Elsevier

Food Chemistry

Volume 212, 1 December 2016, Pages 27-34
Food Chemistry

Microchannel emulsification study on formulation and stability characterization of monodisperse oil-in-water emulsions encapsulating quercetin

https://doi.org/10.1016/j.foodchem.2016.05.154Get rights and content

Highlights

  • Monodisperse O/W emulsions encapsulating quercetin were formulated.

  • Uniformly sized droplets with d3,2 of 28–29 μm were generated by MCE.

  • Appropriate emulsion compositions and operating conditions for MCE were found.

  • The collected O/W emulsions had high coalescence stability at 4 and 25 °C.

  • Encapsulation efficiency of quercetin was about 80% after 30 d of storage at 4 °C.

Abstract

The study used microchannel emulsification (MCE) to encapsulate quercetin in food grade oil-in-water (O/W) emulsions. A silicon microchannel plate (Model WMS 1-2) comprised of 10,300 discrete 10 × 104 μm microslots was connected to a circular microhole with an inner diameter of 10 μm. 1% (w/w) Tween 20 was used as optimized emulsifier in Milli-Q water, while 0.4 mg ml−1 quercetin in different oils served as a dispersed phase. The MCE was carried by injecting the dispersed phase at 2 ml h−1. Successful emulsification was conducted below the critical dispersed phase flux, with a Sauter mean diameter of 29 μm and relative span factor below 0.25. The O/W emulsions remained stable in terms of droplet coalescence at 4 and 25 °C for 30 days. The encapsulation efficiency of quercetin in the O/W emulsions was 80% at 4 °C and 70% at 25 °C during the evaluated storage period.

Introduction

Quercetin (3,3′,4′,5,7-pentahydroxyflavanone) is categorized as a flavonol and belongs to the family of flavonoids (Ross & Kasum, 2002). By definition, quercetin is an aglycone (lacking an attached sugar) with a brilliant citron yellow colour that is entirely insoluble in water, sparingly soluble in oil medium, and readily soluble in a variety of polar solvents (Kelly, 2011). The solubility of quercetin in the aqueous phase can be greatly improved by attaching glycosyl groups at hydroxyl positions (Hollman et al., 1999). Flavonols are present in many vegetables, flowers, nuts and fruits (Häkkinen, Kärenlampi, Heinonen, Mykkänen, & Törrönen, 1999). They are also abundant in a variety of medicinal plants, such as Ginko bioloba, Solanum trilobatum, and many others (Kelly, 2011). The estimated intake of flavonols ranges from 20 to 50 mg d−1. Most of the dietary intake is as flavonol glycosides of kaempferol, myricetin and quercetin (Cao, Zhang, Chen, & Zhao, 2010).

Quercetin exhibits a wide range of biological activities, including anticancer, antioxidant, antitoxic, antithrombotic, anti-ageing, metal chelating and antimicrobial activities (Borska et al., 2010, Kelly, 2011). Similarly, it has an impact on obesity, sleep and mood disorders (Joshi et al., 2005, Kelly, 2011). Recently, quercetin has been used in many sport supplements in order to reduce post-exercise immune system perturbations (Davis, Carlstedt, Chen, Carmichael, & Murphy, 2010). The bioavailability and absorption of quercetin depend upon the nature of the attached sugar, solubility modifications, and the types of emulsifiers used in different systems (Scholz & Williamson, 2007). Despite its significant biological activities, quercetin has very poor oral bioavailability. The main disadvantages of using quercetin in therapeutics and functional foods are its poor solubility in aqueous and oil media, very low bioavailability, poor permeability and crystallization at ambient temperatures (Borghetti et al., 2009, Pouton, 2006). To overcome these disadvantages, it is essential to develop an efficient delivery system for quercetin that improves its stability and release at the appropriate target site.

