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Effect of Solvent Type and Drying Method on Protein Retention in Chitosan-Alginate Microcapsules Edith I Ahonkhai, Ikhuoria M Arhewoh and Augustine O Okhamafe Abstract Purpose: The effect of solvent used in dissolving chitosan (membrane material) and the microcapsule drying method used, on protein retention in chitosan-alginate microcapsules were studied since these factors affect the physicochemical characteristics of the coating membrane. Method: The microcapsules were prepared by extruding a solution containing alginate and BSA into chitosan/calcium chloride solution prepared with different acid solvents - acetic acid, formic acid, tartaric acid and hydrochloric acid. A portion of the microcapsules was air-dried at ambient temperature while the remaining portion was freeze-dried. The elution of protein from the microcapsules in simulated gastric fluid was monitored spectrophotometrically at λmax 280 nm. Results: Tartaric acid effected the highest mean protein retention (54%) after 9 h followed by acetic acid (35%), hydrochloric acid (31%) and formic acid, (30%). There appears to be a link between the pKa of the acids and the degree of chitosan-solvent interaction on the one hand, and protein retention on the other hand. Increase in elution pH from 1.2 to 5.0 did not significantly (P>0.05) affect protein retention. Furthermore, there was no significant difference (p>0.05) between the protein retention capacities of air-dried and freeze-dried microcapsules as both types showed protein retention of 50% after 5 h. Conclusion: Tartaric acid was the most suitable solvent for enhancing protein retention in chitosan-alginate microcapsules in simulated gastric fluid. Keywords Tartaric acid, chitosan, solvent type, microcapsules, air-drying, freeze-drying.

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