## 3 Results and Discussion  
### Core-in-Wall Emulsions (CIWEs)  
Success in microencapsulation of lipids by spray drying and the stability and functionality of the dry microcapsules are significantly influenced by the formation, physico-chemical and rheological properties, stability, and functionality of the CIWE [52; 53]. The formation and properties of CIWE are governed by the combined influence of the physico-chemical and surface activity of the wall constituents, the mass ratio of wall-to-core (W:C) in the CIWE, the emulsification and homogenization process conditions and the inherent properties of the core [30; 53]. It has been established that, in the case of protein-stabilized CIWE, the colloidal characteristics and stability of the emulsion as well as the oxidative stability and functionality of the dry microcapsules are significantly affected by the formation, composition, structure, and rheological properties of stable protein-based films at the O/W interfaces during the emulsification and homogenization stages of the microencapsulation process [30; 31; 34; 44; 53; 54]. Except for a few cases, where a limited manifestation of bi-modality was evident, CIWEs exhibited a unimodal particles size distribution (Figure 1). In all cases, CIWEs were subjected to four successive homogenization steps, in the single-stage configuration, at 50 MPa. This process significantly challenged the emulsification properties of the surface-active constituents of the emulsion, the WHPI, especially when WS containing only 2.5% WHPI was used at a W:C ratio of 50:50 and 25:75. In the absence of a low-pressure second homogenization stage, every pass through the homogenization valve increased the overall interfacial surface area in the CIWE. The latter presented a significant challenge to the adsorption of proteins at the newly formed O/W interface. The proteins had to become adsorbed at the O/W interface at a rate and to the extent that was needed in order to stabilize this O/W interface and to prevent coalescence or formation of homogenization aggregates [55]. Results (Figure 1) indicated that, even at the low concentration of 2.5%, WHPI was effective in facilitating the formation and stabilization of CIWEs with PSD properties that are desired for microencapsulation by spray drying [34; 44; 51]. The few cases where PSD of CIWEs exhibited limited bi-modality could be attributed to the formation of homogenization clusters, especially at a high oil content and low WHPI concentration [30; 55; 56] and, to some extent, to the adverse effect of viscosity on emulsification efficiency in some of the CIWEs that had been prepared with WSs containing 5.0 or 10.0% WHPI [55]. The mean particle size (d\({}_{3,2}\)) of the CIWEs ranged from 0.26 to 0.46 \(\upmu\)m, and it was significantly (\(p<0.05\)) affected by the combined influence of the W:C ratio in the CIWE and the composition of the WS that had been used for preparing the CIWE (Table 1). In all cases, for a given composition of WS, d\({}_{3,2}\) was proportionally related to the core load in the CIWE (\(p<0.05\)). Mean particle size of CIWE with a W:C ratio of 75:25 was 0.02-0.15 \(\upmu\)m smaller than that in CIWE with W:C ratio of 50:50, while that in CIWEs with a W:C ratio of 25:75 was 0.1-0.35 \(\upmu\)m larger than that of CIWEs with a W:C ratio of 50:50 (Table 1). The extent at which d\({}_{3,2}\) increased with core load was influenced by the solids composition of the WS (Table 1). For example, d\({}_{3,2}\) of CIWEs that were prepared with WS 2.5/17.5, 5.0/15.0, 7.5/12.5, and 10.0/10.0 at a W:C ratio of 75:25 was 62, 69, 62, and 75% of d\({}_{3,2}\) of CIWEs with W:C ratio of 25:75, respectively.