Encapsulation systems for lutein: A review

Accepted Manuscript Encapsulation systems for lutein: A review Benjamin M. Steiner, David Julian McClements, Gabriel Davidov-Pardo

PII:

S0924-2244(18)30296-6

DOI:

10.1016/j.tifs.2018.10.003

Reference:

TIFS 2337

To appear in:

Trends in Food Science & Technology

Received Date: 3 May 2018 Revised Date:

8 October 2018

Accepted Date: 9 October 2018

Please cite this article as: Steiner, B.M., McClements, D.J., Davidov-Pardo, G., Encapsulation systems for lutein: A review, Trends in Food Science & Technology (2018), doi: https://doi.org/10.1016/ j.tifs.2018.10.003. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Abstract:

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Background:

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The increased demand by consumers for clean labels has encouraged industry to search for

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replacements of synthetic ingredients in food products, and in particular, colorants. Lutein, a

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xanthophyll found in marigolds and corn, can be used in food products as a natural colorant

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replacing yellow food dyes. Moreover, lutein is considered a nutraceutical due to its potentially

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beneficial health effects, such as prevention of macular degeneration, role in the development of

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the visual and nervous systems of fetuses, and its antioxidant properties. However, incorporation

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of lutein into foods is often limited because of its low-water solubility, chemical instability, and

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poor oral bioavailability. For this reason, colloidal encapsulation systems have been developed

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to facilitate the incorporation of lutein into aqueous food and beverage products.

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12 Scope and Approach:

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This review focuses on exploring encapsulation options for lutein using various emulsion-based,

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nanoparticle- and microparticle-based and molecular inclusion encapsulation systems, as well as

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additives that can be used to increase its chemical stability in these systems. This review covers

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all aspects of lutein encapsulation, including both food-grade and pharmaceutical-grade

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encapsulation systems.

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Key Findings and Conclusions:

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Though lutein-loaded encapsulation systems are extensively explored in this review, emulsions

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are of the most interest in industry as they are cost efficient and can be designed to increase the

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stability of lutein by selecting the proper emulsifiers and emulsification techniques. Despite the

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extensive amount of research carried out on the encapsulation of hydrophobic bioactive

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molecules such as lutein, there are still opportunities to develop encapsulation systems that

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further protect these molecules during storage and also increase their bioavailability after

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ingestion.

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Keywords: lutein, xanthophylls, nanotechnology, emulsions, biopolymer particles.

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ENCAPSULATION SYSTEMS FOR LUTEIN: A REVIEW

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Benjamin M. Steiner1, David Julian McClements2, Gabriel Davidov-Pardo1,*

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4 California State Polytechnic University Pomona, Human Nutrition and Food Science Department, 3801 West Temple Ave, Pomona, CA 91768, USA 2

University of Massachusetts, Department of Food Science, Chenoweth Lab, Amherst, MA

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01375 USA

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*Corresponding author: [email protected], Tel. +1-909-869-5226, 3801 West Temple Ave,

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Pomona, CA 91768, USA

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1. INTRODUCTION Carotenoids are classified into two classes known as carotenes and xanthophylls. While a carotene consists of a chain of only hydrogens and carbons, xanthophylls also contain hydroxyl

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groups (Bian et al., 2012). Lutein is part of the xanthophyll class and can be found mainly in

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Marigold flowers, egg products, leafy greens, and vegetables such as corn and potatoes (table 1).

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Cataracts are the principle cause of blindness in adults over 40 years of age in developing countries, which has led researchers to identify effect strategies to reduce its prevalence

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(Gottlieb, 2002). Lutein has been shown to be effective at retarding the development of age-

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related macular degeneration, which is attributed to its ability to aid the activation of nuclear

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factor erythroid 2-related factor 2 target genes in human retinal pigment epithelial cells (Frede,

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Ebert, Kipp, Schwerdtle, & Baldermann, 2017). Macular degeneration is the leading cause of

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blindness in people over 65 years old in industrial countries, and may also be inhibited by lutein

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(Gottlieb, 2002). Consequently, there is potential to develop effective diet-based strategies to

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prevent eye disease in both developing and developed countries. The typical American diet

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consists of about 1 to 3 mg of lutein per day, whereas it has been calculated that around 6 mg per

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day is required to reduce the risk of cataract development and macular degeneration (J. S. L. Tan,

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2008). Although no DRI has been established, clinical trials have shown that lutein can be

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administered at 18 mg/day with no adverse effects indicating that it can be safely consumed at

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three times the recommended dose of 6 mg/day without exhibiting any toxicity (Hammond &

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Renzi, 2013; Wallace, Blumberg, Johnson, & Shao, 2015). Therefore, there is a need to provide

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lutein-fortified functional foods to those at risk of eye disease. The antioxidant properties of

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lutein also mean that it can scavenge free radicals within the human body, which may also be

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beneficial for human health in general (C. Yang et al., 2018). Lutein has also been reported to

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play a critical role in the development of brain and cognitive functions (Zielinska, Wesolowska,

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Pawlus, & Hamulka, 2017). These functions are related to its neuroprotective effects, ability to

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modify cell membrane fluidity, oxygen diffusion and ion exchange, and its effects on

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intracellular communication and metabolic pathways in the brain (W. S. Stahl, H, 2001). Lutein

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has also been associated with the development of eyes and the nervous system in fetuses, where

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correlations have been shown between maternal lutein intake and a reduced risk of preterm

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deliveries (Zielinska et al., 2017). Protecting the developing eye from photo-damaging blue light,

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lutein also aids in supporting transmission and visual information by stabilizing microtubules in

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the cytoskeleton while enhancing gap junction communication between glia and neuronal cells

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(Bernstein, Balashov, Tsong, & Rando, 1997; Crabtree, Ojima, Geng, & Adler, 2001; W. Stahl et

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al., 1997). Studies have also shown that the plasma of women during preterm deliveries has

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reduced levels of carotenoids while carotenoid supplementation increased the gestational period

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due to the reduction in oxidation of the placenta, thus reducing premature rupture of membranes

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(Kramer et al., 2009; Sharma et al., 2003).

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The visual appearance of foods plays a large role in consumer acceptability. Color is the first

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quality judgement that most consumers make of food products and helps them ascertain spoilage,

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freshness, quality, and desirability (Maskan, 2001). As “clean labels” increasingly become a

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major focus of the food industry, corporations are looking for ways to make their labels appear

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more consumer-friendly. The demand for natural and clean label ingredients is pushing

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manufacturers to replace synthetic colorants with more natural alternatives (Sloan, 2015, 2017).

