180 August 2008, Vol. 20, No. 8 Lipid Technology

Feature

Effect of emulsifiers on shortenings

Silvana Martini and Maria Lidia Herrera

Silvana Martini is an Assistant Professor at the Department of Nutrition and Food Sciences, Utah State University, 8700 Old Main Hill,750 North 1200 East, Logan, UT 84322-8700, USA; tel.: +1-435-797-8136; fax: +1-435-797-2379; e-mail: silvana.martini@usu.edu; website: http://cc.usu.edu/~smartini

Mar�a Lidia Herrera is Professor at the Faculty of Exact and Natural Sciences (FCEN), Department of Industries, University of BuenosAires, Ciudad Universitaria, 1428 Buenos Aires, Argentina; tel.: +54-11-4576-3300 ext. 274; fax: +54-11-4576-3366; e-mail:cidcamlh@yahoo.com.ar

Summary

The quality of a shortening depends on its physicochemical characteristics. These include amount of solids, texture and melting behavior,among others. The type of shortening, the processing and storage conditions strongly affect these characteristics. Different strategies can beused to formulate shortenings with low trans fatty acids content while maintaining their physicochemical characteristics. This articledescribes some of these strategies and aims to provide information about the different variables that need to be controlled to obtain a highquality shortening.

Introduction

The desired physical characteristics of shortenings can beobtained by either tailoring the chemical composition and/orchanging processing conditions during manufacturing. Short-enings can be used in margarine formulations, as a frying med-ium and for non-dairy applications, such as confections and bak-ing. Depending on the application, specific physicochemicalproperties are expected in a shortening. These include texture,softness, spreadability, solid fat content, crystal morphology,and melting behavior.

For the last century partially hydrogenated oils have beenideal shortenings in term of their functionality; however, due totheir negative effects on cardiovascular disease risk factors, theyare gradually being eliminated from the market. Healthier lipidsources replace trans fatty acids. These replacements includepalm derived oils, interesterified oils and blends with othervegetable oils. Manipulating processing conditions, such as crys-tallization temperature, cooling and agitation rates, can helpimprove the functionality of a shortening with low or no transfats content. The use of additives, i.e. emulsifiers, can alsoimprove the functionality of low trans shortenings. Emulsifiersmay act as lubricants, as anti-sticking agents, they also help inaeration processes and in the generation of structure by modify-ing the crystallization and in extending the shortening shelflife. For example, Herrera and Marquez Rocha (1) demonstrateda significant delay in polymorphic transformation (b9fib) whena sucrose ester emulsifier was added to hydrogenated sunfloweroil. This delay in polymorphic transformation is especiallyimportant to avoid blooming and increase the shelf life in con-fections.

Effect of emulsifiers on the crystallizationbehavior of lipids

Several studies have been performed to evaluate the effect ofemulsifiers on the physical properties of shortenings and their

functionality. Garti reported the effect of different emulsifierson the crystal structure and habit of stearic acid (2). Herrera'sgroup evaluated the effect of emulsifiers with different hydro-phobicity on the nucleation, growth and texture of milk fat (3–5). Sato's group also studied the effect of emulsifiers, mainly dur-ing the crystallization of fats in an emulsified form (6).

Emulsifiers can either induce or delay the crystallization.They can act as nuclei inducing the crystallization of lipid mole-cules and adsorb on the surface of the growing crystals delayingcrystal growth. In addition, due to the similarity between theemulsifier and lipid chemical structure they can co-crystallizeand so delay nucleation and inhibiting crystal growth (2). Insummary, depending on the chemical composition of the short-ening and the emulsifier, an induction or delay in the crystalli-zation mechanism can be expected. Even small changes in thechemical composition can result in significant changes of thephysical characteristics of the shortening as a consequence ofthe cocrystallization of triacylglycerols and emulsifiers. That is,even when shortenings are formulated with the same propor-tion of saturated and unsaturated fatty acids, the position of thefatty acid in the triacylglycerols molecule might be a factor toconsider. For this reason, predicting the emulsifier effect on thecrystallization behavior of a specific blend is very difficult. In anattempt to further understand these interactions, we conducteda study to evaluate the effect of different emulsifiers on the phy-sical properties of shortenings with different chemical composi-tions and therefore different melting points. The effect of sto-rage conditions was also analyzed and discussed (7). Some of ourresults are described below.

