Cinnamon, clove and rosemary essential oils were evaluated for their effects on the growth and
survival of Staphylococcus aureus and Escherichia coli artificially inoculated into minced beef. Fresh
minced beef samples were inoculated with (~ 106 CFU/ml) (6 log CFU/g) of S. aureus and (~ 104
CFU/ml) (4 log CFU/g) of E. coli and left for 30 minutes at room temperature (25οC) to allow
attachment and absorption of bacteria. Initial counts of S. aureus and E. coli in minced beef samples
immediately after innoculation were 10.86 and 7.91 log CFU/g, respectively. Essential oils of
cinnamon (Cinnamomum zeylanicum), clove (Syzygium aromaticum) and rosemary (Rosmarinus
officinalis) (%v/g) were added to the minced beef samples to achieve final concentrations of 0.5, 1 and
1.5%. Sensory (color, odor and texture) and bacteriological (S. aureus and E. coli counts) analyses
were conducted after 3, 6 hrs and every day (24 hrs) during cold storage at 4°C. Initial counts in
minced beef samples decreased following treatment with 1.5% of cinnamon, clove and rosemary oils
for 3 hours by 5.56 log CFU/g (51.19 %), 4.01 log CFU/g (36.92 %) and 2.84 log CFU/g (26.15 %),
respectively, of S. aureus and 3.58 log CFU/g (45.26 %), 2.88 log CFU/g (36.41 %) and 1.23 log
CFU/g (15.55 %), respectively, for E. coli. Growth of S. aureus in minced beef samples was
completely inhibited after treatment with cinnamon oil 1% after 3 days, cinnamon oil 1.5% after 2
days, clove oil 1% after 4 days and clove oil 1.5% after 3 days. As compared with several other mild
preservation procedures, treatment with cinnamon, clove and rosemary essential oils is inexpensive
and uncomplicated method. Results of the present study are envisaged to be useful for commercial
applications of these essential oils as potential food biopreservatives and anti- E. coli and S. aureus
agents in minced meat and other foods, depending upon the desired flavor of such products. |
