Download - Influence of Commercial Saturated Monoglyceride, … of Commercial Saturated Monoglyceride, ... .Myverol ... Kerry,Mexico/USA,andusedasgelatoragents.

Research ArticleInfluence of Commercial Saturated MonoglycerideMono-Diglycerides Mixtures Vegetable Oil Stirring Speed andTemperature on the Physical Properties of Organogels

Omar Gerardo Rocha-Amador1 Jose Alberto Gallegos-Infante1

Qingrong Huang2 Nuria Elizabeth Rocha-Guzman1

Martha Rocio Moreno-Jimenez1 and Ruben F Gonzalez-Laredo1

1 Unidad de Posgrado Investigacion y Desarrollo Tecnologico Departamento de Ings Quımica y BioquımicaInstituto Tecnologico de Durango Bulevar Felipe Pescador 1830 Ote Colonia Nueva Vizcaya 34080 Durango DGO Mexico

2Department of Food Science School of Environmental and Biological Sciences Rutgers UniversityThe New Jersey State University 65 Dudley Road New Brunswick NJ 08901 USA

Correspondence should be addressed to Jose Alberto Gallegos-Infante agallegositdurangoedumx

Received 11 May 2014 Revised 25 July 2014 Accepted 16 August 2014 Published 21 September 2014

Academic Editor Jose M Prieto

Copyright copy 2014 Omar Gerardo Rocha-Amador et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

The objective of this study was to evaluate the influence of gelator vegetable oil stirring speed and temperature on thephysical properties of obtained organogels They were prepared under varying independent conditions and applying a fractionalexperimental design From there a rheological characterization was developed The physical characterization also includedpolarized light microscopy and calorimetric analysis Once these data were obtained X-Ray diffraction was applied to selectedsamples and a microstructure lattice was confirmed Commonly the only conditions that affect crystallization have been analyzed(temperature solvent gelator and cooling rate) We found that stirring speed is the most important parameter in the organogelpreparation

1 Introduction

Gels have been described as materials that are ldquoeasier torecognize than definerdquo [1] Most of the times this problemcomes from industry which develops products with a gelname just to be attractive to consumers [2] Howevergels have been accepted as semisolid materials comprisinglow concentrations (lt15) of gelator molecules to form anetwork self-assembly that entraps the solvent (in organogelsboth nonpolar components) preventing flow due to surfacetension [3]

Gels can be defined both from a rheological behaviorand from a structural feature In a rheological point of viewa gel is a system that does not flow and has the presenceof a plateau region of storage modulus and a low tan120575(lt01) at an angular frequency from 10minus3 to 102 rads Thestructural definition is based on the connectivity of the

system Gel is a system consisting of molecules particlesand chains which are partially connected to each other in afluid medium by crosslinks to the macroscopic dimensionsThen the loss of fluidity is the result of connectivity Bothare operational definitions and may have the possibility ofexclusions [2]

Organogels have been attracting much attention inbiomedical and pharmaceutical fields where the erosionof gels in stomach and intestines is important for drugdelivery [4 5] therefore gels erosion has been applied forthis purpose [6] As oils are safe materials and are suitablefor lipophilic components [7] they are considered a goodoption for organogels elaboration That is why food industryis very interested in this type of systems as a replacementof hydrogenated fats [8] Thus understanding organogelsdefinition is closely related to their characteristics and theircrucial potential to develop new applications

Hindawi Publishing CorporationInternational Journal of Food ScienceVolume 2014 Article ID 513641 8 pageshttpdxdoiorg1011552014513641

2 International Journal of Food Science

Organogels microstructure is possible in part due to fatcrystallization This phenomenon has been widely studied inseveral scientific fields The case of fat oils is very importantdue to their applications in food industry The study ofcrystal nucleation dissolution and agglomeration in theoverall precipitation scheme implies practical difficultiesNucleation and crystal growth are spontaneous processeswhich diminish the energy of the growing particle andnucleation process in order to overcome activation energythat is the critical cluster (critical size) is the cluster withmaximum Gibbs free energy The activation barrier maybe represented by three parameters supersaturation ratioreaction temperature and interfacial energy [9] Followingcrystal formation in organogels can give detailed informationon how their preparation is affecting their final structure

The crystallization behavior is related to concentration ofgelator [10] cooling rate [11 12] and shear rate on fat crystals[13 14] Depending on the system gels are formed by differentforces and interactions and there are some parameters thataffect such as pH ionic force and mechanical forces Theplastic fat gels are formed due to the aggregation of fat crystalsby several forces as van der Waals dipole-dipole hydropho-bic and hydrogen bond interactions between crystals [15]These interactions also give gels a fractal behavior Fractal isa geometric pattern that is repeated at every smaller scale toproduce irregular shapes and surfaces [16]

Hence since the study of organogels is very complex itmust include structural analysis and rheological and thermalbehaviors in order to have a clear understanding on howpreparation parameters are affecting the final product Thusour objective was to evaluate the influence of gelator (typeand concentration) type of vegetable oil stirring speedand temperature preparation on the physical properties ofobtained organogels

