Nutritional Characteristics of Linseed/Flaxseed (Linum Usitatissimum) And Its Application in Muffin Making

Flaxseed, one of the underutilized oilseeds, is a rich source of dietary fiber, n3 fatty acid and protein. Flaxseed powder contained 21.8percent protein and 42.7percent total dietary fiber, which upon roasting reduced to 20.3 and 40.50percent, respectively. Addition of flaxseed powder weakened the dough. Peak viscosity and cold paste viscosity also decreased. The volume of the muffins gradually decreased from 150 to 145 and 120 cc. Muffins prepared from 20percent of raw and roasted flaxseed powder had 10.2 and 9.9percent of protein and 12.8 and 11.7percent of dietary fiber, respectively. n3 fatty acid contents in raw and roasted flaxseed powder were 55.41 and 50.76percent, and the muffins prepared with 20percent raw and roasted flaxseed powder had 12.85 and 11.14percent, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoretic pattern and gel filtration studies showed that high and low molecular weight protein bands were identified in raw and roasted flaxseed powder and in the product. (Authors abstract)

Raw flaxseed powder had a moisture content of 7.1percent, which reduced to 2.4percent upon roasting. The ash content and acid insoluble ash content ranged between 2.8 and 3.06percent and 0.06 and 0.08percent, whereas the protein, fat content and total dietary powder ranged between 20.3 and 21.8percent, 44.7 and 46.4percent, and 40.8 and 42.7percent, respectively, for raw and roasted flaxseed powder. The results show that fat and dietary fiber contents of raw and roasted flaxseed powder were very high compared with wheat flour.  Hence, it is also an excellent source of fat as well as dietary fiber apart from protein. The results indicated that there was a marginal increase in the water absorption from 52.5 to 53.7percent and 55.5percent with increase in the raw and roasted flaxseed blends, respectively. The dough stability was significantly reduced from 8.6 to 2.1 min and 2.5 min indicating the weakening of the dough due to the incorporation of raw and roasted flaxseed powder.  The onset gelatinization temperature of wheat flour was found to be 64C and it gradually reduced to 62.7 and 61.5C with an increase in raw and roasted flaxseed content in the blend. The peak viscosity, which was 969 BU for wheat flour, reduced to 335 BU and 312 BU with incorporation of raw and roasted flaxseed powder in the blend indicating that the swelling power, which is the ability of the starch granules to swell before breakdown, decreased. Hot paste viscosity at 95C showed a decreasing trend with increase in the levels of incorporation of raw and roasted flaxseed powder.

Muffins were prepared by replacing wheat flour at 10, 20, 30 and 40percent levels of raw and roasted flaxseed powder. As the incorporation of raw and roasted flaxseed powder increased from 0 to 40percent, the pH of the batter marginally increased from 6.35 to 6.43. The volume of the cake decreased from 150 to 145 for raw flaxseed muffin and from 150 to 120 for roasted flaxseed powder muffin, whereas the weight of the muffins increased. The protein value increased from 8.5 to 12.4percent and 11.9percent with an increase in levels of raw and roasted flaxseed powder. The fat content of the muffins increased from 29.6 to 37.4percent and 39.9percent with an increase in levels of raw and roasted flaxseed powder, which is again due to the higher fat content in the flaxseed itself. The TDF values significantly increased from 3.1 to 18.3percent and 15.8percent with increase in the raw and roasted flaxseed powder. This showed that incorporation of either raw and roasted flaxseed powder in the formulation helped in increasing dietary fiber content in the muffins. Flaxseed, like any other fiber source, increased the water absorption of the flour. In general, flaxseed affected the pasting characteristics of the wheat flour. Based on the rheological characteristics and sensory parameters, muffins incorporated with 20percent roasted flaxseed powder had better overall acceptable quality compared with 20percent raw flaxseed powder muffins. In addition, there is no significant loss in the nutritional quality characteristics in 20percent roasted flaxseed muffins. (Editors comments)