Thermal Degradation of Acylated and Nonacylated Anthocyanins

Abstract

ABSTRACT: The thermal degradation pathways of acylated and nonacylated anthocyanins from 3 commercial sources have been investigated. Strawberry, elderberry, and black carrot concentrates were purified on XAD‐16‐HP and Sephadex‐LH‐20 columns to remove sugars, amino acids, salts, and phenolic compounds, respectively. The so obtained anthocyanin isolates were heated at 95 °C at pH 1, the optimum stability condition for the flavylium cation. During 7 h of thermal exposure, the samples were monitored by HPLC‐DAD‐MS3 at 280, 320, and 520 nm, respectively, together with spectrophotometric color and anthocyanin assessment. Total anthocyanin content lightness, and chroma, but not hue angle, were appropriate parameters to monitor anthocyanin loss on a statistically significant level. Anthocyanin glycosides were generally cleaved by successive loss of sugar moieties and pentoses were more readily split off than hexoses. Anthocyanin aglycones were further degraded by scission into phloroglucinaldehyde (cyanidin, pelargonidin), 4‐hydroxybenzoic acid (pelargonidin), and protocatechuic acid (cyanidin), the residues of the A‐ and B‐rings, respectively. Most interestingly, acylated cyanidin‐triglycosides from black carrot were degraded into their corresponding diglycoside derivatives, which are not genuine carrot pigments. Moreover, hydroxycinnamic acid glycosides were generated. It is therefore assumed that the thermal burden during processing of anthocyanic food can be deduced by monitoring the colored and colorless compound profiles.