30 research outputs found
Layer-by-layer technique to developing functional nanolaminate films with antifungal activity
The layer-by-layer (LbL) deposition method was used to build up alternating layers (five) of different polyelectrolyte solutions (alginate, zein-carvacrol nanocapsules, chitosan and chitosan-carvacrol emulsions) on an aminolysed/charged polyethylene terephthalate (A/C PET) film. These nanolaminated films were characterised by contact angle measurements and through the determination of water vapour (WVTR) and oxygen (O2TR) transmission rates. The effect of active nanolaminated films against the Alternaria sp. and Rhizopus stolonifer was also evaluated. This procedure allowed developing optically transparent nanolaminated films with tuneable water vapour and gas properties and antifungal activity. The water and oxygen transmission rate values for the multilayer films were lower than those previously reported for the neat alginate or chitosan films. The presence of carvacrol and zein nanocapsules significantly decreased the water transmission rate (up to 40 %) of the nanolaminated films. However, the O2TR behaved differently and was only improved (up to 45 %) when carvacrol was encapsulated, i.e. nanolaminated films prepared by alternating alginate with nanocapsules of zein-carvacrol layers showed better oxygen barrier properties than those prepared as an emulsion of chitosan and carvacrol. These films containing zein-carvacrol nanocapsules also showed the highest antifungal activity (30 %), which did not significantly differ from those obtained with the highest amount of carvacrol, probably due to the controlled release of the active agent (carvacrol) from the zein-carvacrol nanocapsules. Thus, this work shows that nanolaminated films prepared with alternating layers of alginate and zein-carvacrol nanocapsules can be considered to improve the shelf-life of foodstuffs.The authors acknowledge financial support from
FP7 IP project BECOBIOCAP^. M. J. Fabra is recipients of a Juan de la
Cierva contract from the Spanish Ministry of Economy and
Competitivity. Maria L. Flores-López thanks Mexican Science and Technology
Council (CONACyT, Mexico) for PhD fellowship support
(CONACyT Grant Number 215499/310847). The author Miguel A.
Cerqueira is a recipient of a fellowship (SFRH/BPD/72753/2010) supported
by Fundação para a Ciência e Tecnologia, POPH-QREN and FSE
(FCT, Portugal). The authors also thank the FCT Strategic Project of UID/
BIO/04469/2013 unit, the project RECI/BBB-EBI/0179/2012 (FCOMP-
01-0124-FEDER-027462) and the project BBioInd - Biotechnology and
Bioengineering for improved Industrial and Agro-Food processes,^ REF.
NORTE-07-0124-FEDER-000028 Co-funded by the Programa
Operacional Regional do Norte (ON.2–O Novo Norte), QREN, FEDER.
The support of EU Cost Action FA0904 is gratefully acknowledged
Physical characterisation of an alginate/lysozyme nano-laminate coating and its evaluation on ‘coalho’ cheese shelf life
This work aimed at the characterisation of a nanolaminate
coating produced by the layer-by-layer methodology
and its evaluation on the preservation of ‘Coalho’ cheese.
Initially, five alternate layers of alginate and lysozyme were
assembled in an aminolysed/charged polyethylene terephthalate
(A/C PET) and physically characterised by UV/VIS
spectroscopy, contact angle, water vapour (WVTR) and oxygen
(OTR) transmission rates and scanning electron microscopy.
Afterwards, the same methodology was used to
apply the nano-laminate coating in ‘Coalho’ cheese and its
shelf life was evaluated during 20 days in terms of mass
loss, pH, lipid peroxidation, titratable acidity and microbial
count. UV/VIS spectroscopy and contact angle analyses
confirmed the layers’ deposition and the successful assembly
of nano-laminate coating on A/C PET surface. The coating
presented WVTR and OTR values of 1.03×10−3 and 1.28×
10−4 g m−2 s−1, respectively. After 20 days, coated cheese
showed lower values of mass loss, pH, lipidic peroxidation,
microorganisms’ proliferation and higher titratable acidity in
comparison with uncoated cheese. These results suggest that
gas barrier and antibacterial properties of alginate/lysozyme
nanocoating can be used to extend the shelf life of ‘Coalho’
cheese.The author Bartolomeu G. de S. Medeiros is recipient of a scholarship from Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES-Brazil). The author Marthyna P. Souza is recipient of a scholarship from Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE, Brazil) and was recipient of a scholarship from Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES/PDEE-Brazil). The authors Ana C. Pinheiro, Ana I. Bourbon and Miguel A. Cerqueira are recipients of a fellowship (SFRH/BD/48120/2008, SFRH/BD/73178/2010 and SFRH/BPD/72753/2010, respectively), supported by Fundacao para a Ciencia e Tecnologia, POPH-QREN and FSE (FCT, Portugal). Maria G. Carneiro-da-Cunha express is gratitude to the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) for research grant. The present work was supported by CAPES/PROCAD/NF/1415/2007. The support of EU Cost Action FA0904 is gratefully acknowledged
Competitive Adsorption of Mixed Anionic Polysaccharides at the Surfaces of Protein-Coated Lipid Droplets
Charged polysaccharides can improve the stability of protein-coated lipid droplets by forming a protective coating around them. Potentially, the interfacial characteristics of these coatings can be controlled by assembling them from mixed polysaccharides with different molecular characteristics. The purpose of this study was to examine the competitive adsorption of two anionic polysaccharides (carrageenan and pectin) to beta-lactoglobulin coated-lipid droplets. Carrageenan has a higher charge density than pectin, and carrageenan has a linear backbone whereas pectin has a linear backbone with branches. Emulsions (phi = 1 wt % oil, d43 = 0.40 +/- 0.03 microm) were mixed with polysaccharide solutions (0 or 0.04 wt%) at pH 7, then the pH was decreased to promote polysaccharide adsorption. The adsorption of the polysaccharide molecules to the droplet surfaces occurred at a higher pH for carrageenan (pH approximately 5.85) than for pectin (pH approximately 5.45). When polysaccharide mixtures were added at pH 7, the carrageenan molecules preferentially adsorbed to the droplet surfaces when the pH was reduced. At pH 3.5, carrageenan coated droplets had a higher negative charge (zeta = - 38.5 +/- 3.1 mV) than pectin-coated droplets (zeta = - 17.9 +/- 2.0 mV). Carrageenan was much more effective at displacing pectin from the surfaces of pectin-coated droplets, than pectin was at displacing carrageenan from carrageenan-coated droplets. The stability of pectin-coated droplets was better than carrageenan-coated droplets, which was attributed to steric hindrance effects. These results have important implications for the design of delivery systems based on polysaccharide/protein-coated droplets