Effect of emulsifier addition on thecrystallization behavior of shortening withdifferent chemical composition

Four shortenings (B1, B2, B3 and B4), differing in their chemicalcomposition, were crystallized under exactly the same condi-tions without and with the addition of 0.2% of emulsifiers. The

DOI 10.1002/lite.200800038

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Lipid Technology August 2008, Vol. 20, No. 8 181

melting point of the shortenings was of 38, 35, 36 and 388C,respectively. The emulsifiers used for this study were saturatedmono- and di-acylglycerols (s-MDG), unsaturated mono and di-acylglycerols (u-MDG) and sorbitan tristearate (STS). In general,these emulsifiers inhibited the shortening crystallization as evi-denced by a lower melting enthalpy. The only exception to thisrule was when shortening B4 was crystallized with STS. In thiscase, a slight induction of the crystallization was observed. Eventhough emulsifiers inhibited lipid crystallization, the degree ofinhibition was a function of the chemical composition of theshortening and the type of emulsifier used. In particular, theaddition u-MDG to shortenings with high melting points (B1

and B4, l388C, l50% of saturated fatty acids) inhibited the crys-tallization of the lipids in greater extent, resulting in a softermaterial with slightly lower solid fat content. On the otherhand, the crystallization of intermediate melting point shorten-ings (l368C, l45% of saturated fatty acids, B3) was inhibited ingreater proportion by s-MDG, showing lower melting enthalpieswith no significant changes in the hardness and a slight increasein SFC values. Finally, the crystallization of low-melting pointshortenings (l358C, l35% of saturated fatty acids, B2) was inhib-ited by the addition of STS generating softer materials and nosignificant effect on the solid fat content (SFC) value. Theseresults suggest an indirect relationship between the saturationof the emulsifier and the shortening. That is, the more saturatedthe emulsifier, the greater the effect on the crystallization beha-vior of lower melting point shortenings (lower degree of satura-tion) (Table 1). It is also interesting to note that for shorteningswith very similar chemical composition and melting points, theaddition of STS generated significant differences in the physicalproperties. For example, when crystallized with STS theenthalpy in B4 was significantly higher than in B1, with softershortenings and lower SFC values. In addition, a relationshipbetween the melting enthalpies, the hardness and the SFC wasnot observed.

Effect of storage conditions on the physicalproperties of shortenings

Transportation from the production plant to the consumermight change some of the physical properties of a shortening,resulting in a defective product that is not accepted by the con-sumer. Maintaining the quality of shortenings during transpor-tation is not an easy task since several factors affect this quality;from environmental conditions to formulation and processing.When the same shortenings described above were subjected totemperature fluctuations expected during transportation sev-eral interesting results were obtained. Two different tempera-ture-time cycles were designed to reproduce different environ-mental conditions (Fig. 1) with a total of 36 days of storage. Sam-

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Table 1. Enthalpy, hardness and solid fat content values for differentshortenings formulated without and with the addition of emulsifiers(0.2%).

Enthalpy (J/g)

WE u-MDG s-MDG STS

B1 14.8 11.3 13.9 12.1B2 9.2 8.1 9.8 5.3B3 7.6 8.0 6.2 8.2B4 15.7 8.1 12.5 17.7

Penetrometry (mm)

WE u-MDG s-MDG STS

B1 10.4 19.5 20.4 26.9B2 34.9 37.4 – –B3 36.8 – 34.2 37.2B4 15.5 17.3 14.9 36.4

SFC (%)

WE u-MDG s-MDG STS

B1 15.6 14.8 17.0 19.0B2 5.3 3.0 5.0 5.0B3 6.7 3.9 7.1 7.8B4 14.9 13.4 10.8 14.5

WE, without emulsifier; u-MDG, unsaturated mono- and di-acylglycerols;s-MDG, saturated mono- and di-acylglycerols; STS, sorbitan tristearate.

