Structural characterization and antibacterial activity of pearl oyster (Pinctada maxima) shell as affected by calcination temperature

The effect of calcination temperatures (700, 900 and 1100 °C for 5 h) on structural characteristic and antibacterial activity of calcined pearl oyster ( Pinctada maxima ) shell were investigated. Yield of calcined powders (CP) were found in the range of 54.27–93.87 %. Calcium element and whiteness in color of CP significantly increased as calcination temperature increased (P < 0.05). Fourier-transform infrared (FTIR) spectra of all CPs revealed the significant loss of CO 3 2− group at temperature above 700 °C, indicating the decomposition of CaCO 3 during calcination. X-ray diffraction (XRD) indicated that the increasing of calcination temperature promoted the additional formation of calcium oxide (CaO), especially at higher temperature of 900 °C (CP 900). Microstructure studies demonstrated that a finer and tidy structure was observed in CP 900, compared to SP and commercial calcined (CC) powders. Moreover, CP 900 exhibited stronger antibacterial activity against foodborne pathogenic bacteria than did CC and SP. Result highlighted that CaCO 3 in pearl oyster shell was successfully converted to CaO by using calcination process at 900 °C. The prepared CP 900 could therefore be used as a natural antibacterial agent alternative to those synthetic. • Structural transformation of CaCO 3 from pearl oyster shell waste occurred by calcination. • Calcination increases dietary calcium concentration and yields finer particles. • Calcination shell waste at 900 °C (CP 900) successfully convert from CaCO 3 into CaO. • CP 900 could be feasible as a natural active antibacterial, alternatively to the synthetic preservatives.