Recently, the Innovation Team for Phytochemical Components and Omics, led by Professor Li-Tao Tong at the Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences (IFST, CAAS), investigated the effects of magnetic field-assisted freezing on Daifuku quality after thawing and explored the relationships between quality improvement, water state, and structural changes. The findings were published in Food Chemistry under the title “Preserving Daifuku quality via static and pulsed magnetic freezing: Associations with water state and structural changes.” Jiaxin Li, a PhD student enrolled in 2022 in a joint doctoral training programme between CAAS and Wageningen University & Research, is the first author, and Professor Litao Tong is the corresponding author.

Daifuku is a traditional rice-based confection consisting of a glutinous rice wrapper filled with a sweet filling. Its soft and elastic outer layer is a defining feature of its texture. With the expansion of cold-chain distribution and retail networks, maintaining product quality after thawing has become an important challenge in food processing. However, conventional freezing can cause water redistribution and changes in the gel structure of the Daifuku wrapper, resulting in increased hardness, reduced extensibility, and deformation.

In this study, the research team compared the effects of static magnetic fields at different intensities and pulsed magnetic fields at different frequencies during freezing at −20 °C. By combining freezing curve measurements with analyses of microstructure, water state, molecular structure, and textural properties, the researchers investigated changes in Daifuku quality after thawing and the factors associated with these changes.

The results showed that magnetic field-assisted freezing shortened the phase transition time and improved the appearance and texture of Daifuku after thawing. In particular, treatment with a pulsed magnetic field of 6 mT at 0.8 Hz reduced the phase transition time from 53 to 36 minutes, representing a decrease of 32.08%. Compared with fresh samples, the hardness of the Daifuku wrapper increased by approximately 639.6% after conventional freezing, whereas it increased by only 9.45% following this pulsed magnetic field treatment. This treatment provided the best overall texture retention among the freezing conditions tested. Magnetic field-assisted freezing also reduced surface roughness and depressions, while restoring extensibility to a level close to that of fresh samples.

Analyses of water state and molecular structure revealed that magnetic field-assisted freezing reduced the proportion of freezable water in the Daifuku wrapper, promoted a more constrained water state, mitigated the development of short-range molecular order in starch, and better preserved the ordered secondary structures of proteins. These changes were associated with reduced hardening after thawing. Under the experimental conditions, static magnetic fields were more effective in enhancing viscoelasticity and structural support, whereas pulsed magnetic fields performed better in maintaining surface uniformity and overall textural quality. These findings provide valuable insights for optimizing freezing processes for glutinous rice-based frozen foods.

This research was supported by the Chengdu National Agricultural Science and Technology Achievement Transformation Special Fund Project, “Multidimensional Quality Evaluation and Application Research of Rice” (NASC2024KY28), and the Key Research Task of the Zhongyuan Research Center, Chinese Academy of Agricultural Sciences (ZYZX2023010108).

Original article: https://doi.org/10.1016/j.foodchem.2026.151338