Accepted Manuscript Title: Enzymatic esterification of tapioca maltodextrin fatty acid ester Author: Sunsanee Udomrati Shoichi Gohtani PII: DOI: Reference:
S0144-8617(13)00776-5 http://dx.doi.org/doi:10.1016/j.carbpol.2013.07.081 CARP 7989
To appear in: Received date: Revised date: Accepted date:
25-4-2013 29-6-2013 26-7-2013
Please cite this article as: Udomrati, S., & Gohtani, S., Enzymatic esterification of tapioca maltodextrin fatty acid ester, Carbohydrate Polymers (2013), http://dx.doi.org/10.1016/j.carbpol.2013.07.081 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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Enzymatic esterification of tapioca maltodextrin fatty acid ester
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Sunsanee Udomrati1,2, Shoichi Gohtani 3,*
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1. Department of Food Science, The United Graduate School of Agricultural Sciences,
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Ehime University, Ehime, Japan
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2. Institute of Food Research and Product Development, Kasetsart University, Bangkok,
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Thailand
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3. Department of Applied Biological Science, Faculty of Agriculture, Kagawa University,
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Kagawa, Japan
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Correspondence: Dr. Shoichi Gohtani, Department of Applied Biological Science,
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Faculty of Agriculture, Kagawa University, Kagawa, Japan,
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Email: [emailprotected]
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TEL:+81 878 91 3103
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FAX:+81 878 91 3103
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List of abbreviations Maltodextrin decanoate
2. Malto_L
Maltodextrin laurate
3. Malto_P
Maltodextrin palmitate
4. DE
Dextrose equivalent (dimensionless)
5. DS
Degree of substitution (dimensionless)
6. n
Flow behavior index (dimensionless)
7. τ
Shear stress (Pa)
8. τ0
Yield stress (Pa)
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Shear rate (s-1)
M
9. !
ip t
1. Malto_D
Consistency index (Pa.sn)
11. Mw
Weight - average molecular mass (g/mol)
12. ΔH
Transition enthalpy (J/g)
13. Tm
Melting temperature (oC)
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10. k
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14. E24
Emulsification index (dimensionless)
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Abstract In this work new types of hydrophobically modified maltodextrin were prepared
23
by enzyme-catalyed reaction of maltodextrin and three fatty acids: decanoic acid (C-10),
24
lauric acid (C-12) and palmitic acid (C-16). Lipase obtained from T. lanuginosus was
25
found to be a useful biocatalyst in the maltodextrin esterification. Esterified maltodextrin
26
with a degree of substitution (DS) 0.015-0.084 was prepared at the optimum conditions
27
of 60oC for 4 hours. The DS was found to be at its highest when maltodextrin and fatty
28
acids were taken in the ratio 1:0.5.
29
maltodextrin were investigated. All esterified maltodextrin did not completely dissolve
30
in water. Esterified maltodextrin at a concentration of 25% (w/w) exhibited Newtonian
31
flow behaviour similar to that of native maltodextrin. Esterified maltodextrin had a
32
higher viscosity compare to native maltodextrin. X-ray diffraction pattern of esterified
33
maltodextrin indicated crystallization of the fatty acid side chains. The thermal stability
34
of esterified maltodextrin was checked by differential scanning calorimetry (DSC).
35
Esterified maltodextrin was then used as an emulsifier to make n-hexadecane O/W
36
emulsions.
37
characteristics and emulsification index.
38
Keywords: Degree of substitution, Emulsification index, Emulsion, Enzymatic
39
esterification, Maltodextrin
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The functional properties of these esterified
The emulsions were characterized according to their oil droplet
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1. Introduction Maltodextrins have the same general formula as amylose but are of shorter chain
45
length. Maltodextrins are widely used in industry due to their non-toxicity and low price.
46
They are used as thickening agents in food processing, and as binding agents in
47
pharmaceuticals (Biswas et al., 2009). Most polysaccharides are strongly hydrophilic and
48
hence they are not surface active in emulsion. However, a small number of naturally
49
occurring polysaccharides have some hydrophobic characteristics (e.g. gum arabic) or
50
have been chemically modified to introduce non-polar groups (e.g. some hydrophobically
51
modified starches) and these biopolymers can be used as emulsifiers (McClements, 2008).
52
Maltodextrins also have some disadvantages. Due to the absence of lipophilic groups,
53
maltodextrins are unsuitable for oil-in-water emulsion systems. With the development of
54
food science and technology, attempts are being made to improve maltodextrin properties
55
via chemical modification, hydrolysis processes, and production units (Zheng et al.,
56
2007).
