**10.1 Introduction**

The use of essential oils (EO) dates back to the earliest civilizations: first in the East and the Middle East and later in North Africa and Europe (Franchomme et al., 1990). The Hydrosols (aromatic) were used in India over than 7000 years. Between 3000 and 2000 B.C., the Egyptians made used extensively aromatic plants and other plants to treat the sick. the Persians seem to be the first ones who used the hydrodistillation in 1000 B.C. The use of essential oils was a common practice among the Greeks, several books have been published on the subject. Examples of this literature are "Natural History" by Pliny, "The Aphorisms" by Hippocrates, "odor treatment" by Theophrastus and Dioscorides Pedanius wrote a book on herbal medicine (phytotherapy). The Arabs have made a significant improvement in chemistry and in the distillation of oils by inventing the alembic still by Jaber Ibn Hayan. In the late seventeenth and

Currently, even if the food manufacturing is done according to the standards proposed by the WHO, an important part of the fight against zoonoses must be borne by the consumer, who can be considered an integral link in the chain. We must therefore inform about the risks that may result from errors in food handling. Unfortunately, at present, few initiatives have been undertaken in Africa, unlike the situation in Europe and the United States, where politics at this level is a little more proactive. The operation FightBac ® bases its message on a logo simple and easy to understand for educators, children and operators of processing lines and distribution. CSCC logo are constantly reminded that people must wash their food ("Clean"), separate ("Separate"), Cook ("Cook") and cool ("Chill"). Advice is provided for hand washing, cooking food. The FDA in collaboration with the Center for food Safety and Applied Nutrition (CFSAN) has published a brochure about the risk of salmonellosis associated with eggs (FDA 2002). The CDC ("Centers for Disease Control") has published a leaflet on Salmonella Enteritidis, available on the Internet (Center for Disease Control, 2003). Finally, the educated consumers will, no doubt, more likely to seek medical attention, which will encourage

Salmonella is still a topical; it is in any way, a rearguard battle. They are among the first known causes of food borne illness. It is a collective and a real public health problem. Economically, they are crucial, given the casualties they cause. In recent years, problems related to Salmonella have increased significantly, both in terms of the incidence of salmonellosis, that the severity of human cases. While some countries have managed to reverse the upward trend in the incidence of human salmonellosis, new problems were identified. Since the late 90s, Salmonella strains resistant to a range of antimicrobials including major therapeutic agents in human medicine have emerged and are threatening to cause serious public health problem (Mermin et al., 1999). After a very long incubation period, between 7 and 21 days (sometimes up to six weeks), the disease can take many forms (Hu and Kopecko, 2003). The infection may be asymptomatic or cause very mild symptoms in the case of S. Paratyphi or, conversely, cause typhoid fever, severe disease, with fever and sepsis. It mainly affects young children and teenagers (Bäumler et al., 1998). This resistance results from the use of antimicrobials in both

The use of essential oils (EO) dates back to the earliest civilizations: first in the East and the Middle East and later in North Africa and Europe (Franchomme et al., 1990). The Hydrosols (aromatic) were used in India over than 7000 years. Between 3000 and 2000 B.C., the Egyptians made used extensively aromatic plants and other plants to treat the sick. the Persians seem to be the first ones who used the hydrodistillation in 1000 B.C. The use of essential oils was a common practice among the Greeks, several books have been published on the subject. Examples of this literature are "Natural History" by Pliny, "The Aphorisms" by Hippocrates, "odor treatment" by Theophrastus and Dioscorides Pedanius wrote a book on herbal medicine (phytotherapy). The Arabs have made a significant improvement in chemistry and in the distillation of oils by inventing the alembic still by Jaber Ibn Hayan. In the late seventeenth and

feedback and help to reduce the phenomenon of under-reporting of cases.

**8. Prophylaxis** 

**9. Resistant salmonella** 

human medicine and animal husbandry.

**10. Essential oils 10.1 Introduction** 

eighteenth century, more than 10 essential oils were used. In modern history, the therapeutic properties of essential oils have an increasing importance. Aromatherapy has been used to describe the healing properties of essential oils. Actually, we recognize that essential oils have pharmacological, psychological and physiological effects in humans.

Among the plant species estimated by botanists (800 000 to 1 500 00), only 10% are classified as "aromatic". Aromatic plants synthesize and secrete trace amounts of aromatic essence through hair, secretory pockets or channels. Types capable of developing the components of essential oils are distributed in a limited number of families, Myrtaceae, Lauraceae, Rutaceae, Lamiaceae, Asteraceae, Cupressaceae, Poaceae, Zingiberaceae, such as Piperaceae [Bruneton, 1999]. About 20,000 of plant species in the world are used for food, cosmetics, chemical, pharmaceutical and therapeutic food. Among the 4,000 plant species existing in Morocco, more than 280 plants are currently operating.

