Gellan Hydrogels: Preparation, Rheological Characterization and Application in Encapsulation of Curcumin

Abstract

Hydrogels can be used to protect some labile active principles, as polyphenol-rich substances, that can be added to foods to prepare functional ones. Rheological properties of gels formed through the addition of calcium chloride to gellan solutions were studied. It can be concluded that preparation variables and not only formulation ones are determinant in rheological properties of the resulting gels, as they are not in an equilibrium state but they are continuously evolving during hours to stronger gels corresponding to a denser network. It could be related to the fact that local non-gelled domains are formed surrounded by a shell of gel where Ca 2+ ions take some time to arrive. A minimum Ca 2+ /gellan ratio (CG) is required to reach the gel point (GP), determined as the CG where the ratio loss modulus/elastic modulus (G"/G') collapse for all frequencies. Calcium-induced external gelation of oil-in-water (O/W) emulsions where a curcumin-in-oil solution is the disperse phase and a watery solution of gellan is the continuous phase was used to prepare beads were curcumin is entrapped in order to prevent its degradation. Smaller droplet-sized emulsions were obtained with higher gellan concentrations, since a higher viscosity of the continuous phase allowed to reach the critical Capillary number CaC at lower radius of droplets. An encapsulation yield around 90 % was reached for gellan concentrations of 1 % w/v, and the resulting encapsulated curcumin presented around 6 times slower light degradation than free curcumin-inoil solutions.

Rheological and textural analysis as tools for investigation of drug-polymer and polymer–polymer interactions on the example of low-acyl gellan gum and mesalazine

“…Hydrogels were prepared following a modified method described by Ambebila et al 26 Kinematica Polytron PT-MR 1600 homogenizer (Kinematica AG, Malters, Switzerland) was used to obtain hydrogels with the desired consistency. The gellan solutions and API suspensions were located in a bottle at room temperature and proper amounts of 1.0% w/w gelling agents (CaCl 2 or MgCl 2 ) solutions were added in order to obtain the ion-polymer ratio of 0.002.…”

“…Magnesium acetate, 23 magnesium sulfate, 24 and magnesium chloride 25 were reported as effective gelling agents in numerous works. However, calcium ions are supposed to create slightly stronger structures 26 with higher storage modulus (G 0 ) 27 in comparison to magnesium ions. As the physical properties of the obtained beads have a major impact on such properties as swelling ratio and drug release, 28 the choice of a proper gelling agent is highly important and can also be a factor that allows controlling the drug release.…”

Rheological and spectroscopic study of luminescent Eu3+ -doped gellan gum

“…In the presence of cations, the GG polymer chain cross-links through ionic crosslinking mechanisms, so that a stable gel structure is achieved in a process known as ionotropic gelation (Maiti et al 2011;Morris et al 2012). This process is affected by the concentration and chemical nature of the cation present in the solution and has been described (Silva-Correia et al 2011; Costa et al 2018) for mono-and divalent ions, such as Na + , K + , Ca 2+ , and Mg 2+ (Boni et al 2016;Ambebila et al 2019). However, there are gaps in the study of GG associated with lanthanide ions, whereas the GG chains bear groups that can act as coordination environment for these ions, which are generally trivalent cations that greatly impact the GG structure.…”

Bioactive foamulsion gels: a unique structure prepared with gellan gum and Acanthophyllum glandulosum extract

“…26 To stabilize the foamulsions, we used gellan, which forms viscous solutions or gels at markedly lower concentrations than other hydrocolloids such as alginate, carrageenan, pectin or gelatin. 27 Gellan gum (GG) is an anionic polysaccharide with a tetrasaccharide repeating sequence consisting of ⊎-D-glucose, ⊎-Dglucoronate and ⊍-L-rhamnose (2:1:1). It is widely used as a gelling and thickening agent in various food products, such as dairy, confectionery, baking, low-fat sauces and beverages.…”