Elsevier

Food Chemistry

Volume 366, 1 January 2022, 130614
Food Chemistry

Understanding how starch constituent in frozen dough following freezing-thawing treatment affected quality of steamed bread

https://doi.org/10.1016/j.foodchem.2021.130614Get rights and content

Highlights

  • How wheat starch constituent in frozen dough affected bread quality was evaluated.

  • Freezing-thawing treatment disrupted the hierarchical structure of starch.

  • Freezing-thawing treatment increased the characteristic viscosity of starch paste.

  • Starch structure and functionality were closely correlated with bread quality.

  • The enhanced hydroscopicity and rearrangement of starch allow the inferior quality.

Abstract

Understanding how starch constituent in frozen dough affected bread quality would be valuable for contributing to the frozen products with better quality. To elucidate the underlying mechanism, starch was fractionated from multiple freezing-thawing (F/T) treated dough and reconstituted with gluten. Results showed that F/T treatment destructed the molecular and supramolecular structures of starch, which were more severe as the F/T cycle increasing. These structural disorganizations made water molecules easier to permeate into the interior of starch granules and form hydrogen bonds with starch molecular chains, which elevated the peak, breakdown, setback and final viscosity of starch paste. In addition, F/T treatment resulted in decreased specific volume (from 1.54 to 0.90 × 103 m3/Kg) and increased hardness (from 42.98 to 52.31 N) for steamed bread. We propose the strengthened water absorption ability and accelerated intra- and inter-molecular rearrangement of starch molecules and weak stability of “starch-gluten matrices” would allow interpreting deteriorated bread quality.

Graphical abstract

Schematic showing the interrelationship between starch constituent in frozen dough and steamed bread quality.

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Introduction

As one of the traditional Chinese staple food, steamed bread has been widely consumed owing to its unique flavour, excellent quality and nutritional function, which has attracted increasing attention in the world (Zhu, 2014). Furthermore, the relatively low temperature during the steaming process could reduce the contents of acrylamide and furan through inhibiting the occurrence of Maillard reactions, and simultaneously better guard the bioactivity of wheat flour protein (Wang, Jin, & Xu, 2015). Thus, steamed bread is highly favored and recommended due to its staple role in China, which is vital for national nutrition.

Accompanying the economic development and rapid urbanization progress of China, the industrialization of steamed bread becomes increasingly promising. Frozen dough has been of great interest in recent years because of its excellent characteristics including constant availability of fresh products, consistent and standardized quality uniform, lower costs, and unifying transportation (Sang et al., 2018). Although frozen dough has many advantages, the quality of dough gradually deteriorates during the process from storage to final consumption, which resulted in inferior dough strength and poor quality attributes of its final products (e.g., steamed bread, bread) (Yang et al., 2019, Yu et al., 2020). Numerous studies had confirmed that the deteriorated quality of frozen dough was closely associated with the loss of yeast viability and disruption of gluten structure, which were driven by ice crystallization and recrystallization (Lu et al., 2021, Luo et al., 2018). For example, long-term frozen storage and multiple freezing-thawing cycles could reduce the yeast fermentation capacity, diminish gassing power, and weaken the gluten network with the formation of ice crystals in dough, leading to increased firmness, inferior loaf volume and palatability (Bhattacharya et al., 2003, Meziani et al., 2012, Wang et al., 2018). Despite researches into the role of gluten and yeast in the quality of frozen dough products have been broadly performed, quality deterioration phenomenon of frozen dough has been not completely solved yet, which may be related to the lack of mechanism on how starch multi-scale structure and characteristics affect the performance of frozen dough and its final products. Hence, understanding the mechanism on quality deterioration from the view of starch constituent has become greatly meaningful for the development of frozen dough technology, especially for the industrialization progress of steamed bread.

Starch, which accounts for about 75% of solids in frozen dough, and the alterations in starch intrinsic hierarchical structure might affect its water absorption ability, pasting properties, rheological behaviors and the formation and stability “gluten-starch matrix”, eventually leading to unpredictable effects on quality attributes of final products (Bhattacharya et al., 2003, Yang et al., 2019, Yu et al., 2020). Specifically, starch makes diverse contributions in controlling the moisture, viscosity, texture, consistency, mouth-feel, shelf-life and nutrition, which are important for food processing and quality of finished products (BeMiller & Huber, 2015). The extent of starch contribution to food quality mainly relies on starch gelatinization behaviors in the presence of water, which refers to thermal and pasting properties (Xie, Qi, Xu, Shen, Wang, & Zhang, 2020). For instance, peak viscosity of starch have been found to be vital in determining the textural quality of steamed bread (Bredariol et al., 2019, Giannou et al., 2003). For regulating the pasting behaviors of starch, it is indispensable to understand the characteristics of starch multi-scale structures (i.e., molecular and supramolecular structure). Amylose and amylopectin molecules are the basis of starch supramolecular structure, which assemble on different levels to construct a supramolecular structural system, mainly including the double- or single-helices, the short-range ordered structure, the crystalline structure, the lamellar nano-structure, and the whole granule (Wang, Ding, Xiao, Liu, Zhang, & Zhang, 2020). Therefore, understanding how starch constituent in frozen dough following freezing-thawing treatment affected quality of steamed bread is vital for accelerating the industrialization pace of final products.

