Key Laboratory of Agri products Physics Processing

Zhenjiang, China

Key Laboratory of Agri products Physics Processing

Zhenjiang, China

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Qian J.-Y.,Jiangsu University | Qian J.-Y.,Key Laboratory of Agri products Physics Processing | Ma H.-L.,Jiangsu University | Ma H.-L.,Key Laboratory of Agri products Physics Processing | And 4 more authors.
Modern Food Science and Technology | Year: 2013

The effect of pulsed magnetic field (PMF) with the intensity of 3T and 30 pulses combined with temperature (50~100°C), ultrasonic (200 W, 5~30 min), and nisin (100~350 IU/mL) on the inactivation of Bacillus. subtilis (B. subtilis) was investigated. The results showed that after pretreated by PM F, the survival rate decreased with the increase of the temperature, ultrasonic power and the nisin concentration, and the lowest survival rate (3.17%) was achieved when B. subtilis were treated by PMF followed by the temperature at 100°C. The survival rate decreased with the the increase of treatment time by ultrasonic and the lowest survival rate of 8.18% was obtained when B. subtilis were treateded by PMF followed by ultrasonic at the power of 200 W with working time of 5 s and the interval of 10 s for 30 min. Increase in concentration of nisin led to the reduce of survival rate of B. subtilis. The combined treatments of PMF followed by nisin at 350 IU/mL exhibited a lowest survival rate of 19.21%. The inactivation effect was better when B. subtilis were treated by PMF followed by temperature, ultrasonic, and nisin than treated by temperature, ultrasonic, and nisin followed by PM F, which was in agreement with the phenomenon observed by the SEM. The morphology of B. subtilis changed and the cells shrunk after the combined treatments. The release of cytoplasmic contents of B. subtilis occurred after the treatments of PMF followed by nisin.


Qian J.-Y.,Jiangsu University | Qian J.-Y.,Key Laboratory of Agri Products Physics Processing | Ma H.-L.,Jiangsu University | Ma H.-L.,Key Laboratory of Agri Products Physics Processing | And 5 more authors.
Journal of Pure and Applied Microbiology | Year: 2013

The pulsed magnetic field (PMF) is a non-thermal method for inactivating microorganisms at lower temperatures and preserving the food sensory and nutritional qualities. In the present study, inactivation performances of Bacillus subtilis with the various pulsed magnetic field (PMF) intensities and pulses were well investigated. Results showed that the B. subtilis survival rate generally decreased with the increasing intensity (>1.5T) and pulse numbers (>15) and a minimum survival rate of 33.87% was obtained at an intensity of 3.3 T and pulse number of 30. However, lower intensity (≤1.5T) and PMF pulse numbers (≤15) enhanced the B.subtilis growth. By comparing the determination coefficients (r2), bias factors (Bf), accuracy factors (Af) and root mean square errors (RMSE), the Weibull distribution model with the highest r2 and the lowest BMSE was selected as the optimal kinetic model to describe the PMF inactivation process. Scanning Electron Microscope (SEM) observations indicated that PMF inactivated the B. subtilis cells by deformating the cell surface and damaging the cellular membrane. These findings for the first time present the kinetic model and the cell death mechanism during the PMF inactivation process, and will provide a useful reference for further PMF sterilization application.

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