2 Materials and Methods

21Materials Three different vegetable oils (soybean canolaand corn oil) were used They have important differencesin composition of saturated fatty acids (SFA) monoun-saturated fatty acids (MUFA) and polyunsaturated fattyacids (PUFA) The approximate compositions of soybean(SFA 1565 MUFA 2278 and PUFA 5774 WessonBrand) canola (SFA 736MUFA6327 andPUFA2814Wesson Brand) and corn (SFA 1294 MUFA 2757 andPUFA 5467 Mazola Brand) were considered These oilswere bought at a local supermarket in New Brunswick(New JerseyUSA)Myverol (mainlymonoglycerides glycerylmonostearate 49 glyceryl monopalmitate 48 and cal-cium silicate 3) and Myvatex (mixture of monoglyceridesand diglycerides soy monoglycerides 35ndash45 stearic acidmonoester with propane-1-2-diol 40ndash50 sodium 2-stearoyllactate 10ndash15 and calcium silicate 3) were provided byKerry MexicoUSA and used as gelator agents

22 Gels Preparation Gelators Myverol (MV) and Myvatex(MX) at three different concentrations (8 9 and 10) wereheated (70 80 and 90∘C) on glass containers until completemelting and then either vegetable oil (soy (SY) canola (CA)

or corn (CN)) was added Samples were stirred (T 25 digitalUltra-turrax IKA North Carolina USA) for five minutesat three independent speeds (3600 7200 and 12000 rpm)to homogenize them then samples were cooled to roomtemperature and stored in refrigerator for 24 hours

23 Rheological Tests Dynamic frequency sweep tests wereperformed in a rheometer (ARES Rheometer 902-30004TA instruments New Castle DE USA) using parallel platesgeometry (25mm diameter) under the following experimen-tal settings strain 01 temperature 20∘C frequency sweep01ndash100 rad sminus1 and a gap of 1mm The 1198661015840 and 11986610158401015840 modulescomplex viscosity and delta tangent for each experimentalsample were obtained

24 Polarized Light Microscopy Polarized light micropho-tographs of organogels were obtained using a polarizedlight microscope Linkam Brand (T95 System controller T95Linksys 32 soft 2009 Tadworth UK) It was equipped witha Q imaging camera (Color RTV 10 BIT) using an OlympusTH4-100 Halogen lamp power supply unit (LTS120 tempcontrolled stage) Images were taken at 20∘C and video wastaken using the Camtasia Studio V 70 (Build 1426 2010Techsmith Corporation Okemos MN USA)

25 Differential Scanning Calorimetry Thermal behavior ofsamples was studied using a differential scanning calorime-ter (DSC Q2000 TA instruments Schaumburg Ill USA)equipped with refrigerated cooling system (RCS 40 TAInstruments Schaumburg Ill USA) Samples were heated at120∘C (30min) for deleting fat thermal memory Up to threecycles of heating were used depending on the experimentalsample Gelation temperature and melting enthalpy for eachexperimental sample were recorded

26 X-Ray Diffraction X-ray diffraction experiment wasdeveloped by the use of a PXRD conduced with a DM-2200T automated system (Ultima Rigaku Tokyo Japan) withCu K120572 radiation 120582 = 15406A Patterns were collected at2120579 angles of 3∘ to 50∘ at a scan rate of 2∘min A graphitemonochromator was used and the generator power settingswere fixed at 40 kV and 40mA Spectra were analyzed withspecialized software (Xpowder Pro Ver 20100130 WoburnMassachusetts USA) for clarifying peaks applying a singlefunctional filter smoothing and five cycles of Fourier decon-volution

27 Fractal Dimension The fractal dimension of the sampleswas calculated using (1) according to a describedmethod [17]which is based on the Avrami relationship Consider

ln (1 minus 119883cr) = minus119896119905119863

(1)

where 119883cr is the crystallinity of the system 119905 is time 119896 is aconstant and 119863 denotes the dimension of growing 119863 and119896 were calculated by nonlinear estimation using Levenberg-Marquardt algorithm (Statistica v 70 Tulsa OK USA) Crys-talline fraction of samples was calculated adjusting values

International Journal of Food Science 3

from complex viscosity of the system removing complexviscosity of the solvent

119883cr =120578lowast

(119905) minus 120578

120578lowast

(infin) minus 120578

(2)

28 Microstructural Parameters A universal relation hasbeen developed [18] but in the present work a previousrelationship was used [19] supported by earlier theoreticalwork [20] in order to evaluate structural parameters Inthis experimental work a three-dimensional colloidal net-work was considered as being composed of interconnectedflocs and the fractal dimension was used to quantify therelationship between the average floc size and the particleconcentration of the colloidal network The fractal natureof fat crystal networks has been already presented [21] andexplained the power-law relationship followed by 1198661015840 andthe solid fat content (SFC) data for fat samples with lowsolid fat content (lt10) Rheological data from experimentalwork can lead us to obtain a parameter related to elasticmodulus 120601 (the solid fraction previously obtained by 119883cr)120582 and 119898 obtained by nonlinear estimations (Statistica v 70Levenberg-Marquardt algorithm Tulsa OK USA) One has