The AFNOR NF T 75-006 (AFNOR, 1986) defines the essential oil as "a product made from a vegetable raw material, either by steam or by mechanical means from the exocarp, Citrus, or by dry distillation. Essential oils (EO), also called "essences" are aromatic substances, volatile and oily consistency, contained in plants [Balz, 1986 - Lardry and Haberkorn, 2003]. Most plants contain (Eo), but usually in lower quantities. Only plants known as "aromatic" produce essential oils in sufficient quantity. They are usually concentrated in a particular area of the plant such as leaves, bark or fruit, and generally when they occur in various organs from the same plant, they have different compositions (Conner, 1993). The synthesis and accumulation of essential oils, classified as secondary metabolites, are generally in the specialized histological structures, often located on or near the surface of the plant (Brunechon, 1987): pockets (citrus exocarp ) of a storage (eucalyptus), secretory canals or blisters containing resin (conifers), or glands in cuticular (conical epidermal cells on the flowers of Rosaceae), trichomes or secretory glandular trichomes on the leaves of solanaceous or Lamiaceae (Gershenzon, 2000) (Figure 8). It is important to note that several categories of these secretory tissues can coexist simultaneously in the same species, even within the same organ (Fahn, 1979 - Fahn, 1988). For example, to the Lamiaceae family, it is within the secretory hairs, in Myrtaceae in pockets secretory or secretory channels in Asteraceae. Essential oils can be stored in various organs of the plant: flowers (oregano), leaves (lemon grass, eucalyptus), bark (cinnamon), wood (rosewood, sandalwood), roots (vetiver), rhizomes (sweet flag), fruits (star anise) and seeds (caraway). Essential oils are complex mixtures consisting of several compounds, mainly terpenes. Terpenes are formed by one or more isoprene units (Tedder, 1970; Brunechon, 1987), constituting a diverse family both structurally and functionally. Mainly mono-and sesquiterpenes (with 10 and 15 carbon atoms) are the most encountered the diterpenes (20 carbon atoms). Essential oils can also contain aliphatic or aromatic compounds. These terpenoids have an ecological role in plant interactions, such as allelopathic agents. They can be inhibitor of germination, but also during plant-animal interactions, as a protective agent against predators such as insects.

They are also involved, through their characteristic odors in the attraction of pollinators (Langenheim, 1969). Some plants may have an odor similar due to a common molecule present in significant amounts in the essential oil. According to the economic environment, it would be profitable to produce plant species may provide an essential oil with high molecular compound, and therefore generally better (Tedder, 1970).

Herbs that produce essential oils have been the subject of various researches particularly in the field of perfumery. A range of products to smell more or less pronounced depending on the concentration of volatile compounds collected from the essential oils produced by steam distillation or expression of the peel fruit (Tedder, 1970;Brunechon, 1987).

Use Thyme Essential Oils for the Prevention of Salmonellosis 315

The majority of the components of EO are monoterpenes; they represent 90% of most essential oils. They are volatile usually easily driven by steam, have often pleasant odor (Lamart, 1994). By the diversity of their structure, they can be classified into several groups (Bakkali, 2008) (Table 3). Several factors may be responsible of the chemical polymorphism of essential oils. The most important are climate, soil, time harvest and method of storage and retrieval. Genetic factors (Echeverrigaray, 2001) and the growth cycle (Hance, 2003) may also influence this variability…(Bakkali, 2008). The use of essential oils is of great interest in many areas. Thus, the species most studied for their antibacterial and antifungal properties (biological activities) belong to the Lamiaceae family: Thyme, oregano, savory, lavender,

Essential oils are very complex natural mixtures that can hold about 20-60 components with very different concentrations. The main group composed by terpenoids or isoprenoids is a family of secondary metabolites widely distributed in the plant kingdom. More than 22000 compounds have been identified (Connolly 1992). Their classification is based on the number of repetition of the basic unit of isoprene: hemiterpene (C5), monoterpene (C10), sesquiterpene (C15), diterpene (C20), sesterpene (C25), triterpene (C30), tetraterpene (C40) and polyterpene. The major terpene components of essential oils are monoterpene and sesquiterpene. Isoprenoid biosynthesis of essential oils can be simplified into three phases: Isopentenyl diphosphate (IPP) Biosynthesis, condensation of IPP units and formation of prenyl diphosphates and Conversion of prenyl-diphosphates. The condensation of isopentenyl diphosphate (nucleophilic entity) to dimethylallyl diphosphate (electrophilicentity) leads to geranyl diphosphate (GPP, C10), precursor of monoterpenes. A further condensation type head-to-tail of IPP on the GPP leads to farnesyl diphosphate (FPP, C15), the precursor of sesquiterpenes. The prenyl transferases allow prenyl chain elongation

Fig. 5. Biosynthetic precursors of the main metabolic constituents of essential oils

mint, rosemary, sage and hyssop.

**10.3 Biosynthesis of essential oil** 

by addition of one molecule of IPP.

Fig. 2. Glandular trichomes of mint gardens observed in electron microscope scan (1000 ×) before (a) and after (b) extraction by steam distillation [Lucchesi, 2005].
