influence of lactic acid ester on chocolate quality

Influence of lacticacid ester on

chocolate quality

Olga Jovanovic* andBiljana Pajin

University of Novi sad, Faculty of Technology,Department of Carbohydrate Foods Technology,Bul. Cara Lazara 1, 21000 Novi Sad, Yugoslavia(tel.: +381-21-350122; fax. +381-21-450413;

e-mail: [email protected])

Influence of concentration of emulsifier Lactem P 22 (lacticacid ester of monodiglyceride) as blooming inhibitor on thequality and fat bloom stability of laboratory made samplesof chocolate was investigated. This ingredient was addedduring the pre-crystallization process of chocolate mass.The pre-crystallization was performed in the laboratorycrystallizer modified Brabender pharinograph, where therheological characteristics of the pre-crystallized fluid cho-colate mass were measured. The experiments were per-formed according to the factorial plan 32 (two factors onthree levels). Statistical results processing was performedaccording to the Response Surface Methodology. Physicscharacteristics of chocolate—hardness and lightness—wereobtained by instrumental methods. The results has shownthat Lactem P 22 improve fat bloom stability of chocolatesamples but decrease sensory quality of chocolate. Bettersensory quality of chocolate was achieved with combina-tion of the crystallization promoter—Dynasan 118. The bestsensory quality of chocolate has been obtained with 0.5%Dynasan 118 and 1 and 2% Lactem P 22. Samples ofchocolate which was pre-crystallized on 23�C and with 3%Lactem P 22, showed the highest fat bloom stability.# 2003 Elsevier Ltd. All rights reserved.

IntroductionChocolate manufacturing is a very complex physical

and chemical process which requires numerous techno-logical operations and the addition of different addi-tives, to achieve the products of suitable physical andchemical attributes and an attractive appearance andtaste. The quality of a finished product highly dependson the behaviour of cocoa butter, featuring as the fatphase, that is its crystallization attributes (Ziegleder,1992). The tempering is undertaken to induce stablecocoa butter crystal formation throughout the chocolatemass (Jovanovic, Karlovic, Jakovljevic, & Pajin, 1998).This means that in the process of chocolate productionspecial attention has to be paid to the phenomena ofcrystallographic and phase transformations in theprocess of hardening, which occurs in two steps: duringpre-crystallization, that is process of the tempering ofthe chocolate mass, and during the final crystallization,that is hardening (Jovanovic, Karlovic, & Jakovljevic,1995). The pre-crystallization process could be inducedby the addition of different kinds of additives whichregulate the rheological characteristics of the chocolatemass, speeding up the crystallization process (Player,1986). The action of solidifying cocoa butter while theentire mass is being agitated or stirred is termeddynamic crystallization. The fat blooming of chocolateoccurs during the process of the natural aging of cho-colate, but it can also be the result of a technologicalmistake, that is in case the pre-crystallization processhas not been carried out properly, as well as in case ofinadequate storage. Some scientists consider bloomingto be consequence of cocoa butter crystal increase as aresult of simultaneous effect of some physical and che-mical factors: Ostvald’s phenomenon, polymorphictransformation, temperature oscillation, separation oftriglyceride by the melting point, migration and mixingother kinds of fat with cocoa butter (Garti & Sato,1988; Ziegleder, 1994). Blooming is a process whichtakes place throughout the whole chocolate mass andmanifests itself as white and grey stains or crust on thechocolate surface (Bricknell & Hartel, 1998).

In order to decrease the process of blooming differentkinds of emulsifiers, which in melted chocolate improveforming the stable crystals in V polymorph form, whilein the final product—hardened chocolate slow downtheir polymorph transition to VI polymorph form, are

0924-2244/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.doi:10.1016/j.tifs.2003.09.011

Trends in Food Science & Technology 15 (2004) 128–136

Viewpoint

* Corresponding author.

used (Player, 1986; Schlihter-Aronhime, Saring, &Garti, 1988). Emulsifiers, because of their limited abilityof mixing with fats cause a disorder in the crystal struc-ture of a triglyceride molecule. In this way, the liquidphase increases that is all polymorphic transformationsare promoted except for the fifth crystal form into thesixth one, which slows down the fat blooming process(Garti, Schlichter, & Saring, 1986; Timms, 2003). In theproduction of chocolate and chocolate like productsome of the emulsifiers could be successfully added forslow down of the fat blooming: sorbitane tristearate,polisorbat 60, sorbitan monostearate, poliglicerol estersof fatty acids, lactic acid esters of mono and diglycerides(Player, 1986).

The aim of this paper is to investigate the quality ofsome laboratory-made chocolate samples and their fatbloom stability depending on the concentration of anemulsifier—bloom inhibitor—a lactic acid mono-gliceride, commercially named Lactem P 22, and theconcentration of the crystallization promoter—tri-stearin—Dynasan 118, which is added in the pre-crys-tallization phase. The chocolate quality was assessedafter the moulding, hardening and stabilization of thesamples by determine the physical, mechanical and sen-sory attributes, as well as the fat bloom stability of thechocolate samples. Based on our preliminary investiga-tions of the pre-crystallization process of the chocolatemass on different pre-crystallization temperatures with

the addition of Lactem P 22, it was deduced that theoptimal quality is achieving using the temperature of27�C. For this reason this temperature of pre-crystal-lization was applied in this work (Jovanovic, 1996).

