SPECIAL ISSUE ARTICLE

Engineering the Functionality of Blends of Fully Hydrogenatedand Non-Hydrogenated Soybean Oil by Addition of Emulsifiers

Nuria C. Acevedo & Alejandro G. Marangoni

Received: 13 February 2014 /Accepted: 2 May 2014# Springer Science+Business Media New York 2014

Abstract The objective of this work was to functionalizemixtures of fully hydrogenated soybean oil (FHSO) and soy-bean oil (SO) to match rheological behavior and structure of apartially hydrogenated, high-trans fatty acid roll-in shortening(APPS control). Physical blends of FHSO and SO were pre-pared at mass ratios ranging from 10:90 to 40:60 FHSO:SO.Different emulsifiers were added in concentrations of 0, 1 and3% (w/w). Themixtures were crystallized in a scraped surfaceheat exchange (SSHE), with A and B units arranged in twoconfigurations, ABA and AAB. Polymorphism, solid fat con-tent and oil binding capacity, as well as rheological, thermaland structural properties were determined and compared tothose of the APPS control. The results showed that 30:70FHSO:SO formulations with 1 % glycerol monopalmitate,crystallized in an ABA unit votator configuration had compa-rable properties to those of the APPS control. Despite achiev-ing desirable physical and rheological properties, the nano-and microstructural elements of the FHSO:SO blends weresignificantly smaller than those of the APPS control whichmay suggest that functionality for these fats can be accom-plished by addition of specific additives and control of crys-tallization conditions, regardless of bulk chemicalcomposition.

Keywords Scraped surface heat exchanger . Rheology . Oilbinding capacity . Nanostructure . Mesostructure

Introduction

In the wake of the U.S. Food and Drug Administration’sdecision to remove partially hydrogenated fats (PHF) fromthe GRAS (generally recognized as safe) list, recent attentionhas been focused on the removal of such fats frommanufactured food products as they contain high levels oftrans fatty acids. Trans fatty acids are recognized as a risk factorfor coronary vascular diseases, insulin resistance and obesity,complemented by systemic inflammation; the features of met-abolic syndrome [1–4]. Therefore, the complete elimination ofPHF from the food supply has become a food industry priority.However, trans fat replacement is challenging from a qualitystand point since many consumers expect a specific texture andmouth sensation in high-fat product. In addition, food industriesseek the replacement of trans fat in their products by formula-tions with equivalent functionality without affecting costs.

Fully hydrogenated fats, considered as containing zerotrans fatty acids have been proposed as a viable substitutefor partially hydrogenated fats. In particular, much attentionhas been focused on fully hydrogenated soybean oil (FHSO)due to its relatively low cost, and high content of stearic acid(approximately 85 %). Stearic acid is non-atherogenic and itsintake is not associated with an increased risk of cardiovascu-lar disease [5–7]. Nevertheless, there are some difficulties toovercome associated with the use of fully hydrogenated fats.The main issue is that fully hydrogenated fats have a highmelting point and high solids’ content, which gives them avery hard and waxy consistency. A certain reduction in theirmelting points can be achieved by blending with liquid oilalong with judicious use of shear and emulsifier additionduring crystallization [8, 9]. However, the “freezing pointdepression”, a colligative property which is achieved by oildilution, causes only a modest decrease in the melting point.Even when diluted, the fully hydrogenated fat:oil mixtureslack plasticity and remain too hard for possible applications.

N. C. Acevedo (*)Department of Food Science and Human Nutrition, Iowa StateUniversity, 2312 Food Sciences Building, Ames, IA 50011-1061,USAe-mail: nacevedo@iastate.edu

A. G. MarangoniGuelph-Waterloo Physics Institute. Centre for Food & Soft MaterialsScience. Department of Food Science, University of Guelph, 50Stone Road East, Guelph, ON, Canada N1G 2W1

Food BiophysicsDOI 10.1007/s11483-014-9340-9

Emulsifiers are important ingredients in bakery shorteningsand are among the most frequently used types of food addi-tives. The addition of only small amounts of emulsifier cansignificantly contribute to the final product properties [10].Emulsifiers can play an important role on fat crystallisation,among other physical properties they can affect nucleation(promotion or inhibition), crystal morphology and growth,as well as polymorphism and solid fat content (SFC) [11]. Inthe review from Smith [11] a comprehensive summary of theways emulsifiers might influence fat crystallization is provid-ed. It has been reported that emulsifiers interact with triacyl-glycerols primarily through their hydrophobic groups [12].Thus, the maximum effect on crystallization occurs whenthe emulsifier’s acyl group is similar (in length and numberof double bonds) to those present in the fat [13–15]. Inaddition, it has been suggested that the particular effect ofthe emulsifier depends on whether or not its molecules areentirely incorporated into the matrix during crystal growth. Inthe case of a high similarity, incorporation into the crystallinenetwork will occur at the growth site and crystallization willbe promoted, while in the case of a significant structuraldifference, further crystallization will be inhibited [12, 16, 17].

Several authors reported that increasing undercooling re-duces the effect of an emulsifier. At high undercooling,growth rates are high and the emulsifier has a considerableless chance to be adsorbed at the growth site and exerts itseffect [18, 19]. Moreover, it was suggested that, to influencethe crystallization process of the fat (mixture), a certain con-centration is needed which will depend on the mechanisminvolved [20].

