Chapter 13. Post-extraction Processes: Improvement of Functional Characteristics of Extracts

Abstract

The biological activity of natural extracts is not only determined by their chemical composition. Other parameters, such as the physical characteristics of the product (particle size and morphology, crystalline/amorphous structure) as well as the combination of the active extract with carriers or co-active materials, play a major role. With this perspective, post-extraction and formulation methods are described in this chapter. Elimination of residual solvents and other contaminants as required by the regulations for commercialization is discussed first. Particle reduction techniques are presented next; they are essential both for obtaining a desired product size and morphology, as well as for increasing the bioavailability of active compounds with limited solubility in water. Formulation processes, which are used to protect sensitive active compounds, or for providing additional functionalities to the product, are also presented. The techniques discussed include top-down milling and homogenization processes, and bottom-up crystallization, emulsion-template, spray-drying, and supercritical fluid processes, to produce micro or nanoparticles, microcapsules, or microcomposites, as well as multifunctional nanocarriers such as micelles or liposomes. Finally, the formulation of quercetin and grape polyphenols as important natural antioxidants for a variety of applications as a food supplement and cosmetic ingredient are presented as case studies, with a special focus on the improvement of bioavailability and stability of the active compounds.