1198661015840

= 120582120601119898

(3)

The Hamaker constant was determined following reportedmethodology [18 22] where 119860 is the Hamaker constant 119886is the diameter of the particles within a floc and 119889 is theaverage distance between clusters Microscopy images wereanalyzed using Corel Photo-paint X4 (Ver 1400567 MenloPark CA USA) applying channel separation (CMYK) inorder to obtain floc and distance parameters as clearly aspossible Consider

120582 sim

1198603

1205871198861198892

(4)

29 Statistical Analysis Comparisons and calculations ofparameters were obtained by nonlinear estimation withStatistica Software (Ver 70 2007 Tulsa OK USA) usingLevenberg-Marquardt algorithm Mean effects on interac-tions between processing parameters and fractal dimensionsand microstructural parameters were determined by screen-ing design (JMP Ver 70 2007 Cary NC USA)

3 Results and Discussion

31 Dynamic Rheology Oscillatory rheological data fororganogelsmadewith canola oil are shown in Figure 1Highervalues of 1198661015840 were observed for MV gels at higher frequenciesused at 10 gelator concentration 70∘C and 12000 rpm Theelastic module (1198661015840) is associated with the solid behavior ofthe sample Thus this value may indicate that at highershear rates structural order produced by lipid chains (ieacylglycerides) is organized in a more stable configurationas a function of more contact between molecules that lowerthe necessary energy for self-organization and structurebuilding Similar findings have been reported previously [13]

1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)

Figure 1 Frequency sweep comparison of canola oil samples 1198661015840module (filled) 11986610158401015840 module (empty) Gelators used Myverol (MV)and Myvatex (MX)

1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)

Figure 2 Frequency sweep comparison of corn oil samples 1198661015840module (filled) 11986610158401015840 module (empty) Gelators used Myverol (MV)and Myvatex (MX)

Theoretical analysis of gels indicated that small particlescould be aggregated to form large clusters with tenuouschain-like and self-similar structures that eventually spanthe entire enclosing space [23] This behavior not only wasinfluenced by shear rate but also seems to be influenced bythe type of gelator used as can be seen in Figures 1 2 and3 From these Figures it can be observed that at the sameconditionsMVorganogels always give higher elasticmodulesin comparison with the MXThe mechanisms of aggregationof gelators in organogels occur primarily through van derWaals forces specific intermolecular hydrogen bondingelectrostatic forces120587-120587 stacking or Londondispersion forces[24]Thus in function of the solvent and the gelatormoleculewhich type of intermolecular force predominates to stabilizethe self-assembly primary structure the growth mode andfinally the organogel microstructure and its thermomechan-ical properties is determined [25] However the relationshipbetween gelator chemical structure and its gelling capability isnot evident a priori inmost cases [26] However it is desirablefor gel modules to maintain a stable behavior during thecomplete frequency range Solid behavior is predominant in


Table 1 Gelation enthalpy comparison for organogel samples

Process conditions Δ119867 glowast

Gelator () Stirring 1min Temperature (∘C) Canola Corn SoyJg Jg Jg

Myverol 8 3600 70 590 (018) 487 (030) 580 (017)Myvatex 8 3600 90 572 (106) 454 (010) 238 (016)Myvatex 8 12000 70 494 (033) 596 (008) 557 (004)Myverol 8 12000 90 556 (006) 578 (046) 614 (026)Myvatex 9 7200 80 538 (048) 426 (018) 740 (020)Myverol 9 7200 80 704 (071) 652 (079) 683 (027)Myvatex 10 3600 70 661 (011) 560 (060) 666 (015)Myverol 10 3600 90 887 (025) 742 (030) 790 (045)Myverol 10 12000 70 750 (035) 731 (054) 780 (046)Myvatex 10 12000 90 587 (062) 628 (031) 579 (018)lowastMean (standard deviation)

1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)

Figure 3 Frequency sweep comparison of soy oil samples 1198661015840module (filled) 11986610158401015840 module (empty) Gelators used Myverol (MV)and Myvatex (MX)

all samples at the experimental shear range used so it can beconsidered suitable for an excipient

Similar behavior was observed in the organogels preparedwith different oils (Figure 3) except for soy oil (SY) whichseems to have a different effect producing more elastic gelsat the same conditions SY seems to be favored by its highersolid fatty acids content which gives more elastic modulesto Myvatex gelator samples An explanation of this behaviorhas been already reported [25] In there candelilla waxand amides derived from (R)-12-hydroxystearic acid weretested as gelators of safflower oil observing that the increasein the hydrocarbon chain length raises both the organogelresistance to deformation and its instant recovery capacityHowever the extended recovery capacity of the gel decreased

As can be seen in Figure 3 the behavior of each samplemade with different oil at the same conditions changessignificantlyThis may be related to the different compositionof vegetable oil and how each component is reacting atdifferent preparation conditions Although the higher elasticmodules are obtained with canola (CA) and corn (CN) oilsamples in general CA gave the higher elasticity samples in

comparison with those made with CN and SY This behaviorcould be related to the monounsaturated fatty acids (MSFA)and polyunsaturated fatty acids (PUFA) contents It appearsthat single unsaturation helps to join molecules into morestable structures

