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.

Since Z‐isomers of lycopene are more bioavailable and show a higher antioxidant capacity than the (all‐E)‐isomer, it is important to investigate foods containing high amount of the Z‐isomer and develop practically feasible method for Z‐isomerization of (all‐E)‐lycopene. First, we investigated the E/Z isomer ratio of lycopene in raw and commercially available processed tomato products using an improved normal‐phase HPLC method. The tomato products contained 4.6–33.4% of Z‐isomers to the total lycopene, (5Z)‐lycopene being the most abundant Z‐isomer. The oil‐containing products like tomato sauce and tomato soup suffered heat processing contained a higher percentage of Z‐isomers of lycopene (27.4–33.4%). Subsequently, the impact of the amount and types of oils added on thermal Z‐isomerization of (all‐E)‐lycopene contained in tomato puree was investigated. Increased addition of olive oil to tomato puree increased the production of lycopene Z‐isomers upon heating at 120°C. (all‐E)‐Lycopene contained in tomato puree was converted to Z‐isomers in the range of 39.2–50.7%, when 5% of vegetable oil (linseed, soybean, corn, sesame, rapeseed, rice bran, safflower seed, olive, sunflower seed, or coconut oils) or animal fat (beef tallow and pork lard) was added before heating at 120°C for 30 min. When sesame oil was employed, the total Z‐isomerization ratio and (5Z)‐lycopene content were significantly increased. Practical applications: The dietary intake of lycopene offers many health benefits such as decreased risk of cancer and arteriosclerosis. Lycopene has a large number of geometric isomers caused by E/Z isomerization at arbitrary sites within the eleven conjugated double bonds, and the functionalities such as antioxidant capacity and bioavailability of the Z‐isomers are higher than those of the all‐E‐isomer. This study clarified the foods richly containing Z‐isomers of lycopene and demonstrated thermal Z‐isomerization of (all‐E)‐lycopene contained in tomato puree with edible oils and fats. These findings will contribute to effective intake of lycopene and the development of facile isomerization of (all‐E)‐lycopene to Z‐isomers in the fields of food, drink, and dietary supplement manufacturing, as well as for daily cooking at home. The Z‐isomers of lycopene contents in processed tomato products and thermal isomerization of (all‐E)‐lycopene to the Z‐isomers with edible oils and fats were investigated. The tomato products cooked with oils contained higher levels of the Z‐isomers, and sesame oil had excellent promoting effect of thermal Z‐isomerization of (all‐E)‐lycopene.

We modeled condensation phenomena within cylindrical nanopores as a possible replacement for the Kelvin model that underestimates nanometer order pore sizes. The proposed model follows the simple concept of a continuum assumption similar to that for the Kelvin model. The difference was in the introduction of the contribution of the pore-wall potential and the curvature-dependent surface tension in our model. A molecular dynamics (MD) technique developed by the authors for isotherm determination was employed to test the concept and the model. Several isotherms for N2-like Lennard-Jones (LJ) particles in a silicatelike cylindrical pore with various diameters from 2 to 4 nm were obtained through MD simulations, and a relation between pore diameter and critical condensation pressure was determined. The present model successfully described the relation to demonstrate its reliability. The validity of the proposed model was examined also from the aspect of the shape of the meniscus and the pressure profile in the condensed phase, and gave fairly good agreement.

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Macroalgae are one of potential sources for carotenoids, such as fucoxanthin, which are consumed by humans and animals. This carotenoid has been applied in both the pharmaceutical and food industries. In this study, extraction of fucoxanthin from wet brown seaweed Undaria pinnatifida (water content was 93.2%) was carried out with a simple method using liquefied dimethyl ether (DME) as an extractant in semi-continuous flow-type system. The extraction temperature and absolute pressure were 25 °C and 0.59 MPa, respectively. The liquefied DME was passed through the extractor that filled by U. pinnatifida at different time intervals. The time of experiment was only 43 min. The amount of fucoxanthin could approach to 390 μg/g dry of wet U. pinnatifida when the amount of DME used was 286 g. Compared with ethanol Soxhlet and supercritical CO2 extraction, which includes drying and cell disruption, the result was quite high. Thus, DME extraction process appears to be a good method for fucoxanthin recovery from U. pinnatifida with improved yields.