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Effect of partially gelatinized corn starch on the rheological properties of wheat dough
LWT - Food Science and Technology 66 (2016) 324e331
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Effect of partially gelatinized corn starch on the rheological properties of wheat dough Zong-qiang Fu a, 1, Li-ming Che b, 1, Dong Li a, **, Li-jun Wang c, *, Benu Adhikari d a College of Engineering, National Energy R & D Center for Non-food Biomass, China Agricultural University, P. O. Box 50, 17 Qinghua Donglu, Beijing 100083, China b College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China c College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing, China d School of Applied Sciences, RMIT University, Melbourne City Campus, VIC 3001, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 June 2015 Received in revised form 18 October 2015 Accepted 20 October 2015 Available online 23 October 2015
Ten, twenty and thirty percent (g/100 g) of wheat flour was substituted with partially gelatinized corn starch or ungelatinized corn starch and the rheological properties of the resultant dough samples were investigated. The apparent viscosity of dough increased with the increase in the concentration and degree of gelatinization of partially gelatinized starch samples except in the case of dough substituted with starch sample with high gelatinization degree (96.78%) at 30 g/100 g concentration. The presence of partially gelatinized starch increased the storage (G0 ) and loss (G00 ) moduli values and decreased the frequency sensitivity of dough samples. The dough prepared from wheat flour alone (control) showed the highest creep compliance and the lowest elastic recovery. In brief, the rheological properties of dough were influenced by the degree of substitution more than by the degree of gelatinization of substitutes. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Rheological properties Viscosity Creep Recovery Partially gelatinized starch
1. Introduction Starch is the main component of wheat flour (about 80 g/100 g) and contributes to the formation of texture and quality of dough (Yang, Song, & Zheng, 2011). In many food applications, functional properties of starch can have important implication on the quality of end-use products (Hung & Morita, 2005). The different amylose/ amylopectine ratio (Lee, Swanson, & Baik, 2001), granule structure (Goesaert et al., 2005) and granule size (Sebe ci c & Sebe ci c, 1996) of starch in wheat flour influences the texture, stability and elasticity of dough and bread. In order to meet some specific requirements dough is commonly mixed with modified starches (Hung & Morita, 2004; Korus, Witczak, Ziobro, & Juszczak, 2009; Miyazaki, Maeda, & Morita, 2008). Pregelatinized starch is a physically modified starch which can reconstitute in cold water directly and provides desirable
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (D. Li), [email protected] (L.-j. Wang). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.lwt.2015.10.052 0023-6438/© 2015 Elsevier Ltd. All rights reserved.
pasting and texturizing characteristics (Miyazaki, Van Hung, Maeda, & Morita, 2006). Due to these advantages, pregelatinized starch is commonly used in dough. Onyango, Mutungi, Unbehend, and Lindhauer (2011) added pregelatinized starch to the glutenfree dough and they found the presence of pregelatinized starch increased the viscosity of the liquid phase and enhanced the network created by the native starch granules. Xue, Sakai, and Fukuoka (2008) used microwave heating to partially gelatinize starch in dough for making noodles. They found that the cooking time of noodles produced by using partially gelatinized dough was reduced significantly compared to the un-gelatinized noodles. From the results of these studies, addition of pregelatinized starch can modify the properties of dough and the quality of the products. However, these studies did not show clearly about a relationship between the addition of partially gelatinized starch and the rheological properties of dough. Pregelatinized starch is a modified starch in which the crystalline zones in the starch granules are partially or completely destroyed. Different degrees of gelatinization in the partially gelatinized starch give rise to a diverse granule structure having different degree of crystallinity (Fu, Wang, Li, & Adhikari, 2012). This difference in degree of crystallinity in partially gelatinized
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starch is expected to influence the performance of dough. However, research on the effects of residual crystallinity and the characteristics of partially gelatinized starch granules on the rheological properties of dough is not reported. In these contexts, the objective of this work was to study the effect of partially gelatinized corn starch on the rheological properties of wheat dough. The rheological tests included steady shear flow, frequency sweep and creep-recovery. This would provide better understanding of the rheological properties of wheat dough containing partially gelatinized starch. 2. Materials and methods 2.1. Materials Wheat flour was obtained from Beijing Guchuan Flour Group Co., Ltd. (Beijing, China). Its protein and moisture contents were 10.8 g/100 g and 7.3 g/100 g, respectively. Commercial gluten powder was obtained from Juancheng Jianfa Flour Co., Ltd. (Shandong, China). Its moisture content was 5.9 g/100 g. Native corn starch having 10.0 g/100 g moisture content was obtained from Hebei Zhangjiakou Yujin Food Co., Ltd. (Hebei, China). Partially gelatinized starch samples were obtained by controlled gelatinization of starch at 64 C (S64), 68 C (S68) and 70 C (S70) as previously reported (Fu et al., 2012). Corn starch suspension at a starch concentration of 10.0 g/100 g was prepared by adding 20.0 g of predried corn starch into deionized water at 24 ± 1 C. Each batch of dispersion was thoroughly stirred at 300 rpm (in beakers) for 15 min using a thermostated water bath maintained at 64 C, 68 C and 70 C. These partially gelatinized starch dispersions were spray dried using a bench-top spray drier (GPW120- II, Shandong Tianli Drying Equipment Inc., China). The inlet temperature, exhaust aspiration level, the flow rate of the air and feed rate used in the spray drying process were set at 200 C, 95%, 0.375 m3/h and 7.2 mL/min, respectively. Partially gelatinized starch was also prepared at 25 C (S25) by stirring corn starch slurry for 15 min at 25 C followed by spray drying. The degree of gelatinization of S25, S64, S68 and S70 samples was determined using a differential scanning calorimeter (DSC-Q10, TA Instruments, New Castle, USA) and was found to be 32.30%, 47.75%, 69.40% and 96.78%, respectively. 2.2. Dough preparation In each formulation, 10, 20 and 30 g/100 g of native and partially gelatinized corn starch containing 10.8 g/100 g of gluten powder was substituted for wheat flour. A fixed amount of water was added to each sample to attain 42 g/100 g moisture content on wet basis. The dough samples were mixed for about 10 min and allowed to stabilize for 20 min in a sealed container before further tests. The dough formulations containing the mixture of native corn starch and gluten powder and only wheat flour (100 g/100 g) were used as control. 2.3. Rheological tests Rheological measurements were performed using AR2000ex rheometer (TA Instruments Ltd., Crawley, UK). The temperature was maintained at 30 C using a water bath connected to a Peltier system. An aluminum parallel plate geometry was chosen to conduct steady shear flow tests (20 mm diameter, 1 mm gap). The frequency sweep tests and creep-recovery tests were conducted using parallel plate geometry having 40 mm diameter and 1 mm gap. A thin layer of silicone oil was applied on the rim of the samples in order to prevent evaporation. The linear viscoelastic region was determined for each sample through strain sweep tests
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at 0.1, 1 and100 Hz, respectively (data not shown). Viscoelastic properties (storage moduli G0 and loss moduli G00 ) of all the samples were determined within the linear viscoelastic region. A stabilization time of 15 min was applied to all the samples before measuring. 2.3.1. Steady shear flow tests The steady shear flow tests were performed over a shear rate range of 0.01e10 s1 to measure the apparent viscosity. The apparent viscosity versus shear rate data were fitted by using the Cross model (Moreira, Chenlo, & Torres, 2011) as given by Eq. (1):
h ¼ h∞ þ
ho h∞
1 þ ðkgÞð1nÞ
(1)
where h (Pa s) is the apparent viscosity, g (s1) is the shear rate, ho and h∞ (Pa s) are the viscosity values at zero and infinite shear rates, respectively. Similar, k (s) is the time constant and n is the flow behavior index. The value of h∞ can be obtained from the experimental results corresponding to the equilibrium viscosity obtained at the end of shearing. In the cases where ho [ h∞ and h [ h∞, it can be assumed that ho e h∞ z ho and hf / 0 the Eq. (1) can be rewritten as Eq. (2) (Ravi & Bhattacharya, 2004).
