Production and Characterization of Edible Beads Using Natural Calcium Extracted from Catfish Bone Powder through Direct and Reverse Gelation Techniques

The significant number of catfish heads generated during processing represents an underutilized resource rich in calcium and proteins. This study aimed to valorize this waste by extracting natural calcium from catfish bone powder and using it to produce edible alginate beads through direct and reverse gelation techniques. Natural calcium was extracted from 0.4% catfish bone powder using microwave digestion at 300 W for 60 seconds with 0.1 M citric acid. In the direct gelation process, alginate solutions at concentrations of 0.4, 0.5, 0.6, 0.8, and 1.0% were dropped into the extracted calcium solution. The lowest concentration to form a gel was 0.5%, but 1.0% was selected for firmer gel formation. Reverse gelation involved dropping calcium solutions with 0, 10, 20, 30, and 40% gelatin into a 0.5% alginate solution, with the 20% gelatin formulation exhibiting the highest hardness and thus was chosen. The characteristics and stability of edible beads produced by both gelation methods were comparatively evaluated. Chemical composition analysis showed higher protein and calcium levels in reverse gelation beads than in direct gelation beads. Additionally, beads from reverse gelation demonstrated superior textural properties and greater acceptability compared to direct gelation beads. Both bead types showed limited storage stability when kept in water, as measured by changes in diameter. However, storage in 0.1 M citric acid solution significantly improved their stability. In conclusion, natural fish bone calcium effectively induces alginate gelation by both direct and reverse methods. Reverse gelation produced nutritionally enhanced, acid-stable edible beads, presenting a promising approach for fish waste valorization with potential applications in acidic beverages. This method offers both economic and environmental benefits by transforming fish processing by-products into functional ingredients.