Accepted Manuscript
Effects of ultrasound assisted dough fermentation on the quality of steamed bread
Denglin Luo, Ruoyan Wu, Jie Zhang, Kangyi Zhang, Baocheng Xu, Peiyan Li, Yunxia
Yuan, Xuan Li
PII:
S0733-5210(18)30209-1
DOI:
10.1016/j.jcs.2018.07.016
Reference:
YJCRS 2610
To appear in:
Journal of Cereal Science
Received Date: 13 March 2018
Revised Date:
25 May 2018
Accepted Date: 27 July 2018
Please cite this article as: Luo, D., Wu, R., Zhang, J., Zhang, K., Xu, B., Li, P., Yuan, Y., Li, X., Effects
of ultrasound assisted dough fermentation on the quality of steamed bread, Journal of Cereal Science
(2018), doi: 10.1016/j.jcs.2018.07.016.
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ACCEPTED MANUSCRIPT
Effects of Ultrasound Assisted Dough Fermentation on the Quality of Steamed
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Bread
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Denglin Luoa, Ruoyan Wua, Jie Zhangb, Kangyi Zhangc, Baocheng Xua, Peiyan Lia, Yunxia Yuana,
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Xuan Lia
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a. College of Food and Bioengineering, Henan University of Science & Technology, Luoyang
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471023, Henan Province, China
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b. School of Food Science and Technology, Henan University of Technology, Zhengzhou 450001,
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Henan Province, China
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c. Center of Agricultural Products Processing, Henan Academy of Agricultural Sciences, Zhengzhou,
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450008 Henan Province, China
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Corresponding author’s telephone: +86-379-64282342, Email: luodenglin@163.com
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Abstract
Ultrasound is used to enhance the fermentation of wheat dough to produce steamed bread. The
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quality of steamed bread stored for different time was analyzed using the texture analyzer.
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Ultrasound treatment had significant impact on the hardness and specific volume of steamed bread
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(p<0.05). Compared with the control, the hardness of fresh steamed bread reduced by 22.4% and the
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specific volume increased by 6.7% at ultrasound power density of 23.08 W/L and ultrasonic time of
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40 min. During the storage of steamed bread, the hardness with ultrasound was remarkably lower
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than that of the control, and the difference was even more evident with prolonging storage time. The
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springiness with ultrasound was lower than that of the control when storage time was no higher than
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48h. Generally, ultrasound assisted dough fermentation can improve the quality of the steamed bread.
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Key words: ultrasound; steamed bread; fermentation; storage; quality; hardness
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1. Introduction
Steamed bread has been a stable food in China for nearly 2,000 years. As a kind of daily
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fermented pasta, there is obviously different from bread in the raw materials and processing. The
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materials of steamed bread used commonly are plain wheat flour, water and yeast. These materials
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are mixed to develop a dough, then it ferments at a certain temperature (35-38 °C) and humidity
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(relative humidity of 81%-85%) for 30-60 min, followed by sheeting, molding, proofing and
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steaming. The quality of steamed bread is determined by materials characteristic, as well as the
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recipe and processing conditions. During the processing, the fermentation is an important operation
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which can affect the quality of products, including the hardness, springiness, specific volume, spread
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ratio and cohensiveness, as well as other sensor parameters (Sha et al., 2007).
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In recent years, the applications of power ultrasonic (10-1000 W cm-2) in food processing has
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gained more and more interest as it can produce physical, mechanical and chemical effects to alter
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food properties. Ultrasound technology has been used to improve the productivity and quality of food
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through intense pressure, strong shear and temperature gradient depending on the medium of
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propagation. A lot of research has been conducted about incorporating power ultrasound in food
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industry, particularly to modify ingredients properties, facilitate food processing and improve product
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quality (Carrillo-Lopez et al., 2017). Ultrasound has been used to reduce the total fermentation time
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of yoghurt by 0.5 h after inoculation, and to mix the dough to improve the quality of cakes and bread
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(Wu et al., 2000; Tan et al., 2011; Pa et al., 2014). The dough mixed by ultrasound had lower density
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and flow index, higher puffing rate and viscosity, and produced higher quality of sponge cakes (Tan
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et al., 2011). Compared with the control (without ultrasound), the physical properties of bread with
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ultrasonic-assisted dough mixing were significantly improved. The volume of the bread increased by
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19%, and the mass and density decreased by 2.1 % and 17%, respectively (Pa et al., 2014). The total
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time required for dough freezing under ultrasound (288 or 360W) was reduced by more than 11%
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and the dough springiness was significantly increased, and there was no significant changes in the
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flavor of the dough (Hu et al., 2013). The foaming capability and the emulsifying stability of wheat
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gluten sonicated both increased with increasing ultrasonic power (Zhang et al., 2011).