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Due to its natural gold color, lutein has been used to replace annatto in Prato cheeses, thus

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enhancing the color of these products as well as adding antioxidant properties (Sobral et al.,

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2016). The yellow color associated with lutein is directly related to the 10 conjugated double

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bonds found in the molecule as well as the cyclic structures on both sides (Figure 1) which

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absorbs shorter wavelengths with hue values of ~99o to 105o (Melendez-Martinez, Britton,

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Vicario, & Heredia, 2007).

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Although many foods naturally contain high levels of lutein (Sommerburg, Keunen, Bird, & van Kuijk, 1998), its low water solubility limits absorption in the gastrointestinal tract thereby

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reducing its bioaccessibility (B. X. Li, Ahmed, & Bernstein, 2010; Uzun, Kim, Leal, & Padua,

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2016). Here, bioaccessibility is taken to be the amount of lutein actually released from the food,

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incorporated in the mixed micelle phase, and available for absorption from the gastrointestinal

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tract (McClements, Li, & Xiao, 2015). Bioavailability, on the other hand, has a broader sense

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and refers to the lutein that has been actually absorbed by the intestinal cell epithelium and

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reached the site of action. Indeed, recent research has shown that an appreciable amount of lutein

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(~60%) is not absorbed because of its low water-solubility and difficulty to be incorporated in

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mixed micelles in the gastrointestinal tract (Kopec, Gleize, Borel, Desmarchelier, & Caris-

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Veyrat, 2017). Moreover, lutein is prone to oxidation and other degradative reactions, which

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also limits its stability during extraction, storage, and utilization (Boon, McClements, Weiss, &

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Decker, 2010). The conjugated double bonds in lutein are especially labile to degradation when

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the molecule is exposed to environmental stresses (such as pH, heat, and light exposure), which

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leads to color fading and bioactivity reduction (Sant'Anna, Gurak, Marczak, & Tessaro, 2013). In summary, the main challenges to incorporating lutein into commercial food products

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are its low water-solubility, limited chemical stability, and low oral bioavailability. Colloidal

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encapsulation systems can be used to overcome these difficulties and facilitate the incorporation

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of lutein as a colorant and nutraceutical into functional foods and beverages. A great deal of

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research has currently being carried out on encapsulation systems based on different types of

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colloids, including emulsions, hydrogels, coacervates, molecular complexes, liposomes, and

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many others (Aditya, Espinosa, & Norton, 2017; Dordevic et al., 2015; J. Yang et al., 2018).

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Research on encapsulation of lutein has been mainly conducted in the pharmaceutical,

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supplement, and food fields. This review summarizes and compares different colloidal

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encapsulation systems that have been developed to improve the water-dispersibility, chemical

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stability, and bioavailability of lutein. This information will be useful for selecting the most

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appropriate encapsulation system for commercial applications.

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2. LUTEIN EXTRACTION

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Lutein is mainly extracted from plant sources where it is primarily present in an esterified form where both oxygens are covalently linked to fatty acids. Consequently, the ester bonds

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have to be broken to release free lutein. Saponification of lutein esters has been shown to give

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greater yields compared to lipase catalyzed hydrolysis (Sujith, 2012). The most common

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extraction method for lutein is through the use of organic solvents due to the high hydrophobicity

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of xanthophylls. Extraction of lutein from marigold flowers using liquefied dimethyl ether

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showed a 20% increase of yield compared to supercritical CO2 and hexane extraction methods

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(Boonnoun, Tunyasitikun, Clowutimon, & Shotipruk, 2017). The use of acetone and enzymatic

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hydrolysis using commercial lipases as well as supercritical CO2 has been used for the industrial

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extraction of lutein, however, organic solvents such as hexane, isooctane, and toluene are needed

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(Mora-Pale, Perez-Munguia, Gonzalez-Mejia, Dordick, & Barzana, 2007). Researchers have

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been attempting to develop “greener” extraction methods to replace those using environmentally

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unfriendly solvents. For instance, lutein extraction from spinach waste using ethanol and water

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was shown to give a comparable extraction (70%) as the conventional method using acetone

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(Derrien, Badr, Gosselin, Desjardins, & Angers, 2017). A single-step extraction method has been

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shown feasible for extracting lutein from microalgae using binary solvents (1/1 ethanol/ether, 3/1

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ethanol/ether, 1/1 ethanol/hexane, and 3/1 ethanol/hexane) (Gong, Wang, & Bassi, 2017).

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Dimethylformamide extraction showed a 47% increase in yield and has produced more reliable

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results when compared to acetone extraction methods (Stiegler, Bell, & Maness, 2004).

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Regardless of the extraction method used, lutein is difficult to handle and use because of its strong hydrophobicity. The solubility of lutein in water can sometimes be improved by extracting

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it in the form of small crystals. Indeed, supercritical CO2 treatment has been shown to reduce the

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size of the lutein crystals extracted from marigold petals using ethanol from 3.4 to 1.5 µm

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(Boonnoun, Nerome, Machmudah, Goto, & Shotipruk, 2013b). Furthermore, utilizing a mixture

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of hexane and ethyl acetate as a mobile phase for chromatography indicates that there is no

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significant effect in morphology between concentrations of lutein at 1.5 to 3.2 mg/mL nor flow

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rates of 15 mL/min to 25 mL/min, though the reduction of particle size was noted to decrease

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from 2 to 0.8 µm depending on SC-CO2 flow rates (Boonnoun, Nerome, Machmudah, Goto, &

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Shotipruk, 2013a). Table 2 shows a summary of the different extraction methods discussed

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above.

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3. ENCAPSULATION SYSTEMS FOR LUTEIN AND XANTHOPHILLS

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Encapsulation is a process whereby the active material is embedded in or covered by a

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protective wall material (Madene, 2006). The resulting system usually consists of a suspension

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of colloidal particles containing the active material inside. Figure 2 depicts a diversity of

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encapsulation systems that can be used to encapsulate highly hydrophobic nutraceuticals like

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lutein. This barrier increases viability by preventing evaporation, migration, or reaction of the

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product with any adverse environmental conditions. Encapsulation, in turn, increases the shelf

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life of the active components and can promote optimized delivery. Moreover, encapsulation can

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prevent crystallization and precipitation of bioactives that have high hydrophobicity and melting

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point, such as lutein. This approach may also increase the bioavailability of hydrophobic

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bioactives. When designing encapsulation systems for the food industry, several factors must be

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kept in mind (McClements, 2007; Joseph & Bunjes, 2013; McClements, 2018):

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The encapsulation systems must be constructed from permitted pharmaceutical or food-grade materials, taking into consideration their toxicology.

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processing operations for economic feasibility purposes. •

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bioactive component. •

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compound and retaining them during storage. •

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The encapsulation system should release the bioactive compound at a controlled rate at the site-of-action or absorption in the human body.