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ip t
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The introduction of an ester group into polysaccharide constitutes an important
58
achievement because the ester group results in modifying the polysaccharides’ original
59
hydrophilic nature and obtaining amphiphilic polysaccharide. Amphiphilic polymers
60
have hydrophilic and hydrophobic subregions, therefore they can act like low-molecular-
61
weight surfactants and they may present good ability for oil emulsification probably due
62
to steric stabilization with respect to their macromolecular structure (Sadtler et al., 2002).
63
Enzymatic processes offer an attractive alternative route for the synthesis of oligo- and
64
polysaccharide esters. Selective processes catalyzed by enzymes may be performed
65
under mild conditions of temperature and pressure, thereby avoiding polymer degradation
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(van den Broek & Boeriu, 2013). Enzymatic catalysis also reduces the use of toxic
67
reactants. Enzymatic routes may be preferable because the chemical processes include
68
extreme pH conditions, solvents that push the limits of acceptability for health
69
(Alissandratos et al., 2010). Enzymatic modification may be of interest for the synthesis
70
of macromolecules with targeted food and biomedical applications (Kaewprapan et al.,
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2012). Presently there has been little research on enzymatic esterification of maltodextrin.
72
The purposes of the present study are: (a) to investigate optimum condition for
73
esterified maltodextrin production by enzymatic esterification; (b) to study the
74
physicochemical properties of esterified maltodextrin; (c) to study emulsifying activities
75
of esterified maltodextrin in n-hexadecane O/W emulsions.
76
2. Materials and methods
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2.1. Materials
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Tapioca maltodextrin of dextrose equivalent value of 16 was supplied by Corn
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Products Co., Ltd. (Bangkok, Thailand). The weight average molecular weight (Mw) was
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5182 g/mol (Udomrati et al., 2013) as measured by multi-angel laser-light-scattering
81
(MALLS) (DAWN EOS, Wyatt tech. Corp., USA). Lipase obtained from Thermomyces
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lanuginosus (Sigma-Aldrich, Switzerland). Enzyme activity was about 100,000 U/g.
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Decanoic acid (C-10), Lauric acid (C-12), and Palmitic acid (C-16) were purchased from
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Sigma-Aldrich (Switzerland). All the other chemicals used were of analytical grade.
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2.2. Esterified maltodextrin preparation Maltodextrin and fatty acid in the ratio of 1:0.1, 1:0.5 and 1:1 (mole of D-glucose
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unit/mole of fatty acid) was used. Maltodextrin (1 g) was dissolved in 2 ml DMSO, 350
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µl of lipase enzyme was added and incubated in waterbath at 50 to 70oC. Incubation time
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was 2 to 8 hours. Three fatty acids were investigated; decanoic acid, lauric acid and
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palmitic acid.
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supernatant was poured off and three additional ethanol extractions were performed prior
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to drying of the precipitate in hot air oven at 50oC.
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2.3. Proton nuclear magnetic resonance (1H NMR) spectra
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The ethanol
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The ester formed was precipitated by adding ethanol.
The 1H NMR spectra of the samples were recorded with a NMR (ALPHA 600,
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JEOL, Japan). The sample was dissolved in DMSO-d6 and the solution concentration
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was 15% (w/w). The measurement was operated at 70oC. All chemical shifts are
99
reported in parts per million (ppm) using TMS as references, which is usually used as an
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internal standard for NMR measurements at elevated temperature. The 1H NMR spectra
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of the esterified maltodextrin showed three protons of the terminal methyl group of the
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acyl chain, as a triplet, around 0.85 ppm.
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corresponded to the signals from the four protons of the glycoside structure. The degree
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of substitution (DS) was obtained from the ratio of area of the proton peak at 0.865 ppm
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to that of the proton peak between 4.58 and 5.50 ppm, according to Eq. (1):
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The peaks between 4.58 and 5.50 ppm
(1)
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where 3 is the number of protons from the signal of the methyl proton, and IAGU is the
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integral for the 4 protons of the anhydroglucose unit (AGU) between 4.58 and 5.50m
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ppm (Kapusniak & Siemion, 2007).
