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Polymers 2014, 6(7), 2018-2036; doi:10.3390/polym6072018
Article

Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties

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Received: 1 October 2013; in revised form: 12 June 2014 / Accepted: 30 June 2014 / Published: 14 July 2014
(This article belongs to the Special Issue Natural Polymers 2014)
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Abstract: Thin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low elasticity and high sensitivity to moisture. Modifying the films to target specific behaviors depending on environmental conditions can enable a variety of commercial applications for casein-based films. The mechanical properties of solvent-cast (15% solids) calcium-caseinate/glycerol films (CaCas:Gly ratio of 3:1) were characterized as a function of processing and environmental conditions, including film thickness, solution formulation and ambient humidity (from 22% to 70% relative humidity (RH) at ~20 °C). At constant RH, the elongation at break (EAB) had a strong positive dependence on the film thickness. When RH increased, the tensile strength (TS) and modulus (E) decreased approximately linearly, while EAB increased. From 0.05% to 1% (w/w) of citric pectin (CP) was then incorporated into CaCas/Gly films following seven different formulations (mixing sequences), to alter the protein network and to evaluate the effects of CP on the tensile properties of CaCas/Gly/CP films. At constant film thickness and ~60% RH, the addition of 0.1% or 1.0% CP to the films considerably increased or decreased EAB, TS and E in different directions and to different extents, depending on the formulation, while optical micrographs also showed vastly differing network configurations, suggesting complex formulation- and stoichiometry-dependent casein-pectin interactions within the dried films. Depending on the desired film properties and utilization conditions, pectin may be a useful addition to casein film formulations for food packaging applications.
Keywords: high-methoxyl pectin; milk protein; edible film; food packaging high-methoxyl pectin; milk protein; edible film; food packaging
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Bonnaillie, L.M.; Zhang, H.; Akkurt, S.; Yam, K.L.; Tomasula, P.M. Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties. Polymers 2014, 6, 2018-2036.

AMA Style

Bonnaillie LM, Zhang H, Akkurt S, Yam KL, Tomasula PM. Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties. Polymers. 2014; 6(7):2018-2036.

Chicago/Turabian Style

Bonnaillie, Laetitia M.; Zhang, Han; Akkurt, Serife; Yam, Kit L.; Tomasula, Peggy M. 2014. "Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties." Polymers 6, no. 7: 2018-2036.


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