Sodium caseinate films containing linseed oil resin as oily modifier

• The use of a novel oily modifier to enhance water dependant properties of sodium caseinate films is investigated.
• The properties of the films depend strongly on the interactions between sodium caseinate and oily resin.
• The hydrophilic character of the films is significantly reduced with the incorporation of the linseed oil resin.
• The increase in film's opacity with oily resin content is relatively low, as compared with similar systems.

Modified sodium caseinate films were prepared by casting of film forming emulsions prepared by adding different contents of a linseed oil based resin (LOR) into the aqueous protein solution. Infrared spectroscopy of the formed films revealed that physical interactions between the main component of the film and the oily modifier were developed. The films were also characterized in terms of water vapor permeability, water absorption, optical, mechanical and thermal properties. Water vapor permeability and equilibrium moisture content decreased with the addition of LOR, reaching their minimum values (59% reduction in WVP and about 70% reduction in EMC, respect to the corresponding values of the neat SC film) with the incorporation of 10 and 15 wt% of LOR, respectively. As expected, contact angle measured using a polar solvent and opacity increase (respect to the neat SC film) when the lipid modifier is used in the formulation, although the increment in the last property is lower than the reported in similar works. The presence of LOR decreased tensile modulus and strength but the elongation at break is not significantly affected.

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