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In general, most studies focus on the influence of power ultrasound on the physicochemical
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characteristics of various starches and proteins, or detection ultrasound used for determining the
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characteristic of dough and products, such as rheology properties, bread volume and density, and
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textural profiles (Arvanitoyannis et al., 2017). While there are few reports on the quality changes of
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steamed bread after wheat dough was sonicated during fermentation. Therefore, this paper mainly
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intends to explore the feasibility of steamed bread produced by ultrasonic-assisted dough
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fermentation. Changes in textural profiles and storage characteristic of steamed bread were analyzed
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for hardness, springiness, specific volume, spread ratio, cohesiveness, recovery, chewiness, total
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moisture content and weighted score.
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2. Materials and Methods
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2.1 Materials
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Wheat flour with 9.64% protein (Lushuiyuan brand, Yugong Agricultural products limited
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company, China), active dry yeast (Angle brand, Angel Yeast Co., Ltd., China).
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2.2 Preparation of steamed bread
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The optimized formula of steamed bread for the control was determined according to the
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previous experiments, containing 100 g wheat flour, 48 ml distilled water, and 1.2 g dry yeast (1.2%)
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(Liu et al., 2016). The flour was added in a mixer (HM740, Hanshang Corp., Ltd., China). Then, the
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yeast was dissolved in the 36 °C distilled water and poured into the mixer to mix for 20 min. The
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mixed dough fermented in a fermentation tank (TQ-15, Topkitch Corp,, Ltd., China) for 40 min at
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36 °C and 83% of relative humidity. After the first fermentation, the dough was rounded and molded
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into a round billet. The second fermentation performed for 10 min at the same conditions as above
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first fermentation. Then the fermented dough was steamed with boiling water for 25 min and cooled
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for 1 h to room temperature for analysis (Luo et al., 2017). All samples were analyzed in triplicate
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and the results were reported as the mean of three replicates.
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The formula and mixing process of the dough with ultrasound was the same as the control. The
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prepared dough was put into a fresh plastic bag. A hollow straw of 15 cm was inserted into the bag
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and tied tightly to prevent outside water from permeating and to keep open with the outside air. The
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bag with dough was put into an ultrasonic bath (KQ-500DE, Kun Shan Ultrasonic Instrument Co.,
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Ltd, Kun Shan, 40 kHz of frequency) with water for sonication. The bag was located at 3 cm below
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the water level and 7 cm from the bottom (Fig. 1). The water temperature in the bath was maintained
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at 36-38 ° C. Ultrasonic power density and treatment time was selected from 15.38 W/L to 38.46
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W/L and from 20 min to 50 min, respectively. The fermentation (except for the first fermentation
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time) and steaming conditions were the same as the control. All samples were analyzed in triplicate
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and the results were reported as the mean of three replicates.
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2.3 Determination of the specific volume and spread ratio of steamed bread
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The specific volume of steamed bread is the ratio of volume to mass. The volume was measured
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using the rapeseed replacement method. The spread ratio was obtained by measuring the height and
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the bottom width of the three different positions on the bread using a vernier caliper, and the average
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value was recorded.
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2.4 Textural analysis of steamed bread
The texture of steamed bread was measured using a texture analyzer (Instron Universal 5544,
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Instron Co., USA) equipped with a 25 kg load cell and an aluminum cylindrical probe (P/36D). Three
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cube blocks of 20 × 20 × 20 mm from the center of the steamed bread were taken as the samples.
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Measurements were conducted with a test speed of 1 mm/s, and the deformation level was set 60% of
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the sample height. After the first compression, the probe returned to the height before compression
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and balanced for 5s, then the second compression started, as described for the first compression.
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After two compressions were completed, a TPA curve was obtained to calculate parameters.
