Characterization of starch structures isolated from the grains of waxy, sweet, and hybrid sorghum (Sorghum bicolor L. Moench)

Xuemin Kang; Wentao Zhu; Tongcheng Xu; Jie Sui; Wei Gao; Zhiquan Liu; Haichun Jing; Bo Cui; Xuguang Qiao; A M Abd El-Aty

doi:10.3389/fnut.2022.1052285

Characterization of starch structures isolated from the grains of waxy, sweet, and hybrid sorghum (Sorghum bicolor L. Moench)

Front Nutr. 2022 Dec 13:9:1052285. doi: 10.3389/fnut.2022.1052285. eCollection 2022.

Authors

Xuemin Kang^{1

2

3}, Wentao Zhu^{2

3}, Tongcheng Xu⁴, Jie Sui⁴, Wei Gao^{2

3}, Zhiquan Liu⁵, Haichun Jing⁵, Bo Cui^{1

2

3}, Xuguang Qiao¹, A M Abd El-Aty^{2

6

7}

Affiliations

¹ Department of Food Science and Engineering, Shandong Agricultural University, Taian, China.
² State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China.
³ School of Food Science and Engineering, Qilu University of Technology, Shandong Academy of Sciences, Jinan, Shandong, China.
⁴ Shandong Academy of Agricultural Science, Jinan, Shandong, China.
⁵ Institute of Botany, Chinese Academy of Sciences, Beijing, China.
⁶ Department of Pharmacology, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
⁷ Department of Medical Pharmacology, Medical Faculty, Ataturk University, Erzurum, Turkey.

Abstract

In this study, starches were isolated from inbred (sweet and waxy) and hybrid (sweet and waxy) sorghum grains. Structural and property differences between (inbred and hybrid) sweet and waxy sorghum starches were evaluated and discussed. The intermediate fraction and amylose content present in hybrid sweet starch were lower than those in inbred sweet starch, while the opposite trend occurred with waxy starch. Furthermore, there was a higher A chain (30.93-35.73% waxy, 13.73-31.81% sweet) and lower B₂ + B₃ chain (18.04-16.56% waxy, 24.07-17.43% sweet) of amylopectin in hybrid sorghum starch. X-ray diffraction (XRD) and Fourier transform infrared reflection measurements affirm the relative crystalline and ordered structures of both varieties as follows: inbred waxy > hybrid waxy > hybrid sweet > inbred sweet. Small angle X-ray scattering and ¹³C CP/MAS nuclear magnetic resonance proved that the amylopectin content of waxy starch was positively correlated with lamellar ordering. In contrast, an opposite trend was observed in sweet sorghum starch due to its long B₂ + B₃ chain content. Furthermore, the relationship between starch granule structure and function was also concluded. These findings could provide a basic theory for the accurate application of existing sorghum varieties precisely.

Keywords: chain length distribution (CLD); hydrolysis rate; inbred and hybrid sorghum starch; lamellar structure; ordered structure.