Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. The interest in essential oils and their application in food preservation has been amplified in recent years by an increasingly negative consumer perception of synthetic preservatives. Furthermore, food-borne diseases are a growing public health problem worldwide, calling for more effective preservation strategies. The antibacterial properties of essential oils and their constituents have been documented extensively. Pioneering work has also elucidated the mode of action of a few essential oil constituents, but detailed knowledge about most of the compounds’ mode of action is still lacking. This knowledge is particularly important to predict their effect on different microorganisms, how they interact with food matrix components, and how they work in combination with other antimicrobial compounds. The main obstacle for using essential oil constituents as food preservatives is that they are most often not potent enough as single components, and they cause negative organoleptic effects when added in sufficient amounts to provide an antimicrobial effect. Exploiting synergies between several compounds has been suggested as a solution to this problem. However, little is known about which interactions lead to synergistic, additive, or antagonistic effects. Such knowledge could contribute to design of new and more potent antimicrobial blends, and to understand the interplay between the constituents of crude essential oils. The purpose of this review is to provide an overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents, and to identify research avenues that can facilitate implementation of essential oils as natural preservatives in foods.

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Essential oils in food preservation: mode of action, synergies, and interactions with food matrix components.

The authors acknowledge the financial support from the Spanish Ministerio de Educacion y Ciencia through Project AGL2010-20694, from Universidad Politecnica de Valencia through Project PAID-06-11-2013 and from Conselleria de Empresa, Universidad y Ciencia (Project GV/2013/152).

Essential oils as additives in biodegradable films and coatings for active food packaging

The epidemiology and public health importance of toxocariasis: a zoonosis of global importance.

Characterization of antioxidant-antimicrobial κ-carrageenan films containing Satureja hortensis essential oil.

Preparation and characterization of active films based on chitosan incorporated tea polyphenols

Antioxidant chitosan based edible films were developed incorporated with Zataria multiflora Boiss essential oil (ZEO) (5 and 10 g/L) and grape seed extract (GSE) (10 g/L) alone and in combination. The physico-mechanical, wettability, swelling index, color, total phenol and antioxidant characteristics of the films were investigated. Films without any agents were used as control sample. All films, with the exception of 10 g/L GSE + 10 g/L ZEO film, exhibited lower strength and elongation values, and only the addition of 10 g/L ZEO to GSE film improved the water vapor transmission rate of chitosan films. Only GSE containing films had higher swelling index. The incorporation of GSE and ZEO into chitosan film increased the wettability of the surface, total phenol and antioxidant activity. Neat chitosan and ZEO incorporated films had a light yellowish color, whereas GSE + ZEO films were gray.

Characterization of antioxidant chitosan film incorporated with Zataria multiflora Boiss essential oil and grape seed extract

Aims: To investigate effects of various concentrations of the essential oil of Cuminum cyminum L. seed alone and in combination with nisin on survival of vegetative forms of Bacillus cereus and Bacillus subtilis in a food model (commercial barley soup) and their ultrastructure.



Methods and Results:  Gas chromatography–mass spectrometry analysis indicated that cumin aldehyde (29·02%) and α-terpinen-7-al (20·70%) constituted the highest amount of the essential oil. The lowest concentration of the essential oil significantly affected the growth of the bacteria at 8°C but not at 25°C. Synergistic effect of the essential oil in combination with the lowest concentration of nisin was observed on the bacteria at 8°C. Evaluation of the sensory properties showed that concentration of 0·15 μl ml−1 of the essential oil was the most acceptable.



Conclusions:  The essential oil of C. cyminum L. seed showed the most bactericidal effects on B. cereus at 8°C. Ultrastructural studies of vegetative cells confirmed the synergistic destructive effects of the essential oil and nisin on membrane and cell wall of the bacteria.



Significance and Impact of the Study:  Utilization of essential oil of C. cyminum L. seed in combination with nisin can inhibit growth of food-borne pathogens in food.

Synergistic antibacterial activity of the essential oil of Cuminum cyminum L. seed and nisin in a food model.

The effects of Mentha longifolia L. essential oil during ripening and storage probiotic Feta cheese were studied, in relation to viability and cellular ultrastructure of Lactobacillus casei. The addition of the essential oil in the concentrations from 0.0 to 0.03% was trialled: the 0.03% treatment resulted in the highest viability of L. casei and the lowest pH value compared with other treatments (P < 0.05). Electron microscopy showed that essential oil caused no harm to L. casei. This study demonstrated the favourable effects of M. longifolia on optimal maintenance of L. casei at the end of cheese storage period.

Effects of Mentha longifolia L. essential oil on viability and cellular ultrastructure of Lactobacillus casei during ripening of probiotic Feta cheese

Background : The visceral larva migrans (VLM) is a syndrome observed in human infection with helminth larval eggs such as the Toxocara spp. that usually infects dogs and cats. Among the risk factors involved in the occurrence of VLM, partic­ularly importance of these animal populations, an investigation was carried out for the presence of Toxocara spp. eggs in public parks in the city of Urmia, West Azerbaijan Province, Iran. Methods : Samples were collected from total 26 existing public parks in Urmia from December 2003 to March 2004. Soil samples were collected from 3-4 distinct sites in the same area. The floating material was analyzed under the light micro­scope. Results : Toxocara spp. eggs were found in 8 samples of total 102 taken samples from 26 public parks showed a contami­nation rate of 7.8%. The number of observed Toxacara eggs in each microscopic field was varied from 1-8. Conclusion : Low rate of contamination with Toxocara spp. eggs in Urmia parks might be due to lower dog population and cultural differences of present study in this city in comparison of other cities of the world.

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Toxocara Spp. Eggs in Public Parks of Urmia City, West Azerbaijan Province Iran

Medically important arthropods, including fleas, play an important role in causing clinical disorders and disease in man and domestic animals. This study was conducted to determine the seasonal flea infestations for domestic dogs from different geographic regions of Iran. A total of 407 fleas, belonging to 5 different species, were recovered from 83 domestic dogs from 3 regions. There was a distinctive pattern of species distribution and infestations with the highest infestation rates observed in a temperate climate and higher rainfall. Additionally, fleas were observed over all seasons, except February and March, with the highest infestation rate observed in August (24.7%) and the lowest rate in January (1.7%). They also parasitize dogs with a different spectrum of species. The cat flea, Ctenocephalides felis (67.5%), exhibited the highest prevalence among all flea species found on dogs. Thus, climatic conditions and seasonal patterns impact on flea infestation and must be considered in developing control programs.

Mojtaba Hadian

Papers

Characterization of antioxidant chitosan film incorporated with Zataria multiflora Boiss essential oil and grape seed extract

Synergistic antibacterial activity of the essential oil of Cuminum cyminum L. seed and nisin in a food model.

Effects of Mentha longifolia L. essential oil on viability and cellular ultrastructure of Lactobacillus casei during ripening of probiotic Feta cheese

Toxocara Spp. Eggs in Public Parks of Urmia City, West Azerbaijan Province Iran

Survey of flea infestation in dogs in different geographical regions of Iran.