Current research mainly focused on the influence of long-term frozen storage and temperature fluctuations on granular features, crystalline structure, gelatinization properties and leaching materials (such as amylose, protein, and lipid) (Szymońska and Wodnicka, 2005, Tao et al., 2016, Tao et al., 2016). And the aboved studies mostly focused on the different starch suspensions with freezing treatment. However, little information can be observed on the hierarchical structural and functional changes for starch isolated from frozen dough. A real frozen dough system is sophisticated with diverse constituents such as starch, protein, lipid, and non-starch polysaccharides. Particularly, few studies have been focused on the changes of molecular (e.g., helical structures, and short-range molecular orders) and lamellar structures for starch subjected to freezing process. Therefore, how the structure and physicochemical properties of starch change in frozen dough during freezing-thawing process should be highly concerned. Moreover, the systematic study on understanding how multi-scale structural and functional changes of starch isolated from frozen dough affected quality of steamed bread is still not fully uncovered, especially for starch isolated from freezing-thawing frozen dough. In other words, understanding the relationship among starch multi-scale structure, starch functionality and quality attributes of steamed bread is valuable for contributing to the frozen products with better quality.

Against this background, fractionation and reconstitution experiment was applied to determining the role of starch constituents on quality of steamed bread. This work was to illustrate the combined roles of multi-scale structures and functionality properties of starch suffered by multiple freezing-thawing treatment in determining the quality attributes of steamed bread. Combined analytical methods covering multiple length-scale orders were used to investigate the molecular and supramolecular structure features and the thermal and pasting properties of wheat starches isolated from multiple freezing-thawing treated dough. The results of this study will provide a profound understanding of how starch constituent determined the quality of frozen dough products.

Section snippets

Materials

Wheat flour was purchased from Jinyuan Grain and Oil Co. (Zhengzhou, China), and the moisture, ash, protein and starch contents of this flour were 12.4%, 0.5% (dry basis), 12.8% (dry basis) and 76.5% (dry basis), respectively. Wheat gluten (G5004, protein content, >75.0%, dry basis) was acquired from Sigma-Aldrich (USA). All other chemical reagents needed in this research were of analytical grade.

Preparation of frozen dough

Frozen dough was produced according to the method of Tao, Zhang, et al. (2016), with minor

Helical structures of wheat starch

The changes in helical structures of wheat starch isolated from fresh and F/T-treated dough can be quantitatively calculated through 13C CP/MAS NMR. The spectra of native and F/T-treated starches are presented in Fig. S1. The overlapping peak at 68–78 ppm and another three distinct peaks at 94–106, 81–84, and 58–65 ppm were observed, which were associated with the C2, 3, 5, C1, C4, and C6 of glucose unit in starch molecular chain. Normally, three obvious peaks in the C1 region suggested that

Conclusion

In this work, freezing-thawing cycle treatment for multiple times (2, 6 and 10 times) was performed to clarify how starch constituent in frozen dough affected quality attributes of steamed bread. The different number of freezing-thawing cycles had a significant effect on the hierarchical structure and functional properties of starch isolated from dough. Repeated freezing-thawing treatment could lead to the dissociation, unwinding and/or amorphization of starch molecular structure, irregular

CRediT authorship contribution statement

Ke Xu: Methodology, Validation, Formal analysis, Writing – original draft, Visualization. Chengdeng Chi: Formal analysis, Investigation, Data curation, Writing – original draft, Visualization. Zhenyun She: Methodology, Validation. Xingli Liu: Writing - review & editing. Yanyan Zhang: Resources, Writing - review & editing, Supervision. Hongwei Wang: Conceptualization, Methodology, Resources, Supervision, Writing - review & editing, Supervision, Funding acquisition. Hua Zhang: Resources,

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This research was financially supported by the National Key Research and Development Program of China (no. 2018YFD0400600), the National Natural Science Foundation of China-Henan Joint Fund (no. U2004147), the National Natural Science Foundation of China (no. 31801578), the Science and Technology Project of Henan Province (no. 212102110328), the Science and Technology Project of Henan Province (no. 202102110301), and the Major Science and Technology Innovation Project of Zhengzhou (no.

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Ke Xu and Chengdeng Chi contributed equally to this work.

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