32 Polarized Microscopy Obtained micrographs (Figure 4)showed thatMyvatex tends to crystallize as spherulitic formssome of them with larges spaces between these spheruliteswhile samples prepared with Myverol crystallized as fibrillarnetworks So this could explain the higher elastic moduleson samples prepared with this gelator It was reported [10]that the higher number of hydroxyl groups related to thediacylglycerides was correlated with a lack of gelation intothe organogels This gives further evidence to the fact thathydrogen bonding is critical to the organogelation

33 Differential Scanning Calorimetry Statistical analysis ofenthalpy data showed that gelator type and its concentra-tion (119875 lt 005) were the most important factors thatinfluence enthalpy (Table 1) The statistical analysis showeda very complex phenomenon influenced by the followinginteractions oil lowast oil concentration lowast gelator and gelatorlowast temperature Organogels obtained with Myvatex gelatorshowed two different nucleation stages related to the presenceof twomain types ofmolecules (mono- and diacylglycerides)so probably distributed free energy makes gels tend tocrystallize as spherulites rather than as a needle shapednetwork However not only the gelator is important but alsoits concentration and several interactions including vegetableoil type and temperature are important At this point it isinteresting to highlight that the temperature factor does nothave influence on the enthalpy of organogels Thus duringcooling both components might develop a mixed molecularpacking with vegetable oils [27] On the other hand Myvatexgelator (MX) does not seem to be affected significantly byany preparation conditions Finally it is clear that the use ofMyverol at higher concentrations produces organogels withhigher values of gelation enthalpies indicating more stablestructures


CA

CN

SY

(a)

CA

CN

SY

(b)

Figure 4 Gels prepared with canola (CA) corn (CN) and soy (SY) oils at concentration 9 7200 rpm and 80∘C of gelators Myvatex (a)and Myverol (b)

34 X-Ray Diffraction A comparison of 119889 spacing data wasdone in order to elucidate not only possible arrangements inpacking but also the most probable polymorphic forms inbatches Since they were complex mixtures of components(nonpure components) at least two different packings andpolymorphswere selectedThefirst selectionwas the onewithmore intensity

In Table 2 it can be noticed that most of the structuresobtained are mainly 120573 polymorphs because most of them areamorphous materials and 119887 crystals are present only in partAlthoughMX also gave a good structure it was only possibleunder the highest energy conditions

In order to compare different samples behaviors with arepresentative value fractal dimension and microstructuralparameters were obtained and presented below

35 Fractal Dimension Samples fractal dimensions (Table 3)were obtained from rheological behavior according to others[17] on which we should obtain crystalline fraction of eachsample based on complex viscosity behavior and then getfractal parameter from nonlinear estimation Once fractaldata was obtained ANOVA test was developed looking forsome important influence The model obtained was toocomplex and 119905-student was not sensitive enough to detectmeans without a significant error Even in general no meanswere detected some interesting effects were found whengelators and oils were blocked

Several authors have used rheological determination offractal dimensionality [23] Also several works on formationof organogels studied and correlated by Avrami exponent(119899) with fractal dimensionality have been reported [17 28]


Table 2 Comparison of lattice spaces of experimental organogels

Oil Gelator[gelator]

()RPM1min

Temperature(∘C)

119889 spacing at highest intensity (A) Probable packing Probable polymorphicMain Secondary Main Secondary

CA MV 10 12000 70 495 466 456 444 435 Monolayer bilayer 120573 120572

CA MV 10 3600 90 498 466 455 435 Bilayer Monolayer 120573 Sub-120572CA MV 9 7200 80 458 449 435 412 Bilayer Monolayer 120573 Sub-120572CN MX 10 12000 90 458 448 438 412 Bilayer Monolayer 120573 Sub-120572CN MV 10 12000 70 445 437 419 401 393 Monolayer Bilayer 120572 120572

CN MV 10 12000 90 498 461 435 413 391 Monolayer Lamellar 120573 Sub-120572CN MV 9 7200 80 505 468 458 446 435 421 Monolayer Bilayer 120573 120572

SY MV 10 12000 70 463 454 438 413 397 Monolayer Bilayer 120573 120572


SY MV 9 7200 80 496 457 443 418 409 397 Monolayer Bilayer 120573 120572

Table 3 Physical parameters of organogel samples

Process conditions Fractal Structural parameter Hamaker constantGelator () Stirring 1min Temperature (∘C) Canola Corn Soy Canola Corn Soy Canola Corn SoyMyverol 8 3600 70 162 153 154 16200 14500 11220 333 300 360Myvatex 8 3600 90 156 161 158 4300 4300 5090 75 98 58Myvatex 8 12000 70 152 151 160 3800 2800 4700 87 60 76Myverol 8 12000 90 151 147 158 17000 11200 8900 404 126 195Myvatex 9 7200 80 150 136 148 6600 2900 10500 93 57 96Myverol 9 7200 80 157 157 156 21100 6250 21900 467 257 316Myvatex 10 3600 70 165 149 168 6300 3100 9600 75 70 93Myverol 10 3600 90 154 148 155 18500 15100 15850 406 205 425Myverol 10 12000 70 148 167 150 30000 30500 13500 139 480 313Myvatex 10 12000 90 161 159 157 7000 8050 7500 66 81 83

