Effects of sesame oil and paste (Tahini) on physicochemical and sensory properties of rice cookies

Celiac is a chronic digestive disease. Occurred in gluten - sensitive People. Gluten is a protein Found in grains such as wheat, barley, and rye. Which affect the intestinal villi reducing food substances absorption. The disease may be managed via consuming a gluten – free diet which heals the affected intestine. Rice cookie is an Iranian traditional cookie consisting of flour (wheat and rice), sugar, oil, water, egg and milk powder being suitable for these patients because no gluten is found in the cookie .It is gluten – free, very crispy and is crashed during storage and handling thus it may be stored for a short time . The objective of this study was to replace hydrogenated solid oil with sesame oil (5, 10, 15 %) and tahini (5, 10, 15 %) in rice cookies and measure the physic chemical (moisture, total ash, acid – insoluble ash, acidity, water activity, and weight loss), rheological (viscosity) texture (chewiness, gumminess, hardness) and sensory (taste, aroma, crumb and crust color, texture and total acceptance) properties. Seven treatments with one control. One were designed and the measurement was done in triplicate. Data were analyzed by SPSS 21 software and the means were compared by Duncan tests at 95% confidence level and the diagrams were drawn by Excel 2013. The results of physicochemical test showed that as the level of Sesame oil and tahini increased, moisture, total ash, acid – insoluble ash, acidity, viscosity and water activity decreased and pH and weight loss increased significantly (p≤0.01). Tahini – containing treatment had superior physic chemical properties the reason of moisture loss may be the lack of protein network and migration of moisture from crumb to crust due to the lack of gluten in the samples. Ash content increased because of the presence of insoluble minerals (iron, calcium, magnesium, potassium, sodium, zinc (~ 4-7% g 100mg) in tahini. Acidity decreased because of reduced water activity since it reduced fat auto oxidation thereby decreasing acid products. As the amount of Sesame oil and tahini increased, pH value increased likely due to enzymatic activity of rice flour maintaining moisture, I.e. because the samples containing the oil absorbs less water stimulating hydrogen ions thereby increasing the pH value. Decrease in weight loss, viscosity, and water activity may be directly related to the reduced moisture, i.e. when the moisture of samples decrease by added sesame oil and tahini, increased weight loss and reduced viscosity and water activity are evident. The results of texture meter showed that as the level of sesame oil and tahini increased, chewiness, springiness, cohesiveness and hardness decreased significantly (p≤0.01) and gumminess decreased. The reason of reduced cohesiveness may be the presence of fiber in tahini - containing samples, i.e. .the cohesiveness reduced due to low moisture and high fiber. Texture hardness represent the resistance of food against compressive force. The reason of decrease in hardness may be the fat surrounding the starch granules in rice cookie dough which prevents the granules from adhering to each other when baking thereby reducing the hardness. The results of sensory evaluation showed that as the level of sesame oil taste, aroma and crumb color indexes increased, crust color and texture remained unchanged and total acceptance decreased. As the amount of tahini increased, taste, texture and total acceptance were given the highest score and aroma, crust and In general, tahini – containing treatment were given the highest score for sensory properties. The results revealed that tahini treatments were accepted by the panelists showing significant difference from the control sample. The reason may be higher moisture, viscosity, water activity and the lowest weight loss. The reason of higher scores for aroma and flavor of sesame oil and tahini treatments was the presence of aromatic such as tocopherols. Tocopherols are fat–soluble compounds promoting aroma and flavor of the rice cookies. Given the highest scores of moisture, water activity, viscosity. Texture and the lowest weight loss as well as the best sensory scores for aroma, texture, taste and total acceptance, the treatment containing 5% tahini was selected as the superior one. The results showed that Sesame oil and tahini added to the formulation of rice cookies could improve the physic chemical, texture, and sensory properties. The reason of higher scores for aroma and flavor of sesame oil and tahini treatments was the presence of aromatic such as tocopherols. Tocopherols are fat–soluble compounds promoting aroma and flavor of the rice cookies. Given the highest scores of moisture, water activity, viscosity. Texture and the lowest weight loss as well as the best sensory scores for aroma, texture, taste and total acceptance, the treatment containing 5% tahini was selected as the superior one. The results showed that Sesame oil and tahini added to the formulation of rice cookies could improve the physic chemical, texture, and sensory properties. The reason of higher scores for aroma and flavor of sesame oil and tahini treatments was the presence of aromatic such as tocopherols. Tocopherols are fat–soluble compounds promoting aroma and flavor of the rice cookies. Given the highest scores of moisture, water activity, viscosity. Texture and the lowest weight loss as well as the best sensory scores for aroma, texture, taste and total acceptance, the treatment containing 5% tahini was selected as the superior one. The results showed that Sesame oil and tahini added to the formulation of rice cookies could improve the physic chemical, texture, and sensory properties. The reason of higher scores for aroma and flavor of sesame oil and tahini treatments was the presence of aromatic such as tocopherols. Tocopherols are fat–soluble compounds promoting aroma and flavor of the rice cookies. Given the highest scores of moisture, water activity, viscosity. Texture and the lowest weight loss as well as the best sensory scores for aroma, texture, taste and total acceptance, the treatment containing 5% tahini was selected as the superior one. The results showed that Sesame oil and tahini added to the formulation of rice cookies could improve the physic chemical, texture, and sensory properties.