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Tablets & Capsules March/April 2021 25 • Creates a barrier to prevent interactions with other components and environmental conditions and enhance stability; • Increases bioavailability; • Masks unpleasant tastes and smells; • Sustains potency, increasing product shelf life and consumer repeat use; • Prevents color migration and transfer; • Sustains flavor profile; • Creates small particles, which increases the palatabil- ity of chewable tablets; • Uniformly distributes active in the lipid matrix; and • Creates a free-flowing powder, which promotes easy mixing. Lipid microencapsulation process Lipid microencapsulation forms lipid-active micropar- ticles by co-processing the active(s) with the heated lipid using one of several techniques, including spray congealing (commonly referred to as spray cooling or spray chilling), hot-melt extrusion, and spinning-disk congealing. With spray congealing, the active is first suspended in a melted lipid such as a wax. The suspension is then atomized into a cooling chamber, where turbulent, cool air solidifies the droplets into microparticles. Spray congealing is some- times considered to be a hybrid between spray drying and hot-melt extrusion [2]. With hot-melt extrusion (HME), the active and poly- mers are fed into a twin-screw extruder. The extruder uses heat and pressure to melt the lipid and blend it with the active at the molecular level. The machine's parallel rotat- ing screws then force the blend through a narrow orifice at the extruder's discharge. The active-lipid blend cools as it passes through the orifice, discharging as a solid ribbon, which can then be cooled, cut, and sized. With spinning-disk congealing, the active is uniformly suspended in a melted lipid, then the suspension is dispensed onto a spinning disk. The suspension flows from the center of the spinning disk to the perimeter and forms micron-sized droplets as it becomes airborne at the disk's edge. As the micron-sized droplets cool, the lipid matrix solidifies, forming spherical free-flowing microparticles contain- ing the active. The disk's rotational speed determines the particle size. The micron particle size increases the pal- atability of chewable tablets without grittiness in the oral cavity. Each of these techniques creates solidified microparticles, whose immo- bilized state creates a lipid barrier that protects the active from the surround- ing environment, promoting stability and preventing product degradation. Since the matrix is lipid based, there is no moisture or hydrophilic interface. The lipid covers the active, serving as a barrier, which decreases the propensity Microencapsulation involves the co-processing of one or more actives within a matrix that forms a barrier and protects the actives from unwanted interactions or degradation and/or improves the actives' qualities and properties within a formu- lation. According to a 2020 report released by Globe News- wire, the microencapsulation market is expected to grow at a 12.9 percent compound annual growth rate from 2020 to 2025, driven by demand for taste masking and enhanced shelf life, with added values in personal care products [1]. The barrier matrix protecting the active in a microencap- sulation process can be either polymer-based or lipid-based. Polymer-based microencapsulation encapsulates actives through a coating process. The coating typically consists of an aqueous polymer dispersion that is atomized and sprayed onto the active ingredient particles in a fluid-bed process. The water evaporates from the fluidized bed, leaving the active particles evenly encapsulated within a polymeric coating. The microencapsulation process can use various polymers, such as celluloses and alginates, to coat the active. Lipid-based microencapsulation involves encapsulating one or more actives within a lipid matrix to create spheri- cal lipid-active microparticles with a consistent shape and size. Lipids are fatty acids and derivatives of fatty acids and include four different classifications: 1. Triglycerides from fats and oils (either from satu- rated or unsaturated fatty acids) that are insoluble in water. Examples include stearic acid, oleic acid, and palmitic acid. 2. Phospholipids, which consist of both hydrophilic and hydrophobic regions of the fatty acid. Only two fatty acid molecules are attached to the glycerol, while the third glycerol binding occurs at the phosphate group. Phospholipids can thus immerse and orient into the hydrophobic region of the cell membrane easily. 3. Steroids are complex compounds that do not contain fatty acid properties but are classified as lipid based because they have lipid-like properties, with four fused carbon rings. Waxes, such as carnauba and beeswax, are nonglyceride lipids consisting of one hydroxyl group. Waxes consist of esters of fatty acids and have barrier properties that pre- vent moisture migration. 4. Lipoprotein lipids are complex, consisting of a triglyceride and a cholesterol center, which is then surrounded by phospho- lipid shell. The structure of the outer matrix is hydrophilic, while the inner matrix is lipophilic, therefore drawing a hydropho- bic active inward and stabilizing the active. Lipid microencapsulation allows developers to create stable, scalable formulations for poorly soluble and complex actives. Lipid microencapsulation provides the following advantages: Lipid microencapsulation allows developers to create stable, scalable formulations for poorly soluble and complex actives.