However it was indicated [29] that it may be inappropriateto compare Avrami derived fractal dimensionalities fromseveral systems in which different nucleationmechanisms forgelators are involvedThus there are reports [17] on homoge-neous nucleation with a fractal dimensionality near 2 whileothers [28] found a fractal dimensionality near 1 in a hetero-geneous nucleation systemThus in the present experimentalwork fractal dimensionality was in that range (lower than 2)particularly when using mono- and diacylglyceride blendsindicating a possible heterogeneous nucleation process

As an example when the variable gelator (Myvatex) wasblocked on canola oil (119875 = 0047) the fractal dimension(119863) was affected by the gelator concentration Also whencorn oil temperature was blocked the results indicated thathigher temperatures render higher fractal dimensions Thefractal dimensions (119863) determined by the particle countingmethod are sensitive to the spatial distribution of particlesin the crystal network Higher fractal dimensions occurin networks that are more ordered whereas networks thatarise from a more disordered nucleation and growth processresult in lower fractal dimensions [22]The fractal dimensionvalue found in the present work was lower [17] similar [29]and higher [28] than other reports Having greater fractaldimensions signifies more homogeneously distributed massandor more uniformly filled spaces [30]

Even though we did not find any significant mean onRPM versus 119863 parameters independently of the gelator 119863fractal dimension tends to decrease as RPM increases Thiscould mean that as the shear rises there is an increase indisorder of the structure which is contrary to reports fromothers [13 14] This could also indicate that different condi-tions are affecting gels structure and there is not necessarily acodependence on shear rate and order of the structure

36 Microstructural Parameters The 120582 parameter was ob-tained for each experimental condition (Table 3)The highestvalue of 120582 was found for Myverol (mainly monounsatu-rated fatty acids) in comparison with Myvatex The gelatormolecules are related to the nature of the short-range weakforces and the strong solvent dependence on the molecu-lar self-assembling capabilities [31] so that molecules withhigher molecular weight could affect crystal growth andits consequence on fiber interpenetration among vicinalspherulites

However not only gelator molecule is important butsolvent nature and interaction solvent-gelator are importanttoo In this way experimental data was blocked for thetwo gelators in separated assessments Results showed thatMyverol is affected by the type of oil used for the sample(119875 = 00085) by the oil-concentration interaction (119875 = 004)


and the concentration quadratic effect as well (119875 = 00072)Meanwhile for Myvatex the oil effect was also important(119875 = 00766) but contrary to Myverol it was affected by theoil quadratic (119875 = 043) and the temperature quadratic effects(119875 = 0032)

Thermal parameters could be helpful to explain thisbehavior because they are associated with the moleculespolarity and the energy of the molecular interactions thatare established with the crystal structure of gelators in theirneat and organogel states [31] Thus the energy related tothe organogel depends on the energy of the noncovalentinteractions involved during the molecular self-assembly Ascan be seen higher enthalpies were observed for Myverolin comparison to Myvatex like a structural parameterMonoglycerides are known to be good initiators of fatcrystallization and the matching in saturation and carbonchain length of both the gelator fatty acids and the oil phaseare important in the particular lipid-lipid interactions [32]

For the Hamaker constant (Table 3) gelator appearsas a main effect (119875 le 00001) followed by the stirringspeed (119875 = 0052) as well as the interaction gelator-stirring speed (119875 = 0088) This could indicate how stirringconditions are affectingmolecular alignment Also the bilayerpacking seems to be favored by the particularities on CAoil composition of mainly the high MUFA and low PUFAcontents Most of samples analyzed for CN and SY oils weremainly indicating monolayer packings

4 Conclusions

It was found that stirring speed affects significantly thestructure of the organogelsThose prepared withMyverol aresignificantly affected by stirring conditions unlike Myvatexgels Also the first gelator tends to form needle shaped net-work structures with better intermolecular forces accordingto their Hamaker constant and XRD analysis

The stirring speed should be an important parameter totake into account as well as the gelator and its concentrationIt was found that temperature does not seem to be an impor-tant parameter in gels preparation Finally it is importantto point out that most of the influence of the stirring speedconditions is apparently related to the oils higher MUFA andlow PUFA contents

Conflict of Interests

The authors declare that there is no conflict of interestsregarding this paper

Acknowledgments

The authors acknowledge the financial assistance of theMexican Council of Science and Technology (CONACyT)and the Mexican Education Ministry (SEP-DGEST) Alsothey recognize the support fromSchool of Biological Sciences(Food Science Department) of Rutgers University wheremost of the experimental work was performed

References

[1] D J Lloyd ldquoThe problem of gel structurerdquo Colloid Chemistryvol 1 pp 767ndash782 1926

