Effects of Pulsed Microwaves on Aspergillus parasiticus in Rice
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Abstract:
The potential application of pulsed microwave radiation in the control of Aspergillus parasiticus growth in rice during storage was evaluated in terms of fungal growth and cell membrane permeability. The parameters evaluated were microwave dose, pulse width, total time, and interval time. The results showed that fungal DNA, protein, and electrolyte leakage, as well as intracellular Ca2+ fluorescence intensity, of A. parasiticus increased with an increase in microwave intensity, followed by a slight decrease. This indicated that pulsed microwaves could cause electroporation of the cell membrane, leading to increased cell membrane permeability and accelerated leakage of the cytoplasm. Moreover, threshold values of pulsed microwave irradiation on A. parasiticus under thermal and non-thermal conditions included the following: pulsed microwave dose of 5 to 7.5 W/g, pulse width of 200 ms, total processing time of 20 s, and interval time of 150 ms. Beyond these threshold values, fungal growth was significantly inhibited, according to the Gompertz equation. Additionally, the pulsed microwave radiation caused the mycelial surface of A. parasiticus to become rough, with a crimped and shrunken appearance, which further confirmed that pulsed microwaves could alter the A. parasiticus cell membrane and its permeability.
