Ingredient interactions usually occur in food matrix, which may affect their functions and properties. This study aimed to investigate the interactive effects of mulberry and corn protein on pigment stability and zein digestibility. The interaction of main compounds in both ingredients, that is, cyanidin-3-O-glucoside (C3G) and zein, was characterized via their structural, morphological, thermal stability, and digestible properties using multi-spectroscopic techniques, scanning electron microscopy, high performance liquid chromatography, and in vitro digestion models. Results showed that zein exhibited a strong binding affinity for C3G via van der Waals forces and hydrogen bonds determined in fluorescence assays. The secondary structure of zein changed due to C3G binding, with a decrease in α-helix and an increase in β-sheet. The particle size of zein decreased after interacting with C3G. The zein complexation with mulberry anthocyanin-rich extracts in a simulative food system did not affect the digestibility of zein significantly but enhanced the thermal stability of pigments slightly. Specifically, anthocyanins did not change the susceptibility of zein to pepsin proteolysis, suggesting that binding sites of C3G might not be the cleavage sites of pepsins. These results provide important insight into the binding mechanism of zein and anthocyanins and might help guide the design of anthocyanin-based functional food. PRACTICAL APPLICATION: Zein, as a storage protein widely distributed in corn flour, was commonly co-existing with anthocyanins in starchy food. This study provides insights into the molecular interactions between zein and cyanidin-3-O-glucoside. However, the interaction might not impact the zein digestion but enhance anthocyanin thermal stability. The findings of this work could throw light on the selection of ingredients rich in zein and anthocyanins in the food industry.
Keywords: binding; corn flour; mulberry; phenolics; protein digestion.
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