[Antibacterial properties of some spice plants before and after heat treatment]

This study was carried out to understand the antibacterial properties of some spice plants before and after heat treatment in boiling water. The samples included the core and the outer layers of onion, the white and the green parts of green onion, garlic bulb, ginger, ginger root, sweet pepper, chili pepper, brown pepper, and mustard. The test microorganisms included Escherichia coli, Salmonella typhimurium, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus, Mycobacterium phlei, Streptococcus faecalis, Bacillus cereus, and Micrococcus luteus. Raw garlic bulb could inhibit all of the test strains. The antibacterial activities of green onion are slightly weak than that of onion. However, green onion could inhibit P. aeruginosa and M. luteus, but onion could inhibit E. coli, P. vulgaris, S. faecalis, and B. cereus. Ginger and ginger root could only inhibit M. luteus. Chili pepper could inhibit V. parahaemolyticus and P. vulgaris. Brown pepper could also inhibit P. vulgaris. Sweet pepper and mustard showed no antibacterial activity to all of the test strains. In general, antibacterial components in the spice plants were heat labile. All the spices tested lost their antibacterial activities within 20 min at 100 degrees C.