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2.4. Interfacial tension
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Interfacial tension between n-hexadecane and pure water containing esterified
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maltodextrin was measured by means of drop volume method employing a computer-
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controlled apparatus (DVS-2000, Yamash*ta Giken, Japan) at 25
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apparatus can automatically determine the n-hexadecane-water interfacial tension from
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the maximum volume of the pendant drop detached from the glass syringe immersed in
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the n-hexadecane.
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2.5. Solubility
0.01oC.
The
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Esterified maltodextrin powder (30-50 mg) were suspended in 5 ml water, stirred
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for 30 min then centrifuged at 4000 rpm for 15 min. The supernatant was collected, dried
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in an oven at 90oC and weighted. Solubility (%) was calculated as follows:
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(2)
2.6. Rheological analysis
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Shear stress (τ) and viscosity of esterified maltodexrin solutions of 25% (w/w)
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concentrations were measured using a cone and plate type viscometer. The samples were
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measured with a viscometer (DV-III Ultra, Brookfield, USA) using cone number CPE-40.
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The angle and the gap between the cone and plate were 0.8o and 13.0 µm, respectively.
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Samples were placed in the measurement cell of the viscometer and allowed to
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equilibrate at 25oC. The shear stress of the sample was measured in the range of shear
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rate 5 to 225 s-1. Experimental data was fitted to the Herschel-Bulkley model (Nikovska,
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2010; Jafari et al., 2012) which is represented by the equation shown below;
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! ! ! 0 ! k !!
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.
cr
n
(3)
where τ is the shear stress (Pa), τ0 is the yield stress (Pa), ! is the shear rate (s-1), n is the
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dimensionless flow behavior index, and k is the consistency index (Pa.sn).
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2.7. X-ray diffraction
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X-ray powder diffraction was carried out using a Nano viewer (Rigaku Co., Japan). The powder samples were measured from 3o to 26o for 2Ө.
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2.8. Differential scanning calorimetry (DSC)
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Transition enthalpy (ΔH expressed as J/g) and melting temperature (Tm) were
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determined by DSC (Diamond DSC, Perkin-Elmer, USA).
Samples of esteried
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maltodextrin (8-10 mg) were sealed in Al pans and heated from -20 to 105oC at 10oC/min
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and rapidly cooled back to -20oC. After cooling, samples were reheated immediately to
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105oC at the same heating rate. An empty pan was used as reference.
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2.9. Emulsion preparation
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Briefly, 6 ml of n-hexadecane oil were added to 4 ml of esterified maltodextrin
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solution (25% (w/w)) in a test tube and hom*ogenized by high speed hom*ogenizer (Ultra
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turrax T25, IKA Janke and Kunke, Germany) at 15000 rpm for 1 minute. Mean diameter
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of oil droplets and microstructure of fresh emulsions were determined.
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2.10. Determination of average oil droplet size
ip t
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The average diameter of oil droplets in emulsions was determined using a laser
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diffraction particle size analyzer (SALD-3000, Shimadzu Co., Ltd, Japan). This
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instrument measures the angular dependence of the intensity of light scattered from a
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dilute emulsion under stirring. To avoid multiple scattering effects, emulsions were
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diluted before measurement.
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measurement to ensure a hom*ogenous dispersion of the emulsion droplets.
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2.11. Microscopic analysis
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Emulsions were stirred continuously throughout the
A microscope (BX51, Olympus, Japan) was used to determine the microstructure
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cr
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of the emulsions at 20x magnification.
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2.12. Emulsifying activity
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The assay for emulsifying activity was modified from the method of Freitas et al.
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(2009) using n-hexadecane oil as the test substance. Emulsification was performed using
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a high speed hom*ogenizer (Ultra turrax T25, IKA Janke and Kunke, Germany) at 10000
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rpm for 1 minute.
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esterified maltodextrin (0-35% (w/w)). After 24 h, the emulsification index (E24) was
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determined as follows:
The aqueous phase was constituted of varied concentrations of
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where he (mm) is the height of the emulsion layer and hT (mm) is the overall height of the
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mixture.
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3. Results and discussion
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3.1. Esterified maltodextrin production
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In Fig. 1, by increasing the reaction temperature from 50 to 60oC, the DS of all
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esterified maltodextrin increased. Further increase in the reaction temperature from 60 to
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70oC caused the reaction efficiency to decrease. This result may be attributed that the
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enzyme lost its full activity by denaturation (Horchani et al., 2010). So we conclude that
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the optimum temperature for enzyme activity of the lipase used in this study was 60oC.
