Effects of potato starch on the properties of wheat dough and the quality of fresh noodles

ABSTRACT

The effects of potato starch on the pasting, rheological, and thermal properties of the dough, and the quality of the noodles were analyzed. The results showed that the addition of potato starch increased the pasting properties parameters of the dough, and increased the adhesiveness and hardness of the noodles; reduced the elastic and viscous modulus of the dough, and increased the springiness of the noodles; increased the freezable water content of the dough, decreased the semi-bound water content, and increased the water absorption of the noodles. The gluten network structure of the dough was destroyed, and the cooking loss and breaking rake of the noodles increased. The color and smoothness of the noodles were improved, the taste was worse. The quality of the noodles was acceptable when no more than 20% potato starch was added.

RESUMEN

En el presente estudio se analizaron los efectos del almidón de papa en las propiedades reológicas, térmicas y de pegado de la masa de fideos, así como en la calidad de los mismos. Los resultados permitieron constatar que la adición de almidón de papa aumentó el valor de los parámetros de las propiedades de pegado de la masa e incrementó la adhesividad y la dureza de los fideos; asimismo, redujo el módulo elástico y viscoso de la masa y elevó la elasticidad de los fideos; además, aumentó el contenido de agua congelable de la masa, disminuyó el contenido de agua semiligada e incrementó la absorción de agua de los fideos. Por otra parte, se destruyó la estructura de la red de gluten de la masa, aumentando la pérdida de cocción y la tasa de rotura de los fideos. Aunque el color y la suavidad de estos mejoraron, el sabor resultó ser menos agradable. En suma, para que la calidad de los fideos sea aceptable no debe añadirse más de 20% de almidón de papa

KEYWORDS:

• Potato starch
• dough
• noodles
• pasting properties
• rheological properties
• thermal properties

PALABRAS CLAVE:

• almidón de papa
• masa
• fideospropiedades de pegado
• propiedades reológicas
• propiedades térmicas

1. Introduction

Noodles are a common traditional food in many countries worldwide. The simple manufacturing process, diversity of types, different tastes, high nutritional value, and convenience of noodles causes them to be favored by people in diverse countries (Zhang & Ma, 2016). Studies of noodles have mainly focused on the effects of the wheat and flour (Kaur et al., 2015; X. L. Cao et al., 2017; Ma et al., 2018), auxiliary materials (Lambrecht et al., 2017), additives (Li, Li, et al., 2017; Pan et al., 2018), and processing methods (Liu et al., 2017) on the noodle quality. With the improvement of living standards and dietary understanding, consumers are gradually favoring certain nutritious noodles and coarse grain noodles, such as buckwheat noodles, oat noodles, tomato noodles, and carrot noodles.

Potatoes are the fourth most produced food crop after wheat, rice, and corn, and a major food crop in Europe and America, and the top vegetable crop in China. Potatoes contain starch, protein, vitamins, trace elements, and other essential nutrients for humans. Potatoes possess good processing properties and taste, and are widely used in the food industry(Tsang et al., 2018). Potatoes can be used as consumer goods or as raw materials to produce other products, including snacks, potato powder, and potato starch. Potato starch is the main component of potato dry matter and the main storage form of the internal energy of potato. Potato starch includes amylopectin and amylose, with amylopectin accounting for about 80% of the total starch. Compared with other cereal starches, potato starch has large granules, high viscosity and water absorption, and good gelatinization characteristics (Ezekiel et al., 2013). Potato starch has a mild taste with none of the typical cereal flavors. Potato can regulate blood glucose content and control chronic diseases such as diabetes (Lee et al., 2018). Potato starch is mainly used as a thickener, emulsifier, filler, adhesive, or other auxiliary raw materials in the food industry (Altemimi, 2018; Li, Zhao, et al. 2017; Saeedyzadeh et al., 2018).

