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Food Science
Procedia Food Science 1 (2011) 1660 - 1665
11th International Conference on Engineering and Food (ICEF11)
Microencapsulation of Macadamia oil by spray drying
Kalaya Laohasongkram *, Tida Mahamaktudsanee, Saiwarun Chaiwanichsiri
Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
Abstract
The microencapsulation conditions of macadamia oil using spray drying were studied. The optimum condition for preparing emulsion using response surface methodology was studied by varying the ratio of sodium caseinate to maltodextrin, ratio of wall material to core material, and homogenizing pressure. Result showed that the appropriated conditions were sodium caseinate : maltodextrin at 1:4, wall material : core material at 60:40 and homogenizing pressure of 200 bar. The conditions of spray drying were investigated and was found that the optimum condition was the feed rate of 1.1 kg/h and inlet temperature of 167oC.
© 2011PublishedbyElsevierB.V.Selectionand/orpeer-review underresponsibilityof11thInternationalCongress onEngineeringandFood(ICEF11)Executive Committee.
Keywords: Microencapsulation; Microcapsule; Macadamia oil; Spray drying
1. Introduction
The macadamia nuts (Macadamia integrifolia) contain approximately 70% oil and their oil is the most highly monounsaturated fatty acids which possibly help lower blood cholesterol, and reduce the risk of heart disease [1]. Macadamia oil has higher the ratio between unsaturated to saturated fatty acids which is extremely susceptible to oxidation due to increased oxidation potential of unsaturated fatty acids [2], affecting the quality and shelf life of such oils
Microencapsulation is a technology that allows sensitive ingredients to be physically enveloped in a protective "wall material" in order to protect these ingredients or "core" materials from adverse reactions, volatile loss, or nutritional deterioration. The selection of wall material for each core material is important; i.e., carbohydrates such as maltodextrins, starches, corn syrup solids, and acacia gums have all been widely used as encapsulating agents. However, these wall materials, in general, have poor interfacial properties and must be modified or used in conjunction with a surface active agent to encapsulate oil-based materials [3]. In contrast, the amphiphilic character and emulsification properties of proteins and, in particular, sodium caseinate (NaCas) would appear to offer the physical and functional characteristics required to encapsulate lipid core materials. Spray drying is the microencapsulation technique most
* Corresponding author. Tel.: +662-218-5520; fax: +662-218-5533. E-mail address: kalaya.l@chula.ac.th.
ELSEVIER
2211-601X © 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of 11th International Congress on Engineering
and Food (ICEF 11) Executive Committee.
doi:10.1016/j.profoo.2011.09.245
commonly used in the food industry and is employed to encapsulate a wide range of ingredients [4, 5, 6]. The process involves four stages: preparation of a dispersion or emulsion; homogenization of the dispersion; atomization of the feed emulsion; and dehydration of the atomized particles [6]. This research aimed to study the optimum condition to produce microencapsulation of macadamia oil by spray drying to prevent oxidation reaction.
2. Materials & Methods
2.1 Materials
Sodium caseinate (NaCas), maltodextrin DE 18 (MD), and lecithin were obtained from Vicky enterprise Co., Ltd., Ber;o Jucker Speical Securities, Co., Ltd., and Ruamkemi 1986 Co., Ltd., Bangkok, Thailand, respectively. Macadamia oil was cold pressed from macadamia and kept at 4 + 1oC.
2.2 Emulsion preparation
Oil was blended with aqueous solution (20% total solid) of NaCas and MD, by varying the ratio of NaCas to MD at 1:3, 1:4 and 1:5, the ratio of wall material to core material at 50:50, 60:40 and 70:30. Then lecithin was added at 1% by weight and the content was homogenized at, 100, 200 and 300 through a single-stage valve homogenizer (APV Gaulin, Inc. model 15MR-8TA, USA) for 4 times. The coded values for preparing emulsion were shown in Table 1. The apparent viscosities of emulsions were measured at 25oC using a viscometer (Viscometer Rheology International Shannon Ltd., model RI:2:L, Ireland) [7]. Oil droplet size was determined by a trinocular phase contrast microscope equipped with ImageJ Basics (version1_38) program (Olympus, model Bx51TF, Japan) [8].
Table 1. The coded values for preparing emulsion
Coded level
Coded variable —
Factor -1 0 1
NaCas:MD A 1:3 1:4 1:5
Wall material: core material B 50:50 60:40 70:30
Homogenized Pressure (bar) C 100 200 300
2.3 Spoay /tying tha amulsian
The emulsion was spray dried using a spray dryer (GEA Niro A/S, model Mobile Minor 2000, Denmark). The feed rate was varied at 1, 1.5 and 2 kg/h and the inlet drying air temperatures was at 160, 180 and 200oC. The microcapsule powder was analyzed for moisture content (Infrared moisture analyzer, Mettler Toledo, model MJ33, Switzerland), bulk density [9], peroxide value and free fatty acid content [10]. The surface and internal structures of the microcapsules were examined under a scanning electron microscopy (JEOL, model JSM-S410LV, Japan) [11]. The particle size of microcapsules were determined using SemAfore program (version 4.01 demo, Finland) [12]. The microencapsulation efficiency was determined according to the method of Hogan at al [11].