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The encapsulation system should be capable of encapsulating high amounts of the bioactive

The encapsulation system should not negatively affect the food matrix that it is contained within.

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The encapsulation system should enhance the bioavailability and/or bioactivity compound.

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The encapsulation system should withstand chemical and physical degradation to protect the

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The encapsulation systems should be constructed using inexpensive ingredients and

3.1 Surfactant-based systems

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In this section, we focus on encapsulation systems that are primarily assembled from natural or synthetic surface-active molecules such as phospholipids without a lipid core in their

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structure.

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3.1.1. Liposomes

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Liposomes consist of bilayer shells of surface-active molecules that may have a variety of

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structures, including single or multiple shells. They have become popular for the encapsulation

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and delivery of hydrophilic, amphiphilic, and lipophilic nutraceuticals because they have both

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polar and non-polar domains inside. The non-polar domains in liposomes capable of hosting

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hydrophobic bioactives are located in-between the bilayers formed by the surfactants, while the

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polar domains are located in the aqueous interior of the liposome. The surfactant bilayers can be

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fabricated from both natural ingredients such as phospholipids, cholesterol, phosphatidylcholine,

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and synthetic ingredients such as Tweens (C. Tan, Feng, Zhang, Xia, & Xia, 2016). These

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systems form spontaneously when surfactants are dispersed in water above their critical micelle

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concentration, but specific processing methods are required to obtain liposomes with bilayers

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that differ in size and composition, such as solvent evaporation, antisolvent precipitation, or

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microfluidization (Takahashi et al., 2006). The chemical stability of carotenoids encapsulated in

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liposomal systems can be enhanced through crystallization of the surfactant tails (Helgason et al.,

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2009). Raman spectroscopy studies have shown that lutein is more effectively encapsulated into

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phosphatidylcholine liposomes than ß-carotene or lycopene (Xia et al., 2015). For liposomes

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formed using supercritical carbon dioxide processing, it was recently reported that the

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encapsulation efficiency and location of lutein within the liposome’s membrane depended on the

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pressures used during their formation, which was attributed to rearrangement of the

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phospholipids and lutein during the depressurization stage (L. S. Zhao, Temelli, Curtis, & Chen,

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2017). The physical stability of liposomes containing lutein can be enhanced by coating them

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with biopolymers, such as chitosan (C. Tan et al., 2016).

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3.2 Emulsion-based systems

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Oil-in-water (O/W) emulsions consist of spherical lipid droplets dispersed within an aqueous medium, with the droplets having a core-shell structure. The hydrophobic core consists of any

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non-polar parts of emulsifiers, carrier oils, and hydrophobic bioactive molecules, whereas the

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polar shell consists of the polar parts of the emulsifiers. The hydrophobic bioactive agents are

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usually dispersed within the hydrophobic core of the lipid droplets. Microemulsion are

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thermodynamically stable systems, while nanoemulsions and regular emulsions are

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thermodynamically unstable, and therefore tend to break down over time (McClements, 2012).

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Emulsion-based encapsulation systems of varying complexity can be created by manipulating

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droplet sizes, coatings, location, and physical states.

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3.2.1 Microemulsions

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comprised of small lipid-rich particles (typically < 100 nm) dispersed in water. The particles

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consist of a hydrophobic core containing the surfactant tails and any non-polar carrier oils or

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bioactive molecules, and a hydrophilic shell comprising the surfactant head groups.

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Microemulsions require a much higher surfactant concentration to prepare than conventional

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emulsions, but the fabrication procedure is usually much simpler and cheaper because they

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should form spontaneously (Setya, 2014). Microemulsions are widely used in the pharmaceutical

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industry to encapsulate hydrophobic drugs and increase their bioavailability in the

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gastrointestinal tract. Studies have shown that successful preparation of microemulsions depends

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on various factors, including proper selection of surfactants, co-surfactants, and oil phases in

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which hydrophobic drugs are contained (Lo, Lee, & Chen, 2016). Microemulsions prepared

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using a food-grade non-ionic surfactant (Tween 80) have been shown to be effective at

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encapsulating both lutein and zeaxanthin in beverages, as well as increasing their bioavailability

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after consumption (Amar, Aserin, & Garti, 2004). Lutein contained in an extract from the

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Rhinacantus nasutus plant encapsulated in microemulsions formed by sonication using Tween

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80, CapryolTM and Transcultol® showed a 6.25% increase in its bioavailability when compared

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to the suspended extract in distilled water (Ho, Inbaraj, & Chen, 2016). The authors also claimed

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to reach an encapsulation efficiency of the carotenoids in the microemulsion of 98.6%.

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3.2.2. Nanoemulsions and emulsions

Nanoemulsions (r = 50 to 100 nm) and emulsions (r = 100 nm to 100 microns) can be

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distinguished based on their droplet size. Differences in lipid droplet size leads to differences in

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physicochemical and functional properties. Nanoemulsions tend to be more stable to creaming

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and flocculation, less optically opaque, and more rapidly digested than emulsions (Kale, 2017).

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Numerous studies have shown that emulsions and nanoemulsions are effective encapsulation

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systems for lutein and other carotenoids. Whey protein isolate (WPI) and polymerized whey

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protein (PWP) were both shown to be good emulsifiers for encapsulating astaxanthin (a

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xanthophyll similar to lutein) in emulsions but there were differences in their ability to stabilize

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the emulsions (Shen, Zhao, Lu, & Guo, 2018). In particular, after one week of storage, lutein-

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loaded nanoemulsions stabilized by PWP became visually stratified at all temperatures which

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was thought to be due to residual ethanol, while those stabilized by WPI remained homogenous

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(C. H. Zhao, Shen, & Guo, 2018). Caprine and bovine casein have both been shown to be

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suitable for forming lutein-loaded emulsions, but the caprine casein gave better stability after

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prolonged storage, i.e., 96 hours at 25 oC (Mora-Gutierrez et al., 2018). Sodium caseinate was

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shown to protect lutein better from chemical degradation than WPI, which was attributed to

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differences in the primary structure of the two proteins (Yi, Fan, Yokoyama, Zhang, & Zhao,

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2016). Sodium caseinate contains phosphate groups that can chelate transition metals and has

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more amino acids that can scavenge free radicals

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Corn gum fiber has been used as an effective emulsifier for forming lutein-loaded

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emulsions and was shown to not negatively impact its bioaccessibility (Feng et al., 2017). The

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nature of the carrier oil used to disperse the lutein may also impact its stability and

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bioavailability. Lutein-loaded emulsions formulated using medium chain triglycerides (MCT) as

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the oil phase were more stable to aggregation and creaming than those formed using long chain

