Effect of pomegranate peel, guar gum and hemicellulase enzyme on the properties of gluten- free sponge cake based on wheat starch

Sponge cake is one of the most demanded and consuming grain products, but due to its gluten content, it is not usable for patients with celiac disease. In recent years, gluten-free products have gained a great attraction. However, producing gluten-free products has several difficulties such as lack of gluten viscoelastic network protein constituents, lower technological quality and advent of some quality problems in production including low volume and weak texture. Some compounds such as certain enzymes and gums with the aim of improving the texture, mouth feeling and general acceptance, as well as imitating viscoelastic properties of gluten could be employed in the formulation of gluten-free products to make them acceptable for the celiac patients. For this purpose, guar gum is used widely as a thickener and stabilizer for producing gluten-free products. Also, addition of enzymes to grains produce could help in increasing the holding water capacity, improving softness and dough flexibility, enhancing texture and final product’s volume. Furthermore, notwithstanding widely researches on the cake, comparing to other production, this production has low nutrition values yet. So, enriched cakes with dietary fiber and natural antioxidants, is one of the goals of the industry. The researches has shown that dried, powdered and extracted pomegranate peel has rich fiber, bioactive materials and high antioxidative characteristics. Therefore, the main purpose of the present research is to study the effect of replacing the pomegranate peel (0-12 %), Guar gum (0-1.5 %) and Hemicellulase enzyme (0-90 ppm), respectively on the physiochemical properties.
Material & Moisture content measurement of moisture by oven, density by using rapeseed seeds displacement method, hardness (STM 200 device), color index of crumb and crust by using CIE Lab colorimetric system that measure L* (brightness), a* (redness) and b* (yellowish), antioxidant activity with spectrophotometery method in 517 nm wavelength, and sensory properties of gluten-free sponge cake based on wheat starch. In association with sensory test,30 panelists was used for checking desirability of mouth texture, appearance texture, smell and taste, color, after-taste and general acceptance with six point hedonic test that they rated samples from most agreeability to most un agreeability. For this aim, the statistical plan of response surface method (RSM) of central composite design (CCD) with three variables and four central points were used and the texture test was applied four times and the other tests were applied three times. For this purpose the Design-Expert 7.0.0 software was utilized for determining of optimum point (a point in which the minimum density and hardness that this parameters considered as a blank in the cake limits), Duncan examination was used for comparing the average of data and analyze of data was implemented with SPSS 16 software.
The results have shown that increasing the percentage of pomegranate peel in the formulation, density and bright and yellowish cakes were decreased and moisture, a* index, DPPH and hardness were increased. From the other hand, increasing the amount of replacing the gum caused to increase density, moisture and hardness. Adding the enzyme had effect in decreasing the light of crust and increasing density and color index in the crust of the cake. Totally was determined pomegranate peel had more effect on the antioxidant activity, density, hardness and colorful properties. Guar gum had fewer effect on this parameters and played most important roll on moisture of cakes. About enzyme can say it didn’t have significant effect on properties of cakes. Then, the optimum points has been defined via the software that the amounts of pomegranate peel and the guar gum were estimated at 9.1 and 0.56 %respectively, and the amount for hemicellulase enzyme calculated as 0 ppm. After that, the properties of the optimum cake were compared with blank cake and in addition to previous tests, sensory test was also performed. Moreover moisture and hardness of optimum cake was investigated in during of 14 days storage (days of 1, 7 and 14).The results have shown the physical, chemical and texture properties of optimum cake were largely similar to the blank samples and the main difference was in taste sensory properties of pomegranate peel that will corrected with the use of flavor agents. Over time, also, moisture was decreased and hardness was increased primarily and decreased later in both of blank and optimum sample. Therefore, gluten-free cake based on wheat starch with 9.1 percent pomegranate peel and 0.56 percent guar gum can be used, that only doesn’t have adverse effect on its properties, but also is acceptable for celiac patient.