the M1 mixture was \(41.78\)\({}^{\circ}\)C, while that in the DSC curve of agglomerate A1 was \(56.24\)\({}^{\circ}\)C. The third small peak did not exist in fresh powders' DSC curves (Figure 14). The DSC cooling curves of the M2 mixture and agglomerates were characterised by a similar shape and course. The temperature ranges from the first to the fourth peaks were, respectively, from \(-18\) to \(-22\)\({}^{\circ}\)C, from \(-26\) to \(-35\)\({}^{\circ}\)C, from \(-44\) to \(-51\)\({}^{\circ}\)C, and from \(-72\) to \(-86\)\({}^{\circ}\)C (Figure 16). The peaks with the highest intensity indicated the presence of docosahexaenoicenoic acid from the n-6 group. The addition of the n-6 fatty acid preparation was very large in the M2 mixture (Table 1). The distinctness of the fatty acid peaks from the n-3 group in stored agglomerates increased compared to that of the peaks from the fresh agglomerates (Figure 14). This was caused by the migration of fats to the surface of the agglomerate particles during storage. There were no influences of the type of wetting liquid on the shape and course of the DSC cooling curves of the stored powders. [PERSON] et al. [8] studied the influences of the storage conditions on the physico-chemical properties of infant milk formula powders prepared with various lactose-to-maltodextrin ratios by spray-drying. The powders were stored for 180 days at 22 and 40 \({}^{\circ}\)C and relative humidities of 11, 23, and 54%.