Conclusion
The treatments applied to reduce the lipid content of walnut seeds modified the proximate composition and colour of the flours obtained. Treatments involving hydraulic pressing and solvent extraction generate flours with higher protein content and lighter colour than those obtained by screw pressing; however, the protein solubility was significantly lower and the WAC was higher, in the former, indicating a greater proteins denaturation.
Electrophoretic profiles confirm the effect of different treatments mainly on albumin and globulin fractions. While albumins were mostly affected by temperature conditions used in the screw-pressing treatments, globulins were strongly influenced in treatments using hydraulic press with further solvent extraction. The major polypeptide band patterns from both total soluble proteins and glutelin fraction showed minor variations between samples obtained under the different treatments employed.
In view of present results and taking into account that: a) globulin, (the second most abundant protein fraction in walnut) is not affected by screw pressing at lower temperatures (25 and 50 °C), and b) flour from screw pressing at 50 °C, showed the highest proteins solubility value and a good WAC, it can be concluded that this process is the most suitable for obtaining partially defatted walnut flour.
Acknowledgements
This research was supported by grant from Secretaría de Ciencia y Tecnología – Universidad Nacional de Córdoba (SECyT-UNC)(26/11). The assistance of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Universidad Nacional de Córdoba, both of which support facilities for this investigation is also acknowledge.