The reaction of gelatin /gum arabic coacervate gels with glutaraldehyde
The consumption of glut by various gelatin/gum arabic (GGA) coacervate gels has been examined over a range of conditions. Both acid- and alkali-precursor gelatins were used to form the coacervates. Glut consumptions by several gelatin gels were also determined. All gels examined consumed 0.3 to 1.6 mmole glut/g gelatin. Acid and alkali GGA gels had similar glut uptakes at 4°C. Glut consumption by acid-precursor GGA gels increased significantly with increasing gelation temperature (4–28°C) due to temperature-dependent changes in gel structure. The use of commercial versus redistilled glut had no detectable effect upon glut uptakes. Reaction of a gel with glut caused a high degree of insolubilization as a result of intermolecular crosslink formation. Most treated gels were at least 85 wt% insoluble at 55°C in phosphate buffer after 4–28 days extraction. That fraction of a gel solubilized by the extraction process contained both gelatin and gum arabic. Thus, despite the fact that gum arabic has little tendency to react with glut, it is effectively entrapped in the crosslinked GGA gel structure. Gels with lowest glut uptakes were the most soluble ones. They also were the only ones with solubilities that increased upon treatment with NaHSO3 before the gel fraction extraction process. Insolubilization of GGA gels by glut causes their swelling behavior and composition to become essentially independent of pH. Composition and swelling behavior of uncrosslinked gels vary markedly with pH due to the reversible nature of the intermolecular bridges responsible for gelation.