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.
Highlights
Food-borne disease is caused by infectious or toxic agents that enter the body by ingestion of contaminated food and/or water
The data in Table (2) showed the active ingredients in the used 3 oils. It is clear from the obtained data that Thymol and Carvacrol are the major ingredients in both Thyme and Oregano as they give the largest peak area when qualitatively analyzed by GC-MS/MS
The obtained minimum inhibitory concentrations (MICs) of Thyme 0.3%, Oregano 0.1%, and Menthol 0.8% were recommended to be used in the preparation of luncheon as these concentrations inhibited the visible growth of Bacillus cereus bacteria which was chosen to be the model for the most resistant strain due to its thick wall and spore-forming capability
Summary
Food-borne disease is caused by infectious or toxic agents that enter the body by ingestion of contaminated food and/or water. Essential oils are plant extracts that perform antimicrobial and antioxidant activities They are healthy and safe ingredients that can be obtained from a variety of plant materials and can do both, reducing the incidence of food-borne diseases and retarding lipid oxidation (Boskovic et al, 2015). These oils are made from very complex mixtures of mainly volatile molecules that are produced by the secondary metabolism of aromatic and medicinal plants. This study is meant to estimate the effect of using the tested EOs on the shelf lifetime of Luncheon when partially or completely replacing the recommended concentration of sodium nitrite
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