Effect of the addition of soybean dregs treated by ultrafine grinding and microwave technology on the quality of crispy biscuits

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Effect of the addition of soybean dregs treated by ultrafine grinding and microwave technology on the quality of crispy biscuits

Fang Wang¹'², Valerii Sukmanov¹'³, Jie Zeng²

Sumy National Agrarian University, Sumy, Ukraine

Abstract

Introduction. The aim of the research is to determine the effect of the addition of soybean dregs treated with ultrafine grinding and microwave irradiation on the quality of crispy pastry.

Materials and methods. The moist soybean dregs were dried at 50 °C for 48 hours and ground in an ultrafine grinding machine KCW- 701S at a frequency of 30 Hz. Obtained soybean flour was processed in a microwave oven, the ratio of beans to water was set to 1:7, at a high level of heating for 6 min, then dried in an oven at 50 °C for 48 h and sieved at 80 mesh. The color (L*, a*, b*) values of the crackers were determined by portable color difference meter (Cr-400 chromatic aberration meter Minolta, Japan).was determined using chromatic aberration meter Cr-400; texture was determined by the TA-XT Plus Texture Analyzer; sensory evaluation was conducted by 100-point hedonic scale for color, flavor, texture and overall acceptability. soy beans grinding

Results and discussion. The increase of the amount of soybean dregs powder (SDP) decreased L* and increased a* values of crispy biscuits, meanwhile b* values were not changed significantly. The color of crispy biscuits became darker (lower L*), more reddish (higher a*), and less yellowish (lower b*) when soybean dreg powder was added at amount of 15-25%. The hardness of crispy biscuits increased gradually with the increase of bean dregs. The hardness reached the maximum of 2328.49 N at addition of SDP 15%. With the addition of SDP at 20%, the firmness of the biscuits decreased slightly. With increasing addition of SDP, the content of dietary fiber in the crispy biscuit increased, thereby reducing the gluten content in the dough and affecting the formation of the gluten network, which led to an increase in the hardness of the crispy biscuit. Increasing of the dietary fiber content ensures retaining of oil in the crispy biscuits, which results in a reduction of the product hardness. The addition of soybean dregs powder affected the sensorial properties of the product. However, there was no significant difference in the overall quality rating of the crispy biscuits containing 15 and 20% SDP.

Conclusion. The addition of bean dreg powder had significant effects on the color, texture and sensorial properties of crispy biscuits compared with control. However, crispy biscuits with the addition of soybean dregs powder in the amount of 15-20% prepared by proposed technology had the crispy taste, golden color, and pleasant soybean flavor.

Keywords: Soybean Dregs Crispy biscuits Ultrafine Grinding Microwave

Introduction

By-products of plant processing are widely used in food preparation (Stabnikova et al., 2021). The soybean dregs is residue from soy milk production containing insoluble components, which remain in the filtration bag (O'Toole & Desmond, 1999). Dry soybean dregs has high content of proteins (24.5-37.5 g/100 g), lipids (9.3-22.3 g/100 g), dietary fiber (14.5-55.4 g/100 g), and is a good source of isoflavones (Bourquin et el., 1996; Rinaldi et al., 2000; Tharanathan & Mahadevamma, 2003; Surel & Couplet, 2005; Pr'estamo et al., 2007; Redondo-Cuenca et al., 2008).

With the development of the soy milk production, the availability of soybean dregs has been gradually increased, and now they are commonly used in the manufacturing of baked goods such as cakes, bread, and biscuits (Yang et al., 2013). Addition the soybean dregs into flour not only improved the flavor of the traditional biscuits, but also provided a new type of healthy food for consumers (Chen, 2013; Yang et al., 2013). However, soybean dregs have poor taste, perishability, and low content of soluble dietary fiber (SDF). Therefore, most of them are used as feed for animals or discarded as waste disposal. In recent years, a large number of studies have been carried out to develop physical technologies to increase the content of water-soluble fibers in bean flour, for example, explosive extrusion has increased the content of SDF in bean flour from 1.34 to 36.28% at an explosive strength of 1.5 MPa within 30 s (Chen et al., 2014). Twin-screw extrusion was applied for soluble dietary fiber extraction from soybean residue. The SDF content of soybean dregs reached 12.65%, which was by 10.60% higher than that of unextruded and boiled soybean dregs (Yan & Chi, 2013). Steam explosion is a kind of physical method recently used in food pretreatment. When the explosion strength was 1.5 MPa for 30 s, the content of soluble dietary fiber of soybean dregs increased from 1.34 to 36.28% (Li et al., 2019). The solubility of bean dregs can be also increased using the high-pressure homogenization due to structural disruption of bean particles and release of fibre and proteins (Fayaz et al., 2019).

