This study investigated an alternative approach to valorizing canola proteins by hydrolyzing them to generate amino acids (AAs). Pre-treatment of cold-pressed (CP) cake and desolventized-toasted (DT) meal with ethanol (99%, v/v) followed by protein separation was studied as process optimizations to maximize protein recovery with higher purity. The optimum ethanol pre-treatment conditions to achieve a meal containing less than 1% oil was reached at a meal-to-ethanol ratio of 1:4 (w:w) and 50°C for 30 min extraction. The protein recovery reached the maximum at pH 12 and a meal-to-solvent ratio of 1:10 (w:v), yielding 73% and 33% recovery from ethanol pre-treated CP and DT meals, respectively, in a single extraction. Untreated and ethanol pre-treated meals were hydrolyzed with 6 M HCl (protein-to-acid ratio of 5 mg:2 mL) for 24 h at 110°C. The ethanol pre-treatment improved AA recovery and released 373 mg AA/g dry CP meal biomass (dbm) compared to 279 mg AA/g untreated CP cake dbm. However, no improvement in AA recovery upon ethanol pre-treatment of DT meal. H2SO4 was examined as an alternative acid. More than 80% of the total AAs of CP proteins were released with 3 M H2SO4, while for DT meal proteins, a 5 M concentration was needed to achieve the same. Commercial canola meals can be utilized for generating free AAs; however, the meal processing history may affect the yield.

The present study investigated the effect of solid-state fermentation (SSF) of cold-pressed (CP) and hexane-extracted (HE) canola meals with Aspergillus niger NRRL 334 and A. oryzae NRRL 5590 on the functionalities of protein products extracted from them. After SSF, proteins were recovered using alkaline extraction-isoelectric precipitation (AE-IP) or salt extraction-dialysis (SE). SSF of the two meal types reduced the protein content of the extracts produced by AE-IP. There were varied effects to solubility, foaming, and emulsifying properties as a result of SSF under the combined influence of functionality pH, strain, meal type, and protein extraction method. The protein isolate produced from CP meal using SE had increased solubility at pH 7 (from 51.8 to 90.7%) when the meal was fermented with A. oryzae. Both strains resulted in an over 2-fold increase in the emulsifying activity index (at pH 7) of AE-IP products from CP meal. For both protein extraction methods, the protein products from A. niger fermented HE meal had better foaming capacity (FC) at pH 7 than the controls (non-fermented), but reduced FC at pH 3. Overall, regardless of meal fermentation, the SE products were richer in protein and had higher oil holding capacity (OHC), whereas the water holding capacity (WHC) was higher for AE-IP isolates. SSF of the meals generally improved the O/WHC of the extracted proteins. The findings suggest that canola protein functionality could be effectively modulated by SSF with different microbial strains under various processing conditions to enhance their applicability in the food industry.

In this study, the effects of solid-state fermentation (SSF), including strain (Aspergillus niger NRRL 334 and A. oryzae NRRL 5590) and fermentation time (24, 48, and 72 h) on the nutritional value of cold-pressed (CP) and hexane-extracted (HE) canola meals were examined. SSF increased the protein content of both types of meals (from ~36 to ~40%) while reducing the oil content of CP meals (from ~12 to 9%). There was a significant reduction (~80%) in the phytic acid content of both types of meals after fermentation using either fungi. Overall, fermented samples showed a decrease in the total phenolic content from 2.7-3.1 to ~1.0 mg gallic acid equivalents (GAE)/g DM (a ~65% reduction), of which specifically the HE meal fermented with A. niger sample had the greatest decrease from 3.1 to 0.6 mg GAE/g DM (~81% reduction). Seventy-two hours of fermentation decreased the in vitro protein digestibility (IVPD) of the meals. In contrast, a shorter fermentation time (24 h) increased the IVPD as compared to the controls (from ~73% to 77-81%), with the exception of the CP meal fermented with A. niger which had decreased IVPD at all fermentation times. Overall, the changes indicate that SSF using A. niger or A. oryzae can be useful to positively modify the composition of different canola meals and improve their nutritional value by significantly increasing the protein content, decreasing the levels of antinutrients, while only slightly reducing IVPD.

Protein from camelina seed is a valuable co-product that can be derived from the meal remaining after oil extraction. The current study describes the types and physicochemical properties of the major proteins present in camelina meal. Seed coat mucilage, which interferes with protein extraction, was removed from whole seeds by digestion with Viscozyme® and lipids were removed with hexane to obtain demucilaged/defatted meal. Protein comprised 51.3% of meal dry matter and the eight essential amino acids comprised 40.8% of total amino acids. The meal polypeptide profile showed bands originating from cruciferin (~44.1 and 51.7 kDa), napin (~14 kDa) and oil body proteins (OBP; ~15-20 kDa) resembling that of other crucifers. Cruciferins (11 isoforms) were the predominant proteins, while vicilins (6 isoforms) also were identified among the proteins soluble at pH 8.5. Among the proteins soluble at pH 3, napins (5 isoforms) comprised the majority, though late embryogenesis abundant proteins also were found. Camelina cruciferin and napin were confirmed to possess predominantly β-sheet and α-helix secondary structures, respectively. Camelina cruciferin structure was highly sensitive to changes in medium pH and underwent acid-induced denaturation at pH 3, but exhibited high thermal stability (>80°C) at neutral and alkaline pHs. The structure of camelina napins was less sensitive to pH. The major proteins associated with oil bodies were oleosins (6 isoforms). Identification and characterization of the properties of camelina meal proteins will enable strategic paths for co-product valorization.