In this research, PSPAs were extracted from fermented purple sweet potato culture which was fermented by Suzhou wine starter (Rhizopus 3.851, 3.866 and Saccharomyces cerevisiae). The components of the PSPAs were determined by reverse-phase HPLC. The stability of the PSPAs was examined at six different pH values between 2.0 and 7.0 and was measured both by UV–vis absorption spectra and CIELAB colour coordinates. The objective of this study was to find a useful way to extract purer PSPAs, and to determine their components and colour stability for their potential application as a natural food colourant.