Materials

1. Chocolate mass—the chocolate mass was
provided by industry and taken at the end ofconcing. Fat content is 34.4%.
2. Emulsifier—lactic acid ester (EU number
E472b)—Lactem P 22 (Producer: DaniscoCultor, Denmark).
In Table 1 are given physicochemical characteristicsof Lactem P 22 by production specification. Figure 1shows a structure formula of Lactem P 22.

1. Promoter of pre-crystallization—tristearin—
Dynasan 118 (Producer: Huls AG, Germany). InTable 2 are shown theDynasan 118 characteristics.
MethodsPlan of experiments

Factorial plan 32 (variation of two variables—theconcentration of the emulsifier and the crystallizationpromoter, on three levels (�1, 0, +1)) was used for thelaboratory preparation of the chocolate. The emulsifierLactem P 22 was applied in the concentration of 1.0, 2.0and 3.0% calculated no fat content in the chocolate,

Table 1. Physicochemical characteristics of Lactic acid esters ofmono and diglycerides Lactem P 22 (Production specification:Emulgatoren & Stabilisatoren fur die Lebensmittelindustrie).

Characteristics
Value
Milk acid content (%)
20–25 Saponification number 270–300 Acid number Max. 4 Melting point (�C) 45 Shape Powder Dosing 1–3% calculated on chocolate,
at the beginning of sample melting
Acceptability daily intake Not specified
Fig. 1. Structure formula of Lactem P 22.

Table 2. Characteristics of monoacid triglyceride-crystal-lization accelerator Dynasan 118

Technological processing
Hydrogenation ofvegetable oil
Shape
White powder Melting point (�C) 70–73 Dosing 0.3–1% calculated on chocolate,
at the beginning of pre-crystallizationprocess

Olga Jovanovic and Biljana Pajin / Trends in Food Science & Technology 15 (2004) 128–136 129

Fig. 3. Schema of the temperature–time process of the laboratory preparation of chocolate by a conventional procedure of pre-crystal-lization: 1. (a) chocolate mass melting, (b) emulsifier adding; 2. chocolate mass tempering; 3. chocolate mass cooling; 4. chocolate mass

heating; 5. hardening moulded chocolate mass.

Fig. 2. The scheme of the laboratory pre-crystallizator: A thermostat, B thermostat, 1 knider, 2 electromotor, 3 dynamometer, 4 arms,5 balance, 6 recorder, 7 brakes. (a) Measurement range 0–10 Nm, (b) mixer speed 63 rpm, (c) paper speed 1 cm/s.

130 Olga Jovanovic and Biljana Pajin / Trends in Food Science & Technology 15 (2004) 128–136

while Dynasan 118 was added in the concentrations of0.5, 0.75 and 1.0% calculated on the sample mass.

Chocolate mass pre-crystallizationThe samples are prepared in a modified Brabender

pharinograph, where the original kneader is connectedwith two ultrathermostates by means of two-way taps(Fig. 2). This enables an immediate temperature changein the kneader and in half a minute in the treated cho-colate mass. The process of pre-crystallization iscontrolled indirectly by the changes of the mass resis-tance on the occasion of mixing, which is registered on aforce/time diagram—a thermoreogram (force expressedas torque in Nm). The torque value is a criterion forthe viscous behaviour of the chocolate mass and isdependant on the crystallization extent of the mass inquestion. The scheme of the applied temperature andtime regimes of the pre-crystallization (according to the

plan of experiments) is shown in Fig. 3. The phase ofpre-crystallization was done at 27�C.

Evaluation of results of chocolate masspre-crystallization

The pre-crystallization process of the examined cho-colate mass is determined by characteristic values onthermoreograms, as shown in Fig. 4.

Statistical treatments of resultsThe results of the thermoreographic measuring and

the indicators of the chocolate quality are statistical work(Statistical 5.0 for Windows was used software), wherethe response functional z is defined by polynomials

z ¼ B0 þ B1cDþ B2cLþ B3 cD2 þ B4cDcL þ B5cL2

where: B0. . ...B5 are coefficients of polynom, cD—con-centration of Dynasan 118, cL—concentration of

Fig. 4. Characteristic values of the thermoreographic curve: �1, nucleation time (min); �2, time to the achieving the torque maximum (min);M0, initial torque (Nm); M0

max, torque maximum (Nm); M0obl, torque of pre-crystallization chocolate mass (Nm).

Table 3. Analytical methods

Quality factors
Principle Reference
Whiteness on surface
Tristimulus colorimetry (whitness by Hunter system) Hunter (1960)
Hardness (penetration value)
Penetrometry Kleinert (1978) Needle mass=175 g, time �=15 s, temperature t=20�C
Sensory characteristics
(a) Total score method ISO 6658:1985 (b) QDA method Leissner (1991)
Fat bloom stability—time to the first sign ofblooming as well as total blooming of chocolate surface

Thermo-cycle test 32/20�C—the sample were alternatelystored at 32 and 20�C every 12 h

Hachiya, Koyano,and Sato (1989)


Lactem P 22, z—the response function for characteristicvalues of the thermoregram.