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2.5 Determination of moisture content of steamed bread
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Total moisture content of steamed bread was determined using direct drying method. A steamed
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bread crumb of 2-3 g was dried to constant weight in an oven at 103-105 ° C. The total moisture
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content (MC) of steamed bread is calculated according to formula (1), where m0 is the raw mass of
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bread sample, m1 is the mass of sample after baking to constant weight. Analyses were performed in
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triplicate and the average value was recorded.
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2.6 Characteristic analysis of steamed bread during storage
The fresh steamed breads were cooled to the room temperature and put into fresh plastic bags
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for storage in a refrigerator at 4 ° C. The textural properties were measured after the storage of 24, 48,
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72, 96, 120 and 144 h.
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2.7 Evaluation of bread quality using comprehensive weighted scoring method (CWS)
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CWS is a trend forecasting method, which is often used to evaluate the optimal weight
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coefficient distribution principle. Each factor is given to a certain weight in CWS, and the weighted
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score is calculated to predict the future value of the factor evaluation according to the relevant
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indicators of the evaluation index of bread(Fu et al., 2015; Zhu et al., 2016). In this study, the most
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important indexes, including hardness, springiness, specific volume, spread ratio and cohesiveness,
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were selected as the weight factors in the evaluation of steamed bread. The weights assigned to these
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five indexes were 40% 20%, 20%, 10% and 10%, respectively. The basic formula of the CWS is
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given in equations (2) and (3). According to the influence of each factor on the result, the weight of
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one factor is positive value if they have a positive influence on the quality of steamed bread and
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otherwise it is negative value. In this experiment, the weight of the hardness is negative, and the
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others are positive.
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Y∗ = w y + w y + ⋯ + w y
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y =
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Where Y* is the weighted composite score for a group, wj is the weight corresponding to each
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indicator, yj’ is the scoring value of each indicator, yj is the actual measured value of each indicator in
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the group, yjmin and yjmax are the minimum and maximum values of the same index among several
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groups, respectively.
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2.8 Data processing and analysis
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The experiment data was done using the Origin 8.0. The statistical analyses were performed by
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one-way analysis of variance (ANOVA). Significance of differences (p < 0.05) was analyzed using
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the Duncan’s test (IBM SPASS Statistics V.19).
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3. Results and discussion
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3.1 Effects of ultrasonic time on the quality of steamed bread
The effects of ultrasonic time on the hardness, springiness, specific volume, spread ratio,
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cohesiveness and weight score of steamed bread were investigated at ultrasonic power density of
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23.08 W/L (Table 1).
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Table 1 showed that ultrasonic time had significant impact on the hardness and specific volume
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of steamed bread (p < 0.05), but induced only slight changes in the springiness, spread ratio and
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cohesiveness. The hardness decreased over ultrasonic time, and when the time was above 40 min,
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there was a significant decrease as compared with the control. At ultrasonic time of 50 min, the
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hardness reduced by 18.2% and 16.2% compared with the control and ultrasonic time of 20 min,
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respectively. A possible reason is that the dough developed more adequately with prolonging the
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ultrasonic time during the fermentation (Ojha et al., 2017). Another reason is perhaps that ultrasound
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cavitation can produce cycles of rarefraction and compression (Liu et al., 2017). In the rarefraction, a
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large number of bubbles in the dough generates and develops, resulting a uniformly distribution in
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the dough, which contributes to high quality of steamed breads with homogeneous and porous
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structure. Additionally, high temperature, high pressure and intense collapse induced by sonication
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maybe destroy the internal hydrogen bonds between protein molecules, weakening the tertiary and
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quaternary structures of proteins (Ozuna et al., 2015). The large protein complexes become soluble
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small aggregates, resulting in a loose network structure of gluten. Therefore, the steamed bread is
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easier to deform under external forces (Higuera-Barraza et al., 2016). All these elements contribute to
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the decrease of the hardness.
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Studies reported that the storage modulus and loss modulus of gluten decreased under
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ultrasound treatment, and the contents of α-helix, β-sheet and β-turn also declined, but the content of
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random coil increased (Hu et al., 2013). This could be explained by the fact that ultrasound cause the
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structure of wheat gluten to unfold, weakening the interactions between gliadin and glutenin and
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reducing the disulfide bonds and polar hydrogen bonds between protein molecules. Tan et al. (2011)
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suggested that the cavitation caused by ultrasound may accelerate the denaturation of proteins in the
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cake due to the shrinkage of bubbles. Protein denaturation is considered as the destruction of the
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secondary bonds such as hydrogen bonds, and the tight and curly structure of protein will become
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loose, leading to a more soft and delicious characteristic of cake. Lomakina et al (2006) observed that
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after ultrasound treatment, the protein and fat particles dispersed more evenly, and the foaming
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capacity of liquid egg white was significantly improved. Therefore, this is perhaps another reason
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that ultrasonic induced a decrease in the hardness of steamed bread by improving the foaming ability
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of proteins.
