IMPROVED METHOD FOR PREPARATION OF FRUIT-SIMULATING ALGINATE GELS

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Abstract
Ca binding, crosslinking and mechanical properties were studied in alginate gels prepared by a 2-step procedure. A thermolabile gelatin gel containing sodium alginate is placed in a calcium lactate solution and diffusion of Ca2+ causes crosslinking of the alginate Ca binds completely to alginate within 48 h but crosslinking continues for more than 72 h, as indicated by gel strength. Retention of ascorbic acid incorporated into these gels was only about 25% after 72 h in the crosslinking bath. To improve retention, an alternate 1-step procedure was adopted, using glucono-delta-lactone (GDL) and dicalcium phosphate dihydrate; this process eliminates residence in the crosslinking bath. Hydrolysis of GDL slowly reduces the mixture''s pH, releasing Ca2+ which then crosslink with the alginate. The GDL process produced a gel matrix with compression behavior similar to those of the 2-step gels. Complete crosslinking took 7 h; ascorbic acid losses were insignificant.