Elsevier

Food Research International

Volume 109, July 2018, Pages 489-496
Food Research International

Microencapsulation of betanin in monodisperse W/O/W emulsions

https://doi.org/10.1016/j.foodres.2018.04.053Get rights and content

Highlights

  • E162 and betanin were encapsulated in W/O/W emulsions.

  • Microchannel emulsification of betanin produce monodisperse emulsions.

  • Betanin stabilizes the W/O/W emulsion.

Abstract

Betanin is the main pigment of the food color beetroot red (E162). Due to the fair heat and light stability of E162, this pigment is mainly used in minimally processed packaged food products. Encapsulation increases the stability of betanin, but detailing on the effect of different sources of betanin on the properties and stability of multiple emulsions are scarce. Here we describe the encapsulation of E162, spray-dried beetroot juice and betanin in a monodisperse food-grade water-in-oil-in-water (W/O/W) emulsions by using microchannel emulsification. We compare the tinctorial strength of the encapsulated pigments and investigate the effect of temperature, storage period and pigment concentration on emulsion stability and color. Betanin increases the overall stability of the W/O/W emulsion, reduce the oil droplet size and improve size distribution when compared to the negative control without pigment and to emulsions containing betanin from other sources.

Introduction

Consumers prefer foods and beverages containing raw natural materials to artificial substances (Oplatowska-Stachowiak & Elliott, 2017; Román, Sánchez-Siles, & Siegrist, 2017). Products without (or with reduced amount of) artificial substances are classified as clean label and have been associated to putative health benefits and lower environmental impact (Asioli et al., 2017). Betanin (betanidin 5-O-glucoside, EEC #E162), the major pigment of the red beetroot, is a water-soluble nontoxic natural pigment belonging to the class of betalains that was approved by the FDA and has been used in foods since 1967 (Herbach, Stintzing, & Carle, 2006). Betalains show higher tinctorial strength compared to anthocyanins, and keep their color in low-acid food (within the pH 3 to 7 range), where the color of anthocyanins is loss due to hemiketal formation (Quina & Bastos, 2018). However, betanin is sensitive to thermal and photochemical decomposition and subject to acid- and base-catalyzed hydrolysis that may cause color alterations that limit its application as a food additive (Attoe & von Elbe, 1981; Attoe & von Elbe, 1984; Bastos & Gonçalves, 2017; Esteves et al., 2018; Goncalves, Da Silva, DeRose, Ando, & Bastos, 2013; Herbach, Stintzing, & Carle, 2004; Khan, 2016).

The encapsulation of betalains in complex matrices increases its persistence in food products (Khan, 2016), and may be useful to expand the application of natural and artificial derivatives as food colorants (Fernandes et al., 2016; Goncalves et al., 2013; Goncalves, Da Silva, et al., 2013; Pavliuk et al., 2017; Rodrigues et al., 2018). There are several techniques for microencapsulation, which include emulsification followed by solvent removal, spray drying and milling. These techniques usually produce polydisperse material, i.e., non-uniform particle sizes, and heat that may not be adequate for temperature-sensitive samples, such as betalains. Water-in-oil (W/O) emulsions, where oil refers to any water-insoluble liquid, are suitable for encapsulating polar substances. However, multiple water-in-oil-in-water (W/O/W) emulsions allow the encapsulation of hydrophilic substances in water with a protecting layer of oil (Dias, Ferreira, & Barreiro, 2015). W/O/W emulsions have been used as delivery systems for plant bioactives, in preventing the exposure of sensitive substances to light oxygen and heat, and for the manufacture of food products with improved sensorial characteristics (Lamba, Sathish, & Sabikhi, 2015; Muschiolik & Dickinson, 2017). Homogenization of water and oil mixtures using a rotor-stator, ultrasound or high rotation result in polydisperse W/O/W emulsions. However, microchannel emulsification (MCE) produces monodisperse emulsions with improved physical stability (Khalid et al., 2014; Kobayashi & Nakajima, 2006; Souilem et al., 2013).

Aqueous beet extract was encapsulated in W/O/W type double-layer emulsion to study intestinal digestion in vitro, but the emulsion obtained is polydisperse and unstable, producing cream after storage at room temperature (Kaimainen, Marze, Järvenpää, Anton, & Huopalahti, 2015). Here we describe the encapsulation of three different sources of betanin in monodisperse W/O/W emulsions prepared by MCE of water, soybean oil and food-grade surfactants. The emulsion formulation was optimized by varying the volume fraction of the internal aqueous phase, the concentration of the hydrophobic and hydrophilic emulsifiers, and the flux of the dispersed phase. The tinctorial strength and color variability of encapsulated E162, powdered beetroot juice and betanin as well as the physical stability of the emulsions kept at 4 °C, 25 °C and 60 °C were monitored over 7 days and compared.

Section snippets

General

All chemicals were purchased from commercial sources with the highest purity available and were used without further purification. Refined soybean oil, d(+)-glucose, and polyoxyethylene (n = 20) sorbitan monolaurate (Tween 20) were purchased from Wako Pure Chemical Industries. Tetraglycerin monolaurate condensed ricinoleic acid ester (CR-310) was obtained from Sakamoto Yakuhin Kogyo Co. Ltd. Aqueous solutions were prepared with deionized water (conductivity 18.2 MΩ cm at 25 °C, Milli-Q,

Formulation of W/O/W emulsions loaded with betanin

E162 (sample A) was encapsulated in a W/O/W emulsion formulated using a W/O emulsion as the dispensed phase and an aqueous solution of Tween 20 as the continuous phase. The effect of formulation conditions on droplet size distribution, average droplet diameter (d3,2) and degree of emulsion dispersion was investigated. Initial experimental conditions were defined as follows: volume fraction of the internal aqueous phase (ϕAi): 30% v/v, concentration of CR-310 (CCR-310): 4% w/w, concentration of

Conclusions

Betanin was encapsulated in W/O/W emulsions using the microchannel emulsification (MCE) technique. The droplets formed have a size of 46 ± 10 μm and are monodisperse. Emulsifying agents suitable for use in food and the use of soybean oil resulted in a W/O/W emulsion that can be used in the preparation of functional foods kept under refrigeration for up to 7 days. The emulsification conditions were optimized and the dispersed phase flux was the most important factor influencing the capillary

Author contributions

APEP, NK, IK and MN performed the experiments. IK, MN, MAN, ELB contributed with reagents, materials, analysis costs and technology. APEP and ELB prepared the manuscript. All authors analyzed the data and revised the manuscript.

Conflict of interest

The authors declare no competing financial interest.

Acknowledgements

We thank the São Paulo Research FoundationFAPESP (ELB, 2014/22136-4, 2016/21445-9), the Brazilian National Council for Scientific and Technological DevelopmentCNPq (ELB, 303341/2016-5), and the University of Tsukuba for financial and fellowship support.

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