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The Fig. 2 shows that the DS reached a plateau after 4 hours for maltodextrin
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decanoate and maltodextrin laurate, while the DS of maltodextrin palmitate reached
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maximum value after 2 h and did not decrease further even after 2 h. This result shows
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that esterification reaches a maximum at 4 h of reaction time for maltodextrin decanoate
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and maltodextrin laurate and 2 h for maltodextrin palmitate. The optimal conditions
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leading to the maximum of DS were at a temperature of 60oC and reaction time of 4 h.
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Fatty acids with 10, 12, and 16 carbons were investigated as acyl donors (Fig. 1 &
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Fig. 2). By increasing the fatty acid chain length, the DS decreased for all reaction
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conditions. These results may be due to the slower mobility of longer fatty acid chain
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length in the reaction system and consequently the rate of reaction of esterification was
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less than small fatty acid molecules.
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The Fig. 3 shows that the DS was controlled by changing the maltodextrin/fatty acid molar ratio. The values of DS ranged from 0.002 to 0.084.
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maltodextrin decanoate and maltodextrin laurate, when the ratio of maltodextrin to fatty
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acid was 1:0.5, the DS value was the highest value. Moreover, it was found that the DS
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decreased as the ratio of maltodextrin to fatty acid reached 1:1. This result was possibly
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due to partial deactivation of the enzyme because of increasing acidity in the system. For
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maltodextrin palmitate with maltodextrin to fatty acid in the ratio 1:0.5 and 1:1, no
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differences of DS were observed, suggesting that similar results could be obtained using a
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higher dilution with less cost. These results show that DS of the products could be
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controlled by varying the reaction conditions, such as the reaction temperature, reaction
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time, and the concentration of the reactants.
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physicochemical properties were determined for the esterified maltodextrins prepared by
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the method at the optimum condition.
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3.2. Physicochemical characterization
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In the below investigation, the
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In the case of
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3.2.1. Interfacial tension
Interfacial tension of native maltodextrin and esterified maltodextrin solutions
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(25%w/w) / n-hexadecane system were measured at 25oC.
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maltodextrin showed interfacial tension of 47 mN/m. After esterification, interfacial
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tension was lowered to 39.68, 40.02, and 41.39 mN/m for maltodextrin decanoate,
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maltodextrin laurate, and maltodextrin palmitate, respectively. From the results of this
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study, it was found that maltodextrin esterification leads to increase the surface activity.
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This is a very important property because the greater the surface activity of esterified
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maltodextrin, the greater emulsification and emulsion stability. Therefore these results
In Table 1, native
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indicate the potential application of esterified maltodextrin in the preparation of O/W
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emulsion. The surface activity of esterified maltodextrin is obtained through enzymatic
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modification that introduces hydrophobic groups into the polymeric structure of the
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maltodextrin. The molecules of esterified maltodextrin could orient themselves at the oil-
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water interface and form an adsorbed monomolecular layer that is able to stabilize the
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emulsion by steric hindrance, and it is possible to produce stable emulsions.
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3.2.2. Solubility
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Solubility of native maltodextrin and esterified maltodextrins in water is shown in
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Table 1. The native maltodextrin was fully water soluble while all esterified maltodextrin
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was slightly insoluble in water. This result is consistent with Qiao et al. (2006) who
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found that esterified starch has lower water solubility compared with the native starch.
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The decrease in water solubility was attributed to the lower amount of remaining
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hydroxyl groups in maltodextrin molecules after esterification. Esterification renders
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maltodextrin more hydrophobic, which would lead to reducing the possibility of
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hydrogen bond formation between hydroxyl groups in the maltodextrin and water, that is,
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by reducing solubility in water (Rajan et al., 2008). As the chain length of fatty acid
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increases, the solubility of esterified maltodextrin in water tended to decreases. These
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results may be attributed to the fact that the solubility of the fatty acid in water decreases
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with increasing the chain length owing to the hydrophobicity.