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triglycerides (LCT) (Surh, Decker, & McClements, 2017). However, other studies have shown

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that the bioaccessibility of carotenoids may be greatly reduced when they are encapsulated in

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MCT oils, which was attributed to the small hydrophobic domains of the mixed micelles formed

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from the relatively short fatty acid chains resulting from their digestion (Salvia-Trujillo, Qian,

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Martin-Belloso, & McClements, 2013). Consequently, it may be necessary to optimize the

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encapsulation systems for both stability and bioaccessibility. The nature of the emulsifier used

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to coat the lipid droplets in lutein-loaded emulsions is also important. Comparing six emulsifiers

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(β-lactoglobulin, β-lactoglobulin/lecithin, biozate-1, biozate-1/lecithin, Tween 20, and Tween

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20/lecithin) for the stabilization of lutein dispersed into MCT emulsions showed that β-

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lactoglobulin and biozate-1, in conjunction with lecithin, gave the most promising emulsions due

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to their smaller droplet size, high resistance to creaming, and increased absorption of lutein

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(Frede et al., 2014). Creating lutein-loaded nanoemulsions using Tween 80 as a surfactant and

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polyvinylpyrrolidone (PVP) as an emulsion stabilizer showed not only a high encapsulation

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efficiency, but also greater resistance to heat, light, and oxygen when compared to lutein

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dispersed in water (without Tween 80 nor PVP) alone (C. D. Zhao, Cheng, Jiang, Yao, & Han,

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2014).

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Nanoemulsions loaded with 20% lutein in corn oil using quillaja saponin surfactants with

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the addition of antioxidants (ascorbic acid) showed increased chemical and physical stability

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when compared with other surfactant/antioxidant combinations (Weigel, Weiss, Decker, &

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McClements, 2018). The use of whey protein isolate (surfactant) has also been investigated in

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conjunction with α-tocopherol (antioxidant) to provide a lutein-loaded nanoemulsion that

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showed greater cellular uptake during in vitro studies (Teo, Lee, Goh, & Wolber, 2017). Mixed

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emulsions comprised of mixtures of lactoferrin-coated and whey protein-coated lutein-loaded oil

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droplets had higher oxidative and physical stability than individual emulsions (X. Li et al., 2018).

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The addition of calcium chloride (30 mmol) to lactoferrin-stabilized emulsions improved lutein

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stability, which was attributed to the creation of a physical barrier around the lipid droplets

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preventing radicals and transition metals from interacting with the lutein (X. Li et al., 2017). A

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summary of previous studies on emulsion-based encapsulation systems for lutein is included in

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Table 3.

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3.2.3. Multilayered emulsions Multilayered emulsions consist of emulsifier-coated lipid droplets coated by one or more layer of biopolymers using an electrostatic deposition method (Bortnowska, 2015; Guzey &

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McClements, 2006). The most common biopolymers used are charged proteins and

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polysaccharides. Protein-coated lipid droplets are unstable when exposed to pH values near their

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isoelectric point, elevated temperatures, high ionic strengths, and other environmental stressors.

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However, their stability can be improved by coating them with a layer of charged

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polysaccharides (Burgos-Diaz, Wandersleben, Marques, & Rubilar, 2016; Guzey &

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McClements, 2006). Lutein-loaded multilayered emulsions containing lipid droplets coated by

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whey protein isolate, flaxseed gum, and chitosan had greater chemical stability than those

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containing droplets coated by protein alone (Xu, Aihemaiti, Cao, Teng, & Li, 2016). Moreover,

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addition of EDTA or alpha-tocopherol to the emulsions further improved the storage stability of

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the emulsions. Multilayers formed from fish gelatin, whey protein isolate, and

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dodecyltrimethylammonium bromide have also been shown to improve the stability of lutein

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(Beicht, Zeeb, Gibis, Fischer, & Weiss, 2013).

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Interfacial composition and structure can also be controlled by covalently attaching polysaccharides to proteins. Emulsions formed from protein-polysaccharide conjugates (creating

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using the Maillard reaction) have better stability to pH, temperature, and ionic strength than

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those formed using protein alone. Maillard conjugates have also been shown to improve droplet

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size, emulsifying activity, emulsifying stability, and creaming, more so when the solutions were

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adjusted to the isoelectric point (Hou, Wu, Xia, Phillips, & Cui, 2017; Pirestani, Nasirpour,

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Keramat, Desobry, & Jasniewski, 2017). Lutein nanoemulsions stabilized by dextran-caseinate

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conjugates were shown to have better pH stability than those stabilized by caseinate alone,

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without compromising lutein bioaccessibility or storage stability (Davidov-Pardo, Gumus, &

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McClements, 2016).

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3.2.4. Solid Lipid Nanoparticles

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Similar to nanoemulsions, solid lipid nanoparticles consist of small emulsifier-coated lipid

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particles dispersed within an aqueous medium. However, solid lipid nanoparticles contain a fully

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or partially crystalline lipid phase rather than a fluid one (Podio, Zara, Carazzone, Cavalli, &

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Gasco, 2000; zur Muhlen, Schwarz, & Mehnert, 1998). If the crystalline core of the particles is

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designed correctly, then it can improve the stability of encapsulate substances by slowing down

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molecular diffusion processes. Solid lipid nanoparticles have been shown to be suitable for

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encapsulating (86-98% encapsulation efficiency) lycopene (another carotenoid) and enhancing

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its storage stability (stable for 3 months at 4oC) while maintaining its bioavailability (Nazemiyeh,

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Eskandani, Sheikhloie, & Nazemiyeh, 2016). MCT mixed with either glyceryl tripalmitate or

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carnauba wax can form stable lutein-loaded solid lipid nanoparticles in aqueous dispersions

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(Mitri, Shegokar, Gohla, Anselmi, & Muller, 2011). Interestingly, the authors only reported

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0.06% lutein degradation in the solid lipid nanoparticles compared to 50% degradation in lutein

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powder suspended in corn oil and 14% degradation in lutein/corn oil nanoemulsions, which is

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thought to be due to the solid lipid nanoparticles ability to protect against UV light as well as

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increase the stability of the xanthophyll as the lutein is primarily localized in the core of the

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particle.

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3.2.5. Multiple emulsions

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Multiple emulsions are essentially emulsions inside emulsions. Due to their ability to protect

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and maintain controlled release of bioactive molecules, many fields are exploring multiple

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emulsions as encapsulation systems (Schmidt, Bernewitz, Guthausen, & Schuchmann, 2015).

