Influence of addition and proportion of blueberry wine residue on dough characteristics

ABSTRACT

Blueberry wine residue was added to low-gluten flour in proportions of 0, 2, 4, and 6%, and the effect on dough properties was studied. The addition of blueberry wine residue reduced the final viscosity and retrogradation value of low-gluten flour dough, and changed the water absorption, formation time, textural characteristics, and colour difference. With increasing amounts of blueberry wine residue, the water absorption, pasting temperature, formation time, hardness, colour, and luster of the dough gradually increased, whereas the stability time, final viscosity, retrogradation value, and chewiness gradually declined. When the amount of blueberry wine residue was 4%, the resulting dough properties were more suitable for the processing of dough products. This study provides a theoretical reference for the application of blueberry wine residues in food.

KEYWORDS:

• Blueberry wine residue
• addition amount
• low-gluten dough
• dough properties

1. Introduction

Blueberry wine residues are a by-product of the blueberry fruit wine brewing process. With the development and growth of the blueberry fruit wine industry, the production of blueberry wine residues has continued to increase. The residues are rich in dietary fibre, anthocyanins, polyphenols, and other active substances (Lee et al., 2002; Su & Chien, 2007), which have good functional properties for the human body (Li et al., 2021; Zeng et al., 2016). At present, most blueberry wine residue is discarded, which not only pollutes the environment, but is also a waste of agricultural and side-line product resources.

People often eat refined wheat flour, which is produced by removing the wheat bran, germ, etc., where some nutrients, dietary fibre, and vitamins will be lost. The functional properties of various pasta made from refined wheat flour are poor. Thus, the addition of grape peel, quinoa, barley, etc., containing functional ingredients, to flour is being actively studied (Cao et al., 2016; F. Zhang et al., 2019; Mironeasa et al., 2018; Ruan et al., 2021) with the aim to improve the nutritional quality of traditional flour products. Sporin et al. (2018) evaluated the rheology and sensory and antioxidant properties of dough, and the resulting bread texture, after adding different proportions of dried, ground grape pomace powder. After adding the grape pomace powder, the dough had a longer fermentation time and stability. Ahmad et al. (2016) studied the effects of different proportions of carrot residue powder with different particle sizes on the characteristics of wheat flour, dough, and cookies. The author’s study found that cookie made by adding carrot powder to flour after 120 mesh have better antioxidant properties and sensory qualities than carrot powder that has been sifted through 72 mesh. J. Chen et al. (2018) added raw potato whole flour to wheat flour and observed the rheological characteristics of the mixed flour dough. With the addition of 20–30% raw potato whole flour, the water absorption, formation time, and stability time of the dough were higher than those of the other groups.

At present, most research on blueberry wine residues focuses on the extraction of functional ingredients, nitrite inhibitors, blueberry jam (N. W. Zhang et al., 2020; W. X. Zhang et al., 2020; Zhou et al., 2018), etc., whereas the effects of blueberry wine residues on low-gluten flour dough have not been reported. Herein, the thermomechanical, gelatinization, and textural characteristics, as well as the colour difference of blueberry wine residue added to low-gluten wheat flour mixed flour dough are determined to clarify the influence of different proportions of blueberry wine residue on the dough characteristics, and to provide a theoretical basis for the application of blueberry wine residues in flour products.

2. Materials and methods

2.1. Materials

Blueberry wine residues were obtained from Guizhou Research Institute. Low-gluten wheat flour which contents 24% wet gluten was acquired from Angel Yeast (Yichang, Hubei province, China.).

2.2. Main instruments

The instruments used and manufacturers are as follows: F2004A Electronic Analytical Balance (Shanghai Jing Tian Electronic Instrument Co., Ltd); Mixolab Hybrid Tester(Chopin Company, France); TCW-3 Rapid Visco Analyzer, RVA (Newport Science Corp, Australia); TA-XT Plus texture analyser (Stable Micro Systems, UK); Ultra Scan PRO colorimeter (Hunter Lab, U.S.A).

2.3. Experimental methods

2.3.1. Pre-treatment of blueberry wine residue

After low-temperature drying(50°C), the blueberry wine residue was crushed to ultrafine particles and then sifted through a 100-mesh sieve for use.

