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Polymers 2015, 7(1), 91-114; doi:10.3390/polym7010091

Application of Humidity-Controlled Dynamic Mechanical Analysis (DMA-RH) to Moisture-Sensitive Edible Casein Films for Use in Food Packaging

Dairy & Functional Foods Research Unit, Eastern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
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Author to whom correspondence should be addressed.
Academic Editor: Taek-Soo Kim
Received: 11 November 2014 / Accepted: 29 December 2014 / Published: 6 January 2015
(This article belongs to the Special Issue Packaging Films)
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Abstract

Protein-based and other hydrophilic thin films are promising materials for the manufacture of edible food packaging and other food and non-food applications. Calcium caseinate (CaCas) films are highly hygroscopic and physical characterization under broad environmental conditions is critical to application development and film optimization. A new technology, humidity-controlled dynamic mechanical analysis (DMA-RH) was explored to characterize CaCas/glycerol films (3:1 ratio) during isohume temperature (T) ramps and steps, and isothermal RH ramps and steps, to determine their mechanical and moisture-sorption properties during extensive T and RH variations. When RH and/or T increased, CaCas/Gly films became strongly plasticized and underwent several primary and secondary humidity-dependent transition temperatures (or transition humidities); the CaCas/Gly network hypothetically rearranged itself to adapt to the increased water-content and heat-induced molecular mobility. Between 5–40 °C and 20%–61% RH, moisture-sorption was rapid and proportional to humidity between transition points and accelerated greatly during transitions. CaCas/Gly films seemed unsuitable for storage or utilization in warm/humid conditions as they lost their mechanical integrity around Tm ~ 40 °C at 50% RH and Tm decreased greatly with increased RH. However, below Tm, both moisture- and heat-induced structural changes in the films were fully reversible and casein films may withstand a variety of moderate abuse conditions. View Full-Text
Keywords: Hydrophilic thin films; dynamic mechanical analysis; environmental conditions; temperature; humidity; edible packaging; casein; tensile properties Hydrophilic thin films; dynamic mechanical analysis; environmental conditions; temperature; humidity; edible packaging; casein; tensile properties
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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. (CC BY 4.0).

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MDPI and ACS Style

Bonnaillie, L.M.; Tomasula, P.M. Application of Humidity-Controlled Dynamic Mechanical Analysis (DMA-RH) to Moisture-Sensitive Edible Casein Films for Use in Food Packaging. Polymers 2015, 7, 91-114.

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