Improved Carotenoid Processing with Sustainable Solvents Utilizing Z-Isomerization-Induced Alteration in Physicochemical Properties: A Review and Future Directions

Abstract

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 CO2 (SC-CO2). 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.

Impact of Light Intensity on Antioxidant Activity of Tropical Microalgae

“…This mechanism of action is further highlighted in our experiments by partial or non-degradation of fucoxanthin in MeOH/DCM extracts which is the only xanthophyll 5,6-epoxide to have its position eight occupied by a ketone group that blocks rearrangement to a 5,8-dihydrofuran ring. In this case, the epoxide isomerization results in a partial isomerization of fucoxanthin into cis-fucoxanthin which is not observed when carotenoids analyses are performed on fresh acetone extracts [61,62].…”

“…Mar. Drugs 2020, 18, 122 6 of 18 results in a partial isomerization of fucoxanthin into cis-fucoxanthin which is not observed when carotenoids analyses are performed on fresh acetone extracts [61,62].…”

Thermal‐ and Photo‐Induced Isomerization of All‐E‐ and Z‐Isomer‐Rich Xanthophylls: Astaxanthin and Its Structurally‐Related Xanthophylls, Adonirubin, and Adonixanthin

“…Namely, several studies have indicated that Z ‐isomers of carotenoids such as lycopene and astaxanthin have higher bioavailability and antioxidant activity than the all‐ E ‐isomers. [ 14–17 ] In addition, Z ‐isomers of astaxanthin and fucoxanthin potentially have higher anti‐inflammatory activity and anticancer activity, respectively, than their all‐ E ‐isomers. [ 18,19 ] Thus, in some cases, the intake of Z ‐isomers of carotenoids, rather than all‐ E ‐isomers, is preferable for human health, and the development of Z ‐isomer‐rich carotenoid products such as supplements is expected.…”

“…In addition, when adonirubin, astaxanthin, and adonixanthin are used for the above applications, it is desirable that their Z ‐isomer (Figure 1d,e) contents are high. [ 14–18 ] However, there have been no reports on the storage stability of the xanthophyll isomers against heating and photo‐irradiation. Therefore, the objectives of this study were to investigate the effect of thermal treatment and photo‐irradiation on the stability of adonirubin, astaxanthin, and adonixanthin having high Z ‐isomer content in comparison with the all‐ E ‐isomers in a model system.…”

Chemical‐Free Approach for Z‐Isomerization of Lycopene in Tomato Powder: Hot Air and Superheated Steam Heating above the Melting Point of Lycopene

“…(all‐ E )‐Carotenoids, including lycopene, are relatively easily isomerized to the Z ‐isomers by heating, light irradiation, and addition of Z ‐isomerization‐accelerating catalysts such as iron(III) chloride and polysulfides . However, to promote the Z ‐isomerization reaction by these methods, it is necessary to dissolve carotenoids in media such as organic chemicals . In recent years, consumers have increasingly demanded discontinuation of the use of these chemicals in food processing.…”