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Hydrophobic bioactives have been encapsulated within stable multiple emulsions formed from

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biopolymers, such as whey protein and gum arabic (Estrada-Fernández et al., 2018). Although to

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the best of the author´s knowledge there has been no reported research of lutein alone being

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encapsulated in multiple emulsions, these types of systems have been successfully used to

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encapsulate other carotenoids and carotenoid-rich extracts containing lutein. For instance, spray

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dried W/O/W emulsions were successfully created to encapsulate an oleoresin from red chilis,

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reaching encapsulation efficiencies of 87.5% and delaying the degradation of the carotenoids

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after 30 days of storage at various water activities (Rodriguez-Huezo, Pedroza-Islas, Prado-

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Barragan, Beristain, & Vernon-Carter, 2004). Multiple emulsions have been shown to protect

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carotenoids from degradation by reducing autoxidation of all-trans retinol to 13-cis retinol, while

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protecting the bioactive component from oxygen, light, and heat (Jimenez-Colmenero, 2013).

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The stability of β-carotene derivatives in O/W/O, W/O, and O/W emulsions loaded with vitamin

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A was compared and showed a retention percentage of 57%, 46%, and 32%, respectively, which

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indicates that the O/W/O systems may be particularly effective (Yoshida, Sekine, Matsuzaki,

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Yanaki, & Yamaguchi, 1999).

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3.3 Biopolymer based encapsulation systems

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3.3.1. Biopolymer microgels Biopolymer microgels consist of small particles, typically around 100 nm to 1000 µm in

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diameter, that are fabricated from proteins and/or polysaccharides (McClements, 2017). They

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may be prepared using numerous methods, including coacervation, thermodynamic

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incompatibility driven phase separation, injection-gelation method, and templating. A number of

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these microgel systems have been investigated for their potential to encapsulate lutein and other

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carotenoids.

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Complex coacervates can be prepared from two biopolymers that are strongly attracted to

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each other due to opposing electrical charges, which yields a two-phase system consisting of a

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biopolymer-rich phase and a biopolymer-depleted phase (Harnsilawat, Pongsawatmanit, &

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McClements, 2006). This phase separated system can be agitated to form a W/W type emulsion

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with the bioactive trapped in the internal aqueous phase. Coacervates made with WPI and gum

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acacia have been shown to effectively encapsulate carotenoids with an encapsulation efficiency

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of around 56% (Ursache et al., 2018). The use of whey protein isolate and gum acacia as

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emulsifiers has also been shown as a promising matrix to create coacervates with sea buckhorn

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carotenoids after supercritical extraction methods were carried out for the removal of the organic

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phase (Mihalcea et al., 2017). Simple coacervates can be formed by antisolvent precipitation of

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a biopolymer in a poor solvent. Zein nanoparticles, stabilized with lecithin, have been formed

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using antisolvent precipitation and shown to be capable of inhibiting the chemical degradation of

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lutein (Chuacharoen & Sabliov, 2016). Biopolymer microgels formed by cross-linking

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carboxymethylpullulan have been shown to be capable of encapsulating, protecting and releasing

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lutein, and may therefore also be suitable encapsulation systems (Mocanu, Mihai, Dulong,

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Picton, & Le Cerf, 2012; Mocanu, Souguir, Picton, & Le Cerf, 2012).

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There is evidence that the inclusion of emulsions within biopolymer hydrogels delays the

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digestion of the lipids contained within the microgels (Gu et al., 2017; S. Mun, Kim, Shin, &

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McClements, 2015). To the best of the author´s knowledge there is currently no published

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research focusing on the bioaccessibility of lutein encapsulated in filled hydrogels. However, the

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bioaccessibility of another carotenoid (ß-carotene) was either similar or greater than that in

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emulsions when encapsulated in filled hydrogels. The proposed mechanism behind the observed

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increase was attributed to the ability of the hydrogels to protect the lipid droplets from

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aggregation in the stomach phase, which promoted lipid digestion in the small intestine phase

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(Saehun Mun, Kim, & McClements, 2015; S. Mun et al., 2015).

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3.3.2. Molecular inclusion complexes Inclusion complexes are formed when an active agent becomes physically trapped within a

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cavity-containing substrate. They can be prepared in either solution or dried forms. The

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physical interactions involved are usually a combination of hydrogen bonding, van der Waal

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forces, hydrophobic effects, and electrostatic effects. Common cavity-containing substrates are

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cyclodextrins. Cyclodextrins are six, seven, or eight-membered cyclic glucose oligomers

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produced from starch that have hollow cavities approximately 5-8 Angstroms in dimensions that

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can contain around 6-17 water molecules (Gouin, 2004). Cyclodextrins are popular for

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encapsulation due to their ability to accommodate and stabilize molecules in their cavity. The

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inclusion complexes persist in both aqueous solutions and solid states (Diamanti, Igoumenidis,

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Mourtzinos, Yannakopoulou, & Karathanos, 2017).

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The encapsulation of lutein within inclusion complexes has been studied by a number of researchers. For instance, lutein has been encapsulated using methyl-ß-cyclodextrin, which

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greatly improved its water-dispersion and bioavailability profiles (Nalawade & Gajjar, 2015).

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Lutein-polyvinylpyrrolidone complexes have also been shown to improve the solubility and

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stability of lutein (Liu, Wang, Li, Tang, & Han, 2016).

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3.4 Spray dried encapsulation systems

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Spray-drying is currently the most commonly used drying technology in the food industry and is

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one of the most widely used methods to produce microcapsules to encapsulate bioactives,

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including lutein (Gharsallaoui, Roudaut, Chambin, Voilley, & Saurel, 2007). During the

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atomization and drying process for every cubic meter of atomized material thousands of square

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meters of contact surface are formed, resulting in a rapid evaporation of solvent and the

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entrapment of the active compound almost instantaneously (Buffo & Reineccius, 2001).

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Research has been conducted to encapsulate lutein through spray drying, so as to create a product

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that is more shelf stable and cheaper to transport due to the lack of water. Lutein has been

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successfully encapsulated in spray dried microcapsules formed with equal proportions of

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maltodextrin, gum Arabic and modified starch. The encapsulation efficiency of this system

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reached 65% and extended the shelf life of lutein by 30% when compared to the non-

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encapsulated lutein extract stored at 40 ºC and 75% relative humidity (Álvarez-Henao, Saavedra,

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Medina, Jiménez Cartagena, Alzate, & Londoño-Londoño, 2018). A combination of gelatin and

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porous starch has also been used to encapsulate lutein by spray drying achieving an

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encapsulation efficiency of 94.4% and creating an encapsulation system that was 100% water

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soluble and that stabilized lutein against degradation in several adverse conditions, such as

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exposure to oxygen, light, and low pH (Wang, Ye, Zhou, Lv, Bie, & Lu, 2012). As mentioned in

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section 3.2.5, spray dried W/O/W emulsions were successfully created to encapsulate a

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carotenoid-rich oleoresin from red chilis (Rodriguez-Huezo, et al., 2004).