It is expected that more than half of the potatoes produced in China will be consumed as a staple food by 2020 in China. China is at the forefront of world potato production, the proportion of processed potato is low, and potatoes are mainly used as snacks (Yang et al., 2017). Noodles made from potato starch and wheat flour would not only complement the national strategy of using potatoes as a staple food, but could also improve the diet of the population and promote the healthy, green, and sustainable development of the potato industry (Xu et al., 2017). In the research of potato starch as a staple food, Nemar et al. (2015) studied the effect of potato starch on bread quality and found that bread with 80% potato starch had better overall quality. Sandhu et al. (2010) studied the relationship between the gelatinization characteristics of potato starch and the quality of noodles, the results showed that potato starch increased the cooking loss of noodles, but made noodles more transparent and smooth. Y. F. Cao et al. (2019) found that wheat flour substituted with potato pulp can be used in the energy-efficient and cost-effective production of steamed bread with improved nutritional value. At present, there is little research on potato starch as a staple food at home or abroad, and there are still many problems to be solved in this area. This study focuses on the effects of potato starch on the properties of dough and quality of noodles. The mechanism by which potato starch affects the quality of noodles is analyzed by exploring the relationship between the dough properties and noodle quality. The optimal amount of potato starch for addition to noodles to maximize the quality is determined. This research can provide a theoretical reference for the production of nutritionally potato starch noodles and also provides a practical basis for the use of potato as a staple food.

2. Materials and methods

2.1. Materials

Xiangxue high-gluten flour was purchased from Cofco Flour Marketing Management (Beijing) Co., Ltd. Xuehua potato starch was purchased from Inner Mongolia Fuguang Food Co., Ltd.

2.2. Dough and noodle preparation

2.2.1. Dough preparation

High-gluten flour weighed on an electronic scale was mixed with potato starch in different ratios to make 300 g of blended flour with a potato starch content of 0%, 5%, 10%, 15%, 20%, 25%, or 30%. An amount of water equivalent to 40% of the mass of the blended flour mass was added, and the blended flour and water were fully mixed. A dough mixer (HM502, Guangdong, China) was used for mixing at 60 rpm for 1 min, 90 rpm for 1 min, and 120 rpm for 8 min to form a uniformly mixed dough. The dough was placed in a sealed bag for 30 minutes.

2.2.2. Noodle preparation

The dough was first rolled into a sheet by using a noodle machine (WA-BYM-15SFT, Wuxi, China) in first gear, after which the dough sheet was folded and rolled again once. This operation was repeated with the noodle machine in the second, third, fourth, and fifth gears to obtain a dough sheet that was approximately 1.5 mm thick. Finally, the dough sheet was cut into raw noodles that were approximately 5 mm wide and 200 mm long.

Water (500 mL) in a pot was heated to boiling with an electromagnetic cooker. Fifteen noodles were placed in the boiling water and cooked until the white core of the noodles disappeared.

2.3. Evaluation of dough properties

2.3.1. Pasting properties of dough

A precise electronic balance was used to weigh out 3 g of the blended flour dough with different potato starch contents. The samples were added to a sample bottle containing 25 mL of water, and a rapid viscosity analyzer (TecMaster, Rochester, USA) was used to measure the pasting properties. Table 1 shows the standard GB/T 24853–2010 test procedure for measuring pasting properties. The experiments were performed in triplicate. The pasting properties include the peak viscosity, trough viscosity, final viscosity, setback value, breakdown value, peak time, and pasting temperature.

Table 1. Pasting test procedure.

Tabla 1. Procedimiento de prueba de pegado.

Time (minutes: seconds)	Value Type	Value
00:00	Temperature	50 °C
00:00	Rotation speed	960 r/min
00:10	Rotation speed	160 r/min
1:00	Temperature	50 °C
4:42	Temperature	95 °C
7:12	Temperature	95 °C
11:00	Temperature	50 °C
13:00	End

2.3.2. Rheological properties of dough

A rotary rheometer (HAAKE MARS III, Massachusetts, USA) was used for evaluation of the rheological properties. A suitable amount of dough was placed on a test plate with a diameter of 20 mm, and the plate spacing was adjusted to 2 mm. Excess dough was scraped off and the dough was left to stand for 5 minutes to release excess stress. A frequency scan was then carried out on the dough in the elasticity range to measure changes in the elastic modulus, G’, viscous modulus, G’’, and loss tangent, tan δ, with the frequency of vibration of the dough. The experiments were performed in triplicate. The test conditions were: temperature: 25°C; strain: 0.1%; frequency range: 0.1–40 Hz.

