antifungal chitosan-based films and coatings containing essential oils for fruit applications

259 Pages·2015·4.86 MB·English

by  Angela Perdones Montero

ANTIFUNGAL CHITOSAN-BASED
FILMS AND COATINGS
CONTAINING ESSENTIAL OILS
FOR FRUIT APPLICATIONS
DOCTORAL THESIS
Ángela Perdones Montero
Supervisors:
Amparo Chiralt Boix
Maria Vargas Colás
Valencia, December 2015

Dra. Amparo Chiralt Boix, Catedrática de Universidad, perteneciente al
Departamento de Tecnología de Alimentos de la Universitat Politècnica de
València.
Dra. Maria Vargas Colás, Profesora Titular de Universidad, perteneciente al
Departamento de Tecnología de Alimentos de la Universitat Politècnica de
València.
Hacen constar que:
La memoria titulada “Antifungal Chitosan-Based Films and Coatings
containing Essential Oils for Fruit Applications” que presenta Dª Ángela
Perdones Montero para optar al grado de Doctor por la Universitat
Politècnica de València, ha sido realizada en el Instituto de Ingeniería de
Alimentos para el Desarrollo (IuIAD – UPV) bajo su dirección y que reúne las
condiciones para ser defendida por su autora.
Valencia, 15 de Octubre 2015
Fdo. Amparo Chiralt Boix Fdo. Maria Vargas Colás

A mi familia

ACKNOWLEDGEMENTS
Me gustaría expresar mis más sinceros agradecimientos a mis directoras de
Tesis, Dra. Amparo Chiralt y Dra. Maria Vargas, por ofrecerme esta gran
oportunidad. Muchas gracias por vuestra dedicación, apoyo, enseñanzas, y
sobre todo por vuestra cercanía, siempre me he sentido muy afortunada
de formar parte de vuestro equipo. Agradezco también su dedicación a la
Dra. Chelo González, a la Dra. Isabel Escriche, a la Dra. Maite Cháfer, a la Dra.
Lorena Atarés y a la Dra. Laura Sánchez. Ha sido un gran placer poder
colaborar con vosotras.
Gracias al “Laboratoire d'Ingénierie et des Biomolécules” y en especial al
Dr. Stéphane Desobry y a la Dra. Elmira Arab Tehrany de la Université de
Lorraine. Gracias a “BioTeam”, al Dr. Luc Avérous y a todos mis compañeros
del “Institute de Chimie et Procédés pour l'Energie, l'Environnement et la
Santé”. Ha sido una experiencia inolvidable haber podido compartir mis
estancias con vosotros.
A todos mis compañeros del laboratorio, los de dentro y los de fuera, los
que están y los que se han ido. De cada uno de vosotros me llevo un
pedacito.
A todos mis amigos, por estar ahí siempre que os necesito.
Por último, a mi familia, vuestro apoyo continuo es fundamental, en esta
etapa de mi vida, y en las que están por llegar. Gracias Albert por estar
siempre a mi lado.

PREFACE
DISSERTATION OUTLINE
This Doctoral Thesis is structured in five sections: Introduction, Objectives,
Chapters, General Discussion and Conclusions. The Introduction section
discusses the state of the art concerning properties and antimicrobial
action of chitosan and essential oils. The Objectives section presents the
general and specific objectives of the Thesis. The obtained results are
presented in five Chapters, as a collection of scientific publications,
including the usual sections: introduction, material and methods and
results and discussion. The General Discussion section discusses, from an
overall perspective, the most relevant results obtained in this Doctoral
Thesis. Finally, the most important conclusions are presented.
According to the general objective of the thesis, different strategies to
obtain chitosan films with antifungal properties, to be applied in fruit
preservation, were used; different homogenization conditions of the
chitosan solutions and lipid emulsions were applied to the film-forming
systems and different essential oils were used, selected on the basis of the
their aroma compatibility with the coated products (strawberries and
tomatoes) and their previously described antifungal activity. The effect of
oleic acid, as emulsifier in the film formulations, was also analysed in its
double action: to facilitate the essential oil emulsification and retention in
the films and to reduce the hygroscopic character of chitosan films. The
blending of chitosan with a neutral and safe polymer, methylcellulose (MC),
was also investigated in coating applications to tomato plants in different
growth stages, to mitigate the possible adverse effects of pure chitosan on
the early stages of the plants. All the obtained results are organized as
follows:
Chapter 1, entitled "Effect of homogenization conditions on
physicochemical properties of chitosan based film-forming dispersion and
films", analyses the effect of the homogenization treatments on the
physicochemical properties of the chitosan-oleic acid film-forming
emulsions and functional properties of the films. Results showed that
microfluidization (high pressure homogenization) led to a significant
decrease in the lipid droplet particle size, depending on the pressure,
which, in turn, reduced the water vapour permeability of the films and
enhanced their stiffness. So, this technique appears to be a suitable
approach to develop chitosan edible films with lipids adapted to a specific
target application.
In Chapter 2, “Application of Chitosan films containing essential oils in
preservation of strawberries”, the effect of chitosan coatings on the
strawberry quality parameters throughout the storage time was studied.
Chitosan coatings did not significantly affect the physicochemical
parameters of strawberries throughout storage, while they slowed down
their respiration rate when lemon essential oil was added to the
formulation. Adding lemon essential oil enhanced the chitosan antifungal
activity against Botrytis cinerea, both in in vitro tests and during cold storage
of inoculated strawberries. The study of the impact of coatings on the
strawberry volatile profile revealed significant changes in the analysed
compounds for both, coatings with and without lemon essential oil.
Nevertheless, sensory appreciation of these changes was only notably for
samples coated with chitosan-lemon oil films. In this sense, possible
sensory advantages of cinnamon leaf essential oil were tested, as described
in Chapter 3.
Chapter 3, “Effect of oleic acid on the essential oil performance in chitosan
matrix”, analyses physical and antimicrobial properties of chitosan films
with different essential oils (basil, cinnamon leaf and thyme), containing or
not oleic acid. This compound was added to favour the stability of the
essential oil emulsions, thus reducing the oil losses by evaporation during
the film drying step. Although this aim was reached and more oil retention
in the film was obtained when oleic acid was added, its incorporation
reduced the antifungal effectiveness of the essential oil containing films, in
line with the encapsulating effect. Nevertheless, all the coatings with
cinnamon leaf were effective in extending the shelf-life of cold-stored
strawberries, mainly at the higher essential oil:polymer ratios.
In Chapter 4 “Effect of chitosan coatings containing essential oils on tomato
plants and fruits“ chitosan-methylcellulose films were applied with the aim
of controlling the growth of Rhizopus stolonifer in tomatoes, in pre- and
postharvest treatments. Coating formulations included methylcellulose, to