Antimicrobial effect of nisin and garlic alcoholic extract on Staphylococcus aureus ATCC 1113 inoculated in Tilapia minced meat at 4 °C

Staphylococcus aureus beyond the cause of food poisoning, can cause wide spectrum of infections in human and is a serious threat in food industry. This study was conducted to evaluate antibacterial effect of alcoholic extract of garlic (Allium sativum) alone and in combination with nisin on inhibition of Staphylococcus aureus in minced meat of the tilapia fish. Garlic Extract was prepared by vacuum evaporation method using the rotary device. The effects of different concentrations of garlic alcoholic extract (0, 1, 2.5, 3.5, 5%) and nisin (0, 0.5 and 2.5 μg / g) and the combinations of nisin (micrograms per gram) and Extract (%) (0.25+3.5), (0.25+5), (0.5+1), (0.5+2.5), (2.5+1), (2.5+2.5) were studied on the growth of the S. aureus at 4 ° C for 21 days. The results showed that the bacterial growth was stopped at 3.5% and 5% concentrations of garlic extract from days 12 and 9 respectively, and It was stopped at 0.5, 2.5 μg/g of nisin from days 9 and 6 respectively. Low concentrations of garlic extract (1 and 2.5%) did not inhibit the growth of bacteria. Combined treatments of extract and nisin were able to stop bacterial growth from day 6 onwards. According to this study, garlic extract and nisin have inhibitory effect on growth of bacteria and they are introduced as a natural preservative of food instead of chemical preservative. This research approved the synergistic effect of nisin and alcoholic extract on the inhibition of the S. aureus growth.