Upcycling dehulled, non-defatted hempseed press cake: Effects of processing on protein structure and technofunctionality of protein isolates

Hempseed (Cannabis sativa L.) press cake, a by-product of oil pressing, offers a promising but underutilized source of functional plant proteins. While solvent defatting is commonly applied after mechanical pressing to further remove residual oils and enhance protein recovery, protein extraction from non-defatted hempseed press cake provides advantages in terms of process simplicity, cost-efficiency, and sustainability. This study evaluated how extraction pH (9.5, 10.5) and temperature (20 °C, 40 °C) influence protein solubility, yields, composition, and structure in protein isolates obtained from dehulled, non-defatted hempseed press cake using alkaline extraction and isoelectric precipitation. Protein yield significantly increased with pH, reaching up to 84.6% dry weight (dw), and isolates contained up to 95.5% protein dw. Elevated temperature significantly enhanced solubility and recovery of 11S globulins, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). While secondary structures were largely preserved (Fourier transform infrared spectroscopy, FTIR), partial denaturation occurred (differential scanning calorimetry, DSC), supporting high re-solubility under acidic conditions. Phytic acid content was reduced by up to 92.7%, and isolates showed light coloration and water holding capacities up to 1.8 g/g protein dw. These results highlight hempseed press cake as a viable raw material for high-purity protein production without defatting. The observed process-structure-function relationships provide a basis for tailoring protein ingredients for specific applications, particularly in acidic beverages or structured plant-based foods.