The effect of flaxseed powder (linum usitalissmum) and DATEM as emulsifier on the qualitative and sensory properties of Doughnut

Introduction: Doughnut is a sweet sparkling snack which is produced chemically or by fermented or by combination of two methods. It is fried at high temperature. Doughnut is among the most popular sweeteners of wheat flour because of its high taste and high energy (Tan & Mitral 2006). Due to the high demand and the mechanization of Doughnut production, it is necessary to add suitable food additives to improve its nutritional value and enhance the technological and sensory properties of such a product. One of the compounds that can be used as a functional material in the baking industry is flaxseed (Linum usitalissmum). Flaxseed is known as a functional food, because it cantains α-linolenic acid (omega-3) and essential amino acids such as methionine and tryptophan. Fiber is another important ingredient in flaxseed, which reduces blood cholesterol, regulates blood sugar and prevents constipation and reduces the risk of colon cancer (Ganorkar & Jain 2013). Technological and textural properties of Doughnut can be improved by using various emulsifiers, such as DATEM (EC472), in addition to improving the nutritional value of this product using flaxseed, texture and consumer satisfaction. DATEM is a derivative of glycerol esterified with edible fatty acids, mono and di-tartaric acid (Dehgan Tnha et al. 2013). Bagherzade et al. (2018) the effects of the emulsifier diacetyl tartaric acid ester of monoglycerides (DATEM) and of the enzyme maltogenic α-amylase separately and combined on the quality and organoleptic properties of pan bread investigated. The results showed that emulsifier DATEM and α-amylase were effective in reducing density. In this regard, combined effects had better result than individual effect of them. Addition of enzyme and/or DATEM emulsifier improved the organoleptic quality of pan bread through reducing firmness and increasing flavor, chewiness, and porosity as compared to control samples.  The aim of this study was to investigate the effect of flaxseed powder as a functional food and DATEM as emulsifier on qualitative and sensory properties of Doughnut.
Material and methods: Thesamples were prepared according to the method described by Entazari et al. (2017). After 7 days of storage at cold room, the moisture content was meseared by drying in an oven at 103 ± 2 ºC, ash by burning in an electric furnace at 550 ºC to produce white color residue, protein using Kjeldahl method, specific volume using the seed displacemen method (AACC 2000), and the porosity and shell color indexes by Image J software (Wilderjans et al. 2008) and The texture was determined using a instran (Dehgan Tnha et al. 2013). Sensory properties were evaluated by 10 trained panelists. The attribute evaluation coefficient was from very bad (1) to very good (5). The results were analyzed using a completely randomized design with factorial trial with two factors and three replications using MSTAT-C software. The first factor was the amount of flaxseed powder in 4 levels (0, 5, 10 and 15%), and the second factor was the amount of DATEM as emulsifier in three levels (0, 0.25 and 50%).
Results and discussion: The results showed that by increasing the amount of flaxseed powder in the Doughnut formulation, the moisture content increased (Table 4). This can be due to high water absorption ability of fiber in flaxseed (Ganorkar and Jain 2013). In this regard, the increase in moisture reported by Ganorkar and Jain (2013) in Cookie, Xu et al. (2014) and Marpalle et al. (2014) in Bread and Ayubi (2018) in cup cake containing flaxseed powder. Addition of DATAM as emulsifier, the moisture content of product increased (Table 4). Similar results have been reported by Dahgan Tnha et al. (2013). Also, the addition of flaxseed powder resulted in decreased porosity and specific volume of the final product after frying process. This can be due to presence of water soluble proteins in flaxseed which reduces the strength of gluten network and as a result the dough is not going to be able to retain the gas produced during baking process. In this regard, Khorsand et al. (2018) showed that with increasing soy flour and lentil flour, the porosity and specific volume of Doughnut decreased. Ayoubi (2018) also reported similar results with increasing the amount of flaxseed powder in a cupcake. Increasing DATEM as emulsifier improved the porosity and specific volume of Doughnut (Table 5). This can be due to the size reduction and the increase in the number of gas cells and its uniform distribution in the product texture (Ziobro et al. 2012). Brooker (2003) also stated that the addition of emulsifiers to the formulation of the baking products would uniformly distribute air bubbles, improve the specific volume and texture of the final product. The hardness of the samples increased with increasing flaxseed powder and decreased with increasing the DATEM as emulsifier (P <0.05). With increasing flaxseed powder, the apparent brightness decreased and the redness of the Doughnut shell increased (P <0.01). The presence of protein and sugars in flaxseed powder, increaseted brownishness color in samples due to the Millard reaction. The darkening of the bread crust color with the replacement of wheat flour with flaxseed powder reported by Ayubi (2018), Xu et al. (2014) and Mentes et al. (2008). While with increasing of DATEM as emulsifiers, the L* index increased and redness (a*) of the shell surface of Doughnut samples decreased (Table 6). The ability of Homogenization and create very fine emulsion droplets by DATEM as emulsifiers, resulted in whitening of the Doughnut (Kim and Walker 1992). Also, with increasing the flaxseed powder in the product formulation, the sensory score of the samples decreased. According to the opinion of the panelists, the treatments containing 5-10% of flaxseed powder had a better flavor than the control sample (Table 7). Probably the reason for the increase in the flavor of the Doughnut contaning less amounts of flaxseed powder was the presence of nutritional compounds, unsaturated fatty acids and aromatic compounds in flaxseed, but at higher concentrations, due to the presence of fiber and gumy compounds, the flavor of the product is covered. The similar results reported by Ganorkar and Jain (2013) on the cookie containing flaxseed. With increasing the DATEM as emulsifier in Doughnut, the score of sensory evalulation of samples increased (Table 7). The overall acceptance score of Doughnut containing 0.25 and 0.5% DATEM compared to the control sample was higher (Table 7), which was in agreement with the results obtained by Dehghan Tnha et al. (2013).
Conclusion: According to the results obtained in this study, the use of 5 to 10% of flaxseed powder and 0.5% of DATEM as emulsifier for production of Doughnut with acceptable qualitative and quantitative properties is recommended.