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

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 (AL25) and 37 degrees C (AL37) and under fluorescent light at 25 degrees C (FL25). 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 (PFSPAs) under AL25, AL37 and FL25 were around 50.7%, 89.0% and 87.0% respectively. The FL25 and AL37 conditions had similar effects on the colourant's total colour change (Delta Eab). The degradation kinetics followed the zero-order reaction models. The PFSPAs 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 PFSPAs as a novel natural colourant in food industry.