Abstract
To understand the abilities of Ca-alginate microcapsules and their specific applications in different fields, it is necessary to determine the physicochemical and structural properties of those formulated microcapsules. In this work, we aimed to study the effect of alginate concentration in the improvement of the encapsulation efficiency (EE) and on the release of phenolic and flavonoid substances. The relationship between the structure of the encapsulated bioactive substance and Ca-alginate network and their effect on the EE and release kinetics have been investigated. The incorporation, structure, morphology, and phase properties of all elaborated materials were characterized by UV-spectroscopy, Fourier transform infrared (ATR-FTIR), scanning electron microscope (SEM), and X-ray diffraction (DRX). The results indicate that increasing the polymer concentration increases the EE and decreases the loading capacity (LC), whereas the effect of alginate polymer concentration on the release was not observed. The release study of bioactive substances showed that the release kinetics is relatively dependent on the structure and the physicochemical characteristics of the bioactive substance, which became clear when the encapsulated compounds were released from the core of calcium alginate microcapsules. Thus, it could be concluded that the pores size of the Ca-alginate network is smaller than the volume of the crocin molecule (2794.926 Å3) and higher than the volume of the gallic acid molecule (527.659 Å3). For the same microcapsules system, the release mechanism is affected by the structure and physicochemical properties of the encapsulated molecules.
Highlights
Microencapsulation technology aims to protect bioactive substances, during processing, improving stability from external harsh conditions in final products and during processing, masking undesirable odors and tastes of ingredients, and the delivery of the encapsulated matter at controlled rates, at a certain time, and in a certain place [1, 2]. e choice of shell material is an important step in order to encapsulate a bioactive substance
Similar results were reported [6, 8, 23, 24]. e results show that increasing the alginate polymer concentration causes a rise of encapsulation efficiency and a decrease of the loading capacity. is verifies our hypothesis that suggests that the increase of the sodium alginate concentration can certainly lead to introduce a higher level of Ca2+ ions responsible of the cross-linking between the alginate chains and, forms a dense cohesive structure. e structural properties of the crocin molecule are responsible for the enhancement of EE and LC compared with the encapsulation efficiency and loading capacity of gallic acid (Table 2)
As part of the ongoing work, a bioactive substance delivery system based on the calcium alginate network was successfully prepared by the ionotropic gelation method using different concentrations of alginate polymer followed by their physicochemical characterization
Summary
Microencapsulation technology aims to protect bioactive substances, during processing, improving stability from external harsh conditions in final products and during processing, masking undesirable odors and tastes of ingredients, and the delivery of the encapsulated matter at controlled rates, at a certain time, and in a certain place [1, 2]. e choice of shell material is an important step in order to encapsulate a bioactive substance. E choice of shell material is an important step in order to encapsulate a bioactive substance. Sodium alginate polymer, obtained from brown algae, has a number of features that makes it appropriate to form hydrogel microcapsules, such as its low cost, high availability, biodegradability, biocompatibility with other agents, and easy synthesis of microparticles [3, 8, 11, 12]. Alginate microcapsules are largely applied in the pharmaceutical industries, as an example, due to their ability to release the bioactive substance through the diffusion mechanism. E diffusion mechanism can be shortened into the transport of bioactive substance from the internal core to the external microcapsule shell [13,14,15,16,17] Another important mechanical property is the release rate, which is mainly related to the porosity of the microcapsules. e release of the encapsulated substance in different applications is mostly due to the diffusion mechanism, as a principal process in controlled release systems. e diffusion mechanism can be shortened into the transport of bioactive substance from the internal core to the external microcapsule shell [13,14,15,16,17]
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