[2] K Nishinari ldquoSome thoughts on the definition of a gelrdquo inGels Structures Properties and Functions M Tokita and KNishinari Eds pp 87ndash94 Springer Berlin Germany 2009

[3] A Vintiloiu and J-C Leroux ldquoOrganogels and their use in drugdeliverymdasha reviewrdquo Journal of Controlled Release vol 125 no 3pp 179ndash192 2008

[4] T Coviello A Palleschi M Grassi P Matricardi G Bocchin-fuso and F Alhaique ldquoScleroglucan a versatile polysaccharidefor modified drug deliveryrdquo Molecules vol 10 no 1 pp 6ndash332005

[5] K Itoh M Yahaba A Takahashi et al ldquoIn situ gelling xyloglu-canpectin formulations for oral sustained drug deliveryrdquo Inter-national Journal of Pharmaceutics vol 356 no 1-2 pp 95ndash1012008

[6] K S Anseth A T Metters S J Bryant P J Martens JH Elisseeff and C N Bowman ldquoIn situ forming degradablenetworks and their application in tissue engineering and drugdeliveryrdquo Journal of Controlled Release vol 78 no 1ndash3 pp 199ndash209 2002

[7] K Iwanaga T Sumizawa M Miyazaki and M KakemildquoCharacterization of organogel as a novel oral controlled releaseformulation for lipophilic compoundsrdquo International Journal ofPharmaceutics vol 388 no 1-2 pp 123ndash128 2010

[8] F R Lupi D Gabriele B de Cindio M C Sanchez and CGallegos ldquoA rheological analysis of structured water-in-olive oilemulsionsrdquo Journal of Food Engineering vol 107 no 3-4 pp296ndash303 2011

[9] L S K Dassanayake D R Kodali S Ueno and K SatoldquoCrystallization kinetics of organogels prepared by rice branwax and vegetable oilsrdquo Journal of Oleo Science vol 61 no 1pp 1ndash9 2012

[10] A J Wright and A G Marangoni ldquoTime temperatureand concentration dependence of ricinelaidic acid-canola oilorganogelationrdquo JAOCS Journal of the American Oil ChemistsrsquoSociety vol 84 no 1 pp 3ndash9 2007

[11] F Maleky N C Acevedo and A G Marangoni ldquoCoolingrate and dilution affect the nanostructure and microstructuredifferently in model fatsrdquo European Journal of Lipid Science andTechnology vol 114 no 7 pp 748ndash759 2012

[12] F M Alvarez-Mitre J F Toro-Vazquez and M Moscosa-Santillan ldquoShear rate and cooling modeling for the study ofcandelilla wax organogelsrsquo rheological propertiesrdquo Journal ofFood Engineering vol 119 no 3 pp 611ndash618 2013

[13] G Mazzanti S E Guthrie E B Sirota A G Marangoni andS H J Idziak ldquoOrientation and phase transitions of fat crystalsunder shearrdquoCrystal Growth ampDesign vol 3 no 5 pp 721ndash7252003

[14] M Chopin-Doroteo J A Morales-Rueda E Dibildox-Alvarado M A Charo-Alonso A de la Pena-Gil and J FToro-Vazquez ldquoThe effect of shearing in the thermo-mechanicalproperties of candelilla wax and candelilla wax-tripalmitinorganogelsrdquo Food Biophysics vol 6 no 3 pp 359ndash376 2011

[15] A Friggeri O Gronwald K J C Van Bommel S Shinkai andD N Reinhoudt ldquoCharge-transfer phenomena in novel dual-component sugar-based organogelsrdquo Journal of the AmericanChemical Society vol 124 no 36 pp 10754ndash10758 2002


[16] A G Marangoni and M Ollivon ldquoFractal character of triglyc-eride spherulites is a consequence of nucleation kineticsrdquoChemical Physics Letters vol 442 no 4ndash6 pp 360ndash364 2007

[17] X Y Liu and P D Sawant ldquoFormation kinetics of fractalnanofiber networks in organogelsrdquo Applied Physics Letters vol79 no 21 pp 3518ndash3520 2001

[18] A G Marangoni and M A Rogers ldquoStructural basis for theyield stress in plastic disperse systemsrdquo Applied Physics Lettersvol 82 no 19 pp 3239ndash3241 2003

[19] S S Narine and A G Marangoni ldquoMechanical and structuralmodel of fractal networks of fat crystals at low deformationsrdquoPhysical Review E vol 60 no 6 pp 6991ndash7000 1999

[20] W-H ShihW Y Shih S-I Kim J Liu and I A Aksay ldquoScalingbehavior of the elastic properties of colloidal gelsrdquo PhysicalReview A vol 42 no 8 pp 4772ndash4779 1990

[21] R Vreeker L L Hoekstra D C den Boer and W G MAgterof ldquoThe fractal nature of fat crystal networksrdquoColloids andSurfaces vol 65 no 2-3 pp 185ndash189 1992

[22] A G Marangoni ldquoElasticity of high-volume-fraction frac-tal aggregate networks a thermodynamic approachrdquo PhysicalReview B Condensed Matter and Materials Physics vol 62 no21 pp 13951ndash13955 2000