Figure 1. Temperature fluctuation ofshortenings during storage.

182 August 2008, Vol. 20, No. 8 Lipid Technology

ples with higher melting points (B1 and B4) were subjected tothe same temperature cycles, while shortenings with lowermelting points (B2 and B3) were subjected to different ones. Asbefore the quality of the shortening during storage depends onthe shortening's chemical composition and on the emulsifierused. It is very interesting to note that the effect of storage condi-tions on samples with very similar chemical composition andmelting points (B1 and B4) was significantly different (Table 2).

Storage promoted the crystallization of lipids in B1 for all thecrystallization conditions used. That is, when B1 was crystallizedwith and without the addition of emulsifiers, the amount ofcrystals increased during storage time. The promotion of crystal-lization was more evident when B1 was crystallized with theaddition of STS and u-MDG. Even though the addition of s-MDGstill promoted crystal formation during storage of B1, this waslower than when the sample was crystallized without emulsi-fier. In summary, the greater promotion of crystal formationduring storage was found for B1 crystallized with STS, followedby u-MDG, then by B1 without emulsifier and the least amountwas found when B1 was crystallized with the addition of s-MDG.When B4 was crystallized without emulsifier and with the addi-tion of STS the amount of crystallized lipid decreased over time,as evidenced by a lower melting enthalpy while a promotion ofcrystal formation was observed when B4 was crystallized with u-MDG and s-MDG, being the first one the most significant.

When low melting point shortenings were crystallized with-out emulsifiers, a promotion of crystallization was observed dur-ing storage. In some cases (B2), the addition of emulsifiersinduced lipid crystallization during storage compared to theshortening crystallized without emulsifiers with higher enthal-pies obtained for B2 crystallized with u-MDG and STS. The excep-tion to this rule was B2 crystallized with the addition of s-MDG,in which the amount of crystals observed after 36 days of storagedecreased by more than 30%, probably as a consequence ofrecrystallization events. In B3, another low melting shortening,

crystallization was promoted during storage for all samples,however, the addition of emulsifier delayed crystallization withonly 8-10% increase in the enthalpy over the entire storage per-iod.

Similarly to the behavior described above, diverse texturechanges were observed over storage. The most interesting find-ing is that even though in some shortening the amount of crys-tals formed during storage increased, the hardness decreasedresulting in softer material. For example, this was the case of B1crystallized without emulsifier and with the addition of u-MDG,and s-MDG. In general, for shortenings with high melting points(B1 and B4), softer materials were obtained when crystallizedwithout emulsifier and stored for 36 days. The addition of emul-sifiers also resulted in a softness increase, for B1 with u-MDG ands-MDG; however, harder samples were obtained for B1 crystal-lized with STS. The same behavior was observed for B4 with sig-nificant harder samples when this shortening was crystallizedwith the addition of u-MDG or STS. Shortenings with lower melt-ing points (B2 and B3) were significantly softer just after theywere produced, but became significantly harder during storage.In summary, the hardness of the shortening was not correlatedwith the amount of crystals formed during storage.

From all the physical parameters evaluated in this study, SFCwas the one that changed the most with storage, with percen-tages of variations between 30–700%. High melting point sam-ples (B1 and B4) suffered a significant decrease in the SFC whilefor lower melting point shortenings, the SFC values significantlyincreased (more than 200%). As describe above, a relationshipbetween the changes in SFC, hardness and amount of crystal-lized material could not be established.

In summary, different systems can be chosen for the particu-lar shortenings and emulsifiers used in this study, depending onthe physicochemical characteristics desired in a shortening. Forexample, if a hard shortening is needed, the best option wouldbe a shortening like B4 without emulsifier or with the additionof s-MDG, since these shortenings suffer less variation in thethree parameters measured in this study (enthalpy, hardnessand SFC). This study also shows that the temperature duringtransportation and storage of low-melting point shorteningsshould be carefully controlled to maintain optimum quality,especially in terms of texture and SFC.

