| Summary: | Due to the high global consumption of eggs, eggshell has become as one of the top domestic, agricultural and industrial wastes. This study determined eggshell characteristics after boiling at 95 °C and steaming at 121 °C, with additional heat treatments using hot air at 200 °C, microwaving at 900 W and infrared at 1050 W. Boiling in water for 60 min inhibited spoilage and pathogenic microorganisms that was the equivalent of steaming at 121 °C for 15 min. Scanning electron microscopy revealed that heat treatments on dried eggshell power modified the pore size and the accumulation of particles on the powder surface. From the X-ray diffraction pattern, all eggshell powder samples presented a peak at 29.40° demonstrating a crystallographic lattice of calcium carbonate with crystallinity in the range 90.20–91.05%. The calcium releasability of the control sample was 205.17–208.40 mg/L. Further treatment using hot air for 10–20 min increased the calcium releasability of the boiled and steamed eggshell powders to 219.95–225.50 and 230.35–305.20 mg/L, respectively while the microwave treatment for 2 min increased the calcium releasability of the boiled and steamed eggshell powders to 230.85 and 244.60 mg/L, respectively. The infrared treatment did not improve the calcium releasability of the sterilized eggshell powders. Up to 2% eggshell powder could be added to the dog biscuit dough. The fortified calcium biscuits contained 507.12 mg calcium/100 g of biscuit, while the Ca-to-P ratio was 1.94:1, which is within the recommended range for dog food.
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