SPSS 22.0 software was used for non-linear regression of the data, and a fitted curve was constructed based on the power law model. The equations of the curve are as follows:

(1)

(2)

In the equations, G’ is the elastic modulus (Pa), G’’ is the viscous modulus (Pa), K’ and K’’ are consistency indices (Pa.sⁿ), f is the frequency (Hz), and n’ and n’’ are superindices.

2.3.3. Thermal properties of dough

Differential scanning calorimetry (DSC, Q20, New Castle, USA) was used to evaluate the thermal properties of the dough. A precise electronic balance was used to weigh out 5‒10 mg of dough. The samples were placed in aluminum trays, which were sealed prior to placement on the DSC measuring rack. Sealed empty aluminum trays were used as a control, and the enthalpy and the endothermic peak temperature of the dough during crystallization were measured. The experiments were performed in triplicate. For the test, the temperature was decreased from 25°C to – 40°C at 5°C/min, maintained for 5 minutes, then ramped to 30°C at 5°C/min.

A water activity meter (AquaLab 4TE, Pullman, USA) was used to measure the changes in the free water in the dough in three replicate measurements. The test temperature was set at 25°C.

2.3.4. Microstructure of dough

A drying oven (SD-06, North Yorkshire, UK) was used to sufficiently dry the 5-mm-wide and 10-mm-long raw noodles. Gold was sprayed on the surface of the test samples, and a conducting adhesive was used to attach the sample to the test platform on the scanning electron microscope (Phenom XL, Eindhoven, Netherlands) for observation of the microstructure. The experiments were performed in triplicate. The magnification of the scanning electron microscope was set to ×1000, and the acceleration voltage was set to 10 kV.

2.4. Noodles quality

2.4.1. Textural properties of noodles

The texture profile analysis testing mode of the texture analyzer (TMS-Pilot type, Washington, DC, USA) was used to measure the textural properties of the cooked noodles. The cooked noodles were rinsed slowly with pure water for 10 s and drained. Three noodles were placed on the platform of the texture analyzer, and their textural properties were measured. The textural properties include the hardness, springiness, adhesiveness, and cohesiveness. The testing parameters were set as follows: the range of the force sensor was 100 N, the deformation percentage was 50%, the testing speed was 2 mm/s, and the initial force was 0.2 N. The experiments were performed in triplicate.

2.4.2. Cooking properties of noodles

Fifteen raw noodles that had been weighed (A₁) were cooked in a pot. The number of broken cooked noodles (n) was counted to calculate the breaking rate according to Equation (3)(3) . The cooked noodles were rinsed slowly in pure water for 10 s, and the rinsing water was poured into a pot and heated until the water had almost completely evaporated. The pot was placed in a drying cabinet (DHG-9030A type, Shanghai, China) until its weight no longer changed. The dried materials were weighed (A₂) to calculate the cooking loss according to Equation (4)(4) . The rinsed noodles were left to stand for 2 min and then weighed (A₃) to calculate the water absorption according to Equation (5)(5) . The experiments were performed in triplicate.

(3)

(4)

(5)

2.4.3. Sensory evaluation of noodles

Sensory evaluation of the noodles was performed based on the Chinese standard of wheat flour for LS/T3202-1993 noodles (as indicated in Table 2) by considering the samples’ characteristics. Five trained people performed the evaluation.

Table 2. Standard of sensory evaluation.

Tabla 2. Estándar de evaluación sensorial.

Item		Full Core	Standard of Evaluation
Appearance	Color	10	White (8–10); Milk white, milk yellow (6–8); Yellow, gray and other colors (1–6)
	Luster	10	Bright (8–10); General (6–8); Dim (1–6)
Taste	Smoothness	10	Smooth (8–10); General (6–8); Not smooth (1–6)
	Adhesiveness	20	Tasty, not sticky teeth (15–20); General (10–15); Sticky teeth (1–10)
	Toughness	20	Chewy (15–20); General (10–15); Mushy (1–10)
	Hardness	20	Hard (15–20); General (10–15); Soft (1–10)
	Smell	10	Scent of wheat (8–10); General (6–8); No scent of wheat (1–6)

2.5. Data analysis

SPSS 22.0 software was used to analyze the data. The mean values and standard deviations of the data were calculated, and different letters at the top right of the data are used herein to indicate significant differences (P < .05) between the mean values based on analysis with the software.