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3.2.3. Rheological properties
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Rheological characteristics of native maltodextrin and esterified maltodextrin
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differed with the acyl donor used, as shown in Table 2. All esterified maltodextrin
Page 12 of 33
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showed a slight increase in apparent viscosity at the shear rate of 225 s-1 and k compared
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to the native maltodextrin. Higher viscosity of esterified maltodextrin compared to that
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of native maltodextrin may be due to the increase in the resistance to flow of the larger
234
molecules (Ibanoglu, 2002) and higher viscosity also might be related to internal
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plasticization (Rajan et al., 2008). Native maltodextrin does not have ester groups, so it
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may not show internal plasticization. This result is consistent with the results of Qiao et
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al. (2006) who found that esterified starch has higher viscosity compared to the original
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starch. The value of n is almost one in native maltodextrin which indicates Newtonian
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flow behavior. These results are consistent with the results of Dokic et al. (1998), Loret
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et al. (2004), and Udomrati et al. (2013) who found that maltodextrin solution exhibits
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Newtonian flow behavior, regardless of concentrations. After esterification, there was no
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change in both the flow behavior and τ0 for all esterified maltodextrin because there was
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no difference in the strength of attractive force in the systems. The increased viscosity of
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esterified maltodextrin adducts versus the native maltodextrin suggests that this material
245
is a good thickener and perhaps can be used as emulsifiers and polymeric surfactant.
247
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ip t
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3.2.4. X-ray diffraction
X-ray diffraction of native maltodextrin and esterified maltodextrin are shown in
248
Fig. 4a. The native maltodextrin showed a broad diffraction peak demonstrating the low
249
crystalline nature. After esterification, the broad peak at about 2Ө = 20o was apparent
250
and this peak showed higher intensity compared to native maltodextrin. These changes
251
are indicative of crystallites occurrence after esterification. The main peak of reflection
252
of palmitic acid was shown in Fig. 4b, the most intense reflection was at about 20o.
253
These results were consistent with those for lauric acid and decanoic acid (data not
Page 13 of 33
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shown).
The main peak of esterified maltodextrin was close to the most intense
255
reflection for fatty acids (~20o). This result indicated that the molecular interactions
256
between native maltodextrin and fatty acid were occurred.
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3.2.5. Differential scanning calorimetry (DSC)
258
Differential scanning calorimetry thermograms for native maltodextrin and
259
esterified maltodextrin are shown in Fig. 5. The first and second of heating scans, the
260
broad melting peak were seen for all samples. Table 3 shows the melting transition data
261
of native maltodextrin and esterified maltodextrin.
262
subjected to the scanning profile twice. For the first scan, the melting temperature (Tm) of
263
native maltodextrin was 63.77oC and that of maltodextrin decanoate, maltodextrin laurate
264
and maltodextrin palmitate was 50.69, 50.36 and 47.50oC, respectively which are lower
265
than its unmodified maltodextrin. Those for the second heating scan were similar. These
266
results may be attributed to the replacement of hydroxyl groups by long-chain fatty acids
267
resulting in a decrease in the inter-molecular hydrogen bonds (Horchani et al., 2010). The
268
Tm of esterified maltodextrin decreased with increasing chain length of the fatty acid used
269
in esterification. These results concur with the results of modified starch reported in
270
Sagar and Merill (1995). The increasing in fatty acid chain length may increase the free
271
volume within the molecules due to the introduction of bulk groups which allowed more
272
molecular mobility, also contributed to the reduction in the Tm (Rajan et al., 2006). Both
273
Tm and ΔH of the first scan are higher than those of the second scan for all esterified
274
samples.
275
recrystallization of the ester groups (Shogren et al., 2010). The ΔH reflects the energy
276
required for disrupting the crystalline structure. DSC results show the ΔH of native
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Each maltodextrin sample was
These changes are due to slow relaxation processes accompanying
Page 14 of 33
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maltodextrin (ΔH=6.86 J/g), maltodextrin decanoate (ΔH=7.35 J/g) and maltodextrin
278
laurate (ΔH=7.26 J/g) have a minimal difference.
279
palmitate was much lower than ΔH of native maltodextrin. The causes may be similar in
280
above-discussed part, due to a decrease in hydrogen bonds between maltodextrin.
281
3.3. Emulsion forming and emulsifying behavior
cr
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However, ΔH of maltodextrin
3.3.1. Influence of esterified maltodextrin on emulsifying index
283
The emulsification index of native maltodextrin and esterified maltodextrin as a
284
function of maltodextrin concentration was tested for n-hexadecane oil (Fig. 6). The
285
emulsification index is an important parameter for evaluating the power of an emulsifier
286
(Freitas et al., 2009; Neta et al., 2012). All esterified maltodextrin have proven to possess
287
emulsion-stabilization capacity as shown by emulsification indices higher than that of the
288
native maltodextrin. The high emulsification indices observed reflect the stability of the
289
emulsions thus formed. No emulsion-stabilizing capacity, with emulsions breaking up
290
after only a few second, was observed for native maltodextrin.