[23] N K O Ojijo E Kesselman V Shuster et al ldquoChanges inmicrostructural thermal and rheological properties of oliveoilmonoglyceride networks during storagerdquo Food ResearchInternational vol 37 no 4 pp 385ndash393 2004

[24] V A Mallia M George D L Blair and R G Weiss ldquoRobustorganogels from nitrogen-containing derivatives of (R)-12-hydroxystearic acid as gelators comparisons with gels fromstearic acid derivativesrdquoLangmuir vol 25 no 15 pp 8615ndash86252009

[25] J F Toro-Vazquez J Morales-Rueda V A Mallia and R GWeiss ldquoRelationship between molecular structure and thermo-mechanical properties of candelilla wax and amides derivedfrom (R)-12-hydroxystearic acid as gelators of safflower oilrdquoFood Biophysics vol 5 no 3 pp 193ndash202 2010

[26] P Terech and R G Weiss ldquoLow molecular mass gelators oforganic liquids and the properties of their gelsrdquo ChemicalReviews vol 97 no 8 pp 3133ndash3159 1997

[27] J A Morales-Rueda E Dibildox-Alvarado M A Charo-Alonso R G Weiss and J F Toro-Vazquez ldquoThermo-mechanical properties of candelilla wax and dotriacontaneorganogels in safflower oilrdquo European Journal of Lipid Scienceand Technology vol 111 no 2 pp 207ndash215 2009

[28] X Huang P Terech S R Raghavan and R G Weiss ldquoKinet-ics of 5120572-cholestan-3120573-yl N-(2-naphthyl)carbamaten-alkaneorganogel formation and its influence on the fibrillar networksrdquoJournal of the American Chemical Society vol 127 no 12 pp4336ndash4344 2005

[29] X Huang S R Raghavan P Terech and R G Weiss ldquoDistinctkinetic pathways generate organogel networks with contrastingfractality and thixotropic propertiesrdquo Journal of the AmericanChemical Society vol 128 no 47 pp 15341ndash15352 2006

[30] A I Blake E D Co and A G Marangoni ldquoStructure andphysical properties of plant wax crystal networks and theirrelationship to oil binding capacityrdquo Journal of the American OilChemistsrsquo Society vol 91 no 6 pp 885ndash903 2014

[31] J F Toro-Vazquez J Morales-Rueda A Torres-Martınez MA Charo-Alonso V A Mallia and R G Weiss ldquoCooling rateeffects on the microstructure solid content and rheological

properties of organogels of amides derived from stearic and (R)-12-hydroxystearic acid in vegetable oilrdquo Langmuir vol 29 no25 pp 7642ndash7654 2013

[32] C Granger P Barey N Combe P Veschambre andM CansellldquoInfluence of the fat characteristics on the physicochemicalbehavior of oil-in-water emulsions based on milk proteins-glycerol esters mixturesrdquo Colloids and Surfaces B Biointerfacesvol 32 no 4 pp 353ndash363 2003


Organogels microstructure is possible in part due to fatcrystallization This phenomenon has been widely studied inseveral scientific fields The case of fat oils is very importantdue to their applications in food industry The study ofcrystal nucleation dissolution and agglomeration in theoverall precipitation scheme implies practical difficultiesNucleation and crystal growth are spontaneous processeswhich diminish the energy of the growing particle andnucleation process in order to overcome activation energythat is the critical cluster (critical size) is the cluster withmaximum Gibbs free energy The activation barrier maybe represented by three parameters supersaturation ratioreaction temperature and interfacial energy [9] Followingcrystal formation in organogels can give detailed informationon how their preparation is affecting their final structure

The crystallization behavior is related to concentration ofgelator [10] cooling rate [11 12] and shear rate on fat crystals[13 14] Depending on the system gels are formed by differentforces and interactions and there are some parameters thataffect such as pH ionic force and mechanical forces Theplastic fat gels are formed due to the aggregation of fat crystalsby several forces as van der Waals dipole-dipole hydropho-bic and hydrogen bond interactions between crystals [15]These interactions also give gels a fractal behavior Fractal isa geometric pattern that is repeated at every smaller scale toproduce irregular shapes and surfaces [16]

Hence since the study of organogels is very complex itmust include structural analysis and rheological and thermalbehaviors in order to have a clear understanding on howpreparation parameters are affecting the final product Thusour objective was to evaluate the influence of gelator (typeand concentration) type of vegetable oil stirring speedand temperature preparation on the physical properties ofobtained organogels

2 Materials and Methods

21Materials Three different vegetable oils (soybean canolaand corn oil) were used They have important differencesin composition of saturated fatty acids (SFA) monoun-saturated fatty acids (MUFA) and polyunsaturated fattyacids (PUFA) The approximate compositions of soybean(SFA 1565 MUFA 2278 and PUFA 5774 WessonBrand) canola (SFA 736MUFA6327 andPUFA2814Wesson Brand) and corn (SFA 1294 MUFA 2757 andPUFA 5467 Mazola Brand) were considered These oilswere bought at a local supermarket in New Brunswick(New JerseyUSA)Myverol (mainlymonoglycerides glycerylmonostearate 49 glyceryl monopalmitate 48 and cal-cium silicate 3) and Myvatex (mixture of monoglyceridesand diglycerides soy monoglycerides 35ndash45 stearic acidmonoester with propane-1-2-diol 40ndash50 sodium 2-stearoyllactate 10ndash15 and calcium silicate 3) were provided byKerry MexicoUSA and used as gelator agents