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The specific volume of steamed bread increased first and then decreased with increasing
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ultrasonic time, approaching the maximum at 40 min, which increased by 9.0% and 14.2% as
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compared with the control and ultrasonic time of 20 min, respectively. The weighted score with
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ultrasound was higher than that of the control when ultrasonic time above 30 min. It indicated that
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ultrasound treatment can improve the quality of steamed bread, reduce the fermentation time and
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enhance productivity. The increase of specific volume is mainly attributed to the following two
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reasons (Pa et al., 2014). One reason is that ultrasound has a positive effect on increasing the yeast
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activity at the beginning of the fermentation (Ojha et al., 2017). The other reason is that sonication is
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helpful to the generation of bubbles in the dough, and the bubbles can provide oxygen for various
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oxidation reactions and yeast propagation. Previous studies reported that ultrasound with low
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frequencies (18-30 kHz) and high intensities promoted the growth of Saccharomyces cerevisiae
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(increased by 33.3%), and shortened the fermentation time (reduced by 4 h) (Lanchun et al., 2003). It
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may be related to the membrane permeability of cell enhanced by ultrasound treatment, promoting
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the transfer rate of oxygen and nutrient required for microbial cells growth and accelerating the
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removal of metabolic wastes from cells (Huang et al., 2017). Sulaiman et al. (2011) revealed that
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ultrasound cycles of 10% and 20% improved the propagation rate of ethanol-producing strains and
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final product concentration, whereas 40% of the ultrasonic cycle had a negative influence on the
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propagation rate and product yield, and the logarithmic growth period of the bacteria ended earlier.
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Therefore, ultrasound with low intensities can promote yeast growth. With the increase of ultrasonic
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time, the dough fermented more fully, and the specific volume of steamed bread increased and the
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hardness reduced. However, the specific volume would decrease again when ultrasonic time was
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higher than 40 min. This is because of excessive fermentation of dough that leads to the collapse of
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gluten structure to some extent.
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3.2 Effects of ultrasonic power density on the quality of steamed bread
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Table 2 showed that ultrasonic power density had a remarkable effect on the hardness,
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springiness and specific volume of steamed bread (p < 0.05), but relatively little influence on the
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spread ratio and cohesiveness. The hardness of steamed bread decreased first and then increased with
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increasing ultrasonic power density, which was significantly lower than that of the control. The
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hardness approached the minimum at ultrasonic power density of 23.08 W/L, reducing by 22.4%
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compared with the control. At lower power densities, ultrasound may damage the hydrogen bonds
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between large protein polymers and decompose them into small soluble protein aggregates, which
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produced steamed breads with relatively loose and soft structure, so the hardness reduced. However,
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when ultrasonic power increased to a certain intensity, the denatured proteins increased, and the
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hydrophobic groups originally existing in the protein molecules were exposed in large numbers,
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which caused the protein particles more likely to aggregate due to intermolecular collision and
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formed a more compact network structure of gluten proteins (Yong et al., 2016). Therefore, the
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hardness of steamed bread increased again. In addition, ultrasound can change the physicochemical
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properties of wheat starch, including solubility and swelling, molecular size and internal structure,
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gelatinization and aging properties, thus affecting the quality of flour products (Zheng et al., 2013).
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Studies have shown that ultrasound can destroy the crystallization zone of starch, leading more
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hydrophilic groups -OH exposed (Hu et al., 2014). The exposed hydrophilic groups of starch interact
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with water or protein by non-covalent bonds, which enhances the hydrophilcity of dough. Therefore,
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the hardness of steamed bread decreased and the shelf life extended. Whereas, when the ultrasonic
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power intense used is strong, it will break down the long chains of starch molecules into shorter
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chains, which means that the relative content of amylose increases (Zhu, 2015). It is well known that
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amylose content is closely related to the short-term aging of steamed bread (< 24 h). The higher the
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content of amylose is, the faster the short-term aging rate of the bread is. Therefore, the hardness will
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increase again as the ultrasonic power density increases further.