2.3.2. Preparation of mixed powder

On the basis of pre-experiments, the appropriate amount of blueberry wine residue for addition to the flour was determined. The blueberry wine residue was added to low-gluten wheat flour in mass fractions of 0% (control), 2, 4, and 6%.

2.3.3. Determination of flour gelatinization characteristics

The effect of different amounts of blueberry wine residue on the characteristics of the low-gluten flour was quantified by using a rapid viscosity analyser, where the prepared mixed powder was accurately weighed (3.5 g) into a dry aluminium box, after which 25 mL of deionized water was added to the aluminium box, and the sample was evenly stirred by using a propeller to disperse the mixed powder into the water. The specific experimental measurement parameters were set in accordance with test standard procedure 1 in GB/T24853–2010. Each sample was analysed in triplicate.

2.3.4. Determination of thermomechanical properties of dough

The Mixolab mixing tester can determine the rheological properties of flour mixed with water to form a dough, dough heated to gelatinization, and dough in the cooling process, which is equivalent to determining the characteristics of dough over the entire process of flour being made into food, reflecting the overall processing of dough from raw to cooked. The specific experimental parameters were as follows: Test mode selection: Chopin +; default mass of mixed flour dough: 75 g; torque of the mixed flour dough: (1.10 ± 0.05) N·m as the standard. The specific test conditions were as follows: The initial temperature was maintained at 30°C for 8 min, after which the temperature was raised to 90°C at a rate of 4°C/min and maintained for 7 min. The temperature was then reduced to 50°C at a cooling rate of 4°C/min and kept for 5 min. The total test process took 45 min, where the rate of kneading and mixing the dough was 80 rpm. The process was repeated thrice for each sample. The following parameters can be obtained throughout the experiment: water absorption, formation time, stabilization time, protein weakening, minimum torque (C2), maximum torque in dough heating stage (C3), maximum torque in dough holding stage (C4), the torque (C5) when the dough is cooled to 50°C, the protein weakening rate (α), the starch gelatinization rate (β), and the starch degradation rate (γ).

2.3.5. Determination of textural properties of dough

A literature method J. F. Chen et al. (2021) was used to determine the textural properties of the dough, with slight changes as follows: 40 g of mixed powder was weighed and made into a dough, where the mixed powder-to-water ratio was 8:5. A 20 g portion of the dough was formed into a cylinder of uniform size, wrapped in plastic wrap, and left for 15 min. Thereafter, a TA-XT Plus texture analyser was used to determine the textural characteristics. The measurement parameters were as follows: P100 probe was selected; the pre-test and post-measurement rates were both 3 mm/s; the test rate was 1 mm/s; the compression ratio was 50%; trigger mode was automatically selected; the trigger force was 0.05 N. Each sample was analysed in triplicate and the average value was recorded.

2.3.6. Determination of the colour difference of the dough

Using the dough made according to method 1.3.4, the brightness (L*), red-green value (a*), yellow-blue value (b*), and total chromatic difference (ΔE) were determined by using a colorimeter. The test was repeated 3 times for each set of samples, and the average was recorded.

3. Data analysis

The results of the experiment were processed and analysed using Excel 2019 and Rstudio-1.4.1103 (New Zealand). Significant differences among values were determined by analysis of variance (ANOVA), at p < .05.

4. Results and analysis

4.1. Effect of blueberry wine residue on gelatinization characteristics of low-gluten dough

The gelatinization characteristics represent the properties of the starch in the mixed powder, the starch particles will expand and break due to heating and water absorption (when placed in water), the viscosity of the dissolved starch solution will increase, the starch birefringence phenomenon will disappear, and the molecule will change from an ordered state to a disordered diffuse structure. The peak viscosity represents the degree of expansion of the starch particles and their ability to combine with water, which is an important indicator of the gelatinization characteristics of the mixed powder; these characteristics are closely related to the quality of the final product (Feng et al., 2021). During the gelatinization process, the peak viscosity, minimum viscosity, and setback value of the mixed powder first decreased and then increased (Table 1), but the difference was not statistically significant compared with the control group (p < .05). This indicates that adding a smaller amount of blueberry wine residues will reduce the peak viscosity, minimum viscosity, and setback value during gelatinization of the mixed powder. The breakdown value mainly reflects the stability of the flour during heating, and dough with a lower attenuation value shows better resistance to shear thinning. The pasting temperature increased as the proportion of blueberry wine residue increased, and the extent of breakdown value decreased, but the change was not statistically significant (p < .05) compared to the control group. When 2% blueberry wine residue was added, the pasting temperature and extent of breakdown value of the mixed powder were the lowest.

