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.
Thongson
C
C
Department of Food Science and Technology, Kasetsart University, Jatujak, Bangkok, Thailand.
Davidson
P M
PM
Mahakarnchanakul
W
W
Weiss
J
J
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