h¼
ho 1 þ ðkgÞð1nÞ
(2)
2.3.2. Frequency sweep tests The frequency sweep tests were performed over the frequency range of 0.1e100 Hz (angular frequency range of 0.6283e628.3 rad/ s). The strain amplitude for these frequency sweep tests was selected as 0.25% based on the strain sweep results (data not shown) in order to confine these tests within linear viscoelastic region. Experimental G0 and G00 were fitted by using Eq. (3) and Eq. (4), respectively.
log G0 ¼ log a0 þ b0 log u
(3)
log G00 ¼ log a00 þ b00 log u
(4)
where u (rad/s) is the angular frequency and a0 , a00 , b0 and b00 are the fitting parameters. 2.3.3. Creep-recovery tests Creep-recovery tests were carried out using a constant shear stress of 50 Pa. The variation in shear strain as a function of the applied stress was measured for 3 min. The applied stress was then removed and change in strain was recorded for further 5 min. Creep data was described with creep compliance rheological parameters, J(t)C (Pa1) ¼ g/s where g is the strain and s is the constant shear stress during creep test. The creep compliance data of dough samples was fitted to the Burgers model by Eq. (5) and Eq. (6) for creep and recovery phases, respectively (Moreira et al., 2011):
JðtÞC ¼ Jo þ Jm ð1 expðt=lÞÞ þ t=ho
(5)
JðtÞR ¼ Jmax Jo Jm ð1 expðt=lÞÞ
(6)
where, Jo (Pa1), Jm (Pa1) and Jmax (Pa1) are the instantaneous, viscoelastic and maximum creep compliance values, respectively. t (s) and l (s) are the phase and mean retardation time values, respectively. ho (Pa s) is the zero-shear viscosity. The percentage recovery of dough was represented by the elastic recovery (%) given by Eq. (7).
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. Sm Je ð%Þ ¼ Sm Sf
(7)
where, Sm and Sf are the maximum and final strain values, respectively. 2.4. Statistical analyses All the tests were carried out at least in triplicate and results are reported as the mean and standard derivation of these measurements. Duncan's multiple comparison tests were used to determine the significant effect of partially gelatinized starch on the rheological properties of dough samples. A 95% (p < 0.05) confidence level was used in all cases and the SPSS statistical package (LEAD Technologies, US) was used for data analysis. 3. Results and discussion 3.1. Effect of substitution on apparent shear viscosity of dough The steady shear flow curves of dough samples are shown in Fig. 1. The apparent viscosity values of all the samples decreased with increase in the shear rate indicating that all the samples exhibited shear-thinning behavior albeit at different levels. The weakening of molecular network in these pastes due to applied shear is responsible for the observed shear thinning behavior (Ravi & Bhattacharya, 2004). The increase of the proportion of partially gelatinized starch in the formulation resulted in the increase of apparent viscosity (Fig. 1B,C,D,and E). As can be seen from Fig. 1, the apparent viscosity values of dough samples partially substituted with S68 and S70 were higher than that of the control samples. The apparent viscosity values of dough samples partially substituted with S68 and S70 were also higher than the apparent viscosity values of the dough samples partially substituted with S25 and S64, which means that apparent shear viscosity of dough also depends on the degree of gelatinization of partially gelatinized starch. The cross model was used to predict the apparent viscosity of the dough. It fitted the testing apparent viscosity very well. The Cross model parameters for dough samples are summarized in Table 1. As the concentration of the partially gelatinized starch in the dough increased, the values of zero-shear viscosity (ho) increased significantly (p < 0.05). The values of ho were also influenced by the degree of gelatinization of substitutes. However, it seems that the concentration of substitutes played a more important role to modify the properties of dough. The values of the parameter (k) of all the dough samples decreased significantly (p < 0.05) with increase in the concentration of the partially gelatinized starch. A decrease in k values due to the increase in the concentration of partially gelatinized starch indicated a lower rate of breakdown of starch granule network in substituted dough samples (Ravi & Bhattacharya, 2004). The flow behavior index (n) is the reflection of the shear-thinning behavior. As the concentration of the substitute increased, the n value decreased significantly (P < 0.05). When the degree of gelatinization of the substitutes increased, the n value also decreased indicating to the increased shear-thinning behavior of these samples. However, the n value of dough sample substituted by S70 was lower than that of the dough sample substituted by S68 when the percentage of substitute was 30 g/100 g. Gelatinized starch can be rehydrated at room temperature and it produces great viscosity and smooth texture (Singh & Singh, 2003). Therefore, it can be used as thickeners in foods and as adhesives in the textile industry (Anastasiades, Thanou, Loulis, Stapatoris, & Karapantsios, 2002). When the wheat flour was judiciously
substituted with partially gelatinized starch and gluten, the starch granules in dough were made to adhere to one another. The attractive force among the granules increased with the increase in the concentration and the degree of gelatinization of substituted starch. As a result, the mobility of starch granules decreased which was reflected in the increase in the apparent viscosity values. We have shown in our earlier study that the swelling power of partially gelatinized starch has a relationship with the degree of gelatinization. For example, the degree of gelatinization of S70 was 96.78% which was higher than that of other partially gelatinized starches and the swelling power of S70 was found to be 7.14 which was the highest among all the partially gelatinized starch samples at 30 C (Fu et al., 2012). The S70 with enhanced water absorption could absorb more water from dough sample. The highest degree of gelatinization of S70 leads to the weakest structure. The large swelling granules of S70 tend to break into small pieces during the shearing process which may play the role of a lubricant. As the percentage of substitution increased, this effect will play an increasingly important role in the rheological properties of dough samples. Consequently, the apparent viscosity of dough sample substituted by S70 was not as high as that of the dough sample substituted by S68 when the percentage of substitute was 30 g/ 100 g. 3.2. Effect of substitution on viscoelastic characteristics of dough Fig. 2 shows the variation in storage (G0 ) and loss (G00 ) moduli of dough samples. All the tested dough samples showed G0 > G00 throughout the frequency range indicating to a more elastic (than viscous) gel structure. It can also be observed that the moduli (G0 and G00 ) of all dough samples increased with increase in the frequency from 0.1 to 100 Hz. The G0 and G00 of control and dough samples substituted by S25 were lower than those of other dough samples. The values parameters a0 , a00 , b0 and b00 for all the dough samples are given in Table 2. The values of these parameters indicate that the substitutes significantly (P < 0.05) altered the dynamic rheological properties of dough samples compared with the control. The a0 > a00 in all the dough samples supported the fact that these dough samples are predominantly elastic than viscous. The values a0 and a00 increased significantly (P < 0.05) with increase in the concentration of the partially gelatinized starch. When the degree of gelatinization of the substitutes increased, the values a0 and a00 changed a little. This observation indicates that when a dough sample is substituted with higher concentration of substitutes, it results in to stronger elastic structure. However, the values a0 and a00 of S70 were lower than those of S68 when the percentage of substitute was 30 g/100 g which is in accordance with the observation made earlier in apparent viscosity data. Regarding the b0 and b00 parameters, the control samples had higher values than other dough samples suggesting that the substitutes decreased the frequency sensitivity of dough samples. As described in Section 3.1., partially gelatinized starch can produce a paste when rehydrated compared to the native starch. Partially gelatinized starch behaves similar to a gum and exhibits similar characteristics (Yu & Ngadi, 2006). Like gums, the partially gelatinized starch imparts greater water holding characteristics to dough which ultimately results into more elastic and firmer consistency. At given moisture content, the storage modulus increased as the concentration of the partially gelatinized starch was increased. The wheat flour dough can be regarded as a composite material where the starch granules act as filler in the continuous gluten matrix (Miyazaki et al., 2006; Sikora et al., 2010). In such a material, the modulus of the composite depends on the ratio of the modulus of the two materials (Larsson & Eliasson, 1997). The starch
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Fig. 1. Experimental steady-shear flow curves for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (>Control; B10 g/100 g; ,20 g/100 g; △30 g/100 g; predicted line).
