Acylated Anthocyanins in Red Onions

Abstract

Chromatographic fractions of the onion pigment profile were examined for acyaltion by alkaline hydrolysis, visible/UV spectral, IR spectral, GLC, and NMR techniques. Results indicative of acylation were shown by alkaline hydrolysis and IR spectral analyses. The suspected acyl portion was shown not to be a cinnamic acid by visible/UV spectral analysis. NMR and GLC methods failed to detect acylation in the onion pigment system. Small amounts of assay material, low sensitivity for detection of some of the possible acyl acids, removal of the acyl by complex formation, loss of the acyl due to high volatility and low acid transfer in partitioning systems are some of the factors identified as interfering with acyl detection.