Quality and Sensory Characteristics of Cookies Fortified with Soybean and Rice Bran Blended Flour

Cookies are the most common bakery product and are generally accepted and consumed by people of all ages and socio-economic levels. They are a common baked food in the human diet that is typically taken with beverages (Ferial and Azza, 2011). They are ready-to-eat, convenient and low-cost food products that contain important digestive and dietary principles (Olaoye et al., 2007). Cookies play an essential role in the baking business due to their diverse sensory and nutritional features (Chappalwar et al., 2013). They provide significant amounts of iron, calcium, protein, calories, fiber and several B-vitamins to our diet and daily nutritional requirements. Cookies and other pastries have traditionally been made with soft wheat flour but they can also be made with non-wheat flour. To increase the nutritional value of cookies, partial replacement of refined wheat flour with soya bean and rice bran flour blends with superior nutritional attributes is required.
       
Soybean, according to Hegazy and Ibrahim (2009), is one of the world’s most important oil and protein crops. Soybean protein is more nutritionally similar to animal protein than other vegetable proteins. Soybean protein accounts for roughly 40% of total solids and is used extensively in the enrichment of cereal-based baked foods (Fukushima, 1999). Soybean has long been utilized as a supplementary diet due to its properties. Soybean is one of these protein sources that, when used to partially replace or complement wheat flour in the production of baked products like biscuits, bread and other confectionery, can significantly improve the nutritional status of such products. As a result, soybean is considered to have the highest food value of any plant food consumed globally (Ndife et al., 2011).
       
Rice bran is an underutilized by-product of rice as a source of value-added food. However, as food demand rises, new and unique ways to utilize the formerly inconspicuous waste item are required to be investigated. Rice bran has been found to have commercial benefits based on its qualities (Nagendra Prasad et al., 2011) and it has various unique traits that make it suitable for niche sectors like food, nutraceuticals and pharmaceuticals. Rice bran composition is mostly determined by the type of rice used and the effectiveness of the milling system (Sharif et al., 2014). During processing, the external layer of the rice is eliminated to get the bran. Rice bran contains 15-22% lipids, 34-52% carbs, 7-11% fiber, 6-10% debris, 8-12% dampness and 10-16% protein, representing 5-8% of the absolute rice bit (Luh, 1991). Rice bran is a good source of E and B vitamins as well as the only natural source of oryzanol. The goal of this study was to produce and evaluate the nutritional qualities of wheat, soybean and rice bran flour blend cookies.

Ingredients
 
The experiment was conducted in May 2019 at the Mycotoxin and Food Analysis Laboratories, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. Soybeans and rice bran were purchased from the merchant store at the Kumasi Central Market. Other ingredients were collected from the Tafo local market in Greater Kumasi, Ghana.
 
Preparation of full-fat soybean flour
 
Full-fat soybean flour was made using the method outlined by Ihekoronye and Ngoddy (1985). Two kilograms of soybean seeds free of dirt and other foreign particles such as stones and leaves, were weighed, cleaned and steeped in tap water for eight (8) hours during preparation. The seeds were then drained, dehulled by hand, boiled for 30 minutes at 100°C and dried in a cabinet dryer (650°C for 12 hrs). To maintain constant drying, the dehulled seeds were mixed every 30 minutes during the drying process. To make cooked full-fat soybean flour, the dry seeds were ground, sieved and the flour obtained was finally packaged in an airtight container until needed.
 
Defatted rice bran preparation
 
Rice bran was defatted twice using a 1:2 (w=v) ratio of rice bran to n-hexane and a stirring speed of 1,500 rpm at 250°C for 1 hour. The mixture was then centrifuged at 5,000 × g and the residue was defatted again using rice bran and n-hexane in a 1:1 (w=v) ratio at 250°C for 30 minutes while stirring at 1,500 rpm. Under a hood, the mixture was centrifuged at 5,000 × g and air-dried overnight. Before use, defatted rice bran was milled and sieved through a 50-mesh screen, then packed in polyethylene bags and kept at 50°C.
 
Sample formulation
 
The five different flour tests were created from a mix of wheat, soya bean and rice grain (Table 1). The five flour test definitions were coded as M₁, M₂, M₃, M₄ and M₅. Every one of the measured flours was consistently mixed by using a blender. The composite flour tests were put away in water/airproof compartments until required. Wheat flour (WF) was utilized as a control flour.
 

 
 
Method of cookies preparation
 
The cookies were made using a mixture of 90%, 80%, 70% and 40% wheat flour; 6%, 12%, 17%, 35% soya bean flour and 4%, 8%, 13% and 25% rice bran powder were used respectively to produce the cookies. Cookies were made according to the Okpala et al., (2013) method with slight modifications. For every 100 g of flour, 40 g of baking fat, 31 g of fresh eggs, 7.8 g of powdered milk, 5 ml of vanilla essence, 25 g of white granulated sugar, 0.3 g of nutmeg, 1 g of baking powder and 1 g of salt were used. With the help of a mixing bowl and a wooden ladle, the sugar and fat were creamed for 45 minutes, until the mixture became light and fluffy. Following that, the beaten eggs were added and creamed for another 15 minutes. The other ingredients were mixed in well to produce soft dough. The dough was lightly kneaded and cut into circular shapes. The cookies were baked for 15 to 25 minutes at a temperature of 185°C. The cookies were preserved in plastic airtight containers after cooling and maintained at room temperature until further analysis was required. A cookie made entirely of wheat flour was used as a control.
 
