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
Highlights
Plant proteins from oilseed by-products are a promising alternative for petrol-based ingredients in technical applications
The results clearly demonstrate the increase of hydrophobicity, thereby improving the application potential of rapeseed proteins as a renewable alternative to conventional additives
The rapeseed protein concentrate (RPC) was chemically modified by the Schotten-Baumann-reaction using lauroyl chloride (LC) and oleoyl chloride (OC)
Summary
Plant proteins from oilseed by-products are a promising alternative for petrol-based ingredients in technical applications. Film-forming properties are of high relevance for such applications As these products are often based on hydrophobic media, the polar nature of proteins can be problematic in regard to product formulation or water-stability [1]. Methods to increase the hydrophobicity of rapeseed proteins while preserving their functional properties are demanded to enhance the applicability in the non-food sector. A promising technique to achieve this is chemical derivatization of free functional groups in the protein with reagents bearing long hydrocarbon chains [9] Thereby, polar residues, such as hydroxyl, sulfhydryl or amino groups can be converted to non-polar residues to increase the overall hydrophobicity. The overall aim was to show the application potential of rapeseed proteins for technical products requiring film-forming properties such as glues, lubricants, paints and varnishes
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