Table 1. Effect of adding amount of blueberry wine residues powder on the gelatinization characteristics of dough starch.

Add amount/%	Pasting temperature/℃	Peak viscosity/cP	Minimum viscosity/cP	Final viscosity/cP	Breakdown/cP	Setback/cP
0 (Control)	51.25 ± 1.52^a	3210 ± 249^a	2280 ± 57^a	4332 ± 216^a	930 ± 149^a	988 ± 214^a
2	50.40 ± 10.14^a	3307 ± 246^a	2302 ± 50^a	4125 ± 384^ab	1027 ± 211^a	818 ± 146^a
4	51.43 ± 1.03^a	3057 ± 264^a	2269 ± 39^a	3753 ± 303^ab	788 ± 84^a	696 ± 85^a
6	57.37 ± 9.02^a	3287 ± 210^a	2364 ± 95^a	3581 ± 339^b	923 ± 112^a	703 ± 129^a

Values are mean ± standard deviation (SD). Different letters (a – f) in the same column indicate significant differences (p < .05) according to ANOVA. The same column of data marked with different lowercase letters indicates significant differences (P < .05), the same below.

2: 2% Blueberry wine residues+98% Low-gluten wheat flour.

4: 4% Blueberry wine residues+96% Low-gluten wheat flour.

6: 6% Blueberry wine residues+94% Low-gluten wheat flour.

Pasting temperature: The temperature at which the viscosity of the specimen begins to increase after the specimen is heated.

Peak viscosity: Under specified conditions, the heated specimen begins gelatinization to the maximum viscosity value reached before cooling.

Peak time: The time from the start of specimen testing to the peak viscosity under specified conditions.

Minimum viscosity: The minimum viscosity value during cooling after the specimen reaches peak viscosity under specified conditions.

Final viscosity: The value of the specimen viscosity at the end of the test under specified conditions.

Breakdown: The difference between the peak viscosity and the lowest viscosity.

Setback: The difference between the final viscosity and the lowest viscosity.

Blueberry wine residue will significantly affect the final viscosity in the gelatinization process; this index decreases as the addition of blueberry wine residues increases. However, with 2% and 4% addition, there was no significant difference in the final viscosity of the two groups of gelatinized mixed powder. With 6% addition of blueberry wine residue, the final viscosity was the lowest (3581.00 cP), which indicates that the mixed powder starch paste has greater hardness at room temperature. Liu et al. (2019) proposed that the decrease in the viscosity of mixed flour dough may be cause the particle size of the added powder is smaller than the particle size of wheat flour, and the intermolecular interaction is enhanced, which increases the resistance during the expansion process, thereby reducing the viscosity.

4.2. Effect of blueberry wine residue on thermomechanical properties of low-gluten dough

4.2.1. Thermomechanical properties of low-gluten dough protein

The water absorption rate indicates the amount of water added when the maximum torque C1 (1.1 ± 0.05 Nm) is reached during the process of kneading dough. As shown in Table 2, the water absorption rate of the dough gradually increased as the amount of blueberry wine residue increased. After adding the blueberry wine residue, the water absorption rate increased from 42.12% to 45.10%, which is a significant difference (p < .05). This is similar to the results reported by H. J. Zhang et al. (2019), which may be attributed to the dietary fibre introduced into in the mixed dough after adding blueberry wine residue. This may be that the cellulose in blueberry residue dilutes the gluten protein content, competes with gluten protein and starch for water molecules, and binds more water with hydrogen bonding, resulting in increased water absorption of mixed flour dough.

Table 2. Effect of adding amount blueberry wine residues powder on the thermomechanical properties of dough starch.