Table 1 Parameters of steady shear flow for wheat dough substituted by different partially gelatinized starch at different concentrations. Additives
Ratio (g/100 g)
Parameters
h0 ( 104 Pa s) Control Native corn starch Native corn starch Native corn starch S25 S25 S25 S64 S64 S64 S68 S68 S68 S70 S70 S70
e 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30
3.26 3.04 3.07 3.77 3.19 5.40 6.56 4.01 6.44 8.92 4.89 7.84 11.05 4.88 7.79 8.97
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.19 0.15a 0.16a 0.17b 0.17a 0.19d 0.10e 0.11b 0.13e 0.14g 0.15c 0.13f 0.49h 0.22c 0.24f 0.07g
k (s) 47.85 50.53 49.28 39.88 47.91 32.31 29.51 37.77 30.55 21.29 35.11 25.30 19.73 35.06 25.00 22.17
R2
n ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
h
1.52 1.88i 1.50hi 1.59g 1.58h 1.42e 0.71d 1.03g 1.00de 1.59ab 1.11f 1.64c 1.10a 0.95f 0.89c 0.92b
0.27 0.30 0.29 0.24 0.28 0.20 0.16 0.23 0.18 0.08 0.21 0.12 0.04 0.21 0.12 0.07
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
h
0.02 0.01i 0.02hi 0.01g 0.01hi 0.01e 0.01d 0.01fg 0.01d 0.01b 0.01ef 0.01c 0.00a 0.01ef 0.01c 0.00b
Values are mean ± standard deviation (n ¼ 3). Values in the same column followed by different lowercase letters indicate to the significant difference (P < 0.05).
0.991 0.999 0.996 0.994 0.997 0.999 0.994 0.998 0.997 0.998 0.999 0.999 0.999 0.999 0.999 0.999
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Fig. 2. Experimental G0 and G00 data for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (G0 :AControl; C10 g/100 g; -20 g/100 g; :30 g/100 g； predicted line; G00 :>Control; B10 g/100 g; ,20 g/100 g; △30 g/100 g).
sample S70 with high water binding capacity may inhibit the development of gluten which lowers the consistency of the gluten network leading the dough to be less resistance to strains (Fustier, Castaigne, Turgeon, & Biliaderis, 2008; Yang et al., 2011). 3.3. Effect of substitution on creep-recovery of dough The creep-recovery curves of dough samples are presented in Fig. 3. As the concentration of substitutes increased, the maximum creep compliance decreased significantly (P < 0.05). As can be seen from this figure, the degree of gelatinization of substitutes also significantly (P < 0.05) altered the maximum creep compliance of dough samples. Wang and Sun (2002) suggested that the maximum creep compliance could be used to characterize the rigidity (firmness) of dough samples. They reported that stronger dough samples which had greater resistance to deformation had smaller creep compliance than softer dough samples. The fact that the dough samples substituted with S68 and S70 exhibited greater
resistance to deformation and showed smaller creep compliance than other dough samples agrees with Wang and Sun (2002)'s observation. The Burgers model parameters for creep-recovery phase calculated using Eq. (5) and Eq. (6) are presented in Fig. 4. The instantaneous, viscoelastic and maximum creep compliance (Jo, Jm and Jmax) all decreased with the increase in the concentration of substitutes. The values of creep compliance for control samples were higher than those for other samples, indicating that control samples were softer. The retardation time (l) is the time required for the applied stress to decrease to 1/e (approximately 36.8%) of its nez-Avalos, Ramosinitial value under constant deformation (Jime Ramírez, & Salazar-Montoya, 2005). As can be seen from Fig. 4C, the retardation time of control samples is higher than those of other samples. Zero-shear viscosity (ho) reflects on the flowability of a material at the end of applied stress. The values of the zeroshear viscosity increased with the increase in the degree of gelatinization of substitutes. This observation indicated that the dough
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Table 2 Parameters of frequency sweep for wheat dough substituted by different partially gelatinized starch at different concentrations. Additives
Ratio (g/100 g)
G0
G00
a0 ( 104 Pa sn) Control Native corn starch Native corn starch Native corn starch S25 S25 S25 S64 S64 S64 S68 S68 S68 S70 S70 S70
e 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30
1.37 1.34 1.54 1.51 1.51 2.12 2.57 2.37 3.49 4.78 2.68 3.76 5.27 2.53 3.73 4.83
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.13 0.09a 0.14a 0.14a 0.13a 0.20b 0.24c 0.13bc 0.16d 0.23e 0.23c 0.35d 0.27f 0.19c 0.26d 0.26e
b0 ( 101) 2.12 2.14 2.04 1.98 2.10 1.91 1.82 1.91 1.71 1.55 1.78 1.64 1.45 1.79 1.63 1.46
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
R2 g
0.05 0.04g 0.06hi 0.02gh 0.08ig 0.04g 0.06f 0.06g 0.02de 0.03b 0.09ef 0.06cd 0.03a 0.06ef 0.03bc 0.03a
0.998 0.997 0.996 0.995 0.998 0.995 0.994 0.996 0.995 0.992 0.996 0.993 0.992 0.996 0.994 0.992
a00 ( 103 Pa sn) 4.39 4.34 4.76 4.61 4.81 6.08 7.09 6.73 8.76 10.81 6.90 8.47 10.35 6.49 8.64 9.37
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.35 0.24a 0.45a 0.35a 0.46a 0.52b 0.43c 0.11bc 0.59d 0.28e 0.42bc 0.56d 0.58e 0.53bc 0.73d 0.72d
b00 ( 101) 2.82 2.92 2.85 2.85 2.86 2.76 2.72 2.75 2.61 2.51 2.69 2.58 2.42 2.67 2.51 2.48
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
fgh
0.06 0.05h 0.08gh 0.06gh 0.07h 0.05efg 0.04ef 0.04efg 0.09bcd 0.03ab 0.08de 0.03bc 0.07a 0.04cde 0.12ab 0.07a
R2 0.993 0.993 0.991 0.992 0.992 0.991 0.990 0.992 0.989 0.986 0.990 0.990 0.986 0.989 0.982 0.990
Values are mean ± standard deviation (n ¼ 3). Values in the same column followed by different lowercase letters indicate to the significant difference (P < 0.05).
Fig. 3. Creep and recovery curves for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (>Control; B10 g/ 100 g; ,20 g/100 g; △30 g/100 g; predicted line).
