Properties of sodium caseinate films reinforced / blended with cellulose derivatives

MARIANA PEREDA; GUILLERMINA AMICA;; ILONA RÁCZ; NORMA E. MARCOVICH

Mar del Plata, Buenos Aires

Congreso; III Encuentro Nacional Materia blanda; 2010

INTEMA

Abstract Currently, there is a growing tendency to utilize environmental friendly materials with the intention of substituting non-degradable materials, thus reducing the environmental pollution resulting from waste accumulation. One of the approaches is to use renewable biopolymers such as polysaccharides, proteins, gums, lipids and their complexes, derived from animals and plants [1]. In particular, sodium caseinate, which is obtained by acid precipitation of casein, easily forms aqueous solutions due to their random- coil nature and ability to form extensive intermolecular hydrogen bonds [2]. On the other hand, cellulose, the principal structural component of plants, is the most abundant source of complex carbohydrates in the world. Water-soluble cellulose derivatives are used for packaging because of their edibility and biodegradability [3]. At the same time they offer good barrier properties, being non-toxic, non-polluting and having low cost [4]. The aim of this work is to improve glycerol/sodium caseinate-based film properties by blending or reinforcing it with cellulose derivates. Carboxy methyl cellulose (CMC) was chosen as the reinforcement filler of sodium caseinate (SC) films; and cellulose acetate (CA) was selected to prepare blends. In both cases, films were prepared by casting and solvent evaporation. The effects of CMC and CA concentration (0, 1, 2 and 3 %wt.) on the properties of the films were analyzed. All the samples were conditioned at 50 % RH three days before each test. Homogeneous, thin, flexible and transparent films were obtained from SC-CMC and SC-CA combinations. However, sodium caseinate films become less transparent with the addition of either CMC or CA; opacity values increases with filler content (from approximately 1500 to 3100 AU nm/mm) for both cellulose derivatives, but this increases was higher for SC-CA samples (up to 2wt% content). The mechanical properties of films were also evaluated. In composite films, tensile strength and elastic modulus increased significantly with increasing cellulose derivatives concentration, leading to stronger films, while the values of deformation decreased, indicating a reduction in film flexibility. This effect was markedly higher in sodium caseinate films modified with cellulose acetate (eb decreases 75 and 30% for 3 wt% CA and CMC sodium caseinate films, respectively).             With the aim of analyze the effect of cellulose derivatives on the surface hydrophilicity of the resultant samples, contact angle measurements (using ethylene-glycol as solvent) were performed. Cellulose addition causes an increase in the superficial hydrophilicity of the reinforced and blended samples with respect to the neat caseinate one, and contact angle values decreased with cellulose concentration, for both samples. References 1.- Imran M.; El-Fahmy S.; Revol-Junelles A.-M.; Desobry S.; Carbohydrate Polymers 81 219–225 (2010). 2.- Mc Hugh T.H.; Krotcha J.M., Food Technology, 97 (1994). 3.- García M.A., Pinotti A., Martino M., Zaritzky N., Food Hydrocolloids 23, 722–728 (2009). 4.- Vasconez M. B., Flores S. K., Campos C. A., Alvarado J., & Gerschenson L.N.. Food Research International, 42(7),762–769 (2009).