In this study, the issues associated with the use of fullyhydrogenated fats will be addressed by the addition of differ-ent emulsifiers to the FHSO:SO mixture with a dual purpose;to destabilize the crystal structure, and thus decrease hardnessand melting point; and/or to affect the surface of thenanocrystals. Changes to the crystals’ surfaces may translateinto modifications in the strength of interaction between crys-tals and hence the mechanical strength of the resultingnetwork.

Additionally, high nucleation rates will be induced bycrystallization under high cooling and shear rates generatedin the scraped surface heat exchanger. It has been previouslydemonstrated that crystallization under shear helps removeheat of crystallization from the sample as well as improvesplasticity and the texture of a fat mixture [21]. This is mainlyachieved by the creation of mixed crystals among triacylglyc-erol (TAG) species present. Furthermore, the three-dimensional crystal network organization and TAG polymor-phic state which are affected by crystallization conditionsstand as key factors defining the functional and rheologicalproperties of a fat-structured product [22, 23].

The aim of this work was to functionalize fully hydroge-nated soybean oil in liquid oil via addition of different

emulsifiers and crystallization in a scraped surface heat ex-changer (SSHE), or votator, at very high shear rates and lowwall temperatures. Different FHSO:SO ratios, ranging from10 to 40 % FHSO, were assessed. Polymorphism, solid fatcontent (SFC), rheological properties and oil binding capacity,as well as the nano- and mesostructure of these blends werecharacterized.

The ultimate goal of this work was to find a combination ofprocessing and compositional parameters which yield a suit-able zero-trans, low saturate, roll-in shortening of potentialuse for bakery applications.

Materials & Methods

Materials

Fully hydrogenated soybean oil (FHSO) and soybean oil (SO)were generously provided by Bunge Canada (Toronto,Canada). The Anhydrous Puff Pastry shortening (APPS con-trol) employed as a control was provided by Bunge Oil SA(Bradley, Il., USA). APPS is made from partially hydrogenat-ed soybean oil and partially hydrogenated cottonseed oil. Allchemicals and organic solvents were purchased from FisherScientific and Sigma-Aldrich (ON, Canada).

The emulsifiers Glyceryl Monostearate (GMS) andSodium Stearoyl Lactylate (SSL) were provided by CaravanIngredients (Lenexa, Kansas, USA). Glyceryl Monopalmitate(GMP), Sorbitan Monopalmitate (SMP) and PolyethyleneGlycol Sorbitan Monostearate (PGMS) were provided byDanisco Canada Inc. (Scarborough, ON, Canada). Theseemulsifiers were commercially available and used withoutfurther purification. Phosphatidylcholine (P-Choline) waspurchased from Sigma-Aldrich (ON, Canada).

Blend Preparation

Physical blends of Fully Hydrogenated Soybean Oil (FHSO)and Soybean Oil (SO) were mixed in different proportionsw/w (40:60; 30:70; 20:80 and 10:90 of FHSO:SO respective-ly). Additionally, in order to study the effect of the addition ofemulsifiers on the physical-chemical properties of the fatblends, six different types of emulsifiers were incorporatedin concentrations of 0, 1 and 3 % w/w. The samples werecrystallized using a scraped-surface heat exchanger (SSHE) orvotator system. The experimental setup of the votator line issketched in Fig. 1. The votator system consists of: a supplypiston pump (CAT Pumps, Minneapolis, Minnesota), twoscraped surface chillers or A Unit (7.62 cm×30.48 cm,Waukesha Cherry-Burrell/SPX, Charlotte North Carolina)and an agitated holding unit or B Unit (10.16 cm×43.61 cm,Waukesha Cherry-Burrell/SPX, Charlotte North Carolina).Fat blends were melted in a vessel and kept at 80 °C for

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30 min to ensure erasing the crystal memory. Each surfactantwas incorporated into the melt under mild mixing conditionsto assure homogeneity; afterwards the mixtures were cooleddown to 70 °C and kept at that temperature until the onset ofcrystallization. The molten mixture was pumped at a flow rateof 0.65 kg/min (39 kg/h) through the votator line. The tubingsystem between each unit and the outlets were well-insulatedto avoid heat loss. In all experiments, the wall temperature ofeach unit was set to reach~−2 °C in unit A, ~15 °C in unit Band ~10 °C in the second unit A. With the purpose of analyz-ing the influence of the crystallization conditions inside thevotator line, 2 different unit configurations were used. Fatblends were collected after passing through two scraped-surface chiller units (unit A) plus one agitated working unit(unit B) in a configuration AAB or ABA. After crystallizationall the samples were held at 20 °C for 3 days to allowcrystallization completion and subsequently stored at a refrig-erator temperature (4 °C) until the moment of characterization.Some mixtures, in particular those with the highest FHSOproportions, couldn’t be processed on the votator due to theircapability to quickly build up in the votator line and thereforecause plugging of the system. On the other hand, some mix-tures with low proportions of FHSOwere discarded since theywere extremely soft making them not suitable for the goal ofthis project.

Solid Fat Content (SFC) Determination

Crystallized samples were introduced into nuclear magneticresonance (NMR) glass tubes and stored for 24 h at 4 °C.Then, the tubes were incubated at the desired temperature for30 min to allow a homogeneous distribution of temperature atthe moment of measurement. SFC was measured by pulsenuclear magnetic resonance (p-NMR) using a BrukerMinispec spectrometer, (Bruker Optics Ltd., Milton, ON,Canada). The reported data corresponds to the average of fiveindividual measurements.

