UV-visible light spectra of Clitoria ternatea L. flower extract during aqueous extraction and storage

Abstract

Spectrophotometry is a widespread method to observe anthocyanin content, colour quality, and chemical change of an anthocyanin-source extract. The spectrogram may vary due to the extraction method, and may also change over time. The present work studied the spectrophotometric varieties of butterfly pea flower (Clitoria ternatea L.) extract using the cell wall disruption method (mortar-pestle: MP; freezing-thawing: FT; 6 min steam blanching: SB; and 6 min hot water blanching: WB) and aqueous extraction temperature (30, 45, and 60°C) for 210 min. The absorbance was monitored every 30 min. The UV-vis light absorbance shift of the extract during storage at 30°C (E30) and 50°C (E50) was also evaluated. Both SB and WB resulted in extracts with a similar spectrogram and effectively suppressed the brown colour development (browning index: 0.27 ± 0.02 and 0.3 ± 0.01, respectively). The cell wall disruption method did not affect the total anthocyanin. Therefore, the blanching process before extraction was appropriate. The most effective extraction parameter yielding the highest anthocyanin and phenolic substances were 60°C for 30 min. The E50 and E30 performed differently during storage. They showed different colour degradation patterns. For the bathochromic shift, the absorbance increased at 265 nm (phenolic substances), and that at 310 nm (acyl groups) occurred in E50. These three unique characteristics might indicate the event of intermolecular co-pigmentation between or among anthocyanin molecules that led to higher anthocyanin stability at 50°C (t0.5 24.78 days) than at 30°C (t0.5 14.28 days).