The effect of the addition of flaxseed meal flour on the physical characteristics of sponge cake

The diet regulation is one of the primary principles for maintenance of physical and mental health. Flax is an annual plant from the genus Linum with the scientific name “Linaceae” which it grows as a shrub. Flaxseed is in the category of the oilseeds. In Iran, the Flaxseed meal wasted even though it is a good source of protein. Flaxseed components that have the health maintenance and nutritional properties are including fiber, lignans and linolenic acid. Furthermore, Flaxseed is a good source of excellent quality protein and soluble fiber and phenolic compounds.
Flaxseed meal from KashanBarij Essence Pharmaceutical Company, converted to flour and half of it was extracted using solvents. 10, 15, 20 percentages of the wheat flour replaced with both types of the prepared flours (NF and PDF). The flaxseed meal flours were detoxified using a microwave. In the cakes preparation, the sugar and oil were mixed. The eggs and the remained materials and water were added and mixed for uniformness of the cake batter. Then, it filled the cake mold and placed into the oven at 200°C for 15 minutes. The volume measurement of the prepared cake was carried out according to the seed displacement method using millet seeds. Three methods consist of texture profile analysis, cut and punch method were used in the four days, first, tenth, twentieth and thirtieth day for textural properties assessment. To evaluate the color parameters (L*a*b*), the photos which were taken from the surface of the cake in the special box were evaluated with image analyzer software. Then the hue angle (H), saturation index (SI) and color changes (ΔE) calculated from following equation. For evaluating the porosity the cake was cut into the slices and put into the special box and photos were taken. The photos were evaluated with image analyzer software and the number of pores was determined. Statistical analysis with the completely randomized design with three replications and means comparison in 95% confidence level were employed using the SPSS-20 software.
By increasing flour substitution, the volume of the cakes reduced. It could be due to increasing flour replacement with cellulose, which makes the gluten network weak that is responsible for keeping gas into the bakery product. These samples contain flaxseed meal flour were softer than the control. It is due to the presence of some gum and fiber in the chemical composition of flaxseed which absorbs moisture and prevents its transfer to the starch. So, the starch crystallization delayed. During storage, the samples contain 20% flaxseed meal flour were harder than the control sample. The cohesiveness decreased during storage until the twentieth day and then increased. It is due to changes in moisture during storage. The cohesiveness of samples increased by increasing the flaxseed meal flour which it can be associated with more gum and fiber as well as protein in the samples. The cohesiveness of the samples containing 20% flaxseed meal flour was less than others on the first day of storage which is due to the high water bonded by larger amounts of gum and fiber. But, on the thirtieth day, even with reducing bonding strength due to retrogradation, the cohesiveness in the samples containing 20% flaxseed meal flour is more than other samples because of larger amounts of moisture in higher percentages. The springiness reduced in all treatments during storage until the twentieth day and then increased which these changes are not significant for the samples containing 20% flaxseed meal flour and the control sample. The springiness was changed according to changes in moisture during storage. The difference in the springiness among the control samples and treatments on the first day, tenth, and thirtieth of storage was not significant. The springiness reduced with increasing the flaxseed meal flour percentage which is due to the weakening of the gluten network. Between all treatments, the only significant difference in the result of the crust cutting test was among the samples containing 20% PDF and control sample and there was no significant difference between other treatments and control sample in all measurement days. The increase of the force needed to cut samples over the time could be attributed to the transfer of moisture from the center to the round of the cake. The addition of flaxseed meal flour and the storage time had a significant effect on the required force to punch the cake. The force required to punch the cakes increased until the thirtieth day which is consistent with the analysis of moisture during storage. The reason for an increase in the required force for punching the cakes due to increasing the flaxseed meal flour percentage was the cake batter viscosity increases which lead to hardening of the cake texture, subsequently. It can be seen that the number and diameter of the pores reduced by increasing the flour substitution percentage. It could be related to the viscosity of the batter. Due to increasing the batter viscosity, the carbon dioxide, and water vapor bubbles in the batter cannot grow well. The L* index decreased by increasing the flour substitution percentage, which reflects the darkening of the surface and the center of the product. By increasing the flour replacement, the redness (a*) and blueness (b*) index, increased and decreased, respectively. The saturation index (SI) of the surface and center for all treatments was less than it for the control samples. Also, the saturation index among the treatments decreased with increasing the flour substitution percentage significantly which it indicated an increase in the color turbidity of the samples. The color changes (ΔE) of the surface and center of the samples increased with increasing the flour substitution percentage which it showed the significant color difference between all treatments and the control sample. The BI of the surface and center of all samples was less than it for the control samples.