Polarized Light Microscopy (PLM)

Polarized light microscopy was used to observe fat micro-structure. To obtain satisfactory reproducibility of slides and

crystal appearance a definite amount of the crystallized sampleplus soybean oil was weighed on a slide in order to maintain a1:1 proportion; then the mixture was homogeneously spreadin all directions and a cover glass was carefully laid over thefat to remove air and complete spreading the fat. Sampleswere imaged using a Leica DM RXA2 microscope withpolarized light (Leica Microsystems, Richmond Hill,Canada) and equipped with a CCD camera (Q ImagingRetiga 1300, Burnaby, BC, Canada). All images were ac-quired using a 40X objective lens (Leica, Germany). Thecamera was set for autoexposure. Openlab 6.5.0 software(Improvision, Waltham, MA, USA) was used to acquire im-ages. Focused images were stored as uncompressed 8-bit (256grays) grayscale TIFF files with a 1,280×1,024 spatial reso-lution. Five images were captured from each of the fivereplicates prepared.

Microstructural analysis was carried out by image analysisemploying the Adobe Photoshop CS 3 software (AdobeSystems Inc., San Jose, California, USA) and filters from theFovea Pro 4.0 software (Reindeer Graphics, Inc., Asheville,NC, USA). A manual threshold was applied to all the picturesto convert the grayscale images to binary images, in order todiscriminate between features and background and to measurethe features sizes. Themicrostructural elements were analyzedusing the filter tools included in the Fovea Pro software. Meansizes values and standard deviations of at least 25 replicatesare reported.

Powder X-Ray Diffraction (XRD) Analysis

XRD data in the wide angle region were collected using aRigaku Multiflex Powder X-ray Diffractometer (Rigakug,Japan). The copper lamp (λ=1.54 Å for copper) was set to40 kVand 44 mA. A 0.57 divergence slit, 0.57 scatter slit and0.3 mm receiving slit were used. The wide angle X-ray dif-fraction analysis (WAXD) was carried out scanning the sam-ples from 16 to 35° at 0.5°/min. MDI’s Jade 6.5 software(Rigaku, Japan) was used to analyze the obtained WAXDpatterns .

Cryogenic Transmission Electron Microscopy (Cryo-TEM)

In order to remove the oil phase and better image singlecrystals. Fat blends were treated as reported previously byAcevedo and Marangoni [24]. Samples were prepared at10 °C as follows. Fat blends were suspended in cold isobutanolapproximately at a ratio 1:50 (in weight) using a glass stirringrod to obtain a uniform suspension. The fat plus isobutanolmixtures were homogenized at 30,000 rpm with a rotor-stator(Power Gen 125, Fisher Scientific) for 10 min. Then, thecrystals were collected by vacuum filtration through a glassfiber filter of 1.0 μm pore size. After filtration, the recoveredsolid was re-suspended in cold isobutanol and re-homogenized

Fig. 1 Schematic representation of the SSHE system used to crystallizethe fat blends

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for 10 min using the rotor-stator in order to obtain a suitabledispersion of crystals. Finally the mixtures were sonicated at10 °C for 60 min using an ultrasonic processor (Bransonic1210R-DTH, Branson Ultrasonic Corporation, Danburry, CT,USA) to complete the dispersion of the fat crystals. Five micro-liters of the obtained dispersion were placed on a copper gridwith perforated carbon film (Canemco-Marivac, Quebec,Canada), and excess liquid was blotted automatically for 2 susing filter paper. A staining aqueous solution of 2 % of uranylacetate was used to enhance contrast. Subsequently, the samplewas transferred to a cryo holder (Gatan Inc., Pleasanton, CA,USA) for direct observation at −176 °C in a FEI Tecnai G2 F20Cryo-TEM operated at 200 kV in low dose mode (Eindhoven,The Netherlands). Images were taken using a Gatan 4 k CCDcamera. Micrographs were stored and analyzed usingDigitalMicrographTM software (USA). Image J 1.42q software(USA) was employed for a semiautomatic analysis procedure.

Oil loss (OL) Determination

Oil loss studies were performed according to the techniquedescribed previously by Dibildox-Alvarado et al [25]. Oncecrystallized, fat blends were molded into discs of 22 mm diam-eter and 3.2 mm of thickness using Polyvinyl chloride (PVC)molds and then transferred to filter papers (Whatman #5, 110-mm diameter). The amount of oil that each sample (prepared asdiscs) lost to filter papers was determined by the difference inweight of the filter papers before and after placing the fat disc onthe paper for 24 h at 20 °C. A “blank” filter paper was includedin all experiments to account for the effects of the treatments onthe paper itself such as the influence of the humidity of thestorage environment. Filter papers must be large enough in orderto avoid the paper saturation with oil during the period ofmeasurement. An average and standard deviation of at least fivereplicates (five separate disks on individual filter papers) isreported. Oil loss (%) was calculated as:

OL %ð Þ ¼ 100−wt:paper 24hð Þ−wt:paper 0hð Þ

wt:paper 0hð Þ � 100 ð1Þ

Small Deformation Rheology

After crystallization samples were placed into the wells ofpolyvinylchloride (PVC) molds (discs of 3.2 mm thick and20 mm in diameter) and then stored at 4 °C until the momentof analysis. Rheological measurements at small deformationswere performed using an AR2000 rheometer (TA Instruments,Mississauga, ON,Canada) with a 2-cm flat plate attachment. Thesample platform temperature was controlled, allowing for tem-perature to be maintained at 20 °C during analysis. Evaluation ofthe linear viscoelastic range (LVR) was determined using oscil-latory stress sweeps from 1 to 1,000 Pa at a constant frequency of

1 Hz. Storage moduli (G’) were determined within the LVR ofthe samples. To prevent slippage, sandpaper (grade 60) wasattached to the lower surface of the geometry and the uppersurface of the Peltier base of the rheometer.