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Fig. 4. Creep-recovery parameters for wheat dough with different additives at different concentrations. Creep phase: (A)e(D); Recovery phase: (E). ( 20 g/100 g; 30 g/100 g).
samples substituted with starch with higher degree of gelatinization exhibited more viscous behavior and greater resistance to flow. The elastic recovery (Je) reflects the extent of bonding among the constituents of dough samples. As can be seen from Fig. 4F, the values of Je changed a lot as the concentration of substitutes increased which indicated less deformation or breakage of the composite network, while the values of Je changed a little as the degree of gelatinization of substitutes increased. The elastic recovery of dough sample substituted with S70 decreased when the percentage of substitute increased from 20 g/100 g to 30 g/100 g. The dough samples substituted with partially gelatinized starch at different gelatinization degree and different level of substitution showed different rheological properties. This can be attributed to the fact that the starch fraction plays an important role for the viscoelastic properties of flour dough (Khatkar & Schofield, 2002). The effect of starch in dough characteristics is largely related to its physical properties, such as size and shape of granules and water
Control;
10 g/100 g;
binding capacity (Witczak, Juszczak, Ziobro, & Korus, 2012). The swelling ability of partially gelatinized starch granules during rehydration process greatly increases with increase in the degree of gelatinization (Fu et al., 2012). The enlarged granules occupy the free space and alter the consistency of dough which increases the resistance of dough against deformation (Witczak et al., 2012). In this regard, Hüttner, Bello, and Arendt (2010) also reported that the increased elasticity of dough was primarily related to the water hydration capacity of starch. 4. Conclusions Dough samples substituted with partially gelatinized starch (at different degree of gelatinization and different degree of substitution) exhibited different rheological properties. The apparent viscosity of dough increased with the increase in the concentration and degree of gelatinization of the partially gelatinized starch
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samples except dough sample substituted with S70 at 30 g/100 g concentration. All the dough samples substituted with partially gelatinized starch showed increase in storage (G0 ) and loss (G00 ) moduli. The wheat dough (control) had higher creep compliance compared to those dough samples substituted with partially gelatinized starch. The elastic recovery (Je) of control dough samples was the lowest. The rheological data of dough samples were fitted to different models. It is found that the experimental results were in good agreement with the model predictions. In a word, the rheological properties of dough were influenced by the degree of substitution more than by the degree of gelatinization of substitutes. Acknowledgments This research was supported by Chinese Universities Scientific Fund (No. 2015SP001), High Technology Research and Development Program of China (No. 2011AA100802) and Science and Technology Support Project of China (No. 2013BAD10B03). References Anastasiades, A., Thanou, S., Loulis, D., Stapatoris, A., & Karapantsios, T. D. (2002). Rheological and physical characterization of pregelatinized maize starches. Journal of Food Engineering, 52(1), 57e66. Fustier, P., Castaigne, F., Turgeon, S. L., & Biliaderis, C. G. (2008). Flour constituent interactions and their influence on dough rheology and quality of semi-sweet biscuits: a mixture design approach with reconstituted blends of gluten, water-solubles and starch fractions. Journal of Cereal Science, 48, 144e158. Fu, Z.-Q., Wang, L.-J., Li, D., & Adhikari, B. (2012). Effects of partial gelatinization on structure and thermal properties of corn starch after spray drying. Carbohydrate Polymers, 88(4), 1319e1325. Goesaert, H., Brijs, K., Veraverbeke, W. S., Courtin, C. M., Gebruers, K., & Delcour, J. A. (2005). Wheat flour constituents: how they impact bread quality, and how to impact their functionality. Trends in Food Science & Technology, 16, 12e30. Hung, P. V., & Morita, N. (2004). Dough properties and bread quality of flours supplemented with cross-linked corn starch. Food Research International, 37(5), 461e467. Hung, P. V., & Morita, N. (2005). Thermal and rheological properties of dough and bread as affected by various cross-linked corn starch substitutions. Starch/ €rke, 57, 540e546. Sta Hüttner, E. K., Bello, F. D., & Arendt, E. K. (2010). Rheological properties and bread making performance of commercial wholegrain oat flours. Journal of Cereal Science, 52(1), 65e71. nez-Avalos, H. A., Ramos-Ramírez, E. G., & Salazar-Montoya, J. A. (2005). Jime Viscoelastic characterization of gum Arabic and maize starch mixture using the
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Maxwell model. Carbohydrate Polymers, 62(1), 11e18. Khatkar, B. S., & Schofield, J. D. (2002). Dynamic rheology of wheat flour dough. I. Non-linear viscoelastic behaviour. Journal of the Science of Food and Agriculture, 82, 827e829. Korus, J., Witczak, M., Ziobro, R., & Juszczak, L. (2009). The impact of resistant starch on characteristics of gluten-free dough and bread. Food Hydrocolloids, 23, 988e995. Larsson, H., & Eliasson, A. C. (1997). Influence of the starch granule surface on the rheological behavior of wheat flour dough. Journal of Texture Studies, 28(5), 487e501. Lee, M. R., Swanson, B. G., & Baik, B. K. (2001). Influence of amylose content on properties of wheat starch and breadmaking quality of starch and gluten blends. Cereal Chemistry, 78(6), 701e706. Miyazaki, M., Maeda, T., & Morita, N. (2008). Bread quality of frozen dough substituted with modified tapioca starches. European Food Research and Technology, 227(2), 503e509. Miyazaki, M., Van Hung, P., Maeda, T., & Morita, N. (2006). Recent advances in application of modified starches for breadmaking. Trends in Food Science & Technology, 17(11), 591e599. Moreira, R., Chenlo, F., & Torres, M. D. (2011). Effect of sodium chloride, sucrose and chestnut starch on rheological properties of chestnut flour doughs. Food Hydrocolloids, 25, 1041e1050. Onyango, C., Mutungi, C., Unbehend, G., & Lindhauer, M. G. (2011). Rheological and textural properties of sorghum-based formulations modified with variable amounts of native or pregelatinized cassava starch. LWT e Food Science and Technology, 44(3), 687e693. Ravi, R., & Bhattacharya, S. (2004). Flow behaviour of chickpea (Cicer arietinum L.) flour dispersions: effect of additives. Journal of Food Engineering, 65, 619e624. Sebe ci c, B., & Sebe ci c, B. (1996). Wheat flour starch granule-size distribution and rheological properties of dough. Part 4. Farinographic measurements. Food/ Nahrung, 40(5), 256e260. Sikora, M., Kowalski, S., Krystyjan, M., Ziobro, R., Wrona, P., Curic, D., et al. (2010). Starch gelatinization as measured by rheological properties of the dough. Journal of Food Engineering, 96, 505e509. Singh, J., & Singh, N. (2003). Studies on the morphological and rheological properties of granule cold water soluble corn and potato starches. Food Hydrocolloids, 17, 63e72. Wang, F. C., & Sun, X. S. (2002). Creep-recovery of wheat flour doughs and relationship to other physical dough tests and breadmaking performance. Cereal Chemistry, 79(4), 567e571. Witczak, M., Juszczak, L., Ziobro, R., & Korus, J. (2012). Influence of modified starches on properties of gluten-free dough and bread. Part I: Rheological and thermal properties of gluten-free dough. Food Hydrocolloids, 28, 353e360. Xue, C., Sakai, N., & Fukuoka, M. (2008). Use of microwave heating to control the degree of starch gelatinization in noodles. Journal of Food Engineering, 87, 357e362. Yang, Y., Song, Y., & Zheng, Q. (2011). Rheological behaviors of doughs reconstituted from wheat gluten and starch. Journal of Food Science and Technology, 48(4), 489e493. Yu, L. J., & Ngadi, M. O. (2006). Rheological properties of instant fried noodle dough as affected by some ingredients. Journal of the Science of Food and Agriculture, 86(4), 544e548.
