8 Oleochemistry Products
231
8.3.4.1 Antimicrobial Edible Films and Coatings
An interesting approach, as already mentioned, consists in incorporating antimicrobial/antifungal agents directly into edible films or coatings in a way that they are
slowly released onto the surface of the food to inhibit microbial growth [205]. Such
coatings can also act as a barrier to moisture and oxygen. In particular, edible coatings have become popular in the food industry, because they have competitive costs,
produce less waste being biodegradable and offer effective protection also after the
package opening. Numerous literature studies appeared in the literature on this topic.
For example, Hershko and Nussinovitch [84] studied the behaviour of hydrocolloid
coatings on vegetative materials; Mark [136] reviewed systematically the selection of
edible coatings to maximize quality and shelf life of fresh fruits and vegetables. Components of edible films and coatings can be divided into three principal categories
[205]: (i) hydrocolloids (proteins and polysaccharides as cellulose and derivatives,
starch, chitosan, etc.); (ii) lipids (waxes, acylglycerols and fatty acids), and (iii) composites (a combination of the two previous categories). Despite the large spectrum
of available materials, the choice of materials for a film or coating depends largely
on the final use of the film.
The potential applications and properties of edible films are also subjected to
different reviews [51, 106, 122, 143]. Moreover, the use of a minimum amount
of plasticizers in these films (like sorbitol or glycerol) may be adopted to improve
mechanical properties and the possibility of incorporating active compounds (antimicrobials, antioxidants, nutraceuticals, flavours, colourants) in polymeric matrices is
one of the main advantages of coatings. In particular, as commented above, the
incorporation of EO into polymeric matrices gives them very interesting antimicrobial/antioxidant/antifungal properties (see Table 8.3 for some examples). The major
advantage of this technology is that the diffusion rate of the antimicrobial agent
can be slowed down, keeping high concentrations of the active compounds on the
product surface (where the contamination is prevalent) for extended periods of time.
This makes the process more effective in reducing the levels of microorganism with
respect to the direct application on the product surface through spray solutions [172].
Other important issues are: the nature and amount of EOs, the EO/polymer ratio in
the film and the possible interactions between the polymer and the active compounds.
When the polymer itself, did not show antimicrobial activity, the effect of the EO
generally increased with the EO/polymer ratio [187].
In food applications, film water vapour permeability (WVP) is another fundamental factor affecting the effectiveness of food properties preservation. Low values of
WVP are usually desirable in order to minimize weight losses in the coated product
and the incorporation of EO into polymeric matrices leads to an improvement in the
WVP of films because of the increment in the hydrophobic character of material
[122]. Less clear is the effect of EO addition on oxygen and CO 2 permeability, even
if some studies [122] reported a slight decrease in oxygen permeability of the films
based on alginate with lemongrass oil. In some cases, however, the incorporation of
EOs into a continuous polymeric matrix of edible films, resulted in a decrease of its
mechanical resistance to fracture, because of the structural discontinuities caused by
231
8.3.4.1 Antimicrobial Edible Films and Coatings
An interesting approach, as already mentioned, consists in incorporating antimicrobial/antifungal agents directly into edible films or coatings in a way that they are
slowly released onto the surface of the food to inhibit microbial growth [205]. Such
coatings can also act as a barrier to moisture and oxygen. In particular, edible coatings have become popular in the food industry, because they have competitive costs,
produce less waste being biodegradable and offer effective protection also after the
package opening. Numerous literature studies appeared in the literature on this topic.
For example, Hershko and Nussinovitch [84] studied the behaviour of hydrocolloid
coatings on vegetative materials; Mark [136] reviewed systematically the selection of
edible coatings to maximize quality and shelf life of fresh fruits and vegetables. Components of edible films and coatings can be divided into three principal categories
[205]: (i) hydrocolloids (proteins and polysaccharides as cellulose and derivatives,
starch, chitosan, etc.); (ii) lipids (waxes, acylglycerols and fatty acids), and (iii) composites (a combination of the two previous categories). Despite the large spectrum
of available materials, the choice of materials for a film or coating depends largely
on the final use of the film.
The potential applications and properties of edible films are also subjected to
different reviews [51, 106, 122, 143]. Moreover, the use of a minimum amount
of plasticizers in these films (like sorbitol or glycerol) may be adopted to improve
mechanical properties and the possibility of incorporating active compounds (antimicrobials, antioxidants, nutraceuticals, flavours, colourants) in polymeric matrices is
one of the main advantages of coatings. In particular, as commented above, the
incorporation of EO into polymeric matrices gives them very interesting antimicrobial/antioxidant/antifungal properties (see Table 8.3 for some examples). The major
advantage of this technology is that the diffusion rate of the antimicrobial agent
can be slowed down, keeping high concentrations of the active compounds on the
product surface (where the contamination is prevalent) for extended periods of time.
This makes the process more effective in reducing the levels of microorganism with
respect to the direct application on the product surface through spray solutions [172].
Other important issues are: the nature and amount of EOs, the EO/polymer ratio in
the film and the possible interactions between the polymer and the active compounds.
When the polymer itself, did not show antimicrobial activity, the effect of the EO
generally increased with the EO/polymer ratio [187].
In food applications, film water vapour permeability (WVP) is another fundamental factor affecting the effectiveness of food properties preservation. Low values of
WVP are usually desirable in order to minimize weight losses in the coated product
and the incorporation of EO into polymeric matrices leads to an improvement in the
WVP of films because of the increment in the hydrophobic character of material
[122]. Less clear is the effect of EO addition on oxygen and CO 2 permeability, even
if some studies [122] reported a slight decrease in oxygen permeability of the films
based on alginate with lemongrass oil. In some cases, however, the incorporation of
EOs into a continuous polymeric matrix of edible films, resulted in a decrease of its
mechanical resistance to fracture, because of the structural discontinuities caused by