In order to predict the product’s processing and/or end-useperformance the yield stress values (σ*) were determinedfrom the rheological data as the stress (in Pa) required toproduce a decrease in G’ of 10 % of the LVR region. Thereported data are the average of 6–10 individual replications.

Statistical Analysis

Data were processed using GraphPad Prism 5 software(GraphPad Software, Inc., San Diego, CA, USA). Reported

Table 1 Oil Migration data (%) of blends with different fully hydroge-nated soybean oil:soybean oil ratios and crystallized using differentconfigurations in the scraped surface heat exchanger

FHSO:SO (%)

Formulation/SSHE configuration 10:90 20:80 30:70 40:60

No Emulsifier ABA ND 6.8 2.4 1.4

No Emulsifier AAB 27.8 19.7 5.9 ND

1%GMS AB 36.9 7.7 1.8 ND

1%GMS ABA 32.7 8.6 2.9 ND

1%GMS AAB 35.6 7.6 2.6 ND

3%GMS AB ND 7.4 ND ND

3%GMS ABA 31.0 5.0 ND ND

3%GMS AAB 34.0 15.4 ND ND

1%SSL AB 30.6 ND ND ND

1%SSL ABA 34.6 21.1 9.4 ND

1%SSL AAB 30.7 18.3 10.2 ND

3%SSL AB 45.4 ND ND ND

3%SSL ABC 30.5 19.8 9.8 ND

3%SSL AAB 41.7 33.5 11.8 ND

1%PGMS ABA ND 17.0 6.6 ND

1%PGMS AAB ND 12.5 6.1 ND

3%PGMS ABA ND 22.6 13.1 ND

3%PGMS AAB ND 19.1 13.3 ND

1%P-choline ABA ND ND 7.9 ND

1%P-choline AAB ND ND 7.1 ND

3%P-choline ABA ND ND 11.6 ND

3%P-choline AAB ND ND 12.1 ND

1%SMPABA ND ND 15.2 ND

1%SMPAAB ND ND 5.6 ND

3%SMPABA ND ND 15.7 ND

3%SMPAAB ND ND 7.8 ND

1%GMPABA ND ND 3.1 ND

1%GMPAAB ND ND 3.8 ND

3%GMPABA ND ND 28.3 ND

3%GMPAAB ND ND 7.3 ND

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values correspond to means and standard errors of the deter-minations. Statistical analysis was performed by one-wayANOVA (p<0.001) using Tukey’s multiple comparisons aspost-test (p<0.005).

Results

Oil Loss

Oil binding capacity of the blends was explored throughthe analysis of the oil loss (OL). Table 1 shows the OL(%) values for all samples assessed. ND (non-determined) cells in the table correspond to blends thatcould not be crystallized in the SSHE. For instance,mixtures containing 40 % FHSO and some of the30 % FHSO plus emulsifier blends plugged the votatorlines and seized the equipment. Additionally, some mix-tures with low proportions of FHSO remained liquid orfluid and could not be used any further. As anticipated,samples with higher amounts of FHSO had lower OLvalues, compared to blends with less FHSO. Fat mix-tures with 40 % FHSO displayed a small amount of OLafter 24 h storage; however, they were very rigid andbrittle. Compared to most fats, the APPS control had arelatively low OL, which is indicative of a high oilbinding capacity. Only a few formulation/votator config-uration combinations displayed OL values comparablewith the APPS control. In particular, 30:70 FHSO:SOblends with no added emulsifier (ABA configuration),and containing 1 % of GMS or GMP (in ABA andAAB configurations) displayed relatively low OLvalues, similar to that of the high trans APPS control.

Solid Fat Content (SFC)

Changes in SFC as a function of temperature for the APPScontrol and blends crystallized in the votator before the addi-tion of emulsifier are shown in Fig. 2. Changes in SFC withtemperature were not only dependent on the proportion ofsolid fat in the blends, but also on the configuration of thevotator units. SFC profiles of fat mixtures with 10 % (data notshown), 20 %, 30 % and 40 % FHSO were significantlydifferent to each other (P<0.05), increasing with increases inthe proportion of FHSO in the blend. Blends crystallized withan ABA unit configuration displayed SFC values significantlyhigher (P<0.05) than those observed in AAB samples. SFC ishighly dependent on processing and crystallization conditions.Crystallization with an extra A unit at the end of the process-ing line induced an increase in the SFC at all FHSO propor-tions relative to a configuration where both A units werearranged in series before a B unit. The extra chilling andshearing at the end of the crystallization process for theABA configuration seemed to help the formation of a largeramount of solids, possibly due to a greater time exposure ofthe material to high supersaturation conditions and shear. Thiswould have led to a greater amount of nuclei being formed,eventually resulting in the accumulation of more solid crys-talline material [8, 9, 26–29].

