Abstract:
The aim of this study is to investigate the efficiency of household and single mode microwave at 2,450 MHz with power level of 800 and 850 W, respectively. The household microwave could destroy Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Saccharomyces cerevisiae as well as spores of Aspergillus niger, Penicillium chrysogenum, Rhizopus oryzae, Aspergillus nidulans and ascospores of Emericella nidulans within 90 seconds. Endospores of B. subtilis were completely destroyed within 300 seconds. The single mode microwave applicator killed above mentioned microorganisms and fungal spores within 90 seconds. Endospores of B. subtilis were decreased to 2.5 log. Ascospores and spores of R. oryzae were killed within 120 seconds. SEM photographs of treated microbial cells, endospores and fungal spores revealed the damage of cell wall of bacteria and yeast as well as endospores. Fungal spores wall were deformed. The application of household microwave for 60 seconds could reduce moisture content in paddy grains to 15.7-32.9%. The paddy grains were 100% contaminated with fungi in the genus of Aspergillus, Penicillium, and Rhizopus. After microwave treatment, the number of contaminated fungi was reduced up to 26.7-100%. Therefore, the household and single mode microwave are an alternative method to effectively kill microorganisms in the short time.