Add amount/%	Peak viscosity C3/Nm	Viscosity disintegration value(C3-C4)/Nm	Regeneration endpoint viscosity C5/Nm	Recovery value(C5-C4)/Nm	β /(Nm·min^−1)	γ /(Nm·min^−1)
0 (Control)	1.652 ± 0.004^d	0.070 ± 0.004^d	2.848 ± 0.02^b	1.266 ± 0.01^c	0.262 ± 0.007^c	−0.009 ± 0.002^a
2	1.693 ± 0.006^c	0.137 ± 0.005^c	2.776 ± 0.02^c	1.220 ± 0.02^d	0.206 ± 0.006^d	−0.016 ± 0.004^a
4	1.788 ± 0.007^b	0.328 ± 0.007^b	2.820 ± 0.01^b	1.360 ± 0.00^b	0.348 ± 0.006^b	−0.186 ± 0.007^b
6	1.903 ± 0.009^a	0.401 ± 0.005^a	3.004 ± 0.01^a	1.503 ± 0.00^a	0.469 ± 0.007^a	−0.261 ± 0.005^c

The stability time of low-gluten flour dough is related to the strength of mixed flour gluten. A long stability time indicates that the flour has strong gluten and good kneading resistance. A short stabilization time indicates that the dough strength is weak and the stirring resistance is low (Schmiele et al., 2012). The formation time of the dough reflects the rate at which the gluten protein network is formed. It can be seen from Table 2 that compared with the control group, the stability time of the dough after adding blueberry wine residues decreased, and with increasing addition of the residues, the stabilization time gradually decreased. There was a significant difference in the stability time of the various groups after adding blueberry wine residues (p < .05). With the addition of 4% and 6% blueberry wine residues, the stability time of the dough was significantly different from that of the control group (p < .05). The formation time of the mixed flour dough first decreased and then increased with increasing addition of blueberry wine residues; the formation time of the dough was the shortest (1.25 min) with 2% addition, and the formation time of dough was the longest (4.16 min) with 6% addition. There were significant differences in the formation time of the various groups of dough (p < .05). This indicates that the addition of blueberry wine residues may make the gluten network structure collapse. When blueberry wine residue is added, the mixing-resistance of the mixed flour dough decreases. In summary, when 2% blueberry wine residue was added to the dough, the formation time was shorter and the stabilization time was longer. With the addition of blueberry wine residues, the stabilization time of the dough decreased and the formation time increased. Kang et al. (2019) proposed that this phenomenon may be due to differences in the composition of the protein in the two powders in the raw materials; thus, the gluten protein in the mixed powder will be diluted and the continuity of the dough will be compromised.

The degree of protein weakening (C1–C2) indicates the degree of weakening of the protein network under mechanical force and heat, and characterizes the rate of destruction of the dough during the kneading process, which is inversely proportional to the kneading resistance of the dough. As can be seen from Table 2, when the amount of blueberry wine residue was increased, the degree of protein weakening increased significantly, where the value was inversely proportional to the dough stabilization time. This is similar to the results reported by Shi et al. (2021), which may be because the addition of blueberry wine residue dilutes the concentration of gluten protein in the wheat flour, and the degree of weakening of the mixed powder protein increases with increasing addition of blueberry wine residue; the difference between the groups was significant (p < .05). The α value represents the rate of protein weakening. As shown in Table 2, the rate of protein weakening decreased slightly after the addition of blueberry wine residues, but there was no significant difference between the groups.

4.2.2. Thermomechanical properties of dough starch

The C3 value represents the peak viscosity, which is the maximum torque produced by the mixed flour dough during the heating phase. As can be seen from Table 3, the peak viscosity (C3) increased with increasing addition of blueberry wine residue (p < .05). C3 − C4 is the viscosity disintegration value. The viscosity disintegration value represents the thermal stability and degree of breakage of starch in the mixed flour dough. The greater the viscosity disintegration value, the greater the degree of starch damage, the worse the gelatinization stability of the dough, and the weaker the shear resistance (S. J. Zhang et al., 2020). The viscosity disintegration value (C3 − C4) increased with increasing addition of blueberry wine residue; the difference was significant (p < .05), which indicates that with increasing addition of blueberry wine residue, the proportion of dietary fibre in the mixed powder increases, the damage caused by the starch particles and dietary fibre is also deepened, and the shear resistance of the starch particles in the mixed powder decreases (H. N. Wang et al., 2019).

