Effects of Adzuki Bean Powder on the Quality and Anti-retrogradation Properties of Steamed Cake

To inhibit starch retrogradation and enhance the quality of steamed cakes during storage, in this study, we investigated the effects of different addition levels of adzuki bean powder (ABP) (0%, 8%, 16%, 24%, and 32%) on the water-holding capacity (WHC) and oil-holding capacity (OHC) of composite flour (wheat flour, glutinous rice flour, yam flour, and taro flour at a mass ratio of 15:5:3:2), and on the texture, antioxidant activity, color, specific volume, protein content, and sensory properties of the resulting steamed cakes. Low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to elucidate the anti-retrogradation mechanisms. The results showed that as ABP content increased, the WHC of the composite flour significantly rose from 0.97 g/g to 1.43 g/g (P<0.05). Meanwhile, the OHC exhibited an initial increase followed by a decrease. For the steamed cakes, the specific volume increased from 1.80 mL/g to 2.48 mL/g, protein content rose from 2.17% to 2.72%, and hardness decreased from 683.95 g to 498.59 g. Redness (a^*) increased significantly (P<0.05), while brightness (L^*) and adhesiveness significantly decreased (P<0.05). At the 24% addition level, the total antioxidant capacity, total reducing power, and ABTS⁺· scavenging activity peaked. After 7 d of storage at 4 ℃, the hardness of all the ABP-supplemented groups remained significantly lower than that of the control group (P<0.05). Mechanistic analysis showed that ABP was deeply integrated into the starch-gluten system by strengthening the hydrogen bond network. Addition of 16%~24% effectively sequestered moisture and significantly reduced the short-range molecular order of starch. The proportion of deeply bound water increased by 12.13% to 44.19% relative to the control. This further inhibited starch molecular rearrangement from the perspectives of long-range order and thermodynamics, decreasing the relative crystallinity from 12.08% to 9.01%~9.15% and reducing the retrogradation enthalpy by 15.11%~41.49% compared to the control. In conclusion, the addition of 16%~24% ABP significantly enhanced the quality of steamed cakes and effectively inhibited starch retrogradation during storage.