*Article* **Protective Effect and Mechanism of Soybean Insoluble Dietary Fiber on the Color Stability of Malvidin-3-***O***-glucoside**

**Yang He 1,†, Dongxia Chen 1,†, Yuheng Liu 1, Xiaozhen Sun 1, Wenrui Guo 1, Lingyu An 1, Zhenming Shi 1, Liankui Wen 1, Zhitong Wang 1,\* and Hansong Yu 1,2,\***


**Abstract:** Anthocyanins have great health benefits, especially malvidin. *Vitis amurensis Rupr* are rich in malvidin, and malvidin-3-*O*-glucoside (Mv3G) monomer is the most abundant. However, natural anthocyanins are unstable, which limits their wide application in the food field. Soybean insoluble dietary fiber (SIDF) has high stability, and it can be used as an inert substrate to construct a stable system, which may improve the stability of anthocyanins. The optimal condition to construct a stable system of SIDF and Mv3G at pH 3.0 was determined by an orthogonal experiment. The results indicated that SIDF effectively improved the stability of Mv3G under different pH values (1.0~7.0), high temperature (100 ◦C for 100 min), and sunlight (20 ± 2 ◦C for 30 d) conditions. The absorption peak intensity of the UV–VIS spectrum of SIDF-Mv3G was enhanced, which indicated that there was interaction between SIDF and Mv3G. Fourier transform infrared spectroscopy analyses revealed that the -OH stretching vibration peak of SIDF-Mv3G was changed, which indicated that the interaction between SIDF and Mv3G was due to hydrogen bonding. X-ray diffraction analysis showed that the crystalline morphology of SIDF was opened, which was combined with Mv3G, and SIDF made Mv3G change to a more stable state. Scanning electron microscope analysis showed that SIDF and Mv3G were closely combined to form an inclusion complex. Overall, this study provides valuable information for enhancing the color stability of anthocyanins, which will further expand the application of anthocyanins in the food field.

**Keywords:** anthocyanins; insoluble dietary fiber; stable system; inclusion complex; hydrogen bonding
