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Wednesday, April 02, 2008

Essential Oils as Food Preservatives

Essential oils are commonly being tested as food preservatives...here's a couple of studies regarding their effects:

Study: The antimicrobial efficacy of plant essential oil combinations and interactions with food ingredients.

Gutierrez J, Barry-Ryan C, Bourke P.School of Food Science and Environmental Health, Dublin Institute of Technology, Cathal Brugha Street, Dublin 1, Ireland.

The objective of this study was to evaluate the efficacy of plant essential oils (essential oils) in combination and to investigate the effect of food ingredients on their efficacy. The essential oils assessed in combination included basil, lemon balm (melissa essential oil), marjoram, oregano, rosemary, sage and thyme. Combinations of essential oils were initially screened against Bacillus cereus, Escherichia coli, Listeria monocytogenes and Pseudomonas aeruginosa using the spot-on-agar test. The influence of varying concentrations of essential oil combinations on efficacy was also monitored using E. coli. These preliminary studies showed promising results for oregano in combination with basil, thyme or marjoram. The checkerboard method was then used to quantify the efficacy of oregano, marjoram or thyme in combination with the remainder of selected essential oils. Fractional inhibitory concentrations (FIC) were calculated and interpreted as synergy, addition, indifference or antagonism. All the oregano combinations showed additive efficacy against B. cereus, and oregano combined with marjoram, thyme or basil also had an additive effect against E. coli and P. aeruginosa. The mixtures of marjoram or thyme also displayed additive effects in combination with basil, rosemary or sage against L. monocytogenes. The effect of food ingredients and pH on the antimicrobial efficacy of oregano and thyme was assessed by monitoring the lag phase and the maximum specific growth rate of L. monocytogenes grown in model media. The model media included potato starch (0, 1, 5 or 10%), beef extract (1.5, 3, 6 or 12%), sunflower oil (0, 1, 5 or 10%) and TSB at pH levels of 4, 5, 6 or 7. The antimicrobial efficacy of essential oils was found to be a function of ingredient manipulation. Starch and oils concentrations of 5% and 10% had a negative impact on the essential oil efficacy. On the contrary, the essential oils were more effective at high concentrations of protein, and at pH 5, by comparison with pH 6 or 7.

This study suggests that combinations of essential oils could minimize application concentrations and consequently reduce any adverse sensory impact in food. However, their application for microbial control might be affected by food composition, therefore, careful selection of essential oils appropriate to the sensory and compositional status of the food system is required. This work shows that essential oils might be more effective against food-borne pathogens and spoilage bacteria when applied to ready to use foods containing a high protein level at acidic pH, as well as lower levels of fats or carbohydrates.

Study: Antimicrobial activity of clove and cinnamon essential oils against Listeria monocytogenes in pasteurized milk.

Cava R, Nowak E, Taboada A, Marin-Iniesta F.Grupo de Química de Carbohidratos y Biotecnología de Alimentos, Departamento de Tecnología de Alimentos, Nutrición y Bromatología, Facultad de Veterinaria, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain.

The antimicrobial activity of essential oils of cinnamon bark, cinnamon leaf, and clove against Listeria monocytogenes Scott A were studied in semiskimmed milk incubated at 7 degrees C for 14 days and at 35 degrees C for 24 h. The MIC was 500 ppm for cinnamon bark essential oil and 3,000 ppm for the cinnamon leaf and clove essential oils. These effective concentrations increased to 1,000 ppm for cinnamon bark essential oil, 3,500 ppm for clove essential oil, and 4,000 ppm for cinnamon leaf essential oil when the semiskimmed milk was incubated at 35 degrees C for 24 h. Partial inhibitory concentrations and partial bactericidal concentrations were obtained for all the assayed essential oils. The MBC was 3,000 ppm for the cinnamon bark essential oil, 10,500 ppm for clove essential oil, and 11,000 ppm for cinnamon leaf essential oil. The incubation temperature did not affect the MBC of the essential oils but slightly increased the MIC at 35 degrees C. The increased activity at the lower temperature could be attributed to the increased membrane fluidity and to the membrane-perturbing action of essential oils. The influence of the fat content of milk on the antimicrobial activity of essential oils was tested in whole and skimmed milk. In milk samples with higher fat content, the antimicrobial activity of the essential oils was reduced.

These results indicate the possibility of using these three essential oils in milk beverages as natural antimicrobials, especially because milk beverages flavored with cinnamon and clove are consumed worldwide and have been increasing in popularity in recent years.








*The FDA has not evaluated the statements on this website. The information presented here is for educational purposes of traditional uses and is not intended to diagnose, treat, cure, or prevent any diseases.


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