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It was observed a slight decrease in the springiness of steamed bread with ultrasound (p > 0.05)
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compared with the control. However, there was a significant decrease (p < 0.05) in the springiness at
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the power density of 38.46 W/L when compared with at the power density of 15.38 W/L. The
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springiness is mainly dependent on the glutenin content in wheat proteins, which is related to the
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contents of the inter- and intramolecular disulfide bonds in glutenin. O'Sullivan et al. (2016) reported
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that the size of soy protein did not decrease significantly after sonication. They also used the same
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ultrasonic parameters to deal with wheat protein and conducted the same conclusion. This may be
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attributed to low ultrasonic power densities used, which had no energy enough to destroy the
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disulfide bonds that maintains the denatured polymer structure. When the density is strong enough,
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the cavitation induced by ultrasound such as high temperature and high pressure, can damage
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disulfide bonds and molecular structures of gluten, resulting in a decrease in the strength of gluten
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network. The shear force induced by ultrasound may also destroy the covalent and non-covalent
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interactions between proteins, leading to protein denaturation and secondary structure changes
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(Zhang et al., 2015). Zhang et al. (2016) found that the α-helix content of gluten decreased first and
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then increased with the increase of ultrasonic power, while it is reverse for the content of random coil.
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Therefore, the springiness declined at high power densities.
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The specific volume of steamed bread increased first and then decreased with increasing
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ultrasonic power density, approaching the maximum at 23.08 W/L, which increased significantly by
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6.7% compared with the control (p < 0.05). This may be due to the influence of ultrasound on yeast
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activity. Ultrasound helps to increase yeast activity and promote the matter transfer at lower power
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density, facilitating the incorporation of oxygen required for fermentation, the removal of carbon
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dioxide and the improvement of protein foaming ability. When the ultrasonic power density is high,
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the intense cavitation damages the cell walls and plasma membranes of yeasts seriously, and even
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changes the intracellular components such as endoplasmic reticulum and mitochondria. As a result, it
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will inhibit the growth of yeasts and even kill some active yeasts (Huang et al., 2017).
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3.3 Effects of ultrasound treatment on the characteristics of steamed bread during storage
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Fig. 2 showed that the quality of steamed bread varied over storage time, where steamed breads
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with ultrasound were prepared at ultrasonic time 40 min and power density 23.08 W/L. The hardness
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of steamed bread with ultrasound was remarkable lower than that of the control during the storage,
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and this difference was even more evident with prolonging storage time (Fig. 2a). When the storage
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time was higher than 24 h, the hardness with ultrasound varied slightly with increasing storage time,
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even decreased to some extent, which reduced by 7.75% at storage time 144 h compared to at storage
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time 24 h. However, for the control, the hardness significantly increased with prolonging storage time,
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it increased by 23.78% at storage time 144 h compared to at storage time 24 h. After steamed breads
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were stored for 144 h, the hardness with ultrasound reduced by 33.3% compared with the control.
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When the storage time ranged from 1h to 144 h, the hardness with ultrasound increased by 294%,
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whereas the control increased by 455%. It implied that ultrasound treatment can reduce the hardness
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and prolong the shelf life during steamed bread’s storage. The longer the storage time is, the more
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noticeable the positive effect of ultrasound is.
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The hardness is an important parameter affecting the sensory quality of steamed bread and a
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main index of the aging during the storage and determined by the starch retrogradation, gluten
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structure and moisture content. It is commonly considered that the retrogradation of gelatinized
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starch plays an important role in the hardness. The hardness was significantly lower than that of the
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control after 24 h of storage, which suggested that ultrasound could retard the short-term aging of
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wheat starch. It is well known that the short-term retrogradation is closely related to the content of
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amylose (van den Berg et al., 2009). However, low ultrasonic power densities can not affect the
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structure of amylose and amylopectin significantly, i.e. there were no obvious changes in the contents
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of amylose and amylopectin. Therefore, the differences in the hardness between ultrasound treatment
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and the control may be attributed to the changes of gluten structure or water transfer induced by
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ultrasound. Ultrasound can destroy the non-covalent interactions of protein aggregations, and make
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starch granules more easily embedded in the relatively loose network structure of gluten. Thus, it
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retarded the combination of amylose molecules and free water during the storage, which reduced the
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recrystallization level of starch and suppressing the retrogradation. Hu et al (2014) found that
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ultrasound reduced the stability, molecular weight and degree of polymerization of starch molecules,
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resulting in an increase in the aging of sweet potato starch and a decrease in the hardness, springiness
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and chewiness. Additionally, ultrasound can affect the transfer of water in dough (Jambrak et al.,
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2007).
