## 3 Results and Discussion
### Core Extractability and Microencapsulation Efficiency  
Core extractability (Figure 3) was affected by the combined influence of the composition of the WS and the W:C ratio in the CIWE. The effect of extraction time on the proportion of extracted oil varied very significantly and it was dramatically influenced by the W:C ratio in the CIWEs (Figure 3). Except for the microcapsules that had been prepared with CIWE having a W:C ratio of 25:75 (Figure 3C), the extraction time had only a very small effect on the proportion of core that was extracted from the microcapsules (Figure 3A,B). Results indicated that at a given W:C ratio, core extractability was proportionally related to the lactose content in the CIWE. Based on the results of core extractability, the investigated microcapsules could be divided into three sub-populations. The first consisted of microcapsules prepared with CIWEs at a W:C ratio 75:25 where the proportion of core that was extracted after 2.5 and 30 min ranged from 0.51-0.93 to 0.74-1.1%, respectively (Figure 3A). The second population consisted of microcapsules prepared with CIWEs at a W:C ratio of 50:50 where the proportion of core that was extracted after 2.5 and 30 min ranged from 1.7-3.12 to 2.26-3.45%, respectively (Figure 3B). The third population (Figure 3C) consisted of microcapsules that were prepared with CIWEs at a W:C ratio of 25:75 where the proportion of core that was extracted after 2.5 and 30 min ranged from 9.5-15.8 to 14.6-25.8%, respectively. For microcapsules that were prepared at a W:C ratio of 50:50 and 75:25, the very small changes in core extractability with an extraction time longer than 2.5 min suggested that the total proportion of extractable core (surface oil) mainly consisted of \"free oil\" or lipid droplets that resided at- or a small distance below- the outer surfaces of the dry microcapsules [(45)]. In contrast to the latter, the increase in the proportion of extractable core with extraction time that was evident in the case of microcapsules with a W:C ratio of 25:75 (Figure 3C) suggested that, in these cases, core was also extracted from domains in the interior parts of the dry microcapsules [42; 45; 60; 61]. The relatively higher proportion of extractable core that characterized these microcapsules could be attributed to a higher proportion \"surface fat\" and core droplets that resided at the outer surface of these microcapsules as well as a to core that was extracted from inner domains of the dry microcapsules. The latter has been shown to reflect results of solvent diffusion, flow through capillaries, and flow empty core domains that had already been extracted [42; 62]. In the case of lipids that are susceptible to oxidation, the proportion of \"surface oil\", especially the proportion of \"free oil\", significantly affects the overall oxidative stability, quality, and functionality of the microcapsules and products to which they are added [60]. The overall low proportion of core that could be extracted within 2.5 or 5 min from microcapsules with a W:C ratio of 75:25 and 50:50 indicated a low proportion of \"surface oil\". These results suggest the potential suitability of the investigated systems for effective microencapsulation of lipids. Microencapsulation efficiency (MEE), the proportion of core that was not extracted during 5 min, ranged from 76.5 to 97.2%, and was influenced, to a certain degree, by the composition of the CIWEs (Table 4). Except for two cases, the investigated microcapsules exhibited MEE >93% and, in most cases, MEE was >95%. It has been demonstrated that, in the case of wall systems consisting of whey proteins and lactose, MEE was proportionally related to the proportion of lactose that was included in the wall system [43; 44; 45]. It has been suggested that, in those cases, the lactose formed a glassy phase during spray during that hindered the diffusion of a non-polar solvent through the matrix and thus led to a low core extractability [44; 45].