Study on antibacterial effect of rosemary extract in combination with nisin against staphylococcus aureus in minced meat during refrigerated temperature

Synthetic preservatives have been used as food additives to extend shelf life of foods, but they
are strictly regulated due to toxicological concerns and some health problems. So it is
increasingly attractive to find out effective and nontoxic measures (e.g. use of natural
antimicrobial agent) to delay microbial spoilage. Nisin is a bacteriocin that it is the only
bacteriocin permitted for use in foods. And rosemary is one of the medicinal plants. In this study
the effect of antibacterial property of various concentration of rosemary extract alone (3 and 4
mg/ml), and with nisin (7 µg/ml nisin + 1.5 mg/ml RE and 8 µg/ml nisin + 2 mg/ml RE) against
Staphylococcus aureus in minced meat were assessed throughout 14 days of storage at 4±1˚C.
Leaves and stems of rosemary after drying in the shade were soaking in pure ethanol and
alcoholic extract was obtained. The minimum inhibitory concentration (MIC) of RE and nisin
were determined against S. aureus using the agar dilution method. Assessment of microbial
parameters (total plate count and S. aureus count) was carried out in 0, 1, 3, 7 and 14 days. The
data were statistically significant (P<0.05). The results reveals that treatment with both
concentrations of RE showed significantly lower microbial indexes in comparison with controls,
but treatment with both preservative (nisin & RE) had better results and results were statistically
significant (P<0.05). As a consequence, using of RE with nisin was better than of RE alone.