Development and Characterization of Films Based on Chemically Cross-Linked Gliadins

Abstract

The aim of the present work has been to study the possibility of obtaining modified gliadin films with improved water resistance and mechanical properties by means of promoting intermolecular covalent bonds between polypeptide chains. Prior to casting films, formaldehyde, glutaraldehyde, and glyoxal were used to cross-link proteins at concentrations ranging from 1% to 4% (grams per 100 g of protein). Mechanical properties (tensile strength and elongation at break), water vapor permeability, moisture sorption isotherms, and optical properties of the films produced were evaluated as a function of the cross-linker used. Experimental results showed that some properties of gliadin films were considerably modified. Cross-linking improved the water resistance of films, avoiding their disintegration. Their water barrier properties were also enhanced, but their moisture sorption properties remained unchanged. Formaldehyde imparted greater mechanical strength to films than glutaraldehyde or glyoxal, increasing tensile strength values 10-fold. Addition of the cross-linkers at concentrations in excess of 2.5% did not further improve the mechanical or barrier properties. However, modification with glutaraldehyde or glyoxal imparted an increasingly yellowish tint to the films.

Oxidation of commercial (α-type) zein with hydrogen peroxide improves its hydration and dramatically increases dough extensibility even below its glass transition temperature

“…The dry film zein T g was not affected by the hydrogen peroxide treatments. This is in contrast to work which showed that covalent cross-linking substantially increased the T g of films cast from gliadin in the presence of cross-linking agents (Hernández-Muñoz et al, 2005). The absence of an effect of hydrogen peroxide treatment on zein T g is nevertheless consistent with the SDS-PAGE results (Fig.…”

Development of active bioplastics based on wheat proteins and natural antimicrobials for food packaging applications

“…(9.9 ± 1.2 MPa) cinnamaldehyde were higher than those obtained for cross-linked gliadin films with 40% epichlorohydrin (6.5 ± 0.6 MPa) (Song et al, 2009), or 4% formaldehyde, glutaraldehyde or glyoxal (6.5 ± 0.7 MPa, 2.8 ± 0.8 MPa, and 2.1 ± 0.2 MPa respectively) (Hernandez-Munoz et al, 2005). The cross-linked films conditioned at 75% RH followed a similar pattern regarding σm and E parameters, but the great plasticization effect caused by water brought about a 2-fold reduction in the σm of these films with respect to those conditioned at 50% RH, and the E decreased dramatically, around 16-fold, compared to the cross-linked films conditioned at 50% RH.…”

“…In the case of gliadin films, various procedures have been employed in order to maximize their potential, including chemical cross-linking (Hernandez-Munoz et al, 2005;Hernandez-Munoz et al, 2004a;Hernandez-Munoz et al, 2004b;Hernandez-Munoz et al, 2004c;Reddy and Yang, 2010;Soares et al, 2009;Soares and Soldi, 2010;Song et al, 2009b), blends with other polymers (Li et al, 2010), and enzymatic cross-linking (Michon et al, 1999).…”

“…The most commonly-used general cross-linking reagents are symmetrical bifunctional compounds with reactive groups that may possess chemical specificity for a particular class of functional group on the macromolecules (Peters and Richards, 1977). The cross-linkers generally used for proteins include aldehydes such as formaldehyde, glutaraldehyde and glyoxal (Galietta et al, 1998;Hernandez-Munoz et al, 2005;Marquie, 2001), diisocyanates and carbodiimides (Tropini et al, 2004;Tropini et al, 2000), epoxy compounds (Song et al, 2009;van Wachem et al, 1999), sulfhydryl reagents such as cysteine (Soares et al, 2009), etc. Nowadays, much less toxic cross-linking agents are being explored, especially when films are intended for food applications: those being investigated include genipin (Bispo et al, 2010;Butler et al, 2003;Sung et al, 1999), proanthocyanidin (Kim et al, 2005, carboxylic acids such as citric or malic acid (Reddy et al, 2009), and ferulic and tannic acid (Cao et al, 2007;Zhang et al, 2010).…”

“…Film-forming capacities of agro-proteins have been largely investigated . Wheat gliadins represent a suitable raw material for production of these new bioplastics because of their remarkable functional properties Hernandez-Munoz et al, 2005;Sun et al, 2008).…”