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4. ASPECTS TO CONSIDERED WHEN DEVELOPING LUTEIN ENCAPSULATION SYSTEMS

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4.1 Biological fate

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It is important that any colloidal encapsulation system used does not adversely affect the

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bioavailability of lutein. The bioavailability of lutein and other carotenoids depend upon the

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physicochemical properties of the colloidal particles, such as their concentration, size,

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composition, and interfacial characteristics. These parameters determine how the encapsulation

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system will behave in the gastrointestinal tract, and therefore their bioavailability of the

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encapsulated substance.

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colloidal particles themselves change as their pass through the mouth, stomach, and small

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intestine due to alterations in temperature, pH, ionic strength, and molecular environment

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(Verkempinck et al., 2018).

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Moreover, the size, composition, and interfacial properties of the

In the mouth, an encapsulation system is diluted and exposed to neutral saliva containing

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mucin, salts, and digestive enzymes (amylase), which could cause aggregation, precipitation, and

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hydrolysis of starch-based structures. In the stomach, it is further diluted and exposed to highly

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acidic gastric fluids containing proteases and lipases. The most impacted systems at this point are

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protein-based systems due to hydrolytic action of pepsin and the drastic change in pH. In the

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small intestine, the systems are further diluted with intestinal fluids containing buffers, digestive

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enzymes, and bile salts. In this stage, lutein is released from the lipid phase and solubilized

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within mixed micelles that can be absorbed through the intestinal epithelium. Moreover, proteins

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are further hydrolyzed by trypsin and lipids are further hydrolyzed by pancreatic lipases and

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solubilized by bile salts (Yao, Xiao, & McClements, 2014). In addition, the bioactive agents may

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be chemically transformed, released, and solubilized at the various digestion stages mentioned

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above (McClements et al., 2015; Primozic, Duchek, Nickerson, & Ghosh, 2018).

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solubilized bioactives or bioactive-loaded colloidal particles may be absorbed through the

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epithelial cells through passive or active transport mechanisms then enter the blood or lymphatic

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system (Lin, Liang, Williams, & Zhong, 2018; Yao et al., 2014).

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4.2 Chemical fate

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The

The chemical stability of lutein in a colloidal encapsulation system is crucial for preserving

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its color and nutraceutical activity. The rate of chemical degradation of lutein depends on

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temperature, oxygen, pH, transition metal activity, enzyme activity, and storage time and is

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therefore highly dependent on food type (Boon et al., 2010). Thermal degradation of lutein

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involves multiple steps that ultimately lead to a colorless product (Xiao et al., 2018). Acidic

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environments play a major role in lutein degradation by creating labile 3-hydroxy-3’,4’-

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didehydro-beta,gamma-carotene and 3-hydroxy-2’,3’-didehydro-beta,e-carotene intermediates

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(Nidhi, Sharavana, Ramaprasad, & Vallikannan, 2015). Enzymatic degradation of lutein via

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VvCCD1 found in plants leads to oxidized byproducts such as 3-hydroxy-beta-ionone and C14-

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dialdehyde, known as norisoprenoids (Mathieu, Bigey, Procureur, Terrier, & Gunata, 2007).

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Therefore, colloidal encapsulation system should protect lutein against factors that normally

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promote its degradation. As mentioned above, one strategy that has proven effective is the

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incorporation of antioxidants in encapsulation systems (Teo et al., 2017; Weigel et al., 2018; Xu

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et al., 2016). Techniques based on interfacial engineering, such as creating multilayer interfacial

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coatings, have also proved useful to stabilize lutein (Davidov-Pardo et al., 2016; Hou et al.,

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2017; Pirestani et al., 2017).

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4.3 Appearance

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Lutein can be used as a yellow colorant in food products. The appearance of a product

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containing lutein therefore depends on its chemical degradation rate, as well as the characteristics

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of the particles in the encapsulation systems, such as their size, concentration, and refractive

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index. Color fading due to lutein degradation occurs at nearly double the rate when the

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temperature is increased by 10 oC, while pH plays only a minor role in color degradation

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(Davidov-Pardo et al., 2016). As mentioned above the addition of antioxidants (such as ascorbic

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acid) to lutein-enriched emulsions can effectively inhibit color fading (Weigel et al., 2018). The

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degree of light scattering by a encapsulation system will determine its clarity or opacity (Velikov

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& Pelan, 2008). For applications where optical clarity is not required colloidal encapsulation

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systems containing particles with diameters > 50 nm can be used, but for applications where

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clarity is required the particles should have d < 50 nm.

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4.4 Economic feasibility

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Costs associated with the production of lutein-based encapsulation systems depend on the

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ingredients and fabrication methods employed, which can vary widely from one system to

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another. Emulsions and nanoemulsions can be formed using existing equipment such as high

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shear mixers and homogenizers, but these devices require a relatively high initial investment as

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well as appreciable running and maintenance costs. These types of emulsion-based systems can

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be produced using low-cost simple methods, such as spontaneous emulsification, but these

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methods are limited by the high levels of synthetic surfactant required. Other types of colloidal

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encapsulation systems (such as microemulsions, simple coacervates, and molecular complexes)

457

can also be produced by simple low-cost methods, such as mixing or injection. Spray drying can

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also be considered a economically feasible technique to encapsulate lutein, since this drying

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technique is widely used in the food industry due to the availability of equipment and low cost of

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processing.

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4.5 Safety

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The utilization of nanostructures in the food industry pose questions on food safety and

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toxicology. The small dimensions of these structures further increase the reactivity and

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interaction with the gastrointestinal track (GIT). As a result, better understanding of the GIT fate

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of ingested nanoparticles and their potential toxicity is needed. Nanotoxicology evaluates the

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toxicity effects of nanoscale materials on the health of organisms (Hornyak, 2008). At the

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moment there is a relatively poor understanding of the toxicity of most types of food-grade

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nanoparticles, therefore it is not possible to make a statement about the safety of all nanoparticle

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types. The safety of the nanoscale encapsulation systems must be considered individually,

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considering the food matrix that carries them. In general, organic nanoparticles are often fully

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digested within the human GIT and are not bio-persistent, lessening the toxicology threat of

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these encapsulation systems. Nevertheless, they can become toxic if they increase the

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bioavailability of substances that pose a risk to human health (McClements & Xiao, 2017).

