PubAg

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

Author:

Bonnaillie, Laetitia M., Zhang, Han, Akkurt, Serife, Yam, Kit L., Tomasula, Peggy M.

Source:

Polymers 2014 v.6 pp. 2018-2036

ISSN:

2073-4360

Subject:

calcium caseinate, casein, chemical interactions, chemical structure, food packaging, glycerol, microscopy, microstructure, mixing, modulus of elasticity, oxygen, packaging films, pectins, permeability, relative humidity, temperature, tensile strength, thickness

Abstract:

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.

Agid:

59568

Handle:

10113/59568

http://dx.doi.org/10.3390/polym6072018