Enzymatic, enzymatic-ultrasonic and alkaline extraction of soluble dietary fibre from flaxseed - A physicochemical approach

Flaxseed soluble dietary fibres (SDF) exhibit low viscosity, which makes them a valuable ingredient that does not have much influence on the rheological properties of food products. The aim of this research was to evaluate the effect of enzymatic (EN), enzymatic-ultrasonic at 20 degrees C (EN-US20) and at 55 degrees C (EN-US55), and alkaline extraction (AL) of the physicochemical characteristics of soluble dietary fibres (SDF) from flaxseed. The highest extraction yield of flaxseed gum-FG (17.65 +/- 0.13%) was obtained from AL extraction. Nevertheless, AL extraction resulted in the highest protein content in the FG. Similar SDF, but not the highest content, was obtained in FG using the EN and EN-US20 methods (61.13 +/- 0.35% and 61.53 +/- 1.35% respectively). FG from EN-US55 was characterised by the highest SDF content (68.90 +/- 0.50%), the apparent viscosity of the FG solution ((gamma) over dot = 14.09 +/- 0.2 mPa s) and the lowest thermal transition (T-p = 143.4a +/- 0.06). The FG extracted by different methods appeared to have varied rheological properties, which could make it applicable in food processing as a non-allergic plant-based stabiliser.