Pellets based on polyuronates: Relationship between gelation and release properties

Abstract

Abstract: Three polyuronates: amidated low methoxyl pectin (ALMP), low methoxyl pectin (LMP) and polygalacturonic acid (PGA) were used to encapsulate rutin in pellets, and they were characterized by different techniques (macroscopic properties, calcium and rutin release). The ability of the three polyuronates to bind calcium ions and the viscoelastic properties of gels were performed to relate the properties of the pellets to the gel structures. The pellets size, the water content, the water uptake, the release of calcium and rutin varied depending on the polyuronate used. The pellets size of ALMP were smaller than LMP and PGA with a lower water content, but this matrix was more sensitive to the water uptake, which favored the diffusion of calcium and rutin in a simulated intestinal fluid (Tris-HCl buffer, pH 7.4). This can be explained by the structure of ALMP network inducing the most flexible gel with the lowest viscoelastic moduli and a low affinity for calcium due to the presence of methoxy and amide groups that disrupts randomly the polygalacturonate units in the pectin chain and requires less calcium to form the gel. For the LMP and PGA, the gel properties were stronger than ALMP resulting in a better resistance to water uptake, thus inducing a lower diffusion of calcium and a lower rutin release. Finally, the rutin release was related to the structure and the properties of the network formed before drying due to the nature of polyuronate used during the manufacturing process of pellets.