The dissolution rate of soluble polysaccharides in bean residue increased to 70% after microwave treatment at 200°C for 7 min, while the appearance of new polyphenolic compounds with antioxidant activity was observed at temperatures above 180°C (Tsubaki et al., 2009). The content of soluble dietary fiber in soybean dregs increased 8 times during the treatment with high hydrostatic pressure of 400MPa at 60°C. While there was also an improvement in swelling, water holding capacity and oil holding capacity of soybean dregs (Mateos-Aparicio et al., 2010). However, as far as we know, the treatment of bean dregs by physical techniques has not been used in preparation of baked products, and this topic requires further research.

In our previous research, the SDF contents in bean dregs treated with the above single and combination methods were determined according to the AOAC method (1995). The SDF contents in bean dregs after the ultrafine grinding (U), high pressure (HP), microwaves (M), high-temperature cooking (HTC) and combination technologies U-HP, U-M, U-HTC were 15.15±0.12%, 10.40±0.19%, 13.84±0.13%, 13.87±0.13%, 18.86±0.11%, 19.23±0.19%, and 16.89±0.13%, respectively. Meanwhile, the SDF content in the control sample was only 1.63±0.2% (Wang et al., 2021).

Therefore, the aim of the present research is to determine the effect of the addition of soybean dregs treated with ultrafine grinding and microwave irradiation on the quality of crispy biscuits. It can improve the dietary fiber intake and flavor as well as nutritional value of the crispy biscuits.

Materials and methods

Materials.

Wet soybean dregs were obtained at local markets (Fresh okra has high moisture content, bad taste and mouth feel, and is difficult to store).

Bean dregs powder, low-gluten flour, powdered sugar, butter, corn starch, egg yolks, salt, and baking powder were collected from local markets.

Equipment.

Ultrafine grinder (KCW-701S, Beijing Yujie Yucheng Machinery Equipment Co., Ltd., Beijing, China); Microwave oven (P70D20N1P-G5, Guangdong Galanz Microwave Life Electric Appliance Manufacturing Co., Ltd., Zhongshan, China); Oven (YXD-60C, Guangzhou Saisida Machinery Equipment Co., Ltd., Baiyun Branch, Guangzhou, China.

Methods.

Combination technology.

Ultrafine grinding (U): the wet soybean dregs were dried in a constant temperature drying oven at 50 °C for 48 h, and then ultrafine ground frequency of 30 Hz by an ultrafine grinder (KCW-701S).

Microwave (M): wet bean dregs were treated in a P70D20N1P-G5 microwave oven at a medium heat level for 4 min, then dried in the oven at 50 °C for 48 h and sieved at 80 mesh.

Combination technology: the soybean dregs treated by ultrafine grinding were used as the raw material for combination with high pressure treatment, microwave treatment and high temperature cooking treatment. The ratio of soybean dregs to water was set as 1:3, 1:5, 1:7, 1:9 and 1:11. The other conditions were designed as follows: Ultrafine Grinding-Microwave (U-M): Low, M-Low (between low and medium heat), Med, M. High (between medium and high heat), High heat modes were selected for microwave conditions, and the treatment time ranged from 2 min to 10 min.

The treatment of SDP was conducted according to the methods described in (Wang et al., 2021).

Crispy dough preparation.

The crispy biscuits had the following formulation: low gluten flour and soybean dregs powder (100 g), butter (50 g), powdered sugar (20 g), corn starch (5g), egg yolks (20 g), salt (1g), and baking powder (0.75g). Whisk butter until creamy and pale after the butter is softened, powdered sugar, salt and egg yolks were mixed for 1 min at speed 4 using a KitchenAid Professional mixer KPM5 (St. Joseph, Michigan, USA) to make it smooth, add the flour mixture (low gluten flour, bean dregs powder, corn starch and baking powder) in batches to make a soft dough. Seal with plastic wrap and leave at room temperature for 10 min.

