220
R. Tesser et al.
great impulse is then put into the research of new, highly selective and biodegradable pesticides able to solve both the long-term toxicity to mammals and to reduce
the amount of pesticide used to preserve crop yields. The general framework of the
Green Chemistry processes is nowadays gaining more and more relevance, which is
a natural alternative to traditional synthetic pesticides as a means to reduce the negative impact on human health and the environment and such an alternative could be
very probably represented by EOs. Many nature-oriented materials can be profitably
employed to reduce microbial, fungi and pest populations improving food preservation and increase food production [94, 205]. As a matter of fact, essential oils can
be considered today the best candidate in this field as they are safe, eco friendly and
life compatible [34, 96, 113]. The global essential oils market is projected to register
an estimated CAGR of 9.2%, during the forecast period, 2018–2023 and, in only the
US, the EOs market is projected to reach USD 7.34 billion (13 billion on a world
basis) by 2024.
8.3.2 Components of Essential Oils
It is well known from the literature that EOs are very complex mixtures of many
organic compounds [34, 102, 113] and their composition can be different from plant
to plant and, also, between distinct parts of the same plant [34]. A further source of
variation of EOs composition, for some species of plants, could be the harvesting
seasons and geographical areas of cultivation [16, 42, 62, 137].
The main constituents can be classified into different categories like in the
following list in which also some examples are shown [113]:
• terpenes (hydrocarbons): myrcene, pinene, terpinene and limonene;
• terpenoids (oxygen-containing hydrocarbons);
• acyclic monoterpene alcohols: geraniol, linalool;
• monocyclic alcohols: menthol, 4-carvomenthenol, terpineol, carveol;
• aliphatic aldehydes: citral, citronellal, perillaldehyde;
• aromatic phenols: carvacrol, thymol, safrol, eugenol;
• bicyclic alcohols: verbenol;
• monocyclic ketones: menthone, pulegone, carvone;
• bicyclic monoterpenic ketones: thujone, verbenone, fenchone;
• acids: citronellic acid, cinnamic acid;
• esters: linalyl acetate.
In Fig. 8.7, chemical structures of some compounds frequently present in essential
oils are reported.
An important aspect that can strongly influence the EOs composition, and ultimately also the antimicrobial activity, is the extraction method from the original
matrix. For commercial purposes, the steam distillation is the most commonly used
method for recovering EOs while the extraction by means of liquid carbon dioxide,
at low-temperature and high-pressure conditions, resulted in more expense [144].
R. Tesser et al.
great impulse is then put into the research of new, highly selective and biodegradable pesticides able to solve both the long-term toxicity to mammals and to reduce
the amount of pesticide used to preserve crop yields. The general framework of the
Green Chemistry processes is nowadays gaining more and more relevance, which is
a natural alternative to traditional synthetic pesticides as a means to reduce the negative impact on human health and the environment and such an alternative could be
very probably represented by EOs. Many nature-oriented materials can be profitably
employed to reduce microbial, fungi and pest populations improving food preservation and increase food production [94, 205]. As a matter of fact, essential oils can
be considered today the best candidate in this field as they are safe, eco friendly and
life compatible [34, 96, 113]. The global essential oils market is projected to register
an estimated CAGR of 9.2%, during the forecast period, 2018–2023 and, in only the
US, the EOs market is projected to reach USD 7.34 billion (13 billion on a world
basis) by 2024.
8.3.2 Components of Essential Oils
It is well known from the literature that EOs are very complex mixtures of many
organic compounds [34, 102, 113] and their composition can be different from plant
to plant and, also, between distinct parts of the same plant [34]. A further source of
variation of EOs composition, for some species of plants, could be the harvesting
seasons and geographical areas of cultivation [16, 42, 62, 137].
The main constituents can be classified into different categories like in the
following list in which also some examples are shown [113]:
• terpenes (hydrocarbons): myrcene, pinene, terpinene and limonene;
• terpenoids (oxygen-containing hydrocarbons);
• acyclic monoterpene alcohols: geraniol, linalool;
• monocyclic alcohols: menthol, 4-carvomenthenol, terpineol, carveol;
• aliphatic aldehydes: citral, citronellal, perillaldehyde;
• aromatic phenols: carvacrol, thymol, safrol, eugenol;
• bicyclic alcohols: verbenol;
• monocyclic ketones: menthone, pulegone, carvone;
• bicyclic monoterpenic ketones: thujone, verbenone, fenchone;
• acids: citronellic acid, cinnamic acid;
• esters: linalyl acetate.
In Fig. 8.7, chemical structures of some compounds frequently present in essential
oils are reported.
An important aspect that can strongly influence the EOs composition, and ultimately also the antimicrobial activity, is the extraction method from the original
matrix. For commercial purposes, the steam distillation is the most commonly used
method for recovering EOs while the extraction by means of liquid carbon dioxide,
at low-temperature and high-pressure conditions, resulted in more expense [144].