Different colloidal systems are there to encapsulate vital lipophilic compounds, including emulsions, solid lipid micro- and nano-particles, filled hydrogel particles and polymeric nano-particles (Flanagan and Singh, 2006, McClements and Rao, 2011). These colloidal delivery systems were formulated either with conventional emulsification tools or microfluidic devices (Vladisavljevic et al., 2013). In this study, we used microchannel emulsification (MCE) to encapsulate quercetin in different oil-in-water (O/W) emulsions. MCE is a promising technique for generating monodisperse emulsion droplets with a size variation of less than 5% (Kawakatsu, Kikuchi, & Nakajima, 1997). MCE devices consist of either parallel grooves and terraces or straight-through microholes (Kawakatsu et al., 1997, Kobayashi et al., 2002). The distinguishing features of MCE involve the absence of external shear forces during droplet generation and the droplet size being mainly determined by the MC geometry and composition of dispersed and continuous phase (Vladisavljevic, Kobayashi, & Nakajima, 2012). The droplet generation in MCE takes place due to spontaneous transformation of a dispersed phase passing through the MCs, as a result of the interfacial tension dominant on micron scales (Sugiura, Nakajima, Iwamoto, & Seki, 2001). MCE has been successfully applied to the preparation of simple and multiple emulsions, microspheres and microcapsules (Vladisavljevic et al., 2013). Many hydrophilic and lipophilic compounds have been encapsulated in these systems, such as β-carotene (Neves, Ribeiro, Kobayashi, & Nakajima, 2008), oleuropein (Souilem et al., 2014), γ-oryzanol (Neves, Ribeiro, Fujiu, Kobayashi, & Nakajima, 2008), l-ascorbic acid (Khalid et al., 2014b, Khalid et al., 2015a, Khalid et al., 2015b), ascorbic acid derivatives (Khalid et al., 2014a) and vitamin D (Khalid et al., 2015a, Khalid et al., 2015b).

The aim of this study was to design food grade O/W emulsions encapsulating quercetin using straight-through MCE. The present study investigated the effects of emulsifier type on the droplet generation characteristics and stability of emulsions encapsulating quercetin. Moreover, the effects of different dispersed phase composition on quercetin encapsulation were examined, together with the physical and chemical stability of the formulated emulsions. The results of this study improve the understanding of significant factors that influence the encapsulation, stabilization and utilization of crystalline bioactive compounds in food, cosmetics and pharmaceuticals.

Section snippets

Chemicals

3,3′,4′,5,7-pentahydroxyflavanone (quercetin) was procured from Nacalai Tesque, Inc. (Kyoto, Japan). Dimethyl sulfoxide, polyoxyethylene (20) sorbitan monolaurate (Tween 20, Hydrophilic-Lipophilic Balance (HLB) 16.7) and bovine serum albumin (BSA) were procured from Wako Pure Chemical Industries (Osaka, Japan). Sodium salt of colic acid with >97% (Na-cholate) was procured from Sigma Aldrich (St. Louis, MO, USA). The medium chain triacylglycerides (MCT, sunsoft MCT-7) composed of 25% capric acid

Effect of different emulsifiers on emulsion formulation

Emulsifier molecules play a critical role in the stability of oil droplets in MCE. The charge on the MC array chip surface and its electrostatic interactions with the emulsifiers must be kept in mind during MCE. Uniformly sized oil droplets can be generated from the MCs when the chip surface has a non-attractive interaction with the emulsifier molecules. Moreover, the stability of the droplets correlates with the type of emulsifier in the continuous phase and with whether it preferentially wets

Conclusions

The present study demonstrated the successful formulation of food-grade monodisperse O/W emulsions encapsulating quercetin through straight-through MCE. The results for the effect of different emulsifiers indicate that Tween 20 was the best selection as the emulsifier for this study. Successful droplet generation and monodispersity were achieved at a maximum of 0.4 mg ml−1 quercetin in an MCT oil as the dispersed phase. The selected operating parameters include Jd of 20–40 L m−2 h−1 and V¯c of

Acknowledgments

The first author acknowledges the fellowship from the University of Tokyo for studying at the University of Tokyo and National Food Research Institute, NARO of Japan.

References (39)

  • J. Cao et al.

    The relationship between fasting plasma concentrations of selected flavonoids and their ordinary dietary intake

    British Journal of Nutrition

    (2010)
  • J.M. Davis et al.

    The dietary flavonoid quercetin increases VO(2max) and endurance capacity

    International Journal of Sport Nutrition and Exercise Metabolism

    (2010)
  • J. Flanagan et al.

    Microemulsions: A potential delivery system for bioactives in food

    Critical Reviews in Food Science and Nutrition

    (2006)
  • S.H. Häkkinen et al.

    Content of the flavonols quercetin, myricetin, and kaempferol in 25 edible berries

    Journal of Agricultural and Food Chemistry

    (1999)
  • P.C. Hollman et al.

    The sugar moiety is a major determinant of the absorption of dietary flavonoid glycosides in man

    Free Radical Research

    (1999)
  • D. Joshi et al.

    Protective effect of quercetin on alcohol abstinence-induced anxiety and convulsions

    Journal of Medicinal Food

    (2005)
  • A. Karadag et al.

    Optimization of preparation conditions for quercetin nanoemulsions using response surface methodology

    Journal of Agriculture and Food Chemistry

    (2013)
  • T. Kawakatsu et al.

    Regular-sized cell creation in microchannel emulsification by visual microprocessing method

    Journal of the American Oil Chemists’ Society

    (1997)
  • G.S. Kelly

    Quercetin Monograph

    Alternative Medicine Review

    (2011)
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