Antimicrobial activity of ultrasound-assisted solvent-extracted spices.
OBJECTIVE
The objective of this research was to determine the antimicrobial activity of conventional and high-intensity ultrasound-assisted (HI-US) solvent-extracted Thai spices, including ginger (Zingiber officinale Rose), fingerroot (Bosenbergia pandurata Holtt) and turmeric (Curouma longa Linn).


RESULTS
Extracts were obtained using hexane, isopropanol and a 7 : 3 isopropanol : hexane mixture as solvents with and without HI-US. The antimicrobial activity of the extracts was assayed against four strains each of Listeria monocytogenes and Salmonella Typhimurium DT 104 using an agar dilution assay. Application of HI-US did not alter antibacterial activity against S. Typhimurium, but antilisterial activity of some HI-US spice extracts decreased. Solvent type affected antimicrobial efficacy of extracts with hexane producing the least antimicrobial activity. Fingerroot extracted with isopropanol-hexane and without HI-US had the best antilisterial effect while HI-US-isopropanol fingerroot extract had the greatest antimicrobial efficacy against S. Typhimurium.


CONCLUSIONS
Application of HI-US reduced time of extraction to 5 min, compared with the 24 h required for conventional extraction and maintained antimicrobial activity against Salmonella but slightly reduced activity against Listeria.


CONCLUSIONS
HI-US in combination with proper solvent selection may offer a new tool to optimize extraction of spice essential oil for use as antimicrobial agents, and reduce processing time and costs.
Department of Food Science and Technology, Kasetsart University, Jatujak, Bangkok, Thailand.
C
C
Thongson
P M
PM
Davidson
W
W
Mahakarnchanakul
J
J
Weiss
D019840:2-Propanol; D000900:Anti-Bacterial Agents / Q000302:isolation & purification* / Q000494:pharmacology*; D002621:Chemistry / Q000379:methods; D030024:Curcuma / Q000737:chemistry*; D005520:Food Preservatives / Q000302:isolation & purification / Q000494:pharmacology; D020939:Zingiber officinale / Q000737:chemistry*; D006586:Hexanes; D008089:Listeria monocytogenes / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000302:isolation & purification* / Q000494:pharmacology*; D012486:Salmonella typhimurium / Q000187:drug effects; D012997:Solvents; D017365:Spices; D014465:Ultrasonics
D000900:Anti-Bacterial Agents; D005520:Food Preservatives; D006586:Hexanes; D010936:Plant Extracts; D012997:Solvents; D019840:2-Propanol