Proximate composition
 
Standard analytical procedures (AOAC 2000) were used to analyze the proximate composition (moisture, protein, fat, fiber and carbohydrate) of the wheat-soya-rice bran cookies. The functional properties of wheat-soybean-rice bran blended flour were carried out using Narayana and Narsinga Rao (1982) method with slight modifications.
 
Sensory analysis
 
The five cookie samples were evaluated using Larmond’s (1977) approach. The evaluation included a total of 50 semi-trained panelists. The cookies were assessed using the following parameters; color, taste, flavour, texture and overall acceptance. The coded cookie samples were served in clean plastic plates at room temperature in segregated cubicles with adequate lighting. A random sample presentation was delivered to the panelists. Panelists were told to try out the items and rate them on a five-point scale.
 
Statistical analysis
 
A one-way analysis of variance was performed on the data (ANOVA). Duncan’s multiple range test was used to separate the means using the Statistical Package for the Social Sciences (SPSS) version 20. The significance level was chosen at p<0.05.

Proximate composition of wheat, soybean and rice bran cookies
 
Table 2 shows the proximate composition of the various cookie samples produced. The moisture level varied between 9.6 and 12.20%. The composite samples M₂, M₃, M₄ and M₅ had higher moisture contents of 9.94, 9.99, 10.93 and 12.20% than the control M₁ (9.6%). The moisture content increased from 9.6 to 12.20% with the addition of soy flour and rice bran. However, these findings are in contrast to those of Sutharshan et al., (2001), who found that increasing the quantity of soy flour in the biscuits reduced the moisture content. High moisture content has been linked with a short shelf life of baked products because they inspire microbial growth that leads to spoilage (Elleuch et al., 2011). Cookies fortified with soya bean flour and rice bran had high moisture values that were significantly different (p<0.05).
 

       
Cookie sample M₅ had the greatest ash level (3.54%), while control M₁ recorded the lowest (1.42%). The ash content was found to be 9.94%, 9.99% and 10.93% in cookie samples M₂, M₃ and M₄. As it can be seen in Table 2, the ash content gradually increased from 1.42% to 12.20% as the percentage of soy flour and rice bran increased. The results agree with those of Ayo et al., (2014) on the use of soy flour in biscuits. With the addition of soy flour and rice bran, the fat content of the cookies increased from 2.28 to 13.88%. Sample M₅ had the highest fat content (13.88%), while the control (M₁), which consisted of 100% wheat flour cookies, had the lowest (2.28%). The fat content of samples M₂, M₃ and M₄ were found to be 4.50%, 7.03% and 8.74%, respectively (Table 2). This upward trend is consistent with previous studies (Ayo et al., 2014).
       
According to Reddy (2004), soy flour has 20-24% fat, whereas wheat flour comprises 0.9-1.1% fat, the majority of which is unsaturated. The study’s higher fat content could be attributed to a higher amount of soy flour and rice bran in the cookies. With the addition of soy flour and rice bran, the fiber level of the cookies increased from 0.30 to 4.80%. Cookie sample M₅ had the highest fiber content (4.80%), while the control (M₁) had the lowest (0.30%). The fiber content in samples M₂, M₃ and M₄ were found to be 0.92%, 1.63% and 2.50%, respectively (Table 2). Ayo et al., (2014) showed similar increases in fiber content when malted soy flour was added to prepare biscuits. The protein content was observed to have increased from 10.22% to 18.70% in the current study. Cookie sample M5 had the highest protein level (18.70%), while M₁ had the lowest (10.22%).
       
Fiber content was found to be 11.57%, 13.54% and 14.71% in samples M₂, M₃ and M₄ (Table 2). Several investigations backed up this tendency of higher protein content in the treatments as compared to the control (Ayo et al., 2014). This increase could be due to an increase in the proportion of soy flour and rice bran in the flour blend, as soybean and rice bran are high-protein legumes and cereals that are an excellent complement to lysine-limited cereal protein.
 
Functional properties of wheat-soybean-rice bran blended flour
 
The ability of food products to link with water when water is scarce, such as in dough and pastries is referred to as their “water absorption capacity” (WAC) (Oppong et al., 2015). The highest WAC (37.23 mL/g) was found in the flour composite sample M₅ while the lowest (1.73 mL/g) was found in the control flour sample M₁. The WAC of the flours differed significantly (p<0.05) from one another. The samples’ high WAC could be attributable to their high fibre content since water holding and retention abilities have been found to be improved by fibre.
       