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5. CONCLUSION AND FUTURE TRENDS

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The importance of lutein in physiological functions has been studied extensively. The

benefits of consuming an appropriate amount of lutein aid not only eye health but can have a

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positive impact on the body in whole as it aids in the development of the brain and acts as an

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antioxidant. Moreover, with the current trend in the food industry toward more clean labels,

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professionals in the field are exploring approaches to replace artificial food dyes with natural

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alternatives, such as lutein. The incorporation of lutein into low fat food products is hindered by

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its poor water-solubility, chemical instability, and low oral bioavailability. However, various

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types of colloidal encapsulation systems, such as liposomes, microemulsions, emulsions and

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biopolymeric, are available to improve the encapsulation, protection, and release of lutein.

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Aspects to consider when selecting encapsulation systems for lutein are biological fate,

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chemical stability, food matrix compatibility, and economic feasibility. Overcoming physical and

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chemical degradation of the colloidal encapsulation systems in the gastrointestinal tract can be

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achieved by using colloidal particles that reduce the contact between lutein and reactive

488

substances in foods and the gastrointestinal fluids (such as acids, enzymes, or pro-oxidants).

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Color degradation of lutein can be inhibited by addition of antioxidants or interfacial engineering

490

approaches. Although these options are viable, economic feasibility must be considered. High

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pressure homogenizers have a high initial price but are low maintenance, simple to use, and can

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create large volumes of emulsions, making them a sound financial investment. Techniques such

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as molecular inclusion and antisolvent precipitation have already been explored industrially to

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encapsulate hydrophobic bioactives, although their utilization is less common than emulsion-

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based systems.

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As the market shifts to consumer-friendly labels, future trends will continue to look into

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replacing synthetic with natural ingredients, which makes the identification of effective

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encapsulation systems for lutein increasingly important. Therefore, future trends should focus on

499

developing colloidal encapsulation systems assembled from natural food-grade polymers (such

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as proteins and polysaccharides) and antioxidants (such as plant extracts). The research and

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development performed to create such encapsulation systems should take into consideration their

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safety and public perception regarding the use of nanotechnology in foods.

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6. ACKNOWLEDGMENTS

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Partial funding for this project has been provided by the California State University Agricultural

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Research Institute (ARI). ARI Grant Number 17-04-239. Matching funds were provided by the

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Education/Research grants from the Southern California Institute of Food Technologists Section.

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Research reported in this publication was supported by the MENTORES (Mentoring, Educating,

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Networking, and Thematic Opportunities for Research in Engineering and Science) project,

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funded by a Title V grant, Promoting Post-Baccalaureate Opportunities for Hispanic Americans

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(PPOHA) | U.S. Department of Education, Washington, D.C. PR/Award Number:

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P031M140025. The content is solely the responsibility of the authors and does not necessarily

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represent the official views of the Department of Education.

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Yoshida, K., Sekine, T., Matsuzaki, F., Yanaki, T., & Yamaguchi, M. (1999). Stability of vitamin A in oil-in-water-in-oil-type multiple emulsions. Journal of the American Oil Chemists Society, 76(2), 195-200. Zhao, C. D., Cheng, H., Jiang, P. F., Yao, Y. J., & Han, J. (2014). Preparation of lutein-loaded particles for improving solubility and stability by Polyvinylpyrrolidone (PVP) as an emulsionstabilizer. Food Chemistry, 156, 123-128. doi:10.1016/j.foodchem.2014.01.086 Zhao, C. H., Shen, X., & Guo, M. R. (2018). Stability of lutein encapsulated whey protein nano-emulsion during storage. Plos One, 13(2), 10. doi:10.1371/journal.pone.0192511 Zhao, L. S., Temelli, F., Curtis, J. M., & Chen, L. Y. (2017). Encapsulation of lutein in liposomes using supercritical carbon dioxide. Food Research International, 100, 168-179. doi:10.1016/j.foodres.2017.06.055 Zielinska, M. A., Wesolowska, A., Pawlus, B., & Hamulka, J. (2017). Health Effects of Carotenoids during Pregnancy and Lactation. Nutrients, 9(8), 25. doi:10.3390/nu9080838 zur Muhlen, A., Schwarz, C., & Mehnert, W. (1998). Solid lipid nanoparticles (SLN) for controlled drug delivery - Drug release and release mechanism. European Journal of Pharmaceutics and Biopharmaceutics, 45(2), 149-155. doi:10.1016/s0939-6411(97)00150-1

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Figure captions

Figure 1. Lutein molecular structure.

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Figure 2. Depiction of different encapsulation systems indicating the possible location of lutein. Liposomes are comprised of a phospholipid by-layer without a lipid core. Microemulsions and emulsions have a fluid lipid core surrounded by surfactants, being microemulsions

thermodynamically stable while emulsions are thermodynamically unstable. Multilayered

SC

emulsions are comprised of an oil core surrounded by multiple layers of surfactants. Multiple emulsions can be considered as emulsions within emulsions. Solid lipid nanoparticles are similar

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to nanoemulsions except that they have a solid lipid core. Molecular inclusion complexes are formed when lutein becomes physically located within a cavity-containing substrate, which remains in solution in the system. Biopolymer particles are comprised of a dense polymers network held together by different forces (i.e. electrostatic attraction, hydrophobic attraction,

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etc.) Adapted from: (Joye, Davidov-Pardo, & McClements, 2014)

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Table 1: Lutein Concentration in Various Foods Natural Food Source

Lutein/Zeaxanthin Concentration (µ µg/100 g)

Lutein percentage Reference from

total

carotenoids 17000 – 570000 N/A (depending on cultivars) 1094 54

Egg yolk

(Abdel-Aal

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Marigold Flowers

&

Rabalski, 2015)

(Nolan, et al., 2016; Sommerburg, et al.,

Maize (Corn)

780 (500 – 2300)

60

SC

1998)

(Mangels,

Holden,

180

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Zucchini squash

Pumpkin

Spinach

72

43

Lanza,

1993;

Sommerburg, et al., 1998) (Mangels,

et

al.,

1993; Sommerburg, et al., 1998) (Mangels,

et

al.,

1993; Sommerburg, et al., 1998)

1200 (500 – 1800)

47

EP

Red seedless grapes

54

TE D

Kiwi

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Beecher, Forman, &

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998)

1500 (630 – 2300)

49

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) 10200 15940)

(4400

– 47

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998)

Broccoli

1900 (1800 – 2060)

22

(Mangels,

et

al.,

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1993; Sommerburg, et al., 1998) Yellow squash

38

44

(Mangels,

et

al.,

1993; Sommerburg,

Cucumber

240 (0 – 470)

38

RI PT

et al., 1998)

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998)

1700 (1100 – 2400)

41

(Mangels,

SC

Pea

et

al.,

1993; Sommerburg,

Green pepper

700

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Honeydew

38

Celery

Green grapes

14

EP

Butternut squash

72

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Red grape

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et al., 1998)

3600 (0 – 7200)

