30 research outputs found
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
Phase equilibrium and diffusion of solvents in polybutadiene: A capillary-column inverse gas chromatography study
The capillary-column inverse gas chromatography method was used to measure the diffusion and partition coefficients of ethylbenzene, styrene, and acrylonitrile in polybutadiene (PBD) at infinite dilution of the solvents. Experiments were performed over a temperature range of 50-125 °C. At temperatures well above the glass-transition temperature of PBD, the diffusivities were correlated using an Arrhenius expression. The Arrhenius parameters in turn were intercorrelated and shown to be a function of the occupied volume, thus providing a method for predicting the diffusion of other solvents in the same polymer. Further, the activation energy was predicted using the Duda-Vrentas free-volume approach. The activation energy thus obtained was compared with the activation energy of the Arrhenius approach. The weight-fraction activity coefficient data were compared to the predictions of the group contribution, lattice-fluid equation-of-state, and the UNIquac Functional-group Activity Coefficient (UNIFAC) free-volume models