Anthocyanin composition and storage degradation kinetics of anthocyanins‐based natural food colourant from purple‐fleshed sweet potato

Summary A natural colourant derived from purple‐fleshed sweet potato ( PFSP ) by ultrasound‐assisted solvent extraction was examined in terms of its anthocyanins and 6‐month storage stability under different conditions: avoid from light at 25 ( AL 25) and 37 °C ( AL 37) and under fluorescent light at 25 °C ( FL 25). This PFSP colourant mainly contained the following peonidin anthocyanins: peonidin 3‐p‐hydroxybenzoyl sophoroside‐5‐glucoside, peonidin 3‐feruloyl sophoroside‐5‐glucoside, peonidin 3‐caffeoyl sophoroside‐5‐glucoside, peonidin dicaffeoyl sophoroside‐5‐glucoside, peonidin 3‐caffeoyl‐ p ‐hydroxybenzoyl sophoroside‐5‐glucoside and peonidin caffeoyl‐feruloyl sophoroside‐5‐glucoside. The degradation ratios of PFSP anthocyanins ( PFSPA s) under AL 25, AL 37 and FL 25 were around 50.7%, 89.0% and 87.0% respectively. The FL 25 and AL 37 conditions had similar effects on the colourant's total colour change (ΔEab). The degradation kinetics followed the zero‐order reaction models. The PFSPA s were more stable during storage than other anthocyanins because they mainly consist of di‐acylated and double glycosylated forms of peonidin derivatives. These results may promote the application of PFSPA s as a novel natural colourant in food industry.