γ-Irradiation was used to produce free-standing sterilized edible films based on milk protein, namely, sodium caseinate and calcium caseinate. The nature of the counterion and also the protein and glycerol concentrations were examined. Irradiation of a solution based on calcium caseinate produced more cross-links than a solution based on sodium caseinate. As a consequence, films based on calcium caseinate showed a better mechanical strength. Glycerol was found to play a double role in enhancing the formation of cross-links within caseinate chains, accounting for the increase of the puncture strength, and acting as a plasticizer, being responsible for the improved film extensibility and viscoelasticity. Moreover, the effect of the irradiation on the mechanical properties was strongly dependent on the glycerol/protein ratio, i.e., the formulation of the films. Films of high quality and a satisfactory mechanical behavior were generated at glycerol/protein ratios of 0.5 and 0.67. Keywords: Caseinates; irradiation; sterilized edible films; glycerol; mechanical properties

A series of 2-alkoxyanilines and 2,5-dialkoxyanilines with alkyl chains containing n = 1, 2,4, and 6 carbon atoms have been electropolymerized in acidic conditions and characterized by several techniques. The corresponding neutral polymers were found to be soluble in chloroform and tetrahydrofuran. On the other hand, chronoamperometry experiments have shown that the presence of long alkoxy groups {n -4 and 6) decreases the rate of polymerization, giving materials with a lower degree of polymerization. Electrochemical and spectroscopic measurements have demonstrated that the electron-donating effects of the side chains are more significant for 2,5-dialkoxyanilines and for the corresponding polymers. Moreover, the presence of electron-donating substituents has allowed a better characterization of the charge carriers in fully oxidized polyanilines. Indeed, in agreement with electrochemical results, in situ ESR experiments displayed two signals with similar g values, related to the presence of radical cations formed during the leucoemeraldineemeraldine transition and the emeraldine-pemigraniline transition. However, these radical cations were found to be more localized, with respect to polyaniline. Fully oxidized poly-(2,5-dialkoxyanilines) were found to be partially protonated at pH between -0.5 and 3, by electrochemical quartz crystal microbalance (EQCM) analysis. On the other hand, in situ conductivity measurements suggested that protonated imines do not act as efficient charge carriers. Finally, conductivity of 0.1 S/cm were found for disubstituted materials with short alkoxy groups ( = 1 and 2), whereas a decrease of 3-5 orders of magnitude were observed for materials bearing longer alkoxy groups ( = 4 and 6).

Sterilized biofilms based on soy protein isolate (SPI, S system) and a 1:1 mixture of SPI and whey protein isolate (WPI, SW system) were achieved through the formation of cross-links by means of gamma-irradiation combined with thermal treatments. The effect of the incorporation of carboxymethylcellulose (CMC) and poly(vinyl alcohol) was also examined. gamma-Irradiation combined with thermal treatment improved significantly the mechanical properties, namely, puncture strength and puncture deformation, for all types of films. Irradiated formulations that contain CMC behave more similarly as elastomers. CMC showed also significant improvements of the barrier properties, namely, water vapor permeability, for irradiated films of the S system and for non-irradiated films of the SW system.

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The electrochemical polymerization of ring-substituted anilines (e.g., 2-methylaniline and 2ethylaniline) gave uniform electroactive polymer films which were analyzed by cyclic voltammetry and in-situ spectroelectrochemistry in different acidic conditions. It has been found that the fully oxidized polymers undergo an acid-base transition at pH ~0 which leads to the formation of a protonated (bipolaronic) form. This electronic structure is characterized by an absorption band at 630 and 680 nm for poly(2-methylaniline) and poly(2-ethylaniline), respectively. A similar structure has also been obtained in the fully oxidized poly-(TV-methylaniline), and this bipolaronic form exhibits a maximum of absorption at 770 nm, whatever the pH of the electrolyte. However, in-situ conductivity measurements have revealed an insulating behavior for this charged and fully oxidized form, whereas the partially oxidized (polaronic) structure is conducting. These results are explained by a strong localization of the charge carriers in the fully charged polymers.