Fat blends with 30 % FHSO (Fig. 3) had a SFC-T profilecomparable to the APPS control (Fig. 2). However, a differ-ence in the shape of the curve was observed. While the APPScontrol showed a slight and continuous decrease of SFC withthe increase of temperature, the blends displayed a plateau inthe SFC values at low temperatures, followed by a sharpreduction when the temperature increased. As for the effectof emulsifier addition, there was a decreasing effect on theSFC which varied in magnitude with the type of emulsifier

Fig. 2 SFC-T profiles obtainedfor the fat mixtures without theaddition of emulsifiers andcrystallized using different unitconfigurations in the votator line(a, b, c) and the APPS control (d)

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and concentration. For instance, the addition of 1 % SMP tothe 30:70 ABA blend caused the largest drop in SFC along thewhole range of temperatures; while when added at 3 % con-centrations the reduction in SFC was not as significant. Theseresults are not surprising as it has been previously reportedthat the same additive may have a different effect when addedat different levels, or when the system is subjected to differentdegrees of undercooling or agitation [30]. The reduction in theSFC of blends with emulsifiers compared to those with noadditives showed their crystal-inhibiting properties, possiblyoriginated of their strong interaction with the crystalizingTAGs. According to Katsuragi [17], in circumstances wherethe molecules of the emulsifier associate very strongly withthe TAG molecules, crystallization of the TAG could bedelayed. Additionally, changes in the SFC-T profiles inducedby the presence of emulsifiers were different for both SSHEconfigurations. At concentrations of either 1 or 3 %, largemodifications in the SFC values could be observed using anABAvotator set up, whereas changes were not significant forsamples crystallized using an AAB configuration. These re-sults can be attributed to the extreme cooling treatment re-ceived by samples in the AAB votator set up. As mentionedpreviously, it has been reported that increasing undercoolingreduces the effect of minor component [18, 19].

Similar trends on the effects of both, emulsifiers andvotator configuration, on SFC-T profiles were observed forblends with 20 and 10 % FHSO (data not shown).

Rheological Properties

Rheological properties are strongly correlated with the macro-scopic functionality of fat systems. Figure 4a shows changes inthe storage modulus (G’) of samples with different FHSO:SO

ratios, before the addition of emulsifier. TheAPPS control with aG’ value of ~1 MPa is also shown in Fig. 4. As expected; fatmixtures with larger amounts of FHSO had higher G’ values. Inparticular, 30:70 FHSO:SO blends showed similar values to theG’ of the APPS control. In addition, regardless of the FHSO:SO

Fig. 3 SFC-T profiles obtainedfor 30:70 FHSO:SO mixturescrystallized in the votator linewith an ABA (a,c) or AAB (b,d)configuration, before and after theaddition of 1% (a,b) and 3% (c,d)of different emulsifiers

Fig. 4 Storage moduli (G’) and yield stress values (σ*) obtained for theAPPS control and different FHSO:SO mixtures without emulsifier,crystallized in the SSHE with an ABA or AAB configuration. Differentletters assigned to each bar represent statistically significant differencesbetween the values (P<0.05)

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ratio, samples crystallized using an ABA configuration hadhigher G’ values compared to those crystallized using an AABconfiguration. These results were expected considering thehigher SFC values observed for samples crystallized using anABA configuration (Fig. 2). In general, a higher SFC translatesinto a more solid-like character of the fat, i.e. higher values of G’and yield stress [22, 31, 32].

The yield stress (σ*) is one of the most important macro-scopic properties of fats and fat-containing products since it isstrongly correlated to sensory perception of hardness andspreadability, as well as to material stability. The apparentyield stress of a plastic solid is usually defined as the pointat which, when the stress is increased, the deforming solid firstbegins to show liquid-like behavior. In this work, we consid-ered the stress at the limit of linearity (after a change in G’ of10 %) as the yield stress. Figure 4b shows the results forblends with 20, 30 and 40 % FSHO. As anticipated, yieldstress values were lower in blends with smaller amounts ofsolid fat. Moreover, a decrease of up to 65 % in yield stresswas observed upon crystallization using an AAB configura-tion relative to the ABA set up. Interestingly, 30:70 and 40:60

blends, crystallized using an ABA configuration had yieldstress values similar to that of the APPS control.

The addition of emulsifiers significantly affected themechan-ical properties of the 30:70 FHSO:SO blends (Fig. 5). Severalauthors have previously reported that emulsifiers in food prod-ucts are multifunctional and play a vital role in the final productproperties [10, 33]. Since we were interested in comparing theproperties of the votator-produced blends with emulsifier, tothose from the APPS control, the G’ and σ* values of theAPPS control are also represented in Fig. 5. It can be seen that,with the exception of few cases, the addition of emulsifiersshowed a significant effect in reducing G’. The addition of1 % GMS, P-choline, and GMP led to G’ values comparableor slightly higher than that of the APPS control; while, thepresence of 1 % SSL, PGMS, and SMP induced G’ valuesbelow that of the APPS control. Further increases in the levelsof emulsifiers resulted in a noticeable decrease in G’well belowthe desirable level of theAPPS control. Analogous results can beobserved for σ*. The 30:70 FHSO:SO ABA formulations(Fig. 5) containing 1 % of GMS or GMP exhibited σ* compa-rable to that of the APPS control. Blends with 3 % GMS were

