Identification of Anthocyanins in Purple‐fleshed Sweetpotato and Stability during Various Cooking Conditions

Abstract

We previously selected a purple‐fleshed sweetpotato P40 that prevented colorectal cancer in a murine model. This study is to identify anthocyanins and tested stability. P40 contains anthocyanins up to 13 mg/g dry matter. Total 12 acylated anthocyanins have been identified by HPLC‐MS/MS. The top three anthocyanins are cyanidin 3‐caffeoyl‐p‐hydroxybenzoyl sophoroside‐5‐glucoside, peonidin 3‐caffeoyl sophoroside‐5‐ glucoside, and cyanidin 3‐(6″ ‐caffeoyl‐6″‐feruloylsophoroside)‐5‐ glucoside. Seven acylated cyanidin species and five peonidin species contribute for 69% and 31% of total anthocyanins, respectively. Over 80% belong to cyanidin as measured by acid hydrolysis. Therefore, as a cyanidin‐predominated variety, P40 is unique when compared with other purple‐fleshed sweetpotatoes that usually contain more peonidin than cyanidin. While baking does not impact overall anthocyanins, steaming, high pressure cooking, microwaving, and frying significantly reduce 20% of total anthocyanins. Mono‐acylated anthocyanins show a higher resistance against heat than di‐ and non‐acylated. Among of which, cyaniding 3‐p‐hydroxybenzoylsophoroside‐5‐glucoside exhibits the best thermal stability. Better understanding of sweetpotato anthocyanins and stability may lead the development of a functional product for health benefits (supported by USDA Cooperative KS410–0214022).