Casein films: effects of formulation, environmental conditions, and addition of citric pectin on the structure and mechanical properties

hin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low water-resistance and elasticity. Modifying and customizing the mechanical properties of the films to target specific behaviors depending on environmental conditions would enable a v...

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Bibliographic Details
Published in:Polymers 2014, Vol.6 (7), p.2018-2036
Main Authors: Bonnaillie, Laetitia M, Zhang, Han, Akkurt, Serife, Yam, Kit L, Tomasula, Peggy M
Format: Article
Language:English
Subjects:
calcium caseinate
Casein
chemical interactions
chemical structure
Constants
Film thickness
Food packaging
Formulations
glycerol
Mechanical properties
microscopy
microstructure
mixing
modulus of elasticity
Networks
oxygen
packaging films
Pectin
pectins
permeability
relative humidity
temperature
tensile strength
thickness
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Summary:hin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low water-resistance and elasticity. Modifying and customizing the mechanical properties of the films to target specific behaviors depending on environmental conditions would enable a variety of commercial applications for casein-based films. The static and dynamic mechanical properties of solvent-cast (15% solids) calcium-caseinate/glycerol films (CaCas:Gly ratio 3:1) were measured as a function of processing and testing conditions, including film thickness, formulation, temperature (T) and relative humidity (from 22 to 70% RH through the year). While elongation at break (EAB) decreased strongly with reduced thickness, tensile strength (S) and modulus (E) decreased approximately linearly with increased RH, while EAB improved. Small amounts (0.05 to 1%) of Citric Pectin (CP) were then incorporated in the films using 7 different formulations (mixing sequences) to study CP effects on tensile properties and structure of CaCas/Gly/CP films and enhance mechanical properties and T- and RH-resistance. At constant thickness and ~60% RH, microscopy showed large formulation- and composition-dependent structural changes. Humidity-controlled dynamic mechanical analyses using a DMA-RH attachment configured to Humidity Sweep (20 to 80% RH at 20 deg C) or Temperature Sweep (5 to 90 deg C at 50% RH) modes demonstrated subtle or strong effects of RH, T, composition, and formulation on the dynamic mechanical properties of the films, suggesting changing network configurations, and revealing several T- or RH-induced secondary transitions. DMA-RH information can help understand complex CaCas/Gly/CP binding interactions to optimize casein films.
ISSN:2073-4360
2073-4360
DOI:10.3390/polym6072018