3. Results and analysis

3.1. Effects of potato starch on dough properties

3.1.1. Pasting properties of dough

Table 3 shows that the peak viscosity, trough viscosity, final viscosity, breakdown value, and setback value of the dough increased as the amount of added potato starch increased.

Table 3. Pasting properties of dough.

Tabla 3. Propiedades de pegado de la pasta.

Amount of added potato starch	Peak viscosity (cP)	Peak time (min)	Trough viscosity (cP)	Final viscosity (cP)	Breakdown valve (cP)	Setback value (cP)
0%	1607.0 ± 3.6^e	6.13 ± 0.01^a	1151.0 ± 8.6^f	2246.3 ± 3.1^g	455.6 ± 8.9^b	1095.0 ± 10.4^e
5%	1729.3 ± 31.5^e	6.10 ± 0.08^a	1260.6 ± 13.3^e	2427.3 ± 51.5^f	468.6 ± 18.7^b	1166.6 ± 38.8^d
10%	1856.3 ± 36.4^d	6.15 ± 0.04^a	1383.3 ± 26.6^d	2628.3 ± 31.3^e	473.0 ± 11.5^b	1245.0 ± 5.0^c
15%	1974.0 ± 118.4^cd	6.15 ± 0.08^a	1511.6 ± 103.3^c	2811.6 ± 141.0^d	478.3 ± 15.1^b	1300.0 ± 37.7^bc
20%	2076.3 ± 11.2^c	6.15 ± 0.04^a	1616.0 ± 8.8^c	2974.0± 21.1^c	484.4 ± 5.5^b	1358.0 ± 14.9^b
25%	2205.6 ± 35.1^b	6.06 ± 0.13^a	1740.3 ± 27.0^b	3170.6 ± 52.8^b	492.1 ± 10.5^b	1430.3 ± 34.5^a
30%	2382.6 ± 130.2^a	6.04 ± 0.10^a	1883.3 ± 114.8^a	3362.6 ± 55.7^a	499.3 ± 16.2^a	1479.3 ± 63.3^a

Different alphabets at the top right of numbers in the same column means that differences are significant (P < 0.05). Values are the means of three replicates (means ± standard deviation)

Las distintas letras en la parte superior derecha de los números en la misma columna significan que las diferencias son significativas (P < 0.05). Los valores corresponden a la media de tres réplicas (media ± desviación estándar).

The pasting properties of dough are related to the content of starch and amylose, and the swelling power of starch (Singh et al., 2004). The content of starch increased and the content of gluten protein decreased with the addition of potato starch, thus, the gluten network structure was affected, where the gluten network structure could not fully surround the starch. Potato starch has high swelling power. Therefore, the degree of starch water absorption and gelatinization of the starch increased (Sandhu et al., 2010). The content of amylose in potato starch is higher than that in wheat starch, and the peak viscosity, trough viscosity, and breakdown value are positively correlated with the amylose content (Fu et al., 2016). In addition, the phosphorus in potato starch also affects some pasting parameters such as the peck viscosity (Krystyjan et al., 2016). Thus, the addition of potato starch increased the pasting property parameters, such as the peak viscosity and trough viscosity. Amylose in potato starch readily recombines by hydrogen bonding during cooling, and potato starch has a stronger gelling ability than that of wheat flour, thus the dough setback value increased with the addition of potato starch (Lockwood et al., 2008).

3.1.2. Rheological properties of dough

Figure 1 shows that the elastic modulus, G’, and viscous modulus, G’’, of the dough decreased and the loss factor, tan δ, increased as the amount of added potato starch increased. The test results showed that addition of potato starch affected the viscoelasticity of the dough, which was dominated by the elasticity. The rheological properties of dough depend on the content of gluten and starch, and the granular structure of the starch (J. Li et al., 2014). The addition of the potato starch decreased the overall gluten content. In addition, due to competition of the potato starch and gluten for water, not all of the gluten molecules could absorb enough water to form the gluten network structure. This weakened the dough structure and affected the elasticity and fluidity, leading to an increase in the viscous modulus and elastic modulus (X. L. Cao et al., 2017). The decreasing tendency of G’ and G’’ for the dough with potato starch is consistent with previous research. However, the tendency of tan δ was not consistent with Cao’s results. This difference may be attributed to the complex effects of the non-starch components in potato pulp, such as protein, lipid, and fiber, on the viscoelasticity of the dough.

