## 4 Discussion  
To produce dry microcapsules, i.e., powders from which an oil-in-water emulsion can easily be reconstituted when exposed to an aqueous solution, the emulsions used must exhibit small droplets of oil before the drying step. Moreover, the particle size distribution and the stiffness of the interfacial membrane could have significant effects on the TC release profile from the microcapsules as well as on the encapsulation efficiency upon drying of the emulsion. The different structural properties of the two emulsifiers used may explain the differences observed in the characteristics of the emulsions formed before drying. Indeed, lecithin is a natural small-molecule emulsifier composed of many different phospholipids, and the two most abundant phospholipid species are phosphatidylcholine and phosphatidylcholine. However, the two major components of pea protein are 11S legume protein and 7S victim protein. They have a regular quaternary structure, hexameric for legumin protein and trimeric for victim protein. The total molecular weight of a legumin unit is about 380 kDa. It is a very compact globular protein in which the acidic polypeptides are located outside and the basic polypeptides constitute the hydrophobic core of the protein. 7S victim is a glycoprotein with a molecular weight of approximately 150 kDa. The quaternary structure of pea globulins depends on pH and salt concentration. Given these structural differences, the two emulsifiers have different interfacial properties, such as adsorption kinetics, interfacial tension-lowering kinetics, interfacial rheology, and concentration at the interfacial membrane. If the absorption of lecithin molecules is quite fast, that of globular proteins is slower because it requires a phase of dissociation and unfolding before integrating the oil-water interface. This phenomenon results in a difference in the size of the droplets in favor of the emulsions stabilized with lecithin [17].  
The absolute value of the zeta potential for all emulsions was high enough to induce emulsion stability whatever emulsifier was used, but emulsions prepared with lecithin showed slightly higher values, indicating better stability. This result can be interpreted in terms of the higher final concentration of lecithin at interfacial membranes, since a part of pea protein was insoluble and separated before emulsification. Moreover, the emulsions stabilized using lecithin had smaller average particle size than those emulsified using pea protein.  
Figure 5: SEM image and particle analysis. First line: spray-dried powders (L3S, L7S, P3S, P7S). Second line: freeze-dried powders (L3L, L7L, P3S, P7S).  
The average size of spray-dried powders did not change significantly according to the type of emulsifier and pH, as all emulsions were pulverized under the same conditions, while the average size of freeze-dried particles was significantly bigger. These differences may be due to the fact that spray-drying includes a step of spraying into fine spherical droplets whereas freeze-drying is a sublimation of a frozen emulsion in static mode. Moisture content is an important parameter because of its effect on the powder stability, flowability, stickiness, microbial growth, and oxidation of bioactive compounds. FD powders contain less water content compared to the SD powders; however, both drying processes applied in this study provided acceptable water content ranging from 2.03 to 5.02%, offering the possibility of long storage lifetimes of these antimicrobial powders. In fact, moisture contents ranging between 4 and 6% could be considered suitable for long-term storage [41]. The attainment of microcapsules with interesting properties is the main outcome of this study because the direct application of liquid emulsions in food processing is limited and the encapsulation techniques applied supplied powders with acceptable EE for food applications.