36

33

37

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) (Mangels,

et

al.,

1993; Sommerburg, et al., 1998) (Mangels,

et

al.,

1993; Sommerburg, et al., 1998) 17

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) 32

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) 72

25

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) Brussel sprouts

1300 (920 – 1590)

27

(Mangels,

et

al.,

1993; Sommerburg,

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et al., 1998) Scallions

2100

27

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998) 740 (440 – 1100)

22

(Mangels,

et

RI PT

Green beans

al.,

1993; Sommerburg, et al., 1998)

Apple (red delicious)

45 (42 – 48)

19

(Mangels,

et

al.,

SC

1993; Sommerburg, et al., 1998)

770, 74, 14, 0, 14, 0, <15 0, 260, 100, 0, 0 (respectively)

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EP

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Orange pepper, Orange juice, Orange, Mango, Peach, Nectarine, Yellow/Red pepper, Carrots, Tomato, Cantaloupe, Dried apricots

(Mangels,

et

al.,

1993; Sommerburg, et al., 1998)

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Table 2: Summary of Extraction Methods for Lutein Yield

Dried Marigold Flowers

Dimethyl Ether

20.65 mg/g Marigold Flower

Marigold Flowers

Supercritical CO2 with Organic Solvents (Hexane, Isooctane, and Toluene) Ethanol and Water Extraction

479 µM (62% yield)

Wet Microalgae

Binary Solvents – Ethanol/Ether and Ethanol/Hexane at Various Ratios Various Types Dimethylformemide of Tuftgrass

47% increase compared to acetone extraction 15.91 mg/g Marigold Flower

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Supercritical CO2

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Dried Marigold Flowers

70% lutein and 96% chlorophyll recovery 8.0 mg/g Wet Microalgae

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Dried Spinach By-Products

PostTreatment Deesterification by 2.5%w/v KOHEtOH Enzymatic Hydrolysis Lipase B and Lipozyme Evaporated under nitrogen until analysis by HPLC Added water for phase separation after extraction N/A. Samples were quantified by HPLC

Reference (Boonnoun, et al., 2017)

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Solvent

SC

Source

(Mora-Pale, et al., 2007)

(Derrien, et al., 2017)

(Gong, et al., 2017)

(Stiegler, et al., 2004)

De(Boonnoun, et esterification by al., 2017) 2.5%w/v KOHEtOH and microionization

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Table 3: Summary of Findings for Nanoemulsions and emulsions Emulsifier Whey Protein Isolate

Size (nm) 121 ± 4.9

Oil Type

Antioxidants

Contribution

Ethanol/MCT

N/A

High stability after 1week storage

Encapsulation Efficiency 94.4%

80.4 ± 5.9

Ethanol/MCT

N/A

High bioactive transportation level

95.9%

Caprine Casein

206.44 ± 2.66

Corn Oil

N/A

Improved lutein stability during prolonged storage compared to bovine casein

N/A

Bovine Casein

205.94 ± 2.90

Corn Oil

N/A

Good physical stability

Sodium Caseinate

190

N/A

Corn Gum Fiber

172 ± 2.3

Ethanol /Phosphate Buffer system Corn Oil

Tween 80

208

Medium Chain Triglyceride (MCT) Oil

N/A

Beta-Lactoglobulin

320 ± 0.0

MCT Oil

α-tocopherol

BetaLactoglobulin/Lecithin

280 ± 0.01

MCT Oil

α-tocopherol

Biozate-1

270 ± 0.0

MCT Oil

α-tocopherol

SC N/A

M AN U

N/A

Stable for 7 d at 23oC

(Feng, et al., 2017)

Stable for 28 d at 20oC

(Surh, et al., 2017; C. H. Zhao, et al., 2018)

N/A

Stable for 46 d at 4oC

(Frede, et al., 2014)

N/A

Stable for 46 d at 4oC

(Frede, et al., 2014)

N/A

Stable for 46 d at 4oC

(Frede, et al., 2014)

N/A

Stable for 46 d at 4oC

(Frede, et al., 2014)

N/A

Stable for 46 d at 4oC Stable for 46 d at 4oC Stable for 10 d at 45oC

(Frede, et al., 2014) (Frede, et al., 2014) (Weigel, et al., 2018)

Stable for 22 d at 37oC with 30mM

(X. Li, et al., 2018; X. Li, et al.,

Tween 20

610 ± 0.02 540 ± 0.01 220

MCT Oil

α-tocopherol

MCT Oil

α-tocopherol

Cytotoxic

N/A

Corn Oil

Ascorbic Acid

N/A

317.5

DHA and MCT Oil

N/A

Increased chemical and physical stability when compared to other antioxidant/surfac tant combinations Increased chemical and physical stability

TE D α-tocopherol

EP

(MoraGutierrez, et al., 2018)

79% - 86% dependent on extraction methods 100% at up to 0.12 wt% (240mg pure lutein per 1L nanoemulsion

MCT Oil

AC C

(MoraGutierrez, et al., 2018)

Increased lutein bioaccessibility of 32.4%

260 ± 0.0

Lactoferrin/Whey Protein Isolate

(Shen, et al., 2018)

N/A

Biozate-1/Lecithin

Quillaja Saponin

(Shen, et al., 2018)

Greater oxidative stability than WPI

Small and stable droplet sizes, high encapsulation efficiency, high resistance to heat, light, and oxygen Small droplets and physically stable Physically stable; increased uptake of lutein Physically stable; Increased uptake of lutein Physically stable; Increased uptake of lutein Cytotoxic

Tween 20/Lecithin

Reference

RI PT

Polymerized Whey Protein

Storage Stability N/A; freeze dried for digestion studies N/A; freeze dried for digestion studies Lutein decreased by 8% after 96h at 25oC; emulsions were stable length of study Lutein decreased by 11% after 96h at 25oC, emulsions were stable length of study Stable for 16 d at 25oC

N/A

(Yi, et al., 2016)

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CaCl2 added

2017)

AC C

EP

TE D

M AN U

SC

RI PT

when compared to independent emulsions

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AC C

EP

TE D

M AN U

SC

RI PT

Figure 1

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Figure 2

Molecular Inclusion Complex

M AN U

SC

Multiple Emulsions

RI PT

Multilayer Emulsion

AC C

EP

TE D

Lutein

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Highlights: Lutein can be used to replace synthetic yellow colorants

•

Lutein can be considered as a nutraceutical ingredient in functional foods

•

Incorporating lutein in aqueous products is challenging due to its hydrophobicity and instability

RI PT

•

Encapsulation is a viable method for delivering lutein in food products

•

Emulsions are the most common delivery system for lutein

AC C

EP

TE D

M AN U

SC

•