Accelerated death kinetics of Aspergillus niger spores under high-pressure carbonation

Abstract

The death kinetics of Aspergillus niger spores under high-pressure carbonation were investigated with respect to the concentration of dissolved CO2 (dCO2) and treatment temperature. All of the inactivation followed first-order death kinetics. The D value (decimal reduction time, or the time required for a 1-log-cycle reduction in the microbial population) in the saline carbonated at 10 MPa was 0.16 min at 52 degrees C. The log D values were linearly related to the treatment temperature and the concentration of dCO2, but a significant interaction was observed between them.

FIG. 1.

Schematic diagram of the apparatus for microbial inactivation under high-pressure carbonation.

FIG. 2.

Inactivation behaviors of A. niger spores in carbonated saline. The saline was carbonated at 10 MPa, and the concentrations of dCO₂ were ∼21.7 to ∼24.2 γ. Symbols indicate results of experiments in carbonated saline at 44°C (×), 46°C (▪), 48°C (▴), 50°C (•), and 52°C (⧫); in physiological saline at 52°C (○); and in McIlvaine buffer (pH 3.0) at 52°C (□)

FIG. 3.

Inactivation behaviors of A. niger spores in carbonated (closed symbols) and noncarbonated (□) saline. Carbonations were carried out to the saturated levels at 5 MPa (×), 8 MPa (▴), 10 MPa (•), and 19 MPa (▪).

FIG. 4.

Effect of the treatment pressure on the inactivation of A. niger spores at a fixed concentration (15.5 γ) of dCO₂. The treatment temperature was 50°C.

FIG. 5.

Effect of dCO₂ concentration on the inactivation of A. niger spores under carbonation at 10 MPa.

FIG. 6.

Relationship between the log D value and dCO₂ concentration.

FIG. 7.

Effect of the interaction between the treatment temperature and dCO₂ concentration on the log D values of A. niger spores under carbonation.