Search

Carotenoids-natural fat-soluble pigments-have attracted considerable attention because of their potential to prevent of various diseases, such as cancer and arteriosclerosis, and their strong antioxidant capacity. They have many geometric isomers due to the presence of numerous conjugated double bonds in the molecule. However, in plants, most carotenoids are present in the all- E -configuration. (all- E )-Carotenoids are characterized by high crystallinity as well as low solubility in safe and sustainable solvents, such as ethanol and supercritical CO 2 (SC-CO 2 ). Thus, these properties result in the decreased efficiency of carotenoid processing, such as extraction and emulsification, using such sustainable solvents. On the other hand, Z -isomerization of carotenoids induces alteration in physicochemical properties, i.e., the solubility of carotenoids dramatically improves and they change from a "crystalline state" to an "oily (amorphous) state". For example, the solubility in ethanol of lycopene Z -isomers is more than 4000 times higher than the all- E -isomer. Recently, improvement of carotenoid processing efficiency utilizing these changes has attracted attention. Namely, it is possible to markedly improve carotenoid processing using safe and sustainable solvents, which had previously been difficult to put into practical use due to the low efficiency. The objective of this paper is to review the effect of Z -isomerization on the physicochemical properties of carotenoids and its application to carotenoid processing, such as extraction, micronization, and emulsification, using sustainable solvents. Moreover, aspects of Z -isomerization methods for carotenoids and functional difference, such as bioavailability and antioxidant capacity, between isomers are also included in this review.

This study aims to improve the efficiency of lycopene extraction from gac (Momordica cochinchinensis Spreng.) by the Z‐isomerization induced with microwave irradiation pre‐treatment. Although 93.6% of lycopene exist as all‐E‐isomers in dried gac aril, the total Z‐isomer content reaches 35.6 and 58.5% by microwave irradiation at 900 W for 40 s and at 1050 W for 60 s, respectively. The 35.6 and 58.5% Z‐isomerization treatment improves lycopene content of extract (by 6.0 or 8.5 times for press extraction, 7.8 or 13.5 times for ethanol extraction, and 4.5 or 6.1 times for supercritical CO2 (SC‐CO2)extraction, respectively) compared with no treatment. In addition, the extracts containes high amounts of lycopene Z‐isomers, which have higher bioavailability and antioxidant capacity than (all‐E)‐lycopene. Practical Applications: This study clearly shows that lycopene recovery by press, organic solvent, and SC‐CO2 extraction from dried gac aril improved by the increase in the Z‐isomer content. It indicates that the Z‐isomers are more soluble in oil, organic solvent, and SC‐CO2 than the all‐E‐isomer. Moreover, the thermal Z‐isomerization pre‐treatment increases the content of lycopene Z‐isomers in the extract. Therefore, this procedure is important not only for improving the productivity of lycopene, but also for providing a highly functionalized extract. The effect of the Z‐isomerization, induced by microwave irradiation pre‐treatment of gac (Momordica cochinchinensis Spreng.) aril, on the lycopene recovery and lycopene content of the extracts obtained using press, ethanol, and SC‐CO2 extractions is investigated. For all extraction methods, as the content of Z‐isomers in the raw material increases, the recovery and lycopene content of gac extracts improve. [ABSTRACT FROM AUTHOR]