Table 3. Effect of adding amount of blueberry wine residues powder on the thermomechanical properties of starch.

Add amount/%	Water absorption/%	Stabilization time /min	Time of formation/min	Protein weakening(C1-C2)/Nm	α /(Nm·min^−1)
0 (Control)	42.12 ± 0.14^d	6.0 ± 0.49^a	2.38 ± 0.13^c	0.610 ± 0.00^d	−0.063 ± 0.00^a
2	43.49 ± 0.03^c	5.5 ± 0.25^a	1.25 ± 0.07^d	0.712 ± 0.01^c	−0.061 ± 0.02^a
4	44.61 ± 0.05^b	4.4 ± 0.06^b	3.60 ± 0.23^b	0.772 ± 0.01^b	−0.060 ± 0.02^a
6	45.10 ± 0.16^a	4.3 ± 0.12^b	4.16 ± 0.08^a	0.808 ± 0.01^a	−0.061 ± 0.02^a

The recovery value (C5 − C4) refers to the difference between the terminal viscosity (C5) and the retention viscosity (C4) at the end of cooling to 50°C, reflecting the nature of starch aging and regeneration. The higher the recovery value, the easier it is for the starch to age. As shown in Table 3, the recovery value first decreased and then increased with increasing addition of blueberry wine residue. With 2% addition, the recovery value of the dough was the lowest, and there was a significant difference compared to the other addition groups. The recovery value of the dough at this time was 0.46 Nm lower than that of the no addition group. This indicates that with the addition of 2% blueberry wine residue, the anti-aging performance of starch was improved compared with that of the other addition groups. Han and Koh (2011) proposed that dietary fibre not only affects starch particles, but is also able to interact with starch molecules.

β is the slope of the curve of C2 and C3, indicating the starch gelatinization rate. γ is the slope of the curve of C3 and C4, which reflects the rate of starch degradation by amylase (Liang et al., 2019). As shown in Table 3, after the addition of blueberry wine residue, the hydrolysis rate of starch by amylase in the mixed flour dough increased, and the starch gelatinization rate of the mixed flour dough increased. This phenomenon may be due to the mass fraction of broken starch of blueberry residues increases, and the enzymatic hydrolysis rate increases, and this is similar to Cui’s findings (2021).

4.3. Effect of blueberry wine residue on textural characteristics of dough

As shown in Table 4, with increasing addition of blueberry wine residue, the hardness of the mixed flour dough increased significantly, which is similar to the results reported by Yin et al. (2020). The hardness of the mixed flour dough increased because there is more dietary fibre in the blueberry wine residue. Thus, when blueberry wine residue is added to flour, it will be filled into the gluten network structure, thereby hindering the formation of the gluten network, reducing the gluten and fluffiness of the dough. Due to filling by the blueberry wine residue, the number of pores in the mixed flour dough is reduced, thereby increasing the hardness and recovery of the dough (Huang et al., 2021). In addition, the polyphenols in the blueberry wine residue can form complexes with gluten proteins, thereby increasing the hardness of the dough (L. J. Wang et al., 2021).

Table 4. Effect of adding blueberry wine residues powder on the texture properties of dough.

Add amount/%	Hardness/g	Adhesiveness	Cohesiveness	Chewiness/g	Resilience	Springiness/mm
0 (Control)	1296 ± 62^c	684 ± 63^a	0.58 ± 0.02^b	661 ± 47^b	0.04 ± 0.002^d	0.96 ± 0.005^a
2	1066 ± 49^d	571 ± 67 ^a	0.68 ± 0.01^a	656 ± 40^b	0.04 ± 0.001^c	0.94 ± 0.009^a
4	1413 ± 13^b	585 ± 93 ^a	0.49 ± 0.05^c	751 ± 40^a	0.05 ± 0.002^b	0.95 ± 0.010^a
6	1712 ± 17^a	702 ± 86 ^a	0.40 ± 0.06^d	535 ± 35^c	0.06 ± 0.001^a	0.60 ± 0.040^b

Chewiness: The energy required to chew a solid sample into a steady state when swallowed.