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Emulsification index was further improved for higher esterified maltodextrin
292
concentrations, reaching indices of 100% at maximal concentration of 35% (w/w) for all
293
esterified maltodextrin. The effective emulsification index of emulsion was increased by
294
increasing esterified maltodextrin concentration, since they are known to be able to cover
295
more of the emulsion droplet surface. Emulsification index is higher when the carbon
296
chain length is longer. The lengthy hydrocarbon tails grafted along the polysaccharide
297
backbone may have stronger interaction with the oil surface. These data show that
298
esterified maltodextrin may be used as stabilizers for dispersions of hydrophobic particles
Page 15 of 33
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in aqueous medium. Their absorption at oil/water interface gives rise to the formation of
300
a dense layer of hydrophilic loops providing steric repulsion between particle surfaces
301
(Kaewprapan et al., 2012).
302
hydrophobically modified by enzymatic reaction with fatty acid has been shown to be
303
surface active and to have emulsifying properties.
cr
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So we conclude that maltodextrin that has been
3.3.2. Influence of esterified maltodextrin on oil droplet characteristics
305
Native maltodextrin could not form any emulsion droplets hence there were no
306
particles observed under the microscope as shown in Fig. 7. On the other hand, esterified
307
maltodextrin formed O/W emulsions with particle sizes between 77 and 295 μm (Table 4).
308
Maltodextrin palmitate produced an emulsion with the smallest oil droplets as well as the
309
highest emulsion index (Fig. 6), indicating product better emulsifying ability. The oil
310
droplet size was largest when maltodextrin decanoate was used.
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The droplet size distribution of fresh emulsions, shifted to large droplet sizes as chain length of fatty acid decreased (Fig. 8).
313
strongly dependent on the molecular weight of the fatty acid used for esterification of
314
maltodextrin. The lower molecular weight fatty acid seemed to be less effective in
315
stabilizing emulsions.
316
maltodextrin with shorter fatty acid molecules on surface between oil and aqueous
317
solution, which is disadvantage for inhibition of oil droplet coalescence and thus
318
increases oil droplet size. The esterified maltodextrin with shorter fatty acid molecule is
319
not sufficient for complete emulsion stabilization.
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Emulsions particle size distribution was
Part of the effect may be due to the limitation of esterified
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17 321
Conclusion According to the findings of this research, it was concluded that esterified
323
maltodextrin can be used as an emulsifier and stabilizing agent between aqueous
324
solutions and hydrophobic compounds. The properties of esterified maltodextrin adducts
325
depend on the degree of substitution and type of fatty acid.
326
maltodextrin with fatty acids has an effect on surface activity, hydrophobicity,
327
rheological properties and emulsifying properties.
328
maltodextrin has improved these properties as compared to the native maltodextrin and
329
may be used as an ingredient in applications where viscosity and hydrophobic
330
interactions are desired. Some examples are emulsion stabilizer and emulsifier for food
331
products. Enzymatic esterification is ecofriendly and avoids the use of nasty solvents.
332
Therefore, enzymatically produced esterified maltodextrin can be used directly for
333
various food applications.
334
Acknowledgements
336 337
cr
The esterification of
te
d
M
an
us
The hydrophobically modified
Ac ce p
335
ip t
322
We would like to thank Corn Product Co., Ltd. (Thailand) for generously
donating maltodextrin.
338 339 340 341
Page 17 of 33
18 342
References
343
Alissandratos, A., Baudendistel, N., Flitsch, S.L., Hauer, B., & Halling. P.J. (2010). Lipase-catalysed acylation of starch and determination of the degree of substitution
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by methanolysis and GC. BMC Biotechnology, 10, 82-89.
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cr
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Biswas, A., Shogren, R.L., & Willett, J.L. (2009). Ionic liquid as a solvent and catalyst for acylation of maltodextrin. Industrial crops and products, 30, 172-175.
us
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ip t
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Chakraborty, S., Sahoo, B., Teraoka, I., Miller, L.M., & Gross, R.A. (2005). Enzymecatalyzed regioselective modification of starch nanoparticles. Macromolecules, 38,
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61-68.
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an
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Dokic, P., Jakovljevic, J., & Dokic-Baucal, L. (1998). Molecular characteristics of
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Floury, J., Desrumaux, A., Axelos, M.A.V., & Legrand, J. (2003). Effect of high
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pressure hom*ogenization on methylcellulose as food emulsifier. Journal of food engineering, 58, 227-238.