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Fig. 2b showed that the springiness of steamed bread decreased with prolonging the storage time.
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The springiness of steamed bread with ultrasound decreased by 15% after 144 h of storage compared
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with that after 1 h of storage, whereas it decreased by 13% for the control. This indicated that the
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decrease of the springiness with ultrasound was more pronounced than that of the control for
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long-term storage. However, the springiness with ultrasound was higher than that of the control for
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short-term storage (< 48 h). The springiness of steamed bread is mainly dependent on the gluten
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network. The difference in the springiness of steamed bread between the ultrasound and the control is
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probably because ultrasound improves the uniformity and stability of the structure of gluten network.
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Ultrasound can significantly increase the foaming power of egg albumen (Lomakina and Míková,
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2006). Tan et al (2011) also revealed that cake batter mixed by ultrasound produced a high quality of
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cakes with higher springiness, cohesiveness and resilience and lower hardness. However, when the
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storage time was above 48 hours, the interactions between gluten and water or starch decreased with
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the storage time due to a loose network structure of gluten induced by ultrasound, and the total
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moisture content of steamed bread with ultrasound was lower than that of the control (Fig. 2f),
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resulting in a more easier collapse of gluten structure under ultrasonic treatment.
The chewiness of steamed bread is considered as another index which is closely relevant to the
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flavor of steamed bread. Fig. 2e showed that the chewiness with ultrasound was always lower than
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that of the control, especially after storage 24 h. This was due to the lower hardness of steamed bread
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produced by ultrasound. Fig. 2c and Fig. 2d showed that there was no significant difference between
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the ultrasound and the control in cohesiveness and recovery during the storage.
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4. Conclusion
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Ultrasound assisted dough fermentation had considerable impact on the quality of steamed
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bread. It can improve the quality of steamed bread, especially for the hardness and specific volume.
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With the increase of ultrasonic time, the hardness decreased, and the specific volume increased first
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and then decreased. Ultrasonic power density had a remarkable effect on the hardness, springiness
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and specific volume of steamed bread (p < 0.05), but less pronounced influence on the spread ratio
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and cohesiveness. Ultrasound treatment can reduce the hardness of steamed bread and prolong its
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shelf life during the storage. The decline rate in the springiness with ultrasound was lower than that
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of the control when the storage time was no higher than 48 h, however, it was reverse as the storage
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time prolonged further.
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ACKNOWLEDGEMENTS
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The authors gratefully acknowledge Henan Province University Science and Technology
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Innovation Talent Support Program (16HASTIT020), Science and Technology Innovation Team of
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Henan University of Science and Technology (2015XTD007), Foundation for University Youth Key
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Teacher by Henan Province of China (2012GGJS-076).
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Table captions:
Table 1 Effect of ultrasonic time on the quality of steamed bread
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Table 2 Effect of ultrasonic power density on steamed bread quality
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Time(min)
the control
20
30
40
50
Hardness(N)
6.301±0.07a
6.151±0.32ab
6.122±0.46ab
5.709±0.11b
5.152±0.20c
Springiness
0.942±0.01a
0.940±0.00a
0.946±0.00a
0.943±0.00a
0.939±0.00a
Specific volume(ml/g)
2.88±0.03b
2.75±0.11b
3.06±0.04a
3.14±0.03a
3.07±0.04a
Spread ratio
0.70±0a
0.70±0.04a
0.70±0.01a
Cohesiveness
0.755±0.01a
0.749±0.00a
Weighted score
-6.984
-20.810
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Table 1 Effect of ultrasonic time on the quality of steamed bread
0.69±0.01a
0.67±0.01a
0.756±0.00a
0.757±0.00a
0.748±0.00a
21.018
28.704
16.410
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different letters of the same line (p <0.05).
