Study the effect of rosemary extract on lipid oxidation and growth of staphylococcus aureus in minced beef

Considering the side effects of chemical preservative and attention of food producers to natural
preservatives, evaluation of antioxidant and antimicrobial effect of them in the laboratory and food
models seems to be necessary. The aim of the present study was to determine the effect of rosemary
extract (RE) on lipid oxidation and inoculated staphylococcus aureus in minced beef. Leaves and
stems of rosemary after drying in the shade were soaking in pure ethanol and alcoholic extract was
obtained. Then total phenolics content and minimum inhibitory concentration (MIC) is determined
against S. aureus using the agar dilution method. Two concentration of RE (3 and 4 mg/ml) was
added to the treatments. Assessment of chemical spoilage index (Thiobarbituric acid) and microbial
parameters (total plate count and S. aureus count) is carried out in 0, 1, 3, 7 and 14 days of storage at
4±1˚C. The MIC value and total phenolic content of rosemary was 3 mg/ml and 4.54 (g gallic acid
equivalents/100g extract) respectively. The result reveals that treatment with both concentration of RE
shows significantly lower chemical and microbial indexes in comparison with controls and results
were statistically significant (P<0.05). As a consequence, rosemary extract may be considered as
effective tools in preventing the lipid oxidation and microbial spoilage in minced beef.