Resilience: The ratio of the elastic energy released by the sample upon return during the first compression process to the energy dissipation of the probe during compression.

The viscosity of the dough first decreased and then increased with increasing addition of blueberry wine residue, but the difference was not significant. Compared with the control group, the cohesion decreased as the amount of additive increased, and the difference was significant (p < .05). The decreased cohesion may be due to more facile destruction of the internal structure of the mixed dough with the addition of blueberry wine residue. The chewiness initially increased and then decreased, and was significantly different compared to that of the control group (p < .05). The recoverability increased with increasing addition of blueberry wine residue; the difference was significant (p < .05). The resilience decreased with the addition of 6% blueberry wine residue; the elasticity of the mixed flour dough was significantly different from that of the control group (p < .05), because the blueberry wine residue dilutes the gluten structure, which decreases the elasticity.

4.4. Effect of proportion of blueberry wine residue on colour difference of dough

The effect of different amounts of blueberry wine residues on the colour difference of mixed flour dough is shown in Table 5. The L* value represents the brightness; the larger the L* value, the brighter the dough colour (Y. Q. Zhang et al., 2016). The L* value of the mixed flour dough gradually decreased with an increase of the amount of wine residue added, where the amount of blueberry wine residue had a significant effect on the L*value of the mixed flour dough (p < .05). The L* value of the dough with 0, 2, and 4% blueberry wine residue was 81.75, 57.07, and 46.70, respectively. After adding blueberry wine residues, the dough colour and brightness decreased. The a* value is related to the green – red and the b* value is relative to the blue-yellow. Compared to the dough without blueberry wine residue, the a* value of the mixed flour dough increased significantly (p < .05), whereas the b* value declined significantly, which indicates that with increasing addition of blueberry wine residue, the brightness of the mixed flour dough gradually decreased, the colour became darker, the red deepened, the yellow became lighter, and the colour of the mixed flour dough was darkest with the addition of 6% blueberry wine residue. This may be due to the fact that blueberry wine residues are rich in anthocyanins (Lin et al., 2020; N. W. Zhang et al., 2020), which makes the dough reddish and darker.

Table 5. Effect of adding blueberry dregs powder on the color parameters of mixed dough.

Add amount/%	L*	a*	b*	ΔE
0 (Control)	81.75 ± 0.06^a	1.93 ± 0.05^d	14.82 ± 0.22^a	83.11 ± 0.09^a
2	57.07 ± 0.56^b	5.83 ± 0.12^c	6.53 ± 0.32^b	57.74 ± 0.51^b
4	46.70 ± 0.15c	9.02 ± 0.18^b	6.25 ± 0.10^bc	47.97 ± 0.10^c
6	41.34 ± 0.25^d	12.17 ± 0.20^a	6.00 ± 0.06^c	43.51 ± 0.20^d

5. Conclusion

The effects of blueberry wine residues on the thermomechanical, pasting, and textural properties, as well as the colour difference, of low-gluten flour dough were studied. The addition of blueberry wine residue affected the thermo-mechanical properties, pasting properties, textural properties, and colour difference of low-gluten flour dough. With increasing addition of blueberry wine residues, the water absorption, formation time, retrogradation value, hardness, and chewiness of the dough gradually increased. The stability time, final viscosity, retrogradation value, and cohesion of the dough gradually increased, but may gradually decrease during mastication, etc. With the addition of 6% blueberry wine residue, the water absorption, starch gelatinization rate, and hardness of the mixed flour dough were the highest, and the colour of the mixed flour dough was redder and darker. With the addition of 4% blueberry wine residue, the formation time, pasting temperature, disintegration value, retrogradation value, textural properties, and colour of the low-gluten flour dough were relatively good. This study provides a theoretical reference for the application of blueberry wine residue in flour products for adding value.

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Funding

This work was supported by the Natural Science Foundation of Chongqing Science and Technology Commission [grant number: cstc2019 jcyj-msxmX0785], and Scientific and Technological Research Program of Chongqing Municipal Education Commission [grant number: KJQN201901325; KJQN202101309].