| In this paper, we aimed to develop a new food preservative against microbiology in drink. Peppermint essential oil, Mentha longifolia and Mentha spicata Linn were extracted by distillation and analyzed by GC-MS. Influences of oil phase, the aqueous phase, surfactant and co-surfactant phase on the food-grade microemulsions behavior were described by pseudo-ternary. The physical and chemical indicators of the microemulsion systems as well as their antibacterial properties and mechanism against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisiae and Saccharomyces baillii were determined. The main research findings are as follows:1) GC-MS analysis of the main components of Mentha essential oil showed:the main component of M. longifolia and peppermint essential oils were alcohols, ketones and alkenes. The major constituents of the volatiles were menthol (28.53%-30.67%) and menthone (15.74%-26.89%). M. spicata Linn is mainly composed of piperitenone oxide accounted for 39.74% and limonene accounted 32.56%.2) Effects of different components on the microemulsion phase behavior were evaluated. Results showed that the food-grade microemulsions were difficult to formulate from a three-component systems based on water, oil and single surfactant. Short-chain alcohols and organic salts increased system capacity to solubilize oil microemulsion phase. Tween 80 as a surfactant was best on solubilization. salts. The oil solubilization was dramatically improved in the presence of short-chain alcohols, and sodium ascorbate and potassium sorbate contributed to the improved oil solubilization as hydrotropes, According to the actual situation and the microemulsion applications scalability, ethanol (alcohol oil ratio is preferably 1:1), sodium ascorbate and potassium sorbate were selected to add to the microemulsion system.3) Five oil microemulsion formulation were selected as following, Al, for peppermint oil: ethanol:Tween 80:5% sodium ascorbate:5% potassium sorbate=2.8:2.8:8.4:3:3; A2, for peppermint oil:ethanol:Tween 80:5% sodium ascorbate:5% potassium sorbate=1.8:1.8:8.4: 4:4; B1, peppermint oil:ethanol:Tween 80:water=1:1:2:4; B2, peppermint oil:ethanol: Tween 80:water=3:9:8:4; C2, spearmint and peppermint oil:ethanol:Tween 80:5% potassium sorbate:5% ascorbic acid Na=3.5:3.5:13:10:10; as a microemulsion liquid and measuring the particle size and stability. The particle sizes of all formulations were less than 100 nm. The stabilities of these systems were determined by centrifugation at 4000 g at room temperature for 20 min and 30 d without phase separation. The pH results showed that along the dilution lines, at a certain composition the systems inverted from water-in-oil to oil-in-water microemulsions. demonstrated as U-type microemulsion systems capable of being infinitely and progressively aqueous phase diluted.4) Inhibition tests showed that mint oil microemulsion had good antibacterial activities against bacteria and yeast. The MIC for bacteria was 8-32μl/ml, MBC was 64-128μl/ml, yeast MIC of 16-64 μl/ml, MFC was 64-128μl/ml. Kinetics of killing results showed that the microemulsion at minimum bacterial concentrations killed all bacteria in 90 min.5) Membrane permeability tests showed that MBC peppermint oil and spearmint essential oil microemulsion microemulsion destroyed the bacterial cell wall, causing the destruction and release of nucleic acids. Microemulsion nucleic acid release rate steady at 5-fold dilution of about 51.68% and 67.54%,10 times diluted microemulsion final release rate was stable at 30.05% and 45.68%. The scanning electron microscopy was in good agreement with the bacterial activities by broth dilution method, and indicated excellent growth inhibition activities against E.coil. These findings suggested that the observed antimicrobial activities may be attributed to a disruption and disfunction of bacterial biological membranes. |
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