Conclusions

Shortenings can be tailored to a specific application dependingon the desired functionality. This can be achieved by manipulat-ing the chemical composition of the lipid, by adding the ade-quate emulsifier and by controlling temperature fluctuationsduring transportation. It is interesting to note, however, that forsamples with very similar chemical composition and meltingpoint (B1 and B4) some emulsifiers had a significantly differenteffect. For example, the addition of STS slightly inhibited thecrystallization for B1 but promoted it in B4. In addition, whilestorage of B1 increased the amount of crystals formed, the oppo-site effect was observed for B4. The spatial distribution of fattyacids in the triacylglycerols molecule and different polymorph-isms might be responsible for this different effect.

Future trends

For specific processing conditions, such as crystallization tem-perature, cooling rate, and agitation, several variables influence

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Table 2. Changes in enthalpy, hardness and solid fat content values fordifferent shortenings formulated without and with the addition of emulsi-fiers (0.2%) after 36 days of storage under conditions shown in Fig. 1.Changes are expressed in percentages. A positive value means anincrease of the parameter after storage and a negative value indicates adecrease. For abbreviations see Table 1.

Enthalpy (%)

WE u-MDG s-MDG STS

B1 14.90 29.20 9.30 47.11B2 32.61 65.40 –33.67 75.47B3 15.79 10.00 8.06 0.00B4 –14.01 39.51 15.20 –0.56

Penetrometry (%)

WE u-MDG s-MDG STS

B1 123.08 47.18 15.69 –23.05B2 –84.53 –53.74 n/a n/aB3 –92.93 n/a –90.25 –94.35B4 37.42 –3.47 4.70 –59.34

SFC (%)

WE u-MDG s-MDG STS

B1 –47.43 –62.35 –40.54 –54.21B2 341.51 256.00 683.33 254.00B3 277.61 500.00 517.95 557.69B4 –46.98 –33.33 –36.57 –42.76

Lipid Technology August 2008, Vol. 20, No. 8 183

the stability of a shortening. These include lipid triacylglycerolsand fatty acid composition, triacylglycerols positional isomersand the presence and type of emulsifier. The interactionbetween these variables needs to be addressed to predict thecrystallization behavior and stability of a shortening.

References

1. Herrera, M.L. and Marquez Rocha, F.J. (1996) Effect ofsucrose ester on the kinetics of polymorphic transition ofhydrogenated sunflower oil. J. Am. Oil Chem. Soc. 73, 321 –326

2. Garti, N. (1988) Effects of surfactants on crystallizationand polymorphic transformation of fats and fatty acids. InCrystallization and Polymorphism of Fats and Fatty Acids. Ed.Garti, N. and Sato, K., pp. 267–304.

3. Cerderia, M., Pastore, V., Vera, L., Martini, S., Candal, R.J.and Herrera, M.L. (2005) Nucleation behavior of blendedhigh-melting fractions of milk fat as affected by emulsi-fiers. Eur. J. of Lipid Sci. Technol., 107, 877–885.

4. Martini, S., Cerdeira, M. and Herrera, M.L. 2004. Effect ofSucrose Esters on the Crystallization Behavior of Bulk OilSystems, J. Am. Oil Chem. Soc., 81, 209–211.

5. Puppo, M.C., Martini, S., Hartel, R.W. and Herrera, M.L.(2002) Effect of Sucrose Esters on Isothermal Crystalliza-tion and Rheological Behaviors of Blends of High-MeltingMilk Fat Fraction and Sunflower Oil, J. Food Sci., 67, 3419–3426.

6. Awad, T, Hamada, T. and Sato, K. (2001) Effect of additionof diacylglycerides on fat crystallization in oil-in-wateremulsions, Eur. J. Lipid Sci. Technol., 103, 735–741.

7. Martini, S. and Herrera, M.L. (2008) Physical properties ofshortenings with low-trans fatty acids as affected by emul-sifiers and storage conditions, Eur. J. Lipid Sci. Technol., 110,172–182.

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