Antimicrobial activity of Hibiscus sabdariffa aqueous extracts against Escherichia coli O157:H7 and Staphylococcus aureus in a microbiological medium and milk of various fat concentrations.
Hibiscus sabdariffa L. calyces are widely used in the preparation of beverages. The calyces contain compounds that exhibit antimicrobial activity, yet little research has been conducted on their possible use in food systems as antimicrobials. Aqueous extracts prepared from the brand "Mi Costenita" were sterilized by membrane filtration (0.22-μm pore size) or autoclaving (121 °C, 30 min) and tested for antimicrobial activity against the foodborne pathogens Escherichia coli O157:H7 strains ATCC 43894 and Cider and Staphylococcus aureus strains SA113 and ATCC 27708 in a microbiological medium and ultrahigh-temperature-processed milk with various fat percentages. Extracts heated by autoclaving exhibited greater activity than did filtered extracts in a microbiological medium. Against E. coli, results of 20 mg/ml filtered extract were not different from those of the control, whereas autoclaved extracts reduced viable cells ca. 3 to 4 log CFU/ml. At 60 mg/ml, both extracts inactivated cells after 24 h. There were reduced populations of both strains of S. aureus (ca. 2.7 and 3 log CFU/ml, respectively) after 24 h of incubation in 40 mg/ml filtered extracts. When grown in autoclaved extracts at 40 mg/ml, both strains of S. aureus were inactivated after 9 h. Autoclaved extracts had decreased anthocyanin content (2.63 mg/liter) compared with filtered extracts (14.27 mg/liter), whereas the phenolic content (48.7 and 53.8 mg/g) remained similar for both treatments. Autoclaved extracts were then tested for activity in milk at various fat concentrations (skim [<0.5%], 1%, 2%, and whole [>3.25%]) against a 1:1 mixture of the two strains of E. coli O157:H7 and a 1:1 mixture of the two strains of S. aureus. Extracts at 40 mg/ml inactivated S. aureus after 168 h in skim and whole milk, and E. coli was inactivated after 96 h in 60 mg/ml extract in all fat levels. These findings show the potential use of Hibiscus extracts to prevent the growth of pathogens in foods and beverages.
Department of Food Science and Technology, University of Tennessee, Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
Kristen L
KL
Higginbotham
Department of Plant Sciences, University of Tennessee, Knoxville, 252 Ellington Plant Sciences, 2431 Joe Johnson Drive, Knoxville, Tennessee 37996-4561, USA.
Kellie P
KP
Burris
Department of Food Science and Technology, University of Tennessee, Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
Svetlana
S
Zivanovic
Department of Food Science and Technology, University of Tennessee, Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
P Michael
PM
Davidson
Department of Food Science and Technology, University of Tennessee, Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA; Department of Plant Sciences, University of Tennessee, Knoxville, 252 Ellington Plant Sciences, 2431 Joe Johnson Drive, Knoxville, Tennessee 37996-4561, USA. nealstewart@utk.edu.
C Neal
CN
Stewart
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001628:Beverages / Q000382:microbiology*; D015169:Colony Count, Microbial; D004041:Dietary Fats / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005516:Food Microbiology; D031584:Hibiscus / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology; D010936:Plant Extracts / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development
D000900:Anti-Bacterial Agents; D004041:Dietary Fats; D010936:Plant Extracts