Graduate Research Assistant North Dakota State University Fargo, North Dakota
This study investigated the effects of two demucilaging approaches (e.g., warm water and enzymatic method) on the structural, rheological and tribological properties of flaxseed protein extracted from flaxseed meal through alkaline extraction–isoelectric precipitation method. The chemical composition, color, molecular weight, secondary structure, rheological and tribological properties of flaxseed protein concentrate were analyzed. Results showed that flaxseed protein concentrate (FPC) with higher protein content (66 g/100g, as is basis) was obtained by demucilaging flaxseed with warm water. In contrast, FPC subjected to enzymatic treatment had relatively lower protein content (45 g/100g), higher total phenolic content (45 mg GAE/g protein) and darker green color. Compared to enzymatic treatment of FPC (EFPC), warm water treatment of FPC (WFPC) resulted in larger proportion of high molecular weight protein subunits. Circular dichroism spectra revealed that WFPC had lower proportion of α-helix but higher ratio of β-sheet compared to EFPC. In addition, WFPC solutions exhibited shear thinning rheological behavior, while EFPC showed Newtonian fluid behavior, indicating lower mucilage residues existed in EFPC compared with WFPC. The tribological behavior, which mimics oral lubrication property of a product, was studied at 37 °C with/without addition of artificial saliva. EFPC showed higher friction coefficient (CoF) than that of WFPC, which suggested that EFPC had smooth oral lubrication property. CoF was decreased appreciably in both samples by adding artificial saliva. Overall, demucilaging by warm water is more practical than enzymatic treatment in terms of high protein content, complete molecular structure, and smooth oral lubrication property of FPC.