Direct Extraction of Lipids, β-Carotene, and Polyphenolic Compounds from Wet Microalga Dunaliella salina by Liquefied Dimethyl Ether

Extraction of lipids and high-value products from highly wet microalgae requires significant energy for the drying pretreatment. In this study, we examined the direct extraction of lipids, β-carotene, and polyphenolic compounds from wet Dunaliella salina using liquefied dimethyl ether (DME), which is effective in lipid extraction for biofuel production. The amount of DME-extracted β-carotene was 7.0 mg/g, which was higher than that obtained from the chloroform-methanol extraction. Moreover, the total phenolic content extracted with DME and its antioxidant capacity were slightly higher than those extracted with chloroform-methanol. DME removed almost all the water and extracted 29.2 wt% of total lipids and 9.7 wt% of fatty acids. More lipids were extracted from wet samples by liquefied DME than by chloroform-methanol extraction. The C/N ratio of lipids extracted with DME was 112.0, higher than that of chloroform-methanol. The high C/N ratio suggests that nitrogen-containing phosphatidylcholines may be less easily extracted by liquefied DME and may be highly selective. However, the ratio of saturated fatty acids was 34.8%, lower than that of chloroform-methanol. Na+ and Mg2+ in the culture medium were not extracted using DME. Thus, using the extract with DME has both advantages and disadvantages compared to using the extract with chloroform-methanol; however, it has satisfactory extraction properties. DME is expected to be an environment-friendly alternative solvent because it does not require drying, which is necessary for conventional extraction solvents.

Recent Advances in Lycopene for Food Preservation and Shelf-Life Extension

In recent years, there has been increasing concern about the safety of additives used to extend the shelf-life of food products. As a result, lycopene, a natural phytochemical compound, has attracted attention, as it has been demonstrated to be a potential alternative to traditional artificial antioxidants, with significant health benefits when applied to food preservation. Based on this, this review introduces the specific forms of lycopene currently used as an antioxidant in foods, both in its naturally occurring forms in fruits and vegetables and in artificially added forms involving technologies such as composite coating, active film packaging, emulsion, and microcapsules. In addition, it also provides a comprehensive summary of the effects and progress of lycopene in the preservation of different types of food products, such as meat, seafood, oil, dairy products, fruits, and vegetables, in the last decade. At last, it also points out the limitations of lycopene, including its insolubility in water, dark color, and high sensitivity to heat or light, as well as the potential solutions to load lycopene on suitable carriers, such as combining lycopene with antimicrobial substances or other actives, in order to broaden its applications as an antioxidant in future foods.

High-temperature Supercritical CO2 Extraction of Lycopene from Tomato Powder for Enhancing Z-Isomerization and Recovery of Lycopene

This study aimed to investigate the effect of extraction conditions (temperature, pressure, and entrainer content) on the total Z-isomer ratio and recovery of lycopene in the extracts obtained after supercritical CO₂ (SC-CO₂) extraction of lycopene from tomato powder, with a particular focus on high-temperature conditions (≥ 80°C). The results showed that high-temperature SC-CO₂ extraction promoted the thermal isomerization of lycopene in a temperature-dependent manner up to 120℃. For example, when lycopene extraction was carried out at 80, 100, 120, and 140°C and a pressure of 30 MPa with an entrainer, ethanol, for 180 min, the total Z-isomer ratios obtained were 25.0, 57.2, 67.2, and 67.0%, respectively. The entrainer content also affected the Z-isomer ratio of lycopene, but the pressure had little effect. Interestingly, when SC-CO₂ extraction was performed under high-temperature conditions (≥ 100°C), the extraction efficiency of lycopene was dramatically improved, e.g., when lycopene was extracted at 80, 100, 120, and 140°C under the same other conditions as above, the recovery rates of lycopene were 4.6, 28.5, 79.9, 84.8%, respectively. In general, SC-CO₂ extraction of fat-soluble components is performed at temperatures in the range of 40-80°C because the SC-CO₂ density decreases with increasing temperature, and thus, their solubility (extraction efficiency) decreases. However, our results showed that the lycopene recovery increased in a temperature-dependent manner, which might be due to the solubility enhancement associated with thermal Z-isomerization of lycopene (i.e., lycopene Z-isomers have greater solubility than the naturally occurring all-E-isomer). The high-temperature SC-CO₂ extraction of lycopene from tomato materials not only enhances the Z-isomer ratio of lycopene in the resulting extracts but also improves lycopene recovery. This new finding will greatly contribute to the value addition and cost reduction of natural lycopene sources obtained by SC-CO₂ extraction.