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LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Effect of partially gelatinized corn starch on the rheological properties of wheat dough Zong-qiang Fu a, 1, Li-ming Che b, 1, Dong Li a, **, Li-jun Wang c, *, Benu Adhikari d a College of Engineering, National Energy R & D Center for Non-food Biomass, China Agricultural University, P. O. Box 50, 17 Qinghua Donglu, Beijing 100083, China b College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China c College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing, China d School of Applied Sciences, RMIT University, Melbourne City Campus, VIC 3001, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 June 2015 Received in revised form 18 October 2015 Accepted 20 October 2015 Available online 23 October 2015
Ten, twenty and thirty percent (g/100 g) of wheat flour was substituted with partially gelatinized corn starch or ungelatinized corn starch and the rheological properties of the resultant dough samples were investigated. The apparent viscosity of dough increased with the increase in the concentration and degree of gelatinization of partially gelatinized starch samples except in the case of dough substituted with starch sample with high gelatinization degree (96.78%) at 30 g/100 g concentration. The presence of partially gelatinized starch increased the storage (G0 ) and loss (G00 ) moduli values and decreased the frequency sensitivity of dough samples. The dough prepared from wheat flour alone (control) showed the highest creep compliance and the lowest elastic recovery. In brief, the rheological properties of dough were influenced by the degree of substitution more than by the degree of gelatinization of substitutes. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Rheological properties Viscosity Creep Recovery Partially gelatinized starch
1. Introduction Starch is the main component of wheat flour (about 80 g/100 g) and contributes to the formation of texture and quality of dough (Yang, Song, & Zheng, 2011). In many food applications, functional properties of starch can have important implication on the quality of end-use products (Hung & Morita, 2005). The different amylose/ amylopectine ratio (Lee, Swanson, & Baik, 2001), granule structure (Goesaert et al., 2005) and granule size (Sebe ci c & Sebe ci c, 1996) of starch in wheat flour influences the texture, stability and elasticity of dough and bread. In order to meet some specific requirements dough is commonly mixed with modified starches (Hung & Morita, 2004; Korus, Witczak, Ziobro, & Juszczak, 2009; Miyazaki, Maeda, & Morita, 2008). Pregelatinized starch is a physically modified starch which can reconstitute in cold water directly and provides desirable
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (D. Li), [email protected] (L.-j. Wang). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.lwt.2015.10.052 0023-6438/© 2015 Elsevier Ltd. All rights reserved.
pasting and texturizing characteristics (Miyazaki, Van Hung, Maeda, & Morita, 2006). Due to these advantages, pregelatinized starch is commonly used in dough. Onyango, Mutungi, Unbehend, and Lindhauer (2011) added pregelatinized starch to the glutenfree dough and they found the presence of pregelatinized starch increased the viscosity of the liquid phase and enhanced the network created by the native starch granules. Xue, Sakai, and Fukuoka (2008) used microwave heating to partially gelatinize starch in dough for making noodles. They found that the cooking time of noodles produced by using partially gelatinized dough was reduced significantly compared to the un-gelatinized noodles. From the results of these studies, addition of pregelatinized starch can modify the properties of dough and the quality of the products. However, these studies did not show clearly about a relationship between the addition of partially gelatinized starch and the rheological properties of dough. Pregelatinized starch is a modified starch in which the crystalline zones in the starch granules are partially or completely destroyed. Different degrees of gelatinization in the partially gelatinized starch give rise to a diverse granule structure having different degree of crystallinity (Fu, Wang, Li, & Adhikari, 2012). This difference in degree of crystallinity in partially gelatinized
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starch is expected to influence the performance of dough. However, research on the effects of residual crystallinity and the characteristics of partially gelatinized starch granules on the rheological properties of dough is not reported. In these contexts, the objective of this work was to study the effect of partially gelatinized corn starch on the rheological properties of wheat dough. The rheological tests included steady shear flow, frequency sweep and creep-recovery. This would provide better understanding of the rheological properties of wheat dough containing partially gelatinized starch. 2. Materials and methods 2.1. Materials Wheat flour was obtained from Beijing Guchuan Flour Group Co., Ltd. (Beijing, China). Its protein and moisture contents were 10.8 g/100 g and 7.3 g/100 g, respectively. Commercial gluten powder was obtained from Juancheng Jianfa Flour Co., Ltd. (Shandong, China). Its moisture content was 5.9 g/100 g. Native corn starch having 10.0 g/100 g moisture content was obtained from Hebei Zhangjiakou Yujin Food Co., Ltd. (Hebei, China). Partially gelatinized starch samples were obtained by controlled gelatinization of starch at 64 C (S64), 68 C (S68) and 70 C (S70) as previously reported (Fu et al., 2012). Corn starch suspension at a starch concentration of 10.0 g/100 g was prepared by adding 20.0 g of predried corn starch into deionized water at 24 ± 1 C. Each batch of dispersion was thoroughly stirred at 300 rpm (in beakers) for 15 min using a thermostated water bath maintained at 64 C, 68 C and 70 C. These partially gelatinized starch dispersions were spray dried using a bench-top spray drier (GPW120- II, Shandong Tianli Drying Equipment Inc., China). The inlet temperature, exhaust aspiration level, the flow rate of the air and feed rate used in the spray drying process were set at 200 C, 95%, 0.375 m3/h and 7.2 mL/min, respectively. Partially gelatinized starch was also prepared at 25 C (S25) by stirring corn starch slurry for 15 min at 25 C followed by spray drying. The degree of gelatinization of S25, S64, S68 and S70 samples was determined using a differential scanning calorimeter (DSC-Q10, TA Instruments, New Castle, USA) and was found to be 32.30%, 47.75%, 69.40% and 96.78%, respectively. 2.2. Dough preparation In each formulation, 10, 20 and 30 g/100 g of native and partially gelatinized corn starch containing 10.8 g/100 g of gluten powder was substituted for wheat flour. A fixed amount of water was added to each sample to attain 42 g/100 g moisture content on wet basis. The dough samples were mixed for about 10 min and allowed to stabilize for 20 min in a sealed container before further tests. The dough formulations containing the mixture of native corn starch and gluten powder and only wheat flour (100 g/100 g) were used as control. 2.3. Rheological tests Rheological measurements were performed using AR2000ex rheometer (TA Instruments Ltd., Crawley, UK). The temperature was maintained at 30 C using a water bath connected to a Peltier system. An aluminum parallel plate geometry was chosen to conduct steady shear flow tests (20 mm diameter, 1 mm gap). The frequency sweep tests and creep-recovery tests were conducted using parallel plate geometry having 40 mm diameter and 1 mm gap. A thin layer of silicone oil was applied on the rim of the samples in order to prevent evaporation. The linear viscoelastic region was determined for each sample through strain sweep tests
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at 0.1, 1 and100 Hz, respectively (data not shown). Viscoelastic properties (storage moduli G0 and loss moduli G00 ) of all the samples were determined within the linear viscoelastic region. A stabilization time of 15 min was applied to all the samples before measuring. 2.3.1. Steady shear flow tests The steady shear flow tests were performed over a shear rate range of 0.01e10 s1 to measure the apparent viscosity. The apparent viscosity versus shear rate data were fitted by using the Cross model (Moreira, Chenlo, & Torres, 2011) as given by Eq. (1):
h ¼ h∞ þ
ho h∞
1 þ ðkgÞð1nÞ
(1)
where h (Pa s) is the apparent viscosity, g (s1) is the shear rate, ho and h∞ (Pa s) are the viscosity values at zero and infinite shear rates, respectively. Similar, k (s) is the time constant and n is the flow behavior index. The value of h∞ can be obtained from the experimental results corresponding to the equilibrium viscosity obtained at the end of shearing. In the cases where ho [ h∞ and h [ h∞, it can be assumed that ho e h∞ z ho and hf / 0 the Eq. (1) can be rewritten as Eq. (2) (Ravi & Bhattacharya, 2004).
