Rheological characterization of traditional and light mayonnaises

Rheological Characterization of Ikaditional and Light Mayonnaises Donatella “Department

Peressini”*, Alessandro of Food Science,

“Department

University

of Chemical 87030 (Received

Sensidoni” & Bruno de Cindio”

of Udine,

Via

Marangoni

Italy Engineering and Materials, Arcavacata

Rende.

Coscnza.

20 July 1YY7; accepted

No. 07. 3.1100 Udinc.

University

of Calabria,

Italy

Y February

1098)

ABSTR4 CT Mqvonnaises are oil in water emulsions with a texture that is particular& appreciutc& by consumers. The actual nutritional trend towards low-calorie ftiods has increased the interest in fat substitutes without altering the consistenc:\~ qf’ the product. From this point of view rheological properties may gi:rvea quantitative contribution to texture characterization and control when using different formulations. The rheological approach has been applied to typical commercial normal and light mayonnuises with a fat content ranging fkom 76 to 485%. These materials have shown a viscoelastic hehaviour that was measured by means of both oscillatoq and creep-recovery tests. The storage modulus, the compliance and the yield stress w’ere ,found to increase when increasing the fat content. A modified Bolhin theor?: was used to relate .structural parameters to rheological dynamical meusurements. Thus the emulsion stabiliq was quantified by means of a pseuclol,l~~stic-coorzlinlrtiorl number (2) and the value of G’ at I Pt. From the creep test the value of the yipId stress was determined and in the case of the light muyonnaise M/USerg close to a normal emulsion whereas the corresponding viscoclustic properties were very different. This implies thut to reproduce an assumed texture, it is nccessuty to perjorm all the tests outlined. 0 1998 Elsebirr Science Limited. All r&h ts reserved

7’0 whom

corrcspondcnce

should hc addresxd. 4OY

Fax: 003~ (0)432

SOlh.37.

D. Peressini et al.

410

INTRODUCTION Because of the spread of healthy eating trends, there is an increasing popularity and demand for the so called ‘light’ products, in particular low-calorie and reduced-fat products. In addition to nutrition, fat influences rheological properties and sensory characteristics of foods such as flavour, mouthfeel and texture. These sensory properties are very hard to reproduce in formulations without fats. Therefore it is rather difficult to imitate traditional product quality when preparing low-fat foods. There is the possibility of choosing particular fat substitutes in specific quantities in order to have a product with a texture close to that of traditional mayonnaise. Thus to establish the formulation of the low fat products, food technologists have focused their efforts essentially on fat replacers (Singhal et al., 1991; Setser & Racette, 1992; Akoh, 1995). From a physical point of view mayonnaise is an oil in water emulsion (O/W) (Weiss, 1983) and therefore to produce a dietetic mayonnaise it is necessary to decrease the dispersed phase and to increase the water content. Modified starch, starches, xanthan gum, pectin and carboxymethylcellulose are generally used to stabilize the emulsion and to increase the viscosity of light mayonnaise. In the last decade there is also a trend to prepare water in oil in water (W/O/W) double emulsions as reduced-calorie foods. Recently de Cindio and Cacace (1995) reported that the rheological properties of W/O/W emulsions were similar to those of a simple O/W emulsion with the same volume of the dispersed phase, but with a lower oil content. Therefore double emulsions could be used to reduce differences between traditional and light products. The rheology of mayonnaise was investigated by several authors because of its importance for the choice of formulation, process conditions and quality control (Tunaley et al., 1985; Campanella & Peleg, 1987; Garcia-Navarro et al., 1988; Munoz & Sherman, 1990; Gallegos et al., 1992; Chiralt et al., 1994; Pons et al., 1994; Ma & Barbosa-Canovas, 1995). Mayonnaise shows a yield stress, a pseudoplastic behaviour and time dependent characteristics. The power law, Herschel Bulkley and Casson models have been widely used to describe the flow properties of mayonnaise and salad dressing (Bistany & Kokini, 1983; Paredes et al., 1988, 1989; Ma & Barbosa