Extraction of Fucoxanthin Isomers from the Edible Brown Seaweed Undaria pinnatifida Using Supercritical CO2: Effects of Extraction Conditions on Isomerization and Recovery of Fucoxanthin

Fucoxanthin, a characteristic carotenoid found in brown seaweeds, has been reported to exert beneficial biological activities, including antiobesity and anticancer activities Moreover, the Z-isomers of this compound potentially have greater bioavailability and biological activities than the naturally predominant all-E-isomer. Therefore, the consumption of Z-isomer-rich fucoxanthin through daily meals and dietary supplements may have beneficial effects. In this study, we aimed to investigate the effects of different extraction conditions on the Z-isomer ratio and recovery of fucoxanthin obtained from Undaria pinnatifida using supercritical CO2 (SC-CO2), particularly focusing on the high-temperature conditions that enhance thermal Z-isomerization. High-temperature SC-CO2 extraction at ≥ 120°C was found to enhance the thermal isomerization of fucoxanthin. For example, when the extraction was performed at 40, 80, 120, and 160°C and 30 MPa for 30 min with a co-solvent (ethanol), the total Z-isomer ratios were 11.7, 11.5, 18.7, and 26.5%, respectively. Furthermore, the high-temperature extraction significantly improved fucoxanthin recovery under high-pressure (≥ 30 MPa) conditions in the presence of the co-solvent. For example, when fucoxanthin was extracted at 40, 80, 120, and 160°C under the same conditions as above, the recoveries were 17.5, 20.6, 30.7, and 29.5%, respectively. Hence, the high-temperature SC-CO2 extraction of fucoxanthin from U. pinnatifida would not only enhance health benefits of fucoxanthin via the Z-isomerization but also improve the productivity. Moreover, the use of non-toxic CO2 and a low-toxicity organic solvent (ethanol) ensures that the final fucoxanthin product is safe for consumption. The Z-isomer-rich fucoxanthin obtained using this method is accordingly considered to have potential for use as a dietary supplement.

Application of E/Z-Isomerization Technology for Enhancing Processing Efficiency, Health-Promoting Effects, and Usability of Carotenoids: A Review and Future Perspectives

Carotenoids are naturally occurring pigments whose presence in the diet is beneficial to human health. Moreover, they have a wide range of applications in the food, cosmetic, and animal feed industries. As carotenoids contain multiple conjugated double bonds in the molecule, a large number of geometric (E/Z, trans/cis) isomers are theoretically possible. In general, (all-E)-carotenoids are the most predominant geometric isomer in nature, and they have high crystallinity and low solubility in various mediums, resulting in their low processing efficiency and bioavailability. Technological developments for improving the processing efficiency and bioavailability of carotenoids utilizing the Z-isomerization have recently been gaining traction. Namely, Z-isomerization of carotenoids induces a significant change in their physicochemical properties (e.g., solubility and crystallinity), leading to improved processing efficiency and bioavailability as well as several biological activities. For the practical use of isomerization technology for carotenoids, the development of efficient isomerization methods and an acute understanding of the changes in biological activity are required. This review highlights the recent advancements in various conventional and unconventional methods for carotenoid isomerization, such as thermal treatment, light irradiation, microwave irradiation, and catalytic treatment, as well as environment-friendly isomerization methods. Current progress in the improvement of processing efficiency and biological activity utilizing isomerization technology and an application development of carotenoid Z-isomers for the feed industry are also described. In addition, future research challenges in the context of carotenoid isomerization have been elaborated upon.

One-Step Preparation of Z-Isomer-Rich β-Carotene Nanosuspensions Utilizing a Natural Catalyst, Allyl Isothiocyanate, via Supercritical CO2

This study aims to improve the production efficiency of β-carotene suspensions using a naturally occurring Z-isomerization-accelerating catalyst, allyl isothiocyanate (AITC), via supercritical CO2 (SC-CO2). Namely, utilizing solubility improvement of β-carotene with the Z-isomerization by adding AITC in the SC-CO2-used dispersion process, the encapsulation efficiency of β-carotene was enhanced. The dispersion of β-carotene was conducted by ultrasonic treatment, and there was no involvement of organic solvents in the whole process. When 100 mg of AITC was added in the dispersion process, the encapsulation efficiency (β-carotene content in resulting suspension) was approximately 3.5 times higher than that without addition of the catalyst. Moreover, the Z-isomer ratio of β-carotene in the suspensions significantly improved, that is, it was approximately 12 times higher than the raw β-carotene material. Since Z-isomers of β-carotene are known to have higher antiatherosclerotic and antiatherogenic activities compared to the all-E-isomer, this one-step method not only efficiently produces β-carotene suspensions without organic solvents but also enhances the bioactivities of them.

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

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.