2.4 Statistical analysts
Duncan's multiple range tests were carried out to determine significance of differences among samples at p < 0.05 level, using SPSS for windows (version 16.0) program. The appropriate conditions for emulsion preparation and spray drying conditions were determined from the response surface method (RSM) using the Design-Expert (version 6) program.
3. Results & Discussion
3.C Emylstan praparattan
The results showed that only the ratio of wall material to core material and homogenized pressure significantly affected oil droplet size of the emulsion (p < 0.05). The oil droplet size ranged from 0.51±0.03 to 2.48 ±0.51 micron and decreased as the ratio of wall material to core material and homogenized pressure increased. The effect is obvious when the ratio of wall material to core material increased from 50:50 to 60:40 and homogenized pressure increased from 100 to 200 bar. However at high ratio of wall material to core material and high homogenized pressure the oil droplet size was not significantly changed (Fig. 1). This may be because at low ratio of wall material to core material, there may not be enough coating material to cover the whole surface of the oil droplets to prevent them from coalescence [10]. Another possible reason may be due to greater turbulence and shear forces associated with increased homogenized pressure [11].
From the apparent viscosity measurement it was found that all variables and their interactions affected the viscosity. The apparent viscosity of the emulsions prepared at low ratio of wall material to core material (50:50) increased from 19.34±0.53 to 354.66±3.66 mPa.s when the ratio of NaCas to MD decreased (higher MD), the and homogenized pressure increased (Fig.2). The increase in apparent viscosity was most likely attributed to an increase in the dispersed phase volume and emulsion total solids concentration [11]. From the overlay plots of Fig. 1 and Fig.2 with the oil droplet size of less than 1 ^m [14] and viscosity of 18-179 mPa.s [7, 14] the appropriated condition of emulsion preparation was the ratio NaCas to MD at 1:4, ratio of wall material to core material at 60:40 and homogenized pressure at 200 bar. The oil droplet size and viscosity of the emulsion obtained from the selected conditions were 0.64±0.01 ^m and 37.81±0.63 mPa.s.
Fig. 1 Contour plot of oil droplet size of the emulsion as affected by the ratio of wall material:core material (B) and homogenized pressure(C) at (a) NaCas:MD = 1:3, (b) NaCas:MD = 1:4 and (c) NaCas:MD = 1:5
Fig.2 Contour plot of viscosity of emulsion as affected by ratio of wall material:core material (B) and homogenized pressure (C) at (a) NaCas:MD = 1:3, (b) NaCas:MD = 1:4 and (c)NaCas:MD = 1:5
3.2 Microencapsulation of macadamia oil by spray drying
All microcapsule particles obtained were approximately spherical with some wrinkles or dimples on the surface. The wrinkle at the surface may be due to high inlet drying air temperature causing rapid evaporation of surface water [15, 16, 17]. The inside structure of the microcapsules was found to consisted of both multi-core and simple core which may be due to the viscosity of the emulsion and drying condition [18]. Fig. 3 showed that increasing feed rate resulted in the increases in particle size, moisture content, bulk density, %ME but a decrease in surface oil. While increasing the inlet drying air temperature led to the decrease of particle size, bulk density, and %ME and the increases in surface oil, FFA, and PV. This may be due to the fact that at higher feed rate the microcapsules remained in the drying chamber for a very short time which may not be enough to dry the particles and hence caused agglomeration of the particles [19, 20].
The appropriate drying conditions were determined from the overlay plot of Fig. 3(a) to (g) with the controlled ranges of variables of particle size 7.5-10 ^m, moisture content of 1-3 %wb [21], density of 0.33-0.43 g/cm3 [19], surface oil of 6.5-7.5%, %ME > 88.5%, FFA of 0-0.2% oleic acid, and PV of 0-0.2 meq.O2/kg oil. It was found that the appropriate conditions for spray drying were feed rate of 1.1 kg/h and inlet drying air temperature of 167oC. The properties of the microcapsules obtained were average particle size of 9.75±0.03 ^m, moisture content of 1.00±0.05%, bulk density of 0.36±0.01 g/cm3, surface oil of 7.33±0.59%, %ME of 88.75±0.45%, FFA of 0.170±0.001%oleic acid and PV of 0.198±0.004 meq.O2/kg oil.
4. Conclusion
The appropriate conditions for preparing emulsion were NaCas:MD of 1:4, wall to core materials of 60:40, and homogenized pressure of 200 bar and for spray drying were feed rate of 1.1 kg/h and inlet drying air temperature of 167oC.
Fig.3 Effect of feed rate (A) and inlet drying air temperature (B) on the contour plots of the properties of microcapsules (a) particle size, (b) moisture content, (c) bulk density, (d) surface oil, (e) %ME, (f) FFA, and (g) PV
Acknowledgements
The authors would like to thank the Graduate School of Chulalongkorn University and the Thailand Research Fund - Master Research Grants for financial support and to Mr. Prapat Pimprapote for supplying the macadamia nut of this project.
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Presented at ICEF11 (May 22-26, 2011 - Athens, Greece) as paper FPE127.
