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Composite gel microparticles based on alginate and callus culture pectins with low and high degrees of methylesterification or apple pectin were produced. By varying the chemical composition of the pectic samples and the ratio of alginate to pectin, the gel strength, morphology, and swelling properties of composite microparticles can be altered. The inclusion of increasing concentrations of alginate in gel formulations promoted an increase in the microparticle gel strength and the formation of a smoother surface microrelief independently of the pectin chemical composition. Microparticles based on the pectin with a low degree of methylesterification (DM) and a higher concentration of alginate exhibited an increased swelling degree in the simulated digestive fluids. Microparticles based on the pectin with high DM and low alginate concentration were destroyed in the simulated intestinal fluid within 1 h due to the low Ca2+ content, gel strength, and grooved and rough surface of these microparticles. An increase in alginate concentration of gel formulations based on pectin with high DM led to increased stability of the microparticles in the simulated intestinal and colonic fluids due to increased Ca2+ content, microparticle gel strength and degree of crosslinking. • The ratio of alginate to pectin influences the gel strength and morphology of microparticles. • The ratio of alginate to pectin changes the swelling properties of microparticles. • Increasing concentration of alginate promoted increasing the microparticle gel strength. • Alginate increase stability of the microparticles based on the pectin with low DM • The higher stability of microparticles was due to the higher degree of crosslinking. [ABSTRACT FROM AUTHOR]