Changes in the carotenoid content of apricot (Prunus armeniaca, var Bergeron) during enzymatic browning: beta-carotene inhibition of chlorogenic aciddegradation

Considering the numerous beneficial effects in human health ascribed to car otenoids, studies were performed to investigate the modification of caroten oid amount and composition during apricot enzymatic browning. First works o n bruised apricot purees have shown a trans-beta-carotene isomerisation (20 %) induced by enzymatic browning. To clarify this isomerisation, oxidation of chlorogenic acid in presence of trans-beta-carotene, catalysed by purifi ed apricot polyphenoloxidase (PPO), was followed by HPLC and polarography. Isomerisation rate of trans-beta-carotene in its cis isomer was found to in crease with chlorogenic acid concentration. Moreover, trans-beta-carotene w as shown to be a potent inhibitor of phenol degradation. This inhibition wa s partially ascribed to PPO inhibition (non-competitive inhibitor towards p henol with an apparent Ki close to 0.5 mM, a mixed type inhibitor towards o xygen with an apparent Ki close to 0.15 mM). The additional inhibition was explained by non-enzymatic reactions involving trans-beta-carotene and chlo rogenic acid o-quinones and leading to phenol regeneration and carotene iso merisation. (C) 2000 Society of Chemical Industry.