Location: Dairy and Functional Foods ResearchTitle: Rheological behaviors of edible casein-based packaging films under extreme environmental conditions, using humidity-controlled dynamic mechanical analysis
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2014
Publication Date: 7/22/2014
Citation: S., A., Bonnaillie, L., Tomasula, P.M. 2014. Rheological behaviors of edible casein-based packaging films under extreme environmental conditions, using humidity-controlled dynamic mechanical analysis. Meeting Abstract. https://asas.confex.com/asas/jam2014/webprogram/paper7702.html..
Technical Abstract: Thin casein films for food packaging applications possess good strength and low oxygen permeability but low water-resistance and elasticity. Customizing the mechanical properties of the films to target specific behaviors depending on temperature and humidity changes would enable a variety of commercial applications for casein-based films. The mechanical properties of edible films are vitally important to determine possible uses for the films as replacements for plastic films. Dynamic mechanical analyses under controlled humidity (DMA-RH) can supply useful information about the mechanical properties and network-structure of hydrophilic protein films, including the storage modulus (E'), loss modulus (E''), deformation (swelling and shrinkage), damping behavior (tan-delta), and various transition temperatures (T) and humidities (RH). The properties of polymeric films change significantly above their glass transition temperature, for example, when films soften and their permeability to gas and vapor molecules increases. The dynamic mechanical properties of solvent-cast (15% solids) calcium-caseinate/glycerol films (CaCas:Gly ratio 3:1) were characterized under broad temperature (T=5-90 deg C) and humidity (RH=0-80%) conditions using DMA-RH technology to elucidate their behavior under normal and extreme environmental conditions. Citric pectin (CP, 0.05 to 4%) was then incorporated into CaCas films using 3 different formulations (A, F, G) to examine CP effects on the properties and macrostructure of CaCas/Gly/CP films, and potentially improve the stability of CaCas film under high T and RH. The dynamic mechanical properties of casein films were extremely sensitive to formulation, CP content, temperature and humidity, and DMA-RH technology proved a precise and effective tool to characterize composition/properties trends and point out various ‘phase transition temperatures’, during T-ramps at 50% RH, and ‘phase transition humidities’, during RH-ramps at 20 deg C. ‘Transition’ values of T and RH were considered critical points at which sufficient plasticization with water and/or heat triggered various rearrangements of the CP/protein network, until ultimate film failure at the ‘melting point’. DMA-RH precisely characterized shifts in E’, E’’ and tan-delta caused by subtle formulation or CP-content changes at constant T and RH, as well as shifts in the various transition- and melting-T and RH caused by CP-content and formulation changes. Generally, CP addition improved the environmental stability of CaCas films: melting-T and RH increased from approximately 40 deg C to 60 deg C and ~approximately 8% to 67%, respectively, after addition of 1% CP, depending on formulation. F films showed drastic improvements with CP addition, and G films appeared generally more T- and RH-stable at all CP contents, which would broaden the range of possible food-packaging applications for casein-based films.