Analytical methodsAnalytical methods for the evaluation of labora-

tory prepared chocolate quality are presented inTable 3.

Results and discussionChocolate pre-crystallization

The influence of the Lactem P22 and Dynasan 118concentration on the nucleation time and torque

Figure 5 shows the dependence of nucleation durationon emulsifier concentration and the concentration of the

Fig. 5. The influence of the Lactem P 22 and Dynasan 118 concentration on the nucleation time.


crystallization promoter. These results indicate that theincrease in the Lactem P 22 concentration influences thenucleation duration prolonging it. This means thatLactem P 22 as an emulsifier affects the movement speedof the triglyceride molecules, while Dynasan 118, asa crystallization promoter, increases their orientationto constitute the final structure, that is promotes thecrystallization process. The correlative influence of the

emulsifier and crystallization promoter on the crystal-lization kinetics is determined by multiple regressionanalysis. From this results (coefficient of correlation R is0.9056) we can conclude that the chosen regressionfunction satisfactorily describes our data. Figure 6shows the results of the examination of the Lactem P 22and Dynasan 118 concentrations influence on achievingthe torque maximum. Obtained results proved that

Fig. 6. Influence of Lactem P 22 and Dynasan 118 concentration on time before achieving the torque maximum.


Lactem P 22 results in prolonged time necessary toachieve the torque maximum, that is it decreases thecrystallization speed, which justifies the simultaneousaddition of a crystallization promoter. With a higherconcentration of Dynasan 118, Lactem P 22 had a moreeffective influence on decreasing crystallization speed.High value of the correlation coefficient (R=0.9702)indicates that chosen regression function satisfactorilydescribes the interaction between the concentration ofemulsifier and the crystallization promoter and theirinfluence on time before achieving the torquemaximum.

Characteristics of chocolate samplesSensory characteristics of chocolate samples

The diagram representing the dependence of totalscore for chocolate quality on the concentration of theLactem P 22 and Dynasan 118 concentration is shownin Fig. 7. Increasing of the Lactem P 22 concentrationimproved sensory characteristics of the chocolatesamples, while Dynasan 118 in applied concentration hadno considerable influence on quality. The best sensoryquality was achieved by addition of 0.5% Dynasan 118and 2% Lactem P 22. The chocolate samples have ashining, smooth and glossy surface, a shell-like snap and

Fig. 7. Influence of the concentration of Lactem P 22 and the concentration of Dynasan 118 on chocolate sensory quality.

Fig. 8. Influence of the Lactem P 22 and Dynasan 118 on the penetration value–hardness of the chocolate samples.


fine uniform structure and they are in the category ofexcellent sensory quality.

HardnessFigure 8 shows the penetration values of the choco-

late samples pre-tempered at 27�C depending on theconcentration of the emulsifier Lactem P 22 and thecrystallization promoter. The picture clearly shows thatLactem P 22 has a much influence on the hardness ofthe chocolate samples than the crystallization promoterat the applied pre-crystallization temperature (27�C).Contrary to our expectations, the hardness wasdecreasing with the increase in Dynasan 118 concentra-tion at a relatively small quantity of the emulsifierLactem P 22 (1–3%). These results indicate an interactionbetween the emulsifier which softens the chocolate andthe crystallization promoter which increases the amountof crystal, that is it increases the chocolate hardness.

Fat bloom stabilityFigure 9 shows the dynamics of chocolate blooming

depending on the concentration of Lactem P 22 andDynasan 118. Obtained results indicate an interaction

between Lactem P 22 and Dynasan 118, which isreflected in the increase of fat bloom stability with theaddition of higher concentrations of these materials. Aswe expected, the highest fat bloom stability defined asthe total number of cycles is shown by the samples withthe highest concentration of Lactem P 22 and 1% ofDynasan 118, which at the same time has the biggestnumber of cycles prior to the first sign of blooming.

ConclusionLactic acid monoglyceride and diglyceride, to which

Lactem P 22 belongs according to its composition, arerecommended as additives to improve the shine in theproduction of chocolate-like products (compoundcoatings). Our investigations showed that this emulsi-fier could be used in chocolate production as a bloom-ing inhibitor to achieve satisfactory physical, chemicaland sensory attributes. Minor alterations of certainpre-crystallization parameters proved necessary inorder to apply Lactem P 22 successfully. The mostimportant changes were a lower temperature of pre-crystallization and the addition of a crystallizationpromoter.

Fig. 9. Dynamics of the chocolate samples blooming—blooming test 32/20�C: no bloom, dully, weak bloom,bloom, very bloom, intensive bloom.


AcknowledgementsInvestigations are supported by Ministry of Science

and Technology, Republic of Serbia (Project No.BTN.7.1.6.0441.B). The authors would like to thankDanisco Cultor Denmark for supplying material.

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influence of lactic acid ester on chocolate quality

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