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The control refers steamed bread made at the optimum conditions without ultrasound treatment.
The data shown in the table are average ± SD. There was a significant difference between the
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Table 2 Effect of ultrasonic power density on steamed bread quality
Ultrasonic
power density
0 (the control)
15.38
23.08
30.77
38.46
Hardness(N)
6.087±0.14a
5.002±0.30bc
4.725±0.44c
5.519±0.25b
5.431±0.34b
Springiness
0.933±0.00ab
0.950±0.02a
0.934±0.01ab
0.936±0.00ab
0.922±0.01b
2.84±0.03c
2.98±0.04ab
3.03±0.04a
2.95±0.01ab
2.90±0.03b
Spread ratio
0.70±0.01a
0.69±0.00a
0.70±0.00a
0.71±0.00a
0.70±0.00a
Cohesiveness
0.764±0.01a
0.748±0.00a
0.750±0.00a
0.755±0.02a
0.750±0.01a
Weighted score
-17.143
26.602
34.821
12.635
-8.168
volume(ml/g)
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Specific
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(W/L)
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The data shown in the table are average ± SD. There was a significant difference between the
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different letters of the same line (p <0.05).
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Figure captions:
Fig. 1 The diagram of dough fermentation assisted by power ultrasound
Fig. 2 The hardness(2a), springiness(2b), cohesiveness(2c), recovery(2d), chewiness(2e) and total
moisture content(2f) of the steamed bread prepared by common fermentation method (the control)
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and ultrasound treatment during the storage of 1 h-144 h.
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①ultrasonic bath；②water；③dough；④plastic fresh bag；⑤hollow pipe；⑥transducers
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Fig. 1 The diagram of dough fermentation assisted by power ultrasound
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36
the control
withultrasound
32
28
32.152
27.360
25.914
25.970
29.313
28.268
23.243
20
24.586
23.939
21.726
21.443
20.794
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Hardness(N)
24
12
8
5.873
4 5.447
0
24
48
72
96
120
0.96
the control
with ultrasound
0.92
0.90
0.877
Springiness
0.88
0.86
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0.940
0.939
0.94
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Time(h)
a
0.840
0.855
0.84
0.823
0.820
0.82
0.817
0.797
0.828
0.813
0.80
0.801
0.799
0.78
0
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0.76
0.784
24
48
72
96
120
144
Time(h)
2b
0.8
EP
0.798
0.790
the control
with ultrasound
0.7
Cohesiveness
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0.6
0.5
0.4
0.451
0.401
0.364
0.425
0.369
0.340
0.3
0.340
0.321
0.383
0.334
0.320
0.321
96
120
144
0.2
0
24
48
72
Time(h)
2c
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0.48
0.45
0.447
0.42
0.425
the control
with ultrasound
0.39
0.36
Recovery
0.33
0.30
0.27
0.24
0.18
0.162
0.15
0.154
0.134
0.125
0.125
0.146
0.12
0.133
24
48
0.119
0.109
0.111
0.09
0
72
0.104
96
120
0.105
144
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Time(h)
2d
11
the control
with ultrasound
10
9.442
8.591
8.912
9.199
8
7
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Chewiness
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0.21
7.641
6.986
6
7.463
8.541
7.059
6.163
5.570
4.400
4.044
5
4
5.501
0
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24
48
72
96
120
144
Time(h)
e
40.0
the control
with ultrasound
39.5
39.0
38.5
38.71
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Total moisture content(%)
EP
39.04
39.02
39.03
39.12
38.81
38.76
38.67
38.95
38.73
38.73
38.42
38.30
38.0
38.12
37.5
37.0
0
24
48
72
96
120
144
Time(h)
2f
Fig. 2 The hardness(2a), springiness(2b), cohesiveness(2c), recovery(2d), chewiness(2e) and total
moisture content(2f) of the steamed bread prepared by common fermentation method (the control)
and ultrasound treatment during the storage of 1 h-144 h.
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Highlights:
1. Ultrasound assisted dough fermentation had considerable impact on the quality of
steamed bread.
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2. Ultrasound treatment can improve quality of the steamed bread.
3. Compared to the control, the hardness of fresh steamed bread treated by ultrasound
reduced by 22.4%, and the specific volume increased by 6.7%.
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4. During the storage of steamed bread, the hardness with ultrasound was remarkably
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lower than that of the control.