22 Gels Preparation Gelators Myverol (MV) and Myvatex(MX) at three different concentrations (8 9 and 10) wereheated (70 80 and 90∘C) on glass containers until completemelting and then either vegetable oil (soy (SY) canola (CA)

or corn (CN)) was added Samples were stirred (T 25 digitalUltra-turrax IKA North Carolina USA) for five minutesat three independent speeds (3600 7200 and 12000 rpm)to homogenize them then samples were cooled to roomtemperature and stored in refrigerator for 24 hours

23 Rheological Tests Dynamic frequency sweep tests wereperformed in a rheometer (ARES Rheometer 902-30004TA instruments New Castle DE USA) using parallel platesgeometry (25mm diameter) under the following experimen-tal settings strain 01 temperature 20∘C frequency sweep01ndash100 rad sminus1 and a gap of 1mm The 1198661015840 and 11986610158401015840 modulescomplex viscosity and delta tangent for each experimentalsample were obtained

24 Polarized Light Microscopy Polarized light micropho-tographs of organogels were obtained using a polarizedlight microscope Linkam Brand (T95 System controller T95Linksys 32 soft 2009 Tadworth UK) It was equipped witha Q imaging camera (Color RTV 10 BIT) using an OlympusTH4-100 Halogen lamp power supply unit (LTS120 tempcontrolled stage) Images were taken at 20∘C and video wastaken using the Camtasia Studio V 70 (Build 1426 2010Techsmith Corporation Okemos MN USA)

25 Differential Scanning Calorimetry Thermal behavior ofsamples was studied using a differential scanning calorime-ter (DSC Q2000 TA instruments Schaumburg Ill USA)equipped with refrigerated cooling system (RCS 40 TAInstruments Schaumburg Ill USA) Samples were heated at120∘C (30min) for deleting fat thermal memory Up to threecycles of heating were used depending on the experimentalsample Gelation temperature and melting enthalpy for eachexperimental sample were recorded

26 X-Ray Diffraction X-ray diffraction experiment wasdeveloped by the use of a PXRD conduced with a DM-2200T automated system (Ultima Rigaku Tokyo Japan) withCu K120572 radiation 120582 = 15406A Patterns were collected at2120579 angles of 3∘ to 50∘ at a scan rate of 2∘min A graphitemonochromator was used and the generator power settingswere fixed at 40 kV and 40mA Spectra were analyzed withspecialized software (Xpowder Pro Ver 20100130 WoburnMassachusetts USA) for clarifying peaks applying a singlefunctional filter smoothing and five cycles of Fourier decon-volution

27 Fractal Dimension The fractal dimension of the sampleswas calculated using (1) according to a describedmethod [17]which is based on the Avrami relationship Consider

ln (1 minus 119883cr) = minus119896119905119863

(1)

where 119883cr is the crystallinity of the system 119905 is time 119896 is aconstant and 119863 denotes the dimension of growing 119863 and119896 were calculated by nonlinear estimation using Levenberg-Marquardt algorithm (Statistica v 70 Tulsa OK USA) Crys-talline fraction of samples was calculated adjusting values



119883cr =120578lowast

(119905) minus 120578

120578lowast


(2)


1198661015840

= 120582120601119898

(3)


120582 sim

1198603

1205871198861198892

(4)




1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)


1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)








1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)









CA

CN

SY

(a)

CA

CN

SY

(b)










()RPM1min

Temperature(∘C)



















4 Conclusions





Acknowledgments


References





































119883cr =120578lowast

(119905) minus 120578

120578lowast


(2)


1198661015840

= 120582120601119898

(3)


120582 sim

1198603

1205871198861198892

(4)




1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)


1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)








1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)









CA

CN

SY

(a)

CA

CN

SY

(b)










()RPM1min

Temperature(∘C)



















4 Conclusions





Acknowledgments


References








































1000

10000

100000

1000

10000

100000

01 1 10 100

G998400

(Pa)

G998400998400

(Pa)

Frequency (rad

G998400 MV 8-3600 rpm

G998400 MV 10-12000 rpm

G998400 MX 10-12000 rpm

G998400 MX 8-3600 rpmG998400998400

G998400998400

G998400998400

G998400998400

sminus1)









CA

CN

SY

(a)

CA

CN

SY

(b)










()RPM1min

Temperature(∘C)



















4 Conclusions





Acknowledgments


References




































CA

CN

SY

(a)

CA

CN

SY

(b)










()RPM1min

Temperature(∘C)



















4 Conclusions





Acknowledgments


References






































()RPM1min

Temperature(∘C)



















4 Conclusions





Acknowledgments


References







































4 Conclusions





Acknowledgments


References

































