Effects of Calcium Source and Sodium Alginate to Porous Corn Starch Ratio on the Characteristics of Sodium Alginate-Porous Starch Complex Gel

Sodium alginate-porous starch complex gels were prepared by calcium chloride dripping method and calcium carbonate internal gelation method. Furthermore, hardness, syneresis, swelling characteristics, crystalline structure and microstructure of the complex gels were analyzed. The results showed that the gel properties were significantly affected by calcium source and sodium alginate to porous starch ratio (mass ratio defined as r value). At high r value (r =4∶2 or 5∶1), calcium carbonate caused the formation of gel curds with uniform shape and dense structures, which also showed high gel hardness and low syneresis. Meanwhile, calcium chloride caused the formation of gel beads with uniform shape and hard shell. Due to different gel structures, the initial swelling speed of gel beads was slow and the final swelling ratio was high, while the initial swelling speed of gel curds was fast and the final swelling ratio was relatively low. The gels prepared by these two methods showed high swelling ratio in simulated colonic fluid and low swelling ratio in simulated gastric fluid, indicating good pH response. Microstructure analysis showed there was good compatibility between sodium alginate and porous starch. The results of the present research could provide useful information to develop pH responded delivery system for bioactive substances.