Freitas, F., Alves, V.D., Carvalheira, M., Costa, N., Oliveira, R., & Reis, M.A.M. (2009). Emulsifying behavior and rheological properties of the extracellular polysaccharide
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produced by Pseudomonas oleovorans grown on glycerol by product. Carbohydrate
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Horchani, H., Chaâbouni, M., Gargouri, Y., & Sayari, A. (2010). Solvent-free lipasecatalyzed synthesis of long-chain starch esters using microwave heating:
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Optimization by response surface methodoly. Carbohydrate polymer, 79, 466-474.
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Ibanoglu, E. (2002). Rheological behaviour of whey protein stabilized emulsions in the presence of gum Arabic. Journal of food engineering, 52, 273-277.
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ip t
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Jafari, S.M., Beheshti, P., & Assadpoor, E. (2012). Rheological behavior and stability of
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D-limonene emulsions made by a novel hydrocolloid (Angum gum) compared with
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Arabic gum. Journal of Food Engineering, 109, 1-8.
an
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Kaewprapan, K., Baros, F., Marie, E., Inprakhon, P., & Durand, A. (2012). Macromolecular surfactants synthesized by lipase-catalyzed transesterification of
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Kapusniak, J. & Siemion, P. (2007). Thermal reactions of starch with long-chain
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unsaturated fatty acid. Part 2. Linoleic acid. Journal of food engineering, 78, 323-
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Loret, C., Meunier, V., & Frith, J.W. (2004). Rheological characterisation of the gelation behaviour of maltodextrin aqueous solutions. Carbohydrate Polymers, 57, 153–163.
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McClements, D.J. (2008). Lipid-based emulsions and emulsifiers. In Akoh, C.C. & Min,
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D.B. (Eds.), Food Lipids, Chemistry, Nutrition, and Biotechnology (pp.63-96).
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London: CRC Press.
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Neta, A.A.S., Santos, J.C.S., Sancho, S.O., Rodriques, S., Goncalves, L.R.B., Rodriques, L.R., & Teixeira, J.A. (2012). Enzymatic synthesis of sugar esters and their
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potential as surface-active stabilizers of coconut milk emulsions. Food hydrocolloids
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27, 324-331. Nikovska, K. (2010). Oxidative stability and rheological properties of oil-in-water
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Qiao, L., Gu, Q.M., & Cheng, H.N. (2006). Enzyme-catalyzed synthesis of
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hydrophobically modified starch. Carbohydrate polymers, 66, 135-140. Rajan, A., Prasad, S.V., & Abraham, E. (2006). Enzymatic esterification of starch using
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an
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Sadtler, V.M., Imbert, P., & Dellacherie, E. (2002). Ostwald ripening of oil-in-water
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Shogren, L.R., Biswas, A., & Willett, L.J. (2010). Preparation and physical properties of
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Udomrati, S., Ikeda, S., & Gohtani, S. (2013). Rheological properties and stability of oil-
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in-water emulsions containing tapioca maltodextrin in the aqueous phase. Journal of
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food engineering, 116, 170-175.
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polysaccharide fatty acid esters. Carbohydrate polymers, 93, 65-72.
cr
406
Van den Broek, L.A.M., & Boeriu, C.G. (2013). Enzymatic synthesis of oligo- and
Zheng, M., Jin, Z., & Zhang, Y. (2007). Effect of cross-linking and esterification on
us
405
ip t
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hygroscopicity and surface activity of cassava maltodextrins. Food chemistry, 130,
409
1375-1379.
an
408
Ac ce p
te
d
M
410
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22
Figure caption
411
Fig. 1. Influence of temperature on the degree of substitution (DS). Reaction conditions
412
were maltodextrin:fatty acid molar ratio of 1:0.5, reaction time of 4 hours.
413
Fig. 2. Influence of reaction time on the degree of substitution (DS). Reaction conditions
414
were maltodextrin:fatty acid molar ratio of 1:0.5, reaction temperature of 60oC.
415
Fig. 3. Influence of maltodextrin/fatty acid molar ratio on the degree of substitution (DS)
416
investigated at reaction condition of 4 hours and 60oC.
417
Fig. 4. X-ray diffraction of (a) native maltodextrin and esterified maltodextrin; native
418
maltodextrin (1), maltodextrin decanoate (2), maltodextrin laurate (3), and maltodextrin
419
palmitate (4); (b) Palmitic acid.
