Rapid screening for anthocyanins in cane sugars using ESR spectroscopy

Anthocyanin, which is soluble in water and released into sugar steam during extraction, was investigated in this study. The anthocyanin content in refined sugar, plantation white sugar, soft brown sugar and raw sugar was determined using electron spin resonance (ESR) spectroscopy, which was operated at room temperature, and compared with spectra from standard anthocyanin. The ESR spectra of red and violet anthocyanins was predominantly g ≈ 2.0055, which corresponded to an unpaired electron located in the pyrylium ring. Signals for Fe(III) and Mn(II), which naturally occur in plants, were found in raw sugar, soft brown sugar and standard anthocyanin but were absent from refined sugar and plantation white sugar due to the refining process. In addition, the ESR results were correlated with the apparent colour of the sugar, which was determined using the method of the International Commission for Uniform Methods of Sugar Analysis and inductively coupled plasma optical emission spectroscopy.