Characterization of Hemp Seed Cake and Its Use as a Functional Ingredient for Bakery Application

Hemp seed cake, a by-product of cold-pressing hemp for oil extraction, was characterized for its nutritional composition and content of antioxidant compounds and then was used as a functional ingredient for the fortification of bread and as a model system for bakery application. The whole ground hemp cake (WHC) exhibits high nutritional value, with 28.0% of protein, 52.6% of total dietary fiber, and a significant polyphenol content, characterized by phenolic acids, particularly ellagic acid, ferulic acid, and caffeic acid. In order to explore in depth its composition, the WHC was sieved, and four fractions were obtained; among them, the > 700 µm fraction (mainly the bran) was particularly rich in insoluble dietary fiber (70.3% d.w.) and polyphenols, such as ferulic acid (80.1 mg kg⁻¹), quercetin (738 mg kg⁻¹), and luteolin (492 mg kg⁻¹), whereas finer fractions (< 300 µm) were characterized by higher protein content. Concerning the antioxidant activity, determined through the DPPH^• QUENCHER approach, the 200–300 µm fraction exhibited stronger radical scavenging properties, with aqueous medium more effective than the methanolic one. Incorporation of hemp seed cake flour into bread formulation (5%, 10%, and 20% replacement of wheat flour) significantly enhanced the nutritional profile by increasing protein, dietary fiber, and phenolic content. More particularly, breads functionalized with hemp seed cake flour reached the “high fiber” nutritional claim and exhibited up to 3.9 times more antioxidant activity, compared to the control. These findings highlight the potential of hemp seed cake flour as a functional food ingredient for bakery products.