Isomerization of Paracoccus carotinifaciens-Derived Carotenoids (Astaxanthin, Adonirubin, and Adonixanthin) under Subcritical Water Conditions

Recent studies have shown that Z-isomers of carotenoids exhibit greater bioavailability and tissue accumulation efficiency than the natural isomer, the all-E-isomers. Here, we attempted to carry out the Z-isomerization of Paracoccus carotinifaciens-derived carotenoids (astaxanthin, adonirubin, and adonixanthin) by subcritical water processing. An aqueous solution dispersed with P. carotinifaciens was treated in a pressure-resistant vessel in the range of 140-240 degrees C and 4-16 MPa. The processing pressure in the above range did not affect carotenoid isomerization; however, depending on the heating temperature, the total Zisomer ratio markedly increased, and carotenoid degradation was also accelerated. Moreover, to promote the Z-isomerization efficiency, the effect of adding an entrainer, ethanol, was investigated. The results showed that the addition of ethanol markedly promoted the Z-isomerization efficiency. Finally, we achieved over 50% of the total Z-isomer ratio of P. carotinifaciens-derived carotenoids while inhibiting their degradation by 30 min subcritical water processing.