Effect of Acylation of Rapeseed Proteins with Lauroyl and Oleoyl Chloride on Solubility and Film-Forming Properties

Abstract

Rapeseed proteins show good film-forming properties, giving them a promising potential as bio-based ingredients for the technical industry, e. g. for films and coatings. However, their hydrophilicity often poses problems in regard to water-stability of coatings. Protein modification using fatty acids is known to reduce hydrophilicity, however, it has not been tested to improve film-forming properties of rapeseed proteins before. In the present study, a rapeseed protein concentrate (RPC) was acylated at low and high modification degree using lauroyl chloride and oleyol chloride. The protein solubility was determined and the modified RPCs were used for the preparation of cast-films to measure the changes of mechanical properties (tensile strength, elongation at break), surface energy, oxygen permeability and light transmission. The protein solubility in water was lowered from 100% for the non-modified RPC to < 15% for highly modified RPCs at pH 7. The tensile strength of films increased by factors of 3.5 and 4 for highly modified samples, respectively. Surface energy and oxygen permeability revealed an increase of hydrophobicity that correlated with the modification degree. The light transmission was reduced by modification. The results confirm the increased hydrophobicity of acylated RPCs and demonstrate the potential of modified rapeseed proteins as an ingredient for technical products, such as packaging layers, coatings and adhesives. Graphic Abstract