Fig. 5 Storage moduli (G’) andyield stress values (σ*) obtainedfor the APPS control and 30:70FHSO:SO mixtures crystallizedin the votator line with an ABA orAAB configuration, before andafter the addition of 1 or 3 % ofdifferent emulsifiers. Differentletters assigned to each barrepresent statistically significantdifferences between the values(P<0.05)

Fig. 6 Microstructural elementsof the APPS control (a) and a fatblend crystallized in the scrapedsurface heat exchanger (b). Bothmicrographs correspond to PLMimages

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not possible to crystallize in the SSHE as they plugged thevotator lines and seized the equipment. On the other hand, afurther increase in GMP levels up to 3% reduced σ* well belowthat of the APPS control, reaching an almost zero value. Thelarge reduction in the rheological properties obtained in thepresence of 3 % GMP can be ascribed to a possible non-ideal phase behaviour in the blends leading to lowerSFC (Fig. 3), G’ and σ* (Fig. 5) values than expected,considering the melting points of the individual compo-nents [34].

Addition of other emulsifiers led to a sharp decrease in theyield stress, well below that of the APPS control. It is alsoworth mentioning that for an AAB votator configuration, only1 % P-choline and 1 % GMP led to desirables σ* valuesdefined by the APPS control.

Fat blends made with 20 % FHSO displayed yield stressvalues approximately 2 to 16 times lower than that of theAPPS control, while samples containing 10 % FHSO showedσ* values between 14 and 80 times lower than that of theAPPS control.

Microstructure

Figure 6 shows a representative example of the PLM micro-graphs obtained for the APPS control (Fig. 6a) and the fatblends crystallized in the votator line (Fig. 6b). The micro-structure or all the samples whether they had emulsifier or notwas characterized by a granular texture with fine crystalscombined with a small number of spherulites. These observa-tions agree with earlier works on similar systems [8, 9, 35].

Image analysis yielded an average crystal size of 2.35±0.51 μm in the APPS control (Fig. 7a). In contrast, averagecrystal sizes in the produced blends before and after emulsifieraddition were significantly smaller (P<0.005) than that of theAPPS control (Fig. 7a–c). Blends formulated with any of thesix emulsifiers used in this work showed meso-crystal diam-eters ranging between 0.9 and 1.3 μm.

It can be seen that while some emulsifiers (PGMS, P-choline and SMP) led to a decrease in mesocrystal sizes,GMP promoted meso-crystal growth. GMP incorporation in-duced mesostructural crystallites of ~1.6 μm and thus, closeenough to the size of crystals present in the APPS control(Fig. 7b, c).

According to Garti [36], emulsifiers can alter the surfaceproperties of solid TAG, resulting in the modification ofcrystal habit (size and shape). Foubert et al [37]. and Bassoet al [38]. found that the presence of monoacylglycerol re-duced the induction time and accelerated crystal growth ofpalm oil. Monoacylglycerols can act as nucleation seeds,facilitating aggregation of the triacylglycerol molecules andthus, leading to the formation of a large number of smallcrystals [37–39]. However, our findings revealed that, as seenin Fig. 7b, c, the addition of GMP resulted in the formation of

a structured network composed of mesocrystals larger thanthose of blends without emulsifier. It is probably that althoughnucleation could be promoted by the seeding effect of palm-based monoacylglycerol, crystal growth was delayed by thedisruption of crystallization caused by the co-crystallization ofthe emulsifier molecules with the fat. In fact, Marangoni [40]indicated that it is expected that chemical and structural affin-ity between the crystallizing TAGS and an emulsifier, will

Fig. 7 Mesoequivalent diameter values obtained for the APPS control(far right, black bar) and different FHSO:SOmixtures without emulsifiercrystallized in the SSHE. Solid grey bars: ABA configuration; grid bar:AAC configuration (a). Equivalent diameter values in 30:70 FHSO:SOblends with crystalized with ABA (b) and AAC (c) configurations, beforeand after the addition of 1 or 3 % of different emulsifiers. Different lettersassigned to each bar represent statistically significant differences betweenthe values (P<0.05)

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result in co-crystallization of the molecules. However, as forthe similarity between the stearic acyl of tristearin (maincomponent of FHSO) and the palmitic acyl of GMP, stearicchains are incompatible with palmitic chains which lead to theformation of a eutectic upon co-crystallization. As a result,crystallization process would be disturbed at both the nucle-ation and growth stages, and a decrease in the number and sizeof the crystals would be observed.

On the other hand, the decrease in mesocrystal sizes ob-served as a result of the presence of P-choline can be attributedto TAG-P-choline physical and chemical interactions. Smith[41] reported that P-choline can affect both, nucleation andcrystal growth processes when added to palm oil. Similarly, ina study carried out by Vanhoutte et al. [42], crystallizationbehavior of milk fat upon addition of P-choline was described.These authors hypothesized that P-choline is integrated ongrowth sites of seed crystals due to its lower solubility in themelt. When a phospholipid is adsorbed in the crystal lattice,further growth is obstructed as the addition of the next triac-ylglycerol molecule is prevented by stearic hindrance of thepolar head and the absence of the third fatty acid chain.Consequently, P-choline can retard the onset of crystallizationas well as crystal growth. Moreover, Miskandar et al [12].determined a decrease in the SFC and crystal sizes of palm oil

with 0.09 % lecithin added. A seeding effect of P-choline hasbeen previously reported. Due to its tendency to formmicellesin the HII mesophase (i.e., polar heads oriented towards thecentre and non-polar chains exposed to the exterior), it offers asuitable base for fat crystals nucleation [43, 44]. Thus, ourfindings are in line with previous works, as a significantreduction in crystal size and SFC-T profiles (Fig. 3) wereobserved upon P-choline addition.

