Influence of three types of freezing methods on physicochemical properties and digestibility of starch in frozen unfermented dough

• Published in: Food hydrocolloids 2021-06, Vol.115, p.106619, Article 106619
• Main Authors: Yang, Yong, Zheng, Shuaishuai, Li, Zhen, Pan, Zhili, Huang, Zhongmin, Zhao, Jianzhong, Ai, Zhilu
• Format: Article
• Language: English
• Subjects: Freezing methods; Frozen unfermented dough; Ordered structure; Relative crystallinity; Starch digestibility
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2021.106619

Three types of freezing methods, namely, spiral tunnel freezing method (SF), cryogenic refrigerator freezing method (RF) and liquid nitrogen spray freezing method (LF), were applied to frozen unfermented dough. The particle size distribution and SEM results showed freezing methods reduced the average particle size of starch granules and destroyed the surface microstructure, especially RF, and the damaged starch content and swelling power of starch after treatment increased. Gelatinization and pasting properties of starches changed to varying degrees, indicating freezing methods caused the internal rearrangement of starch molecules. This view could also be inferred from X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FT-IR) data. The relative crystallinity (35.51%–38.56%) and the R1047/1022 (0.562–0.590) were increased, compared with the control (32.44%, 0.559, respectively). Meanwhile, freezing treatment improved the digestibility of starch by promoting the combination of enzymes and starch, especially RF. Larger ice crystals formed by RF with slower freezing rate produced larger damage to starch structure, more likely to promote the binding with enzymes. LF with faster freezing rate had less effect on the starch composition than RF and SF with slower freezing rate. The data obtained clarified the influence of freezing methods on the structure and properties of starch in a yeast-free dough system, and enriched the knowledge regarding the effect of freezing technology on food components. The structure-property relation diagram of starches in frozen unfermented dough treated by three types of freezing methods. [Display omitted] •Effects of three types of freezing methods on starch in a yeast-free dough system.•LF at faster freezing rate had less effect on starch than RF and SF at slower rate.•Freezing methods increased the short-range ordered degree and relative crystallinity.•Freezing improved starch digestibility by promoting the bond of starch and enzymes.