h¼
ho 1 þ ðkgÞð1nÞ
(2)
2.3.2. Frequency sweep tests The frequency sweep tests were performed over the frequency range of 0.1e100 Hz (angular frequency range of 0.6283e628.3 rad/ s). The strain amplitude for these frequency sweep tests was selected as 0.25% based on the strain sweep results (data not shown) in order to confine these tests within linear viscoelastic region. Experimental G0 and G00 were fitted by using Eq. (3) and Eq. (4), respectively.
log G0 ¼ log a0 þ b0 log u
(3)
log G00 ¼ log a00 þ b00 log u
(4)
where u (rad/s) is the angular frequency and a0 , a00 , b0 and b00 are the fitting parameters. 2.3.3. Creep-recovery tests Creep-recovery tests were carried out using a constant shear stress of 50 Pa. The variation in shear strain as a function of the applied stress was measured for 3 min. The applied stress was then removed and change in strain was recorded for further 5 min. Creep data was described with creep compliance rheological parameters, J(t)C (Pa1) ¼ g/s where g is the strain and s is the constant shear stress during creep test. The creep compliance data of dough samples was fitted to the Burgers model by Eq. (5) and Eq. (6) for creep and recovery phases, respectively (Moreira et al., 2011):
JðtÞC ¼ Jo þ Jm ð1 expðt=lÞÞ þ t=ho
(5)
JðtÞR ¼ Jmax Jo Jm ð1 expðt=lÞÞ
(6)
where, Jo (Pa1), Jm (Pa1) and Jmax (Pa1) are the instantaneous, viscoelastic and maximum creep compliance values, respectively. t (s) and l (s) are the phase and mean retardation time values, respectively. ho (Pa s) is the zero-shear viscosity. The percentage recovery of dough was represented by the elastic recovery (%) given by Eq. (7).
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. Sm Je ð%Þ ¼ Sm Sf
(7)
where, Sm and Sf are the maximum and final strain values, respectively. 2.4. Statistical analyses All the tests were carried out at least in triplicate and results are reported as the mean and standard derivation of these measurements. Duncan's multiple comparison tests were used to determine the significant effect of partially gelatinized starch on the rheological properties of dough samples. A 95% (p < 0.05) confidence level was used in all cases and the SPSS statistical package (LEAD Technologies, US) was used for data analysis. 3. Results and discussion 3.1. Effect of substitution on apparent shear viscosity of dough The steady shear flow curves of dough samples are shown in Fig. 1. The apparent viscosity values of all the samples decreased with increase in the shear rate indicating that all the samples exhibited shear-thinning behavior albeit at different levels. The weakening of molecular network in these pastes due to applied shear is responsible for the observed shear thinning behavior (Ravi & Bhattacharya, 2004). The increase of the proportion of partially gelatinized starch in the formulation resulted in the increase of apparent viscosity (Fig. 1B,C,D,and E). As can be seen from Fig. 1, the apparent viscosity values of dough samples partially substituted with S68 and S70 were higher than that of the control samples. The apparent viscosity values of dough samples partially substituted with S68 and S70 were also higher than the apparent viscosity values of the dough samples partially substituted with S25 and S64, which means that apparent shear viscosity of dough also depends on the degree of gelatinization of partially gelatinized starch. The cross model was used to predict the apparent viscosity of the dough. It fitted the testing apparent viscosity very well. The Cross model parameters for dough samples are summarized in Table 1. As the concentration of the partially gelatinized starch in the dough increased, the values of zero-shear viscosity (ho) increased significantly (p < 0.05). The values of ho were also influenced by the degree of gelatinization of substitutes. However, it seems that the concentration of substitutes played a more important role to modify the properties of dough. The values of the parameter (k) of all the dough samples decreased significantly (p < 0.05) with increase in the concentration of the partially gelatinized starch. A decrease in k values due to the increase in the concentration of partially gelatinized starch indicated a lower rate of breakdown of starch granule network in substituted dough samples (Ravi & Bhattacharya, 2004). The flow behavior index (n) is the reflection of the shear-thinning behavior. As the concentration of the substitute increased, the n value decreased significantly (P < 0.05). When the degree of gelatinization of the substitutes increased, the n value also decreased indicating to the increased shear-thinning behavior of these samples. However, the n value of dough sample substituted by S70 was lower than that of the dough sample substituted by S68 when the percentage of substitute was 30 g/100 g. Gelatinized starch can be rehydrated at room temperature and it produces great viscosity and smooth texture (Singh & Singh, 2003). Therefore, it can be used as thickeners in foods and as adhesives in the textile industry (Anastasiades, Thanou, Loulis, Stapatoris, & Karapantsios, 2002). When the wheat flour was judiciously
substituted with partially gelatinized starch and gluten, the starch granules in dough were made to adhere to one another. The attractive force among the granules increased with the increase in the concentration and the degree of gelatinization of substituted starch. As a result, the mobility of starch granules decreased which was reflected in the increase in the apparent viscosity values. We have shown in our earlier study that the swelling power of partially gelatinized starch has a relationship with the degree of gelatinization. For example, the degree of gelatinization of S70 was 96.78% which was higher than that of other partially gelatinized starches and the swelling power of S70 was found to be 7.14 which was the highest among all the partially gelatinized starch samples at 30 C (Fu et al., 2012). The S70 with enhanced water absorption could absorb more water from dough sample. The highest degree of gelatinization of S70 leads to the weakest structure. The large swelling granules of S70 tend to break into small pieces during the shearing process which may play the role of a lubricant. As the percentage of substitution increased, this effect will play an increasingly important role in the rheological properties of dough samples. Consequently, the apparent viscosity of dough sample substituted by S70 was not as high as that of the dough sample substituted by S68 when the percentage of substitute was 30 g/ 100 g. 3.2. Effect of substitution on viscoelastic characteristics of dough Fig. 2 shows the variation in storage (G0 ) and loss (G00 ) moduli of dough samples. All the tested dough samples showed G0 > G00 throughout the frequency range indicating to a more elastic (than viscous) gel structure. It can also be observed that the moduli (G0 and G00 ) of all dough samples increased with increase in the frequency from 0.1 to 100 Hz. The G0 and G00 of control and dough samples substituted by S25 were lower than those of other dough samples. The values parameters a0 , a00 , b0 and b00 for all the dough samples are given in Table 2. The values of these parameters indicate that the substitutes significantly (P < 0.05) altered the dynamic rheological properties of dough samples compared with the control. The a0 > a00 in all the dough samples supported the fact that these dough samples are predominantly elastic than viscous. The values a0 and a00 increased significantly (P < 0.05) with increase in the concentration of the partially gelatinized starch. When the degree of gelatinization of the substitutes increased, the values a0 and a00 changed a little. This observation indicates that when a dough sample is substituted with higher concentration of substitutes, it results in to stronger elastic structure. However, the values a0 and a00 of S70 were lower than those of S68 when the percentage of substitute was 30 g/100 g which is in accordance with the observation made earlier in apparent viscosity data. Regarding the b0 and b00 parameters, the control samples had higher values than other dough samples suggesting that the substitutes decreased the frequency sensitivity of dough samples. As described in Section 3.1., partially gelatinized starch can produce a paste when rehydrated compared to the native starch. Partially gelatinized starch behaves similar to a gum and exhibits similar characteristics (Yu & Ngadi, 2006). Like gums, the partially gelatinized starch imparts greater water holding characteristics to dough which ultimately results into more elastic and firmer consistency. At given moisture content, the storage modulus increased as the concentration of the partially gelatinized starch was increased. The wheat flour dough can be regarded as a composite material where the starch granules act as filler in the continuous gluten matrix (Miyazaki et al., 2006; Sikora et al., 2010). In such a material, the modulus of the composite depends on the ratio of the modulus of the two materials (Larsson & Eliasson, 1997). The starch
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Fig. 1. Experimental steady-shear flow curves for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (>Control; B10 g/100 g; ,20 g/100 g; △30 g/100 g; predicted line).
