Functional properties of rye prolamin (secalin) and their improvement by protein lipophilization through capric acid covalent binding

Secalin (SCL), the prolamin fraction of rye protein, was chemically lipophilized using acylation reaction by treatment with different amounts of capric acid chloride (0, 2, 4, and 6 mmol/g) to enhance its functional properties. It was shown that SCL lipophilization increased the surface hydrophobicity and the hydrophobic interactions, leading to a reduction in protein solubility and water absorption capacity and to a greater oil absorption. In addition, SCL both emulsifying capacity and stability were improved when the protein was treated with low amount of capric acid chloride. Finally, the foaming capacity of SCL markedly increased after its treatment with increasing concentrations of the acylating agent, even though the foam of the modified protein was found to be more stable at the lower level of protein acylation. Technological application of lipophilized SCL as a protein additive in food preparations is suggested

Secalin films acylated with capric acid chloride

Secalin was chemically modified using the acylation reaction with the aim to prepare less hydrophilic protein-based films with features suitable for applications in food packaging. The acylation of secalin was done at different capric acid chloride concentrations (2–6 mmol/g) and confirmed using elementary and Fourier-transform infrared spectroscopy analyses. The water sensitivity of the films prepared with acylated secalin was observed to be significantly improved. The control film elongation at break was ~67% and increased up to 141% at high levels of acylation, whereas tensile strength and Young's modulus increased up to 4.5 and 39.4 MPa, respectively when lower amounts of capric acid chloride were used and, on the other hand, decreased with increasing amounts. Thermal analyses suggested that the glass transition temperature of acylated films was lower at higher capric acid chloride concentrations, whereas the melting temperature increased and the thermal stability improved. Scanning electron microscopy showed a more homogeneous surface of the films obtained with acylated secalin

Rye secalin characterisation and use to improve zein-based film performance

Rye prolamins (secalin) were extracted, characterised and used as biopolymer source to produce plasticised films, as well as composite films in the presence of corn zein. Secalin film showed lower contact angle values and higher moisture content, solubility and swelling index than zein film, whereas the water vapour permeability of the two films was not different. Also, secalin film exhibited lower tensile strength and Young’s modulus and higher elongation at break. The average functional properties of the secalin/zein blend were morphologically confirmed by SEM analysis of the composite film surface that showed a good miscibility and compatibility of the two different biopolymers. These results indicated that secalin films were less hydrophobic and more flexible than those previously prepared by using other prolamins, whereas a material with hydrophobic features similar to those of zein films and a flexibility comparable to that exhibited by secalin films was obtained by preparing a secalin/zein blend

Potential use of glycerol- and/or spermidine-plasticized secalin films as leaf surface coatings for sustainable plant disease management

The effects of spermidine (SPD) on the properties of both secalin (SCL)-based film-forming solutions (FFSs) and their resultant films were studied in the absence or presence of glycerol (GLY) used as primary plasticizer. The average size of SCL particles significantly increased with the increase of SPD concentration, mainly in the presence of GLY, while the negative zeta potential values parallely decreased suggesting a greater stability of the FFSs containing SPD concentrations lower than 1.0 mM. In addition, the decreased contact angle value, compared to water and ethanol solution, indicated that SCL FFSs were highly hydrophobic and that it might be spreaded easily on hydrophobic biological surfaces. SPD could replace GLY in obtaining handleable, homogeneous and performing SCL-based films. The film tensile strength and the Young's module strongly increased in the absence of GLY, reaching values higher than 5 times with respect to controls, whereas elongation at break value of GLY-plasticized films containing 5.0 mM SPD was twice of that of the films prepared without SPD. Conversely, the film moisture content, water solubility and swelling ratio progressively decreased, both in the presence and absence of GLY, up to a SPD concentration of 1.0 mM, whereas the film contact angle increased, confirming the enhancement of its hydrophobicity determined by SPD incorporation. SPD also increased the film barrier properties to gases and water vapor, while the presence of GLY hindered these effects. Finally, SEM analysis of the cross-sections of the SPD containing films showed heterogeneous microstructures, whereas their surfaces appeared rougher than those of the control films. Preliminary experiments carried out by Rosa chinensis Jacq. leaf coating suggest the potential use of SCL-based FFSs spraying in plant disease control. High spreading of the SCL-based FFSs on the entire leaf surfaces, both in the presence and absence of Bordeaux mixture tested as agrochemical, was observed, and the SEM images showed the formation of an evident coating of the leaves. Therefore, these findings suggest the possibility to coat the leaf surface also in vivo with different SCL-based FFSs, giving rise to films possessing tailored functional properties and able to carry and release different agrochemicals