As a source of nutritionally important components, hemp seeds are often dehulled for consumption and food applications by removing the hard hulls, which increases their nutritional value. The hulls thus become waste, although they may contain valuable protein items, about which there is a lack of information. The present work is therefore aimed at evaluating the proteome of hemp (Cannabis sativa L.) at the whole-seed, dehulled seed, and hull levels. The evaluation was performed on two cultivars, Santhica 27 and Uso-31, using LC-MS/MS analysis. In total, 2833 protein groups (PGs) were identified, and their relative abundances were determined. A set of 88 PGs whose abundance exceeded 1000 ppm (MP88 set) was considered for further evaluation. The PGs of the MP88 set were divided into ten protein classes. Seed storage proteins were found to be the most abundant protein class: the averages of the cultivars were 65.5%, 71.3%, and 57.5% for whole seeds, dehulled seeds, and hulls, respectively. In particular, 11S globulins representing edestin (three PGs) were found, followed by 7S vicilin-like proteins (four PGs) and 2S albumins (two PGs). The storage 11S globulins in Santhica 27 and Uso-31 were found to have a higher relative abundance in the dehulled seed proteome (summing to 58.6 and 63.2%) than in the hull proteome (50.5 and 54%), respectively. The second most abundant class of proteins was oleosins, which are part of oil-body membranes. PGs belonging to metabolic proteins (e.g., energy metabolism, nucleic acid metabolism, and protein synthesis) and proteins related to the defence and stress responses were more abundant in the hulls than in the dehulled seeds. The hulls can, therefore, be an essential source of proteins, especially for medical and biotechnological applications. Proteomic analysis has proven to be a valuable tool for studying differences in the relative abundance of proteins between dehulled hemp seeds and their hulls among different cultivars.

The research is focused on the quantitative evaluation of the flaxseed (Linum usitatissimum L.) proteome at the level of seed cake (SC), fine flour—sieved a fraction below 250 µm (FF)—and protein concentrate (PC). The evaluation was performed on three oilseed flax cultivars (Agriol, Raciol, and Libra) with different levels of α-linolenic acid content using LC-MS/MS (shotgun proteomics) analysis, which was finalized by database searching using the NCBI protein database for Linum usitatissimum and related species. A total of 2560 protein groups (PGs) were identified, and their relative abundance was calculated. A set of 33 quantitatively most significant PGs was selected for further characterization. The selected PGs were divided into four classes—seed storage proteins (11S globulins and conlinins), oleosins, defense- and stress-related proteins, and other major proteins (mainly including enzymes). Seed storage proteins were found to be the most abundant proteins. Specifically, 11S globulins accounted for 41–44% of SC proteins, 40–46% of FF proteins, and 72–84% of PC proteins, depending on the cultivar. Conlinins (2S albumins) were the most abundant in FF, ranging from 10 to 13% (depending on cultivar). The second most important class from the point of relative abundance was oleosins, which were represented in SC and FF in the range of 2.1–3.8%, but only 0.36–1.20% in PC. Surprisingly, a relatively high abundance of chitinase was found in flax products as a protein related to defence and stress reactions.