Table 1 Parameters of steady shear flow for wheat dough substituted by different partially gelatinized starch at different concentrations. Additives
Ratio (g/100 g)
Parameters
h0 ( 104 Pa s) Control Native corn starch Native corn starch Native corn starch S25 S25 S25 S64 S64 S64 S68 S68 S68 S70 S70 S70
e 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30
3.26 3.04 3.07 3.77 3.19 5.40 6.56 4.01 6.44 8.92 4.89 7.84 11.05 4.88 7.79 8.97
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.19 0.15a 0.16a 0.17b 0.17a 0.19d 0.10e 0.11b 0.13e 0.14g 0.15c 0.13f 0.49h 0.22c 0.24f 0.07g
k (s) 47.85 50.53 49.28 39.88 47.91 32.31 29.51 37.77 30.55 21.29 35.11 25.30 19.73 35.06 25.00 22.17
R2
n ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
h
1.52 1.88i 1.50hi 1.59g 1.58h 1.42e 0.71d 1.03g 1.00de 1.59ab 1.11f 1.64c 1.10a 0.95f 0.89c 0.92b
0.27 0.30 0.29 0.24 0.28 0.20 0.16 0.23 0.18 0.08 0.21 0.12 0.04 0.21 0.12 0.07
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
h
0.02 0.01i 0.02hi 0.01g 0.01hi 0.01e 0.01d 0.01fg 0.01d 0.01b 0.01ef 0.01c 0.00a 0.01ef 0.01c 0.00b
Values are mean ± standard deviation (n ¼ 3). Values in the same column followed by different lowercase letters indicate to the significant difference (P < 0.05).
0.991 0.999 0.996 0.994 0.997 0.999 0.994 0.998 0.997 0.998 0.999 0.999 0.999 0.999 0.999 0.999
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Fig. 2. Experimental G0 and G00 data for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (G0 :AControl; C10 g/100 g; -20 g/100 g; :30 g/100 g； predicted line; G00 :>Control; B10 g/100 g; ,20 g/100 g; △30 g/100 g).
sample S70 with high water binding capacity may inhibit the development of gluten which lowers the consistency of the gluten network leading the dough to be less resistance to strains (Fustier, Castaigne, Turgeon, & Biliaderis, 2008; Yang et al., 2011). 3.3. Effect of substitution on creep-recovery of dough The creep-recovery curves of dough samples are presented in Fig. 3. As the concentration of substitutes increased, the maximum creep compliance decreased significantly (P < 0.05). As can be seen from this figure, the degree of gelatinization of substitutes also significantly (P < 0.05) altered the maximum creep compliance of dough samples. Wang and Sun (2002) suggested that the maximum creep compliance could be used to characterize the rigidity (firmness) of dough samples. They reported that stronger dough samples which had greater resistance to deformation had smaller creep compliance than softer dough samples. The fact that the dough samples substituted with S68 and S70 exhibited greater
resistance to deformation and showed smaller creep compliance than other dough samples agrees with Wang and Sun (2002)'s observation. The Burgers model parameters for creep-recovery phase calculated using Eq. (5) and Eq. (6) are presented in Fig. 4. The instantaneous, viscoelastic and maximum creep compliance (Jo, Jm and Jmax) all decreased with the increase in the concentration of substitutes. The values of creep compliance for control samples were higher than those for other samples, indicating that control samples were softer. The retardation time (l) is the time required for the applied stress to decrease to 1/e (approximately 36.8%) of its nez-Avalos, Ramosinitial value under constant deformation (Jime Ramírez, & Salazar-Montoya, 2005). As can be seen from Fig. 4C, the retardation time of control samples is higher than those of other samples. Zero-shear viscosity (ho) reflects on the flowability of a material at the end of applied stress. The values of the zeroshear viscosity increased with the increase in the degree of gelatinization of substitutes. This observation indicated that the dough
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329
Table 2 Parameters of frequency sweep for wheat dough substituted by different partially gelatinized starch at different concentrations. Additives
Ratio (g/100 g)
G0
G00
a0 ( 104 Pa sn) Control Native corn starch Native corn starch Native corn starch S25 S25 S25 S64 S64 S64 S68 S68 S68 S70 S70 S70
e 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30
1.37 1.34 1.54 1.51 1.51 2.12 2.57 2.37 3.49 4.78 2.68 3.76 5.27 2.53 3.73 4.83
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.13 0.09a 0.14a 0.14a 0.13a 0.20b 0.24c 0.13bc 0.16d 0.23e 0.23c 0.35d 0.27f 0.19c 0.26d 0.26e
b0 ( 101) 2.12 2.14 2.04 1.98 2.10 1.91 1.82 1.91 1.71 1.55 1.78 1.64 1.45 1.79 1.63 1.46
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
R2 g
0.05 0.04g 0.06hi 0.02gh 0.08ig 0.04g 0.06f 0.06g 0.02de 0.03b 0.09ef 0.06cd 0.03a 0.06ef 0.03bc 0.03a
0.998 0.997 0.996 0.995 0.998 0.995 0.994 0.996 0.995 0.992 0.996 0.993 0.992 0.996 0.994 0.992
a00 ( 103 Pa sn) 4.39 4.34 4.76 4.61 4.81 6.08 7.09 6.73 8.76 10.81 6.90 8.47 10.35 6.49 8.64 9.37
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
a
0.35 0.24a 0.45a 0.35a 0.46a 0.52b 0.43c 0.11bc 0.59d 0.28e 0.42bc 0.56d 0.58e 0.53bc 0.73d 0.72d
b00 ( 101) 2.82 2.92 2.85 2.85 2.86 2.76 2.72 2.75 2.61 2.51 2.69 2.58 2.42 2.67 2.51 2.48
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
fgh
0.06 0.05h 0.08gh 0.06gh 0.07h 0.05efg 0.04ef 0.04efg 0.09bcd 0.03ab 0.08de 0.03bc 0.07a 0.04cde 0.12ab 0.07a
R2 0.993 0.993 0.991 0.992 0.992 0.991 0.990 0.992 0.989 0.986 0.990 0.990 0.986 0.989 0.982 0.990
Values are mean ± standard deviation (n ¼ 3). Values in the same column followed by different lowercase letters indicate to the significant difference (P < 0.05).
Fig. 3. Creep and recovery curves for wheat dough with different additives at different concentrations. (A) Native corn starch; (B) S25; (C) S64; (D) S68; (E) S70. (>Control; B10 g/ 100 g; ,20 g/100 g; △30 g/100 g; predicted line).