Figure 1. Rheological properties of dough. (a) G’, (b) G’’, (c) Tan δ.

Figura 1. Propiedades reológicas de la masa. (a) G’, (b) G’’, (c) Tan δ.

The parameters from the fitted curve (Table 4) show that the determination coefficients, R², of the fitted curves were all greater than 0.9, indicating that the curve fitting is good. The differences between n’ and n’’ were not large, indicating that the sensitivity of the dough to frequency changes was closer after the addition of potato starch.

Table 4. Fitted curve parameters for rheological properties of dough.

Tabla 4. Parámetros de la curva ajustada para las propiedades reológicas de la masa.

Amount of added potato starch	K’ (Pa.s^n)	n’	R^2	K’’ (Pa.s^n)	n’’	R^2
0%	14809	0.194	0.942	5235	0.153	0.948
5%	13901	0.203	0.957	4958	0.161	0.959
10%	12472	0.225	0.966	4646	0.175	0.951
15%	11704	0.228	0.979	4515	0.178	0.952
20%	11100	0.214	0.978	4273	0.187	0.949
25%	9935	0.234	0.983	4030	0.195	0.948
30%	9198	0.223	0.984	3771	0.203	0.936

3.1.3. Thermal properties of dough

Table 5 shows that the enthalpy increased and the amount of total freezable water in the dough increased as the amount of potato starch increased. A shift of the endothermic peak to higher temperature indicates a decrease in the proportion of semi-bound water in the freezable water, a higher water activity indicates more free water content in the dough (Liu et al., 2015). Compared to wheat starch, the molecular chains in potato starch have a lower polymerization degree and undergo stronger water absorption and greater expansion (Atrous et al., 2017). The addition of potato starch reduced the amount of gluten protein, and the ability of starch to bind water is weaker than that of gluten, thus, more water was present in the dough in the form of free water. Therefore, the addition of potato starch increased the total freezable water and free water, but decreased the semi-bound water.

Table 5. Thermal properties and water activity of dough.

Tabla 5. Propiedades térmicas y actividad del agua de la masa.

Amount of added potato starch	Enthalpy (J/g)	Peak temperature (^oC)	Water activity
0	32.37 ± 1.36^e	−3.26 ± 0.10^a	0.9762 ± 0.0006^e
5%	33.43 ± 1.32^de	−3.03 ± 0.11^b	0.9770 ± 0.0004^de
10%	34.67 ± 1.89^d	−2.76 ± 0.14^c	0.9777 ± 0.0006^cd
15%	36.38 ± 1.53^c	−2.50 ± 0.07^d	0.9781 ± 0.0003^c
20%	37.15 ± 1.34^bc	−2.27 ± 0.16^e	0.9789 ± 0.0005^b
25%	38.34 ± 1.66^ab	−1.96 ± 0.13^f	0.9797 ± 0.0004^ab
30%	39.08 ± 1.47^a	−1.63 ± 0.09^g	0.9800 ± 0.0010^a

Different alphabets at the top right of numbers in the same column means that differences are significant (P < 0.05). Values are the means of three replicates (means ± standard deviation)

Las distintas letras en la parte superior derecha de los números en la misma columna significan que las diferencias son significativas (P < 0.05). Los valores corresponden a la media de tres réplicas (media ± desviación estándar).

3.1.4. Microstructure of dough

Figure 2 shows that most of the wheat and potato starch in the dough is surrounded by a gluten network, but some of the starch is exposed outside of the gluten network. As the amount of added potato starch increased, the gluten network was disrupted and more gaps appeared, causing the structure to become loose. When the amount of added potato starch exceeded 25%, destruction of the gluten network was severe, more gaps appeared and the integrity of the gluten was obviously worse. On one hand, addition of potato starch decreased the gluten content, whereas on the other hand, the water absorption of the potato starch prevents gluten from absorbing water to form the gluten network. Therefore, the gluten network structure in the dough was destroyed and became loose.

Figure 2. Microstructure of dough. (a) 0% potato starch, (b) 5% potato starch, (c) 10% potato starch, (d) 15% potato starch, (e) 20% potato starch, (f) 25% potato starch, (g) 30% potato starch.