Crispy biscuits preparation.

Preheat the oven to be preheated, the upper heat is 170 °C, the lower heat is 160 °C, weigh 8 g of the crispy dough, put it into a fixed mold, press it into a consistent biscuit shape and slowly the sample into the prepared baking pan. These samples were baked in an electric oven for 12 minutes. After baking, the crispy biscuits were removed from the oven, left to cool for 1 hour at room temperature, and packed into hermetically sealed plastic bags to prevent drying. All quality measurements were performed in 1 hour after baking.

Crispy biscuits measurements.

Color.

The color (L*, a*, b*) values of the crackers were determined by portable color difference meter (Cr-400 chromatic aberration meter Minolta, Japan). Color measurements were made of crust. All measurements were conducted at least three times. The L* value is a measure of lightness, ranging from black (0) to white (100), the a* value ranges from greenness (-100) to redness (+100), and the b* value ranges from blueness (-100) to yellowness (100) (Yang et el., 2019).

Texture analysis.

Crispy biscuits texture was determined by the TA-XT Plus Texture Analyzer (Stable Micro Systems, London, UK) according to the method described in (Tyagi et al., 2007). The complete biscuits were placed on the test bench of the texture tester, and the texture profile analysis test was carried out with the P/5 probe. Parameters were set as follows: pretest peed, 1.0 mm/s; test speed, 0.50 mm/s; posttest speed, 1.0 mm/s; strain, 30%; interval time, 5 s. Textural parameters, such as hardness, cohesiveness, gumminess and chewiness were determined. Measurements were performed on biscuits (5 mm thick), and the mean of the four measurements was recorded.

Samples were assessed for texture profile analysis with an aluminum cylindrical probe P/5 at ambient temperature (20-25 ^oC). The indicators of hardness, springiness, cohesiveness and chewiness were determined. Each measurement was replicated 5 times.

The data were generated by Exponent software (Exponent stable microsystem, version 5.1.2.0, Stable Microsystems Ltd., UK) provided with the instrument (Figure 1). Attributes of hardness, cohesiveness, gumminess and chewiness were determined. Each measurement was replicated 5 times.

Figure 1. The parameter definition interpretation of qualitative curve analytical method (Szczesniak, 1963; Szczesniak et al., 1963)

Hardness. It is the biggest peak of compression for the first time (Bourne, 2002; Singh et al., 1993).

Cohesiveness. The relative resistance of the test sample to the second compression after the first compression deformation is shown in the curve as the ratio of positive work (Area 2/Area 1) of the two compressions. This value represents the total work required to overcome the attraction between the two surfaces when the probe comes into contact with the sample [27].

Gumminess. It is expressed as the product of hardness and cohesiveness. The result is multiplied by 100 to eliminate decimals (Friedman et al., 1963).

Chewiness. It is only used to describe the test sample in solid state, indicating the energy required to chew the solid sample into a stable state when swallowing. The numerical value is expressed by the product of the stickiness and elasticity (hardness x cohesive elasticity)

Sensory evaluation.

The sensory evaluation was done according to the method (Bose & Shams-ud-Din, 2010). A sensory evaluation of biscuits was conducted initially for color, flavor and texture by a panel of 10 panelists (Qiu & Qi, 2018). All the panelists were the postgraduate students of the Department of Food Science and Technology. A 100-point hedonic rating test was performed to assess the degree of acceptability of these biscuits. Three pieces from each biscuit lot were presented to 10 panelists as randomly coded samples. The test panelists were asked to rate the sample on a 100-point hedonic scale for color, flavor, texture and overall acceptability.

Statistical analysis.

Experiments were conducted at least in triplicate, and the data were statistically analyzed and expressed as the means ± standard deviation (SD). Data were subjected to analysis of variance (ANOVA) using the software package SPSS 12.0 for Windows (SPSS Inc., Chicago, USA) and p<0.05 was used as the standard for significance.

Results and discussion