420
Fig. 5. DSC thermograms of native maltodextrin first heat (A), second heat (B);
421
maltodextrin decanoate first heat (C), second heat (D); maltodextrin laurate first heat (E),
422
second heat (F); maltodextrin palmitate first heat (G), second heat (H).
423
Fig. 6. Emulsification index as a function of maltodextrin concentration for n-hexadecane
424
oil.
425
Fig. 7. Micrographs (20x magnification) of fresh n-hexadecane O/W emulsions stabilized
426
by 25% (w/w) of native maltodextrin (a) maltodextrin decanoate (b), maltodextrin laurate
427
(c), and maltodextrin palmitate (d).
428
Fig. 8. Droplet size distribution of fresh n-hexadecane O/W emulsion stabilized by
429
esterified maltodextrin. Data points are presented in average of three replications with
430
maximum standard deviation of 5 μm.
Ac ce p
te
d
M
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us
cr
ip t
410
Page 22 of 33
23 431
Table 1 Interfacial tension and solubility (%) in water of native maltodextrin and
432
esterified maltodextrin Interfacial tension
%Solubility
ip t
Sample
100
Malto_D
39.68 ± 0.19
87.19 ± 1.28
Malto_L
40.02 ± 0.14
85.96 ± 1.27
Malto_P
41.39 ± 0.24
84.81 ± 2.09
us
47.22 ± 0.28
an
Native
cr
(mN/m)
433
Table 2 Rheological characteristics of native maltodextrin and esterified maltodextrin
435
solution at a concentration of 25 % (w/w) Apparent (mPa.s)
Ac ce p
at 225 s-1
viscosity
n
k (Pa.sn)
τ0 (Pa)
te
Sample
d
M
434
4.62 ± 0.04
1.02 ± 0.01
0.0041 ± 0.0002
0.03 ± 0.00
Malto_D 5.18 ± 0.02
1.02 ± 0.01
0.0046 ± 0.0004
0.04 ± 0.01
Malto_L
4.92 ± 0.05
1.00 ± 0.00
0.0049 ± 0.0002
0.02 ± 0.00
Malto_P
5.59 ± 0.01
0.99 ± 0.01
0.0066 ± 0.0008
0.02 ± 0.00
Native
436 437 438 439 440
Page 23 of 33
24 441 442 443
Sample
First scan
ip t
Table 3 Melting transition data of native maltodextrin and esterified maltodextrin Second scan ΔH (J/g)
Tm (oC)
Native
63.77 ± 0.08
6.86 ± 0.08
69.46 ± 0.49
3.32 ± 0.16
Malto_D
50.69 ± 1.06
7.35 ± 0.46
51.67 ± 0.16
3.72 ± 0.17
Malto_L
50.36 ± 0.77
7.26 ± 0.06
48.24 ± 0.73
3.42 ± 0.18
Malto_P
47.50 ± 0.99
4.27 ± 0.05
47.86 ± 0.16
2.11 ± 0.38
an
us
cr
Tm (oC)
ΔH (J/g)
M
444
Values are mean ± SD (n=3)
446
Table 4 Oil droplet mean diameter of freshly prepared n-hexadecane O/W emulsions
447
stabilized by esterified maltodextrin at 25% (w/w) Mean diameter of oil droplets
Ac ce p
Sample
te
d
445
(μm)
Malto_D
295.52 ± 2.69
Malto_L
243.59 ± 4.14
Malto_P
77.71 ± 0.49
448 449 450
Page 24 of 33
25
453 454 455
The DS of esterified maltodextrin 0.015-0.084 were prepared at the optimum condition.
ip t
452
1.
2. Modified maltodextrin reduced interfacial tension and showed emulsifying activity.
cr
451
Highlights
3. Emulsifying activity increased with the increasing chain length of fatty acid.
us
450
an
456
Ac ce p
te
d
M
457
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M
an
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i
Fig.1
Page 26 of 33
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M
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i
Fig.2
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ed
M
an
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cr
i
Fig.3
Page 28 of 33
Ac ce p
te
d
M
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cr
ip t
Fig.4
Page 29 of 33
Ac
ce
pt
ed
M
an
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cr
i
Fig.5
Page 30 of 33
Ac
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pt
ed
M
an
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i
Fig.6
Page 31 of 33
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ed
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i
Fig.7
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Ac
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Fig.8
Page 33 of 33