Figura 2. Microestructura de la masa. (a) 0% de almidón de papa, b) 5% de almidón de papa, c) 10% de almidón de papa,(d) 15% de almidón de papa, (e) 20% de almidón de papa, (f) 25% de almidón de papa, (g) 30% de almidón de papa.

3.2. Effects of potato starch on noodle quality

3.2.1. Textural properties of noodles

Table 6 shows that with an increasing incorporation of potato starch, the hardness of the noodles first increased and then decreased. Potato starch can form a starch–protein network structure with gluten, and some starch can fill in the gluten network structure, which is conducive for improving the hardness of the noodles. In addition, gelatinization of the starch can improve the hardness (Sandhu et al., 2010). However, the addition of potato starch dilutes the gluten content and reduces the noodle hardness. Therefore, starch addition has two effects on the hardness of the noodles. From the experimental results, when the amount of added potato starch is less than 20%, the structural improvement outweighs the deterioration effect, but when the amount added is more than 20%, structural deterioration dominates structural improvement.

Table 6. Textural properties of noodles.

Tabla 6. Propiedades de textura de los fideos.

Amount of added potato starch	Hardness (N)	Springiness (mm)	Adhesiveness (M.mm)	Cohesiveness (N)
0	1.46 ± 0.02^f	0.52 ± 0.03^d	0.058 ± 0.004^d	0.51 ± 0.03^a
5%	1.69 ± 0.06^e	0.55 ± 0.04^cd	0.061 ± 0.007^cd	0.49 ± 0.04^a
10%	2.04 ± 0.08^d	0.56 ± 0.03^cd	0.071 ± 0.006^c	0.47 ± 0.03^ab
15%	2.31 ± 0.11^c	0.58 ± 0.03^bcd	0.084 ± 0.006^b	0.46 ± 0.02^ab
20%	2.59 ± 0.14^a	0.61 ± 0.04^abc	0.089 ± 0.005^b	0.42 ± 0.03^bc
25%	2.50 ± 0.08^ab	0.63 ± 0.04^ab	0.094 ± 0.004^ab	0.39 ± 0.03^c
30%	2.42 ± 0.10^bc	0.64 ± 0.03^a	0.100 ± 0.007^a	0.37 ± 0.02^c

Different alphabets at the top right of numbers in the same column means that differences are significant (P < 0.05). Values are the means of three replicates (means ± standard deviation)

Las distintas letras en la parte superior derecha de los números en la misma columna significan que las diferencias son significativas (P < 0.05). Los valores corresponden a la media de tres réplicas (media ± desviación estándar).

From the analysis of the rheological properties, addition of potato starch decreased the elastic modulus, G’, of the dough, which caused the springiness of the noodles to increase. From the analysis of the pasting properties of the dough, the addition of potato starch increased the viscosity parameters and surface adhesion. Thus, the adhesiveness of the noodles increased as the amount of potato starch increased.

Cohesiveness is related to internal binding forces in the noodles, especially gluten (Nawaz et al., 2019). The microstructure of the dough showed that as the amount of added potato starch increased, the gluten network was disrupted and more gaps appeared, causing the structure to become loose. The binding forces in the starch–protein network structure were slightly weaker than those of the protein network structure. Thus, the cohesiveness of the noodles decreased slightly after addition of potato starch.

3.2.2. Cooking properties of noodles

Table 7 shows that the water absorption, breaking rate, and cooking loss of the noodles increased remarkably as the amount of added potato starch increased. From the evaluation of the thermal properties, the addition of potato starch increased the water absorption capacity of the dough and increased the water absorption in the noodles. The addition of potato starch increased the starch and free-state starch content and decreased the cohesiveness of the noodles, therefore, the microstructure of the noodles was destroyed and become loose, which caused more starch to be released into the cooking liquid, and increased the cooking loss and breaking rate (Kawaljit & Maninder, 2010).

Table 7. Cooking properties of noodles.

Tabla 7. Propiedades de cocción de los fideos.

