Biomedical Engineering Reference
In-Depth Information
5.5.1
Volatile Compounds
Volatiles are low molecular weight organic compounds (less 250 g/Mol) with high
vapor pressure at room temperature (Hewett et al.
1998
). Plants produce a wide
range of volatile compounds, some are important for fl avor quality in fruits, vegeta-
bles, spices, and herbs, and are generally recognized as safe (GRAS) (Kays
1991
).
The volatile and semi-volatile compounds in plant constituents play important roles
in the plant growth, such as plant-plant competition and cooperative co-evolution,
plant's defense against insects, pests, herbivores and pathogens (Yang et al.
2013
).
Some studies have shown that the exposure of some fresh-cut products to volatile
compounds, such as methyl jasmonate, can signifi cantly reduce the risk of microbial
contamination (Wang and Buta
2003
; González-Aguilar et al.
2010b
). Additionally,
these volatile compounds also reduce the browning effects after cutting the tissues
of fresh produce, and prevents the damage by chilling injury (Wang and Buta
2003
).
Moreover, it has been shown that the application (E) 2-hexanal prevents micro-
bial contamination of the FCFV products, especially against
Botrytis cinerea
and
Aspergillus fl avus
(Gardini et al.
2001
; Fallik et al.
1998
). Likewise, the compounds
released by plant tissue through lipoxygenase pathway, such as six carbon aldehydes,
have been found to inhibit hyphal growth of
Alternaria alternate
and
B. cinerea
(González-Aguilar et al.
2010b
). Furthermore, volatiles compounds such as jasmo-
nates have been used as elicitors as they play key roles as signal molecules in plant
defense responses against biotic stress (microbial contamination). These also induce
the synthesis of antioxidants such as vitamin C and phenolic compounds (Solis
et al.
2004
).
5.5.2
Essential Oils
The most studied bioactive compounds applied to fresh-cut products are essential
oils (EOs). These are volatile and natural complex compounds characterized by a
strong odor, and are formed by aromatic plants as a secondary metabolites (Bakkali
et al.
2008
). EOs represent the most important aromatic fraction of plant and veg-
etal tissues. These compounds are constituted by a complex mixture of terpenes,
alcohols, ketones, aldehydes and esters. The most common constituents within EO
are terpenes. They are made from combinations of several 5-carbon-base (C5)
units called isoprene. Terpenes or terpenoids are active against bacteria, fungi,
virus, and protozoa (Scortichini and Rossi
1991
; Inoue et al.
2004
; Dalleau et al.
2008
; Solis et al.
2004
; Herman
1992
). It was reported that 60 % of EOs derivatives
examined to date were inhibitory to fungi, while 30 % inhibited bacteria (Chaurasia
and Vyas
1977
).
However, the mechanisms of antimicrobial activity are not fully elucidated.
The general accepted hypothesis establishes that the components of EOs acts in
several targets of the bacterial cell. For example, the hydrophobicity of EOs
enables them to partition in the lipids of the cell membrane and mitochondria,
