Studies on some plant extracts as antimicrobials and food preservatives

Abstract

This study was conducted to detect the effect of some essential oil (EOs) extracts (Thyme, Oregano, and Menthol) as natural food preservatives against some food-borne pathogens (salmonella Typhimurium and E. coli, Staphylococcus aureus, Bacillus cereus and listeria monocytogens). The selected extracts were in concentrations ranging from 0.01% to 0.8% v/v using broth dilution technique. The Obtained results revealed that the minimum inhibitory concentrations (MICs) of the used extracts 0.3%, 0.1% and 0.8% for Thyme, Oregano, and Menthol, respectively, depended on the concentrations which inhibited Bacillus cereus as it is considered the most resistant Gram-positive spore-forming strain. Studying the mode of action of the used EOs against Salmonella sp. were performed using Transmission Electron Microscope (TEM) which indicated cell wall and plasma membrane damage. Also, the obtained MICs of EOs were used in preparation of luncheon to study the possibility of its usage instead of or together with the chemicals used for preservation during luncheon processing. The obtained results showed that, in luncheon processing, thyme extract has the same preservative effect as sodium nitrite (125 ppm) when it is used as the lonely preservative substance while using the obtained MICs of the used EO with 50 ppm of sodium nitrite had a reliable preserving effect in luncheon process.