Amount of added potato starch	Water absorption (%)	Cooking loss (%)	Breaking rate (%)
0	92.1 ± 3.9^f	3.78 ± 0.38^f	0 ±0.00^f
5%	104.9 ± 4.7^e	4.46 ± 0.28^e	4.45 ± 1.85^ef
10%	110.2 ± 4.9^de	5.47 ± 0.31^d	6.67 ± 0.00^de
15%	115.3 ± 2.7^cd	5.94 ± 0.21^d	11.09 ± 3.82^cd
20%	119.7 ± 3.7^bc	6.42 ± 0.27 ^c	13.30 ± 0.00^bc
25%	125.4 ± 3.4^ab	7.25 ± 0.25^b	17.77 ± 3.86^ab
30%	129.6 ± 2.9^a	7.94 ± 0.11^a	22.20 ± 3.81^a

Different alphabets at the top right of numbers in the same column means that differences are significant (P < 0.05). Values are the means of three replicates (means ± standard deviation)

Las distintas letras en la parte superior derecha de los números en la misma columna significan que las diferencias son significativas (P < 0.05). Los valores corresponden a la media de tres réplicas (media ± desviación estándar).

3.2.3. Sensory evaluation of noodles

The results of the sensory evaluation are summarized in Table 8. The color and luster, as well as the smoothness in taste, of the noodles improved as the amount of added potato starch increased. Potato starch is white, its brightness and whiteness are higher than those of wheat starch. Therefore, addition of potato starch enhanced the color and luster of the noodles (Nemar et al., 2015). The score for viscosity in taste decreased because the potato starch increased the adhesiveness of the noodles and compromised their taste. The toughness and hardness first increased and then decreased, this result is consistent with the texture test results. The score for smell decreased as the amount of added potato starch increased because potato starch does not have an obvious potato flavor, the original wheat flavor of the noodles was reduced after adding potato starch. The results showed that the overall quality of the noodles was acceptable when the amount of added potato starch was less than 20%.

Table 8. Sensory evaluation of noodles.

Tabla 8. Evaluación sensorial de los fideos.

Amount of added potato starch	Color	Luster	Smoothness	Viscosity	Toughness	Hardness	Smell	Total Score
0	9.5	9.1	9.4	16.8	16.9	16.0	2.0	79.7 ± 1.3^ab
5%	9.5	9.1	9.4	16.3	16.5	17.3	1.9	80.0 ± 1.6^ab
10%	9.5	9.2	9.6	15.8	16.7	17.7	1.9	80.4 ± 1.7^ab
15%	9.6	9.4	9.7	15.4	17.1	18.1	1.7	81.0 ± 1.9^a
20%	9.6	9.5	9.7	14.9	17.4	18.6	1.6	81.3 ± 1.8^a
25%	9.7	9.5	9.8	13.9	17.3	17.5	1.5	79.2 ± 1.8^bc
30%	9.8	9.6	9.8	13.2	17.1	16.7	1.5	77.7 ± 2.1^c

Different alphabets at the top right of numbers in the same column means that differences are significant (P < 0.05). Values are the means of three replicates (means ± standard deviation)

Las distintas letras en la parte superior derecha de los números en la misma columna significan que las diferencias son significativas (P < 0.05). Los valores corresponden a la media de tres réplicas (media ± desviación estándar).

4. Conclusion

The effects of potato starch on the pasting, rheological, and thermal properties of the dough, and the quality of the noodles were analyzed. The addition of potato starch enhanced the pasting properties parameters of the dough, which caused the adhesiveness and hardness of the noodles to be increased; decreased the elastic modulus and the viscous modulus of the dough, which caused the springiness of the noodles to be increased; increased the freezable water and free water content, but decreased the semi-bound water content of the dough, which caused the water absorption of the noodles to be increased; destroyed the gluten network structure of the dough, which caused the cooking loss and breaking rate of the noodles to be increased. The addition of potato starch improved the noodle quality in terms of color, luster, and smoothness, but compromised the smell. The overall quality of the noodles was acceptable when the level of added potato starch was no more than 20%. The correlation between the dough properties and the noodle quality was not evaluated in depth, this can be addressed in a future study.

Disclosure statement

The authors declare that they do not have any conflicts of interest.

Additional information

Funding

The research was supported by the National Natural Science Foundation of China (NO. 51975006); and the Science and Technology project of Beijing Municipal Education Commission (No. KM201810011003).