Dry-Milling Improves the Aqueous Recovery of Galactomannans from Fenugreek Seeds

Seeds of four fenugreek lines cultivated in Alberta and one commercially available fenugreek seed were investigated for anatomical features, nutrient composition, sapogenins and galactomannans. Seeds of all lines had similar anatomical features as assessed by SEM. Contents (%, w/w) of crude lipids, crude proteins, minerals, soluble fiber and insoluble fiber were 7-10%, 26-32%, 3%, 16-21%, and 26-32%. Fatty acid and amino acid profiles were similar in seeds of all lines. Sapogenins were present at levels < 0.5% (w/w) with diosgenin being the predominant species. Galactomannans comprised a substantial proportion of the seed weight (23-37%). Seeds were milled and sieved to separate the outer seed layer (seed coat/aleurone/endosperm) from the inner seed (cotyledon + axis). The majority of galactomannans (85%) were located in the outer seed layer, and recovery of galactomannans from whole seeds, the outer seed layer, and the inner seed were 46%, 89%, and 47%, respectively. Relative to the total seed galactomannan content, galactomannan extraction yields from whole seeds, the outer seed layer, and the inner seed were 16%, 14%, and 7%. Galactomannan purity in gum extracted from whole seeds or the outer layer fraction exceeded 90%, whereas it was only 35% in the inner seed fraction. The data suggest that aqueous extraction of the outer seed layer may be a viable means of extracting high levels of purified galactomannans from fenugreek.