The physical trapping of oils is primarily responsible for oil absorption capacity (OAC) (Singh et al., 2005). The rate at which protein binds to fat in food compositions is measured by OAC (Singh et al., 2005). Low hydrophobic proteins, which show superior lipid binding, could explain flour’s decreased oil absorption capacity (Adeleke and Odedeji, 2010). The flour’s OAC levels ranged from 2.15 to 35.26 ml/g. The OAC content of the flours differed significantly (p<0.05). Table 3 shows that M₅ has a higher oil absorption capacity of 35.26 ml/g. The lowest concentration was 2.15 ml/g for M₁. The OAC in the flour also aids in the enhancement of flavour and mouth feel when it is used in food preparation.
 

       
The bulk density (g/cm³) of flour refers to the density measured without any compression. Flours bulk densities ranged from 0.74 g/cc to 0.99 g/cc. The M5 had the highest bulk density (0.99 g/cc), followed by M₄ (0.92 g/cc) and M₁ (0.74 g/cc). According to the current study, the bulk density of flour is determined by particle size and initial moisture content. The bulk density of composite flour increased as the percentage of other flours added to wheat flour increased. Flour’s high bulk density signifies that it is suitable for use in food preparations.
       
The ability of a protein solution or suspension to emulsify oil is known as “emulsifying ability.” The emulsion ability (EA) of all the flour blends ranged from 43.88% to 64.12%, with the M₅ having the highest EA of 64.12%, followed by M₄ and the control sample M₁ having the lowest EA of 43.88%. The EA of the flours was significantly different (p<0.05). The results of this study are similar to and connected to Iwe et al., (2016) findings of 42.50, 56.78 and 56.67% for rice, cowpea and AYB flours, respectively.         
       
The flour’s foaming capacity (FC) ranged from 12.92 to 23.48 per cent. These findings are similar to those reported by Iwe et al., (2016), who found foaming abilities of 10.41% to 18.17% in soy-wheat and rice bran flour. The ability of a chemical in a solution to produce foam after vigorous shaking is known as foaming capacity (FC). The FC of the flours was significantly different (p<0.05) and the higher the flour’s protein concentration, the better the foaming capacity.
 
Sensory attributes of the wheat, soybean and rice bran flour cookies
 
Sensory evaluation of wheat, soybean and rice bran flour cookies in Table 4 revealed that the sensory qualities of M₃ was deemed to be the best in terms of flavour, taste, texture, colour, crispiness and overall acceptability, while M₁ and M₂ were closest to cookie sample M₃. The flavour of the cookies was reduced from 2.15 to 4.26 as a result of the increased in substitution of soybean flour and rice bran. The flavour scores decreased rapidly as the percentage of flours containing wheat and rice bran increased from 25 and 35%. This has a lot of consequences and it is a crucial criterion in organoleptic evaluation. Taste is the most important component in determining whether or not a product is acceptable and it has the greatest impact on the product’s commercial success. With the increase in the level of soy flour and rice bran substitution, the taste score increased from 2.41 to 4.41. The cookie with M₅ was rated the worst in terms of taste (2.81) while biscuit sample M₃ recorded the highest mean score for taste (4.41).
 

       
The texture of the cookies was increased from 2.95 to 4.46 by increasing the substitution of soy flour and rice bran. The composite biscuit sample M₃ had a high mean score for texture (4.46) followed by sample M₂ with a mean score of (3.50). The control sample M₁ had the third mean value (3.40) and this brought a significant difference (p<0.05) between the texture of the control and composite cookies. The average colour score of the cookies rose from 2.53 to 4.37. Cookie sample M3 had the highest score (4.37) and the lowest colour score (2.53) was for sample M5. As the amount of soy flour and rice bran in the cookies increased, the average colour score decreased.
       
With regard to the crispiness, cookie samples made with 12% soybean flour and 8% brown rice bran powder achieved the highest mean score (4.39) and was significantly different (p<0.05) from the control sample (3.30) and all other composite cookie samples. For overall acceptance, cookie sample M₃ had the greatest mean value (4.56), followed by the control sample M₁ with a 4.51 mean score. The cookie sample M₃, made up of 80% wheat flour, 12% soybean flour and 8% brown rice bran was most accepted by the panelists.

The functional qualities (water absorption capacity, oil absorption capacity, bulk density, emulsion ability and foaming capacity) of the formulation with the maximum replacement of 40%, 35% and 25% of wheat, soybeans and rice bran blended flour achieved relatively the highest values in this study. The dispersibility of the flour blends was reduced as the amount of soybean and rice bran flour substituted increased. Sensory evaluation revealed significant differences (p<0.05) in the flavour, taste, texture, colour and overall acceptability of the cookies produced. The cookie sample made with 80% wheat flour, 12% soybean flour and 8% brown rice bran was the most preferred with an overall mean value of 10.56 and was significantly different (p<0.05) from the control.