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Fig. 4. Creep-recovery parameters for wheat dough with different additives at different concentrations. Creep phase: (A)e(D); Recovery phase: (E). ( 20 g/100 g; 30 g/100 g).
samples substituted with starch with higher degree of gelatinization exhibited more viscous behavior and greater resistance to flow. The elastic recovery (Je) reflects the extent of bonding among the constituents of dough samples. As can be seen from Fig. 4F, the values of Je changed a lot as the concentration of substitutes increased which indicated less deformation or breakage of the composite network, while the values of Je changed a little as the degree of gelatinization of substitutes increased. The elastic recovery of dough sample substituted with S70 decreased when the percentage of substitute increased from 20 g/100 g to 30 g/100 g. The dough samples substituted with partially gelatinized starch at different gelatinization degree and different level of substitution showed different rheological properties. This can be attributed to the fact that the starch fraction plays an important role for the viscoelastic properties of flour dough (Khatkar & Schofield, 2002). The effect of starch in dough characteristics is largely related to its physical properties, such as size and shape of granules and water
Control;
10 g/100 g;
binding capacity (Witczak, Juszczak, Ziobro, & Korus, 2012). The swelling ability of partially gelatinized starch granules during rehydration process greatly increases with increase in the degree of gelatinization (Fu et al., 2012). The enlarged granules occupy the free space and alter the consistency of dough which increases the resistance of dough against deformation (Witczak et al., 2012). In this regard, Hüttner, Bello, and Arendt (2010) also reported that the increased elasticity of dough was primarily related to the water hydration capacity of starch. 4. Conclusions Dough samples substituted with partially gelatinized starch (at different degree of gelatinization and different degree of substitution) exhibited different rheological properties. The apparent viscosity of dough increased with the increase in the concentration and degree of gelatinization of the partially gelatinized starch
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samples except dough sample substituted with S70 at 30 g/100 g concentration. All the dough samples substituted with partially gelatinized starch showed increase in storage (G0 ) and loss (G00 ) moduli. The wheat dough (control) had higher creep compliance compared to those dough samples substituted with partially gelatinized starch. The elastic recovery (Je) of control dough samples was the lowest. The rheological data of dough samples were fitted to different models. It is found that the experimental results were in good agreement with the model predictions. In a word, the rheological properties of dough were influenced by the degree of substitution more than by the degree of gelatinization of substitutes. Acknowledgments This research was supported by Chinese Universities Scientific Fund (No. 2015SP001), High Technology Research and Development Program of China (No. 2011AA100802) and Science and Technology Support Project of China (No. 2013BAD10B03). References Anastasiades, A., Thanou, S., Loulis, D., Stapatoris, A., & Karapantsios, T. D. (2002). Rheological and physical characterization of pregelatinized maize starches. Journal of Food Engineering, 52(1), 57e66. Fustier, P., Castaigne, F., Turgeon, S. L., & Biliaderis, C. G. (2008). Flour constituent interactions and their influence on dough rheology and quality of semi-sweet biscuits: a mixture design approach with reconstituted blends of gluten, water-solubles and starch fractions. Journal of Cereal Science, 48, 144e158. Fu, Z.-Q., Wang, L.-J., Li, D., & Adhikari, B. (2012). Effects of partial gelatinization on structure and thermal properties of corn starch after spray drying. Carbohydrate Polymers, 88(4), 1319e1325. Goesaert, H., Brijs, K., Veraverbeke, W. S., Courtin, C. M., Gebruers, K., & Delcour, J. A. (2005). Wheat flour constituents: how they impact bread quality, and how to impact their functionality. Trends in Food Science & Technology, 16, 12e30. Hung, P. V., & Morita, N. (2004). Dough properties and bread quality of flours supplemented with cross-linked corn starch. Food Research International, 37(5), 461e467. Hung, P. V., & Morita, N. (2005). Thermal and rheological properties of dough and bread as affected by various cross-linked corn starch substitutions. Starch/ €rke, 57, 540e546. Sta Hüttner, E. K., Bello, F. D., & Arendt, E. K. (2010). Rheological properties and bread making performance of commercial wholegrain oat flours. Journal of Cereal Science, 52(1), 65e71. nez-Avalos, H. A., Ramos-Ramírez, E. G., & Salazar-Montoya, J. A. (2005). Jime Viscoelastic characterization of gum Arabic and maize starch mixture using the
331
Maxwell model. Carbohydrate Polymers, 62(1), 11e18. Khatkar, B. S., & Schofield, J. D. (2002). Dynamic rheology of wheat flour dough. I. Non-linear viscoelastic behaviour. Journal of the Science of Food and Agriculture, 82, 827e829. Korus, J., Witczak, M., Ziobro, R., & Juszczak, L. (2009). The impact of resistant starch on characteristics of gluten-free dough and bread. Food Hydrocolloids, 23, 988e995. Larsson, H., & Eliasson, A. C. (1997). Influence of the starch granule surface on the rheological behavior of wheat flour dough. Journal of Texture Studies, 28(5), 487e501. Lee, M. R., Swanson, B. G., & Baik, B. K. (2001). Influence of amylose content on properties of wheat starch and breadmaking quality of starch and gluten blends. Cereal Chemistry, 78(6), 701e706. Miyazaki, M., Maeda, T., & Morita, N. (2008). Bread quality of frozen dough substituted with modified tapioca starches. European Food Research and Technology, 227(2), 503e509. Miyazaki, M., Van Hung, P., Maeda, T., & Morita, N. (2006). Recent advances in application of modified starches for breadmaking. Trends in Food Science & Technology, 17(11), 591e599. Moreira, R., Chenlo, F., & Torres, M. D. (2011). Effect of sodium chloride, sucrose and chestnut starch on rheological properties of chestnut flour doughs. Food Hydrocolloids, 25, 1041e1050. Onyango, C., Mutungi, C., Unbehend, G., & Lindhauer, M. G. (2011). Rheological and textural properties of sorghum-based formulations modified with variable amounts of native or pregelatinized cassava starch. LWT e Food Science and Technology, 44(3), 687e693. Ravi, R., & Bhattacharya, S. (2004). Flow behaviour of chickpea (Cicer arietinum L.) flour dispersions: effect of additives. Journal of Food Engineering, 65, 619e624. Sebe ci c, B., & Sebe ci c, B. (1996). Wheat flour starch granule-size distribution and rheological properties of dough. Part 4. Farinographic measurements. Food/ Nahrung, 40(5), 256e260. Sikora, M., Kowalski, S., Krystyjan, M., Ziobro, R., Wrona, P., Curic, D., et al. (2010). Starch gelatinization as measured by rheological properties of the dough. Journal of Food Engineering, 96, 505e509. Singh, J., & Singh, N. (2003). Studies on the morphological and rheological properties of granule cold water soluble corn and potato starches. Food Hydrocolloids, 17, 63e72. Wang, F. C., & Sun, X. S. (2002). Creep-recovery of wheat flour doughs and relationship to other physical dough tests and breadmaking performance. Cereal Chemistry, 79(4), 567e571. Witczak, M., Juszczak, L., Ziobro, R., & Korus, J. (2012). Influence of modified starches on properties of gluten-free dough and bread. Part I: Rheological and thermal properties of gluten-free dough. Food Hydrocolloids, 28, 353e360. Xue, C., Sakai, N., & Fukuoka, M. (2008). Use of microwave heating to control the degree of starch gelatinization in noodles. Journal of Food Engineering, 87, 357e362. Yang, Y., Song, Y., & Zheng, Q. (2011). Rheological behaviors of doughs reconstituted from wheat gluten and starch. Journal of Food Science and Technology, 48(4), 489e493. Yu, L. J., & Ngadi, M. O. (2006). Rheological properties of instant fried noodle dough as affected by some ingredients. Journal of the Science of Food and Agriculture, 86(4), 544e548.