Nanostructure

Powder X-ray Diffraction

Figure 8a shows the wide-angle X-ray diffraction patterns ofthe APPS control. Both peaks are clearly connected with a β’polymorphic form with short spacing values corresponding tothat of the orthorhombic subcell [45].

An example of the powder X-ray diffraction patterns ob-tained for all the FHSO:SO blends is shown in Fig. 8b. Allsamples, whether or not with emulsifier, displayed threestrong signals at 4.6, 3.8 and 3.7 Å which are characteristicof the β polymorphic form [45]. Thus, XRD patterns clearlyindicate that when the samples were crystallized in the SSHE,

Fig. 8 X-ray patterns obtainedfor the APPS control in the wideangle region (a). Example of anX-ray pattern in the wide angleregion obtained for all thesamples crystallized using thescraped surface heat exchanger

Fig. 9 Cryo-TEMphotomicrographs showing thenano-structure of the APPScontrol (a, b) and 30:70FHSO:SO blends crystallized in ascraped surface heat exchangercrystallizer (SSHE) before andafter adding emulsifier (c–f)

Food Biophysics

the formation of the β polymorph was enhanced which is inclose agreement with former works [46–48].

Nanocrystal Size

The nanostructure of all FHSO:SO mixtures was systemati-cally studied by determination of nano-crystal sizes using theCryo-TEM technique previously developed in our laboratory[24, 49].

The analysis of the nanoscale revealed similar trends tothose found at the mesoscale. Figure 9 shows some examplesof Cryo-TEM micrographs obtained for the 30:70 FHSO:SOsamples before and after adding emulsifier (Fig. 9a–d) and theAPPS control (Fig. 9e, f).

Results from the nanoplatelet size determination revealednanoplatelet lengths and widths of 434±18 nm and 110±4 nm, respectively for the APPS control, while nanoplateletsizes for the 30:70 FHSO:SO blends were significantly small-er than those of the APPS control. Additionally, APPS control

nanoplatelets had a higher aspect ratio (length/width) than anyof the FHSO:SO samples, irrespective of emulsifier type orconcentration, or FHSO content. Previous works [35, 49, 50]demonstrated that external fields markedly affected the nano-scale of fat crystal networks. Acevedo et al [35]. suggestedthat crystallization below a critical shear rate induced thegrowth of nanocrystals, whereas crystallization under highershear rates led to the formation of progressively smallernanocrystallites. The high shear rates and high degrees ofundercooling used in this work were most probably responsi-ble for the small size of the nanocrstals.

To systematically compare the nanostructure of the APPScontrol with that of the FHSO:SO blends, nanoequivalentdiameters to a sphere were calculated. As expected, the anal-ysis yielded nanocrystal equivalent diameters significantlysmaller (P<0.005) in the FHSO:SO blends compared to thoseof the APPS control (Fig. 10). In general, the higher theproportion of FHSO, the larger the nanoequivalent diametersand thus, the closer they were to the nanocrystal sizes of theAPPS control. On the other hand, blends without emulsifierdisplayed larger nanocrystal when crystallized using AABvotator configuration, relative to the ABA set up.Nevertheless, nanocrystal magnitudes were not markedly dif-ferent for both votator configurations. From ABA to AABarrangement nanocrystal sizes increased 9 % and 12 % inblends with 20 and 30 % FHSO respectively.

Samples containing nanocrystals with equivalent diameterssimilar to those present in the APPS control were furtheranalyzed. Figure 10b shows the results of 30:70 FHSO:SOmixtures before and after incorporation of selected emulsifiersat a 1 % level. The presence of SSL and SMP led to a decreasein nanocrystal equivalent diameters compared to blends with-out emulsifier. On the other hand, GMS, PGMS and GMPaddition led to the formation of larger nanocrystals, GMPbeing the surfactant that caused the greatest increase in equiv-alent diameter. It is important to point out that GMP has thesame effect on crystal size at the nano- and mesoscale. Aspreviously mentioned, this effect was probably due to aninterference with the nucleation and growth process as a resultof the molecular incompatibility between palmitic and stearicchains which leads to the formation of an eutectic upon co-crystallization.

It also worth mentioning that the nanocrystals’ aspect ratiosfor all the samples confirmed the visual examination of theCryo-TEM images (Fig. 9): the aspect ratio in the APPScontrol is 4, in contrast with values between 2.5 and 3.4 forthe FHSO:SO samples.

Blend Functionality

We assessed the functionality of the fat blends by comparisonof their properties to those of the APPS control.

