Modified eggshell powder using thermal treatment and its application in Ca-fortified dog biscuits

Area of Science:

• Materials Science
• Food Science
• Biotechnology

Background:

• Eggshell waste presents a significant environmental challenge due to high global egg consumption.
• Valorizing eggshell waste can provide sustainable sources of calcium carbonate.

Purpose of the Study:

• To investigate the effects of various heat treatments on eggshell powder characteristics.
• To determine the impact of these treatments on calcium releasability.
• To evaluate the suitability of treated eggshell powder as a calcium supplement in dog food.

Main Methods:

• Eggshells were subjected to boiling (95°C), steaming (121°C), hot air (200°C), microwave (900W), and infrared (1050W) treatments.
• Scanning electron microscopy (SEM) analyzed surface morphology.
• X-ray diffraction (XRD) assessed crystallinity.
• Calcium releasability was measured using in vitro methods.
• Eggshell powder was incorporated into dog biscuits at 2% concentration.

Main Results:

• Boiling and steaming effectively inhibited microbial growth.
• Heat treatments modified eggshell powder's pore size and particle accumulation.
• All treated eggshell powders exhibited high calcium carbonate crystallinity (90.20-91.05%).
• Hot air and microwave treatments significantly increased calcium releasability compared to control samples.
• Infrared treatment did not enhance calcium releasability.
• Fortified dog biscuits contained 507.12 mg calcium/100g with an optimal Ca-to-P ratio of 1.94:1.

Conclusions:

• Heat treatments, particularly hot air and microwave, can effectively enhance the calcium releasability of eggshell powder.
• Treated eggshell powder is a promising, cost-effective source of calcium for food applications, such as dog food fortification.
• This study demonstrates a sustainable method for eggshell waste valorization.