Isolation and characterization of the anthocyanins derived from red radishes (Raphanus sativus L.) and the protective ability of β‐lactoglobulin against heat‐induced oxidation

摘要

Abstract This study employed the “two‐step dialysis” method and AB‐8 or D101 macroporous resin chromatography to isolate the anthocyanins in red radishes (ARR). The red radish juice was dialyzed twice at 3000 and 500 Da, respectively. UHPLC‐QqQ‐MS/MS revealed 24 types of ARRs, of which pelargonidin (Pg)‐3‐diglucoside‐5‐(malonyl)glucoside (P3D5MG), Pg‐3‐diglucoside‐5‐glucoside (P3D5G), Pg‐3‐(feruloyl)diglucoside‐5‐(malonyl)glucoside (P3FD5MG), Pg, and malvidin (Mv) represented the main compounds. The total anthocyanin content in the ARR prepared via the “two‐step dialysis” method was 29.69% and 18.44% higher than that obtained using AB‐8 and D101 macroporous resins, respectively. The ARRs inhibited heat‐induced β‐lactoglobulin (β‐Lg) oxidation. The amino acid residue microenvironment and secondary β‐Lg structure were modified via ARR binding. The energy involved in P3D5MG and β‐Lg binding was −392 kJ/mol, which was significantly lower than that during the binding process of P3D5M, P3FD5MG, Pg, and Mv to β‐Lg (−338 to −168 kJ/mol). These results indicated that “two‐step dialysis” was a promising method for deriving natural pigment with strong antioxidant activity from red radishes. Practical Application As a natural food colorant, anthocyanins have attracted increasing attention in the food industry in recent years. This study used “two‐step dialysis” to effectively separate ARRs. Moreover, the anthocyanins in ARR can bind to β‐Lg to protect against heating‐induced oxidation. Therefore, ARRs may not only act as a food pigment but also as antioxidants.