Fig. 10 Nano-platelet equivalent diameters for the APPS control and fatmixtures with FHSO proportions ranging from 20 to 40 % and withdifferent units’ configuration in the votator line (a). Nano-platelet equiv-alent diameters for the APPS control and 30:70 FHSO:SO mixturescrystallized with an ABC unit configuration in the votator line (b). Errorbars are displayed however the value is low and therefore they are notvisible in the graph. Different letters assigned to each bar representstatistically significant differences between the values (P<0.05)

Food Biophysics

Table 2 shows a summary of the structure and phys-ical properties of the most promising FHSO:SO blends,as far as matching the properties of the high transAPPS control roll-in shortening. The rheological prop-erties of these fats are very similar to those of theAPPS control. Haighton [51] reported that a fat issufficiently plastic, spreadable and appropriate for bak-ery applications when its yield stress value is in the200–800 Pa range. In contrast, fats with yield stressesabove 1,500 Pa are too hard and at the limit of spread-ability. In general, all the samples in this groupdisplayed a satisfactory yield stress at 20 °C. Onlyblends without emulsifier and containing GMS present-ed relatively high yield stress. Even though, 30:70FHSO:SO blends with 1 % P-choline had mechanicalproperties similar to those of the APPS control, theyreleased a high amount of oil which may limit theirfunctional application.

Comparing the results acquired for the rest of theblends to those of the sample control, it is possible tonote tha t the formula t ion wi th 1 % glycerolmonopalmitate added and crystallized using an ABAvotator configuration had properties that most closelymatched those of the APPS control. However, whilethe blends mechanical properties matched that of theAPPS control, neither the nanostructure, nor the micro-structure corresponded to that of the APPS control.This suggests that possibly the interaction betweennanocrystals and mesocrystals was affected by the pres-ence of emulsifiers in a way that allowed matching themechanical properties regardless of the differences instructure.

Conclusions

This work describes the effects of processing under shearusing a scarped surface heat exchanger and the addition ofdifferent emulsifiers on the physical properties of non-interesterified, fully hydrogenated soybean oil –liquid soyoil blends.

In agreement with the pre-defined criteria reported byHaighton [51] relating yield values of fats to a sensory eval-uation of their spreadability, satisfactorily plastic and spread-able properties were observed in blends with GMP and P-choline. Yet, despite their acceptable yield values, a low oilbinding capacity, well below adequate levels, was observedfor mixtures with P-choline leaving GMP as the adequateemulsifier for these blends functionalization.

We have demonstrated in this study that polymorphism isnot inevitably linked to a particular micro- or nanostructure.Traditionally, β’ crystals have been the most desirable as theyare relatively small and can incorporate a large amount ofliquid oil in the crystal network. However our finding showedthat it is possible to obtain very small β crystals within a fatmatrix having the same characteristics as β’ crystals and thus,good functionality.

Based on our results, it is clear that emulsifiers are efficientmodifiers of the crystal interactions at the meso and nanoscale,even under the drastic crystallization conditions generated inthe SSHE (high cooling and shear rates). It is probably thatchanges induced to the surface of the nanocrystals led toalterations of the strength of interaction between them andhenceforth the mechanical strength of the resulting network.Extended research is currently ongoing to effectively explainsuch effect.

Table 2 Physical, rheological, thermal and structural properties of fullyhydrogenated soybean oil:soybean oil blends, with or without emulsifiersand crystallized in the scraped surface heat exchanger. The selected

blends are considered the most promising systems in comparison to theAPPS control. The numbers represent the average value across 3 to 25replicates and their standard deviation

Physicalproperties

Rheological properties Thermalproperties

Microstructure Nanostructure

OL (%) SFC at20 °C (%)

G’ (MPa) σ* (Pa) Tm (°C) Meso-eq.Diam. (μm)

Nano-eq.Diam.a (nm)

Aspect ratio Polymorphicform

Control 2.8±0.1 36.70±0.2 1.00±0.02 835±97 50.5±0.2 2.35±0.37 247 4 β’

40:60 ABA 1.4±0.1 35.72±0.1 4.40±0.04 1,075±154 62.9±0.2 1.43±0.27 215 2.5 β

30:70 ABA 2.4±0.2 30.08±0.05 2.20±0.02 952±121 61.7±0.3 1.31±0.37 133 2.7 β

30:70 ABA-1%GMS 2.9±0.1 28.66±0.01 1.70±0.08 1,010±104 60.5±0.4 1.14±0.25 155 3.3 β

30:70 AAB −1%GMS 2.6±0.2 29.76±0.03 2.10±0.01 1,292±110 61.0±0.2 1.13±0.21 105 3 β

30:70 ABA-1%GMP 3.1±0.2 30.84±0.12 1.80±0.16 891±95 60.5±0.3 1.29±0.18 180 2.4 β

30:70 AAB-1%GMP 3.8±0.2 30.24±0.16 1.90±0.02 789±91 60.1±0.3 1.57±0.15 ND ND β

30:70 ABA-1%Pchol. 7.9±0.5 29.4±0.07 1.30±0.01 557±34 59.7±0.4 0.86±0.08 ND ND β

30:70 AAB-1%Pchol. 7.1±0.3 29.85±0.12 1.00±0.01 603±37 60.49±0.1 0.86±0.09 ND ND β

a SE<10 %

ND non-determined

Food Biophysics

In this work, it was demonstrated that regardless bulkchemical composition it is possible to achieve the expectedperformance of a shortening by using specific additives andcontrolling crystallization conditions. Thus, the use ofsoybean-based fats as raw materials is a good alternative forthe manufacture of zero trans and low-saturated fats.

Acknowledgments The authors acknowledge The Natural Sciencesand Engineering Research Council of Canada, Advanced Foods andMaterials network and General Mills for the financial support.

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