چكيده لاتين :
Introduction: Celiac disease is an immune-mediated enteropathy triggered by
the ingestion of gluten in susceptible patients (Kennedy et al., 2000). The reaction of celiac patients to gluten leads to the malabsorption of several main nutrients such as folic acid, iron, soluble vitamins, etc. Gluten is the main structural forming protein in baked products which cause the elasticity, cohesiveness and viscosity characteristics of dough. Gluten eliminatiom and its replacement with other protein causes technological problems like poor quality mouthfeel, crumbly structure, and a quick staling (Miñarro et al., 2012). Therefore, a redesign of the gluten-free bakery goods is necessary for obtaining products with suitable qualitative properties and nutritional composition. Therefore, to overcome these technological problems, several additives have been employed to mimic gluten properties. Emulsifiers are used in the baking industry because of their ability to interact with different flour components and other dough ingredients, which causes the softer crumbs (Khatami et al., 2015). Hydrocolloids have positive effects on crumb structure, taste, global acceptability and shelf life. Rice and oak flour also has been used to prepare gluten-free bakery products, such as bread and cake. Rice is naturally gluten-free and contains proteins that are known to be nutritious and hypoallergenic. (Gadallah et al., 2017). The compounds in free gluten oak flour also increase the porosity of product and the consistency of the dough during mixing. This research has developed a cup cake formulation which contains sage seed, guar gum and DATEM based on rice and oak Flour using Response Surface Methodology.
Methods: The purpose of the present study is to prepare an optimal formulation of gluten-free cup cake based on different ratio of oak flour to rice flour (10:50 ratio). In this regard, the effect of equal ratio of hydrocolloids Sage seed and Guar (%0 to 6) and DATEM (%0 to 1) on quality properties of product, including moisture, porosity, density and texture characteristics (firmness, springiness and cohesiveness) were evaluated and modeled using Response Surface Methodology. To compare the control cupcake with optimum samples, chemical and physical analysis, Ash, color (crust and crum) and sensory characteristics were performed to introduce the best products with high nutritional quality, favorable textural features, and reasonable price.
Results and discussion: According to the results, by increasing the ratio of oak flour to rice flour and also enhancing the hydrocolloid concentrations, the density of samples were increased. Fiber in oak flour increased water absorption and delayed gelatinization of starch, which caused a large amount of air bubbles leave the dough before setting the cake texture. The higher concentration of hydrocolloids also prevented the expansion of air bubbles in dough due to higher viscosity and increased the density of sample. The porosity of cake texture was due to stability of gas cells in dough. The porosity was reduced in high concentration of oak flour and hydrocolloids due increasing dough viscosity and non-uniform distribution of gas bubbles. However, emulsifier at suitable concentration reduced the interfacial tension of the liquid phase of the dough. Therefore, the air bubbles can distribute constantly in dough and suitable porosity in cake was created. The effect of Independent variables (ratio of oak flour to rice flour, amount of hydrocolloids and emulsifier) on textural characteristics of gluten-free cake showed that by increasing the ratio of oak flour to rice flour and the amount of Sage seed and Guar, the hardness and cohesion of tissue was increased. This is due to the presence of insoluble fibers of oak flour. Furthermore, by increasing the hydrocolloid concentration, the viscosity was increased and the cell wall of the gases was gotten strengthened, which resulted an increase in tissue hardness. On the other hand, water absorbability and gel-like network of hydrocolloid improved the elasticity and cohesiveness of the tissue. Suitable concentration of DATEM improved textural properties of gluten-free cake. Based on the results, 2 formulations were considered as the best. The level of oak flour to rice flour in the first and second optimal samples were respectively 16.67% and 27.76%, while the amount of hydrocolloid and DATEM were 0.1% and 0.83% in both samples.
Textural hardness of control sample was more than optimal samples during storage. The presence of emulsifier and gums in the gluten-free cakes were the main factors in maintaining moisture and elasticity of texture and reducing staling of samples. Using oak flour in the sample affects the organoleptic properties of product. For example, the presence of oak flour reduces the brightness of gluten-free cake compared to the control. Also, in the sample containing emulsifier (DATEM) and hydrocolloids, the brightness of cake crust was decreased due to the reduction of moisture removal rate. The desirability of texture in control sample was higher than optimal samples, which could be attributed to the presence of oak flour compounds such as fiber, natural pigments, and creation of new colors and odors in product. However, the presence of Sage seed, Guar and emulsifier at suitable levels improve organoleptic properties of product. In nutritional aspect, the content of Mg, P and Fe in both selected optimized samples were significantly higher than the control sample, which was due to the high nutritional value of oak flour.
Conclusion: In this study, different ratio of oak to rice flour was used to produce gluten-free cake with appropriate quality and high nutritional value. Sage seed, Guar gums and DATEM were used for improving quality of free gluten product. By considering the quality characteristics of product, two samples with different levels of oak to rice flour ratio (16.67 and 27.76), 0.1% Sage seed and Guar gum and 0.83% DATEM were introduced as appropriate levels of independent variables in this study. Investigation staling process of samples during storage was found that the use of appropriate amount of gums and emulsifier at medium level of oak flour reduce staling of product. Also, in terms of nutritional, qualitative and overall acceptance of the product, the optimized sample No. 1 (oak flour to rice flour was 16.67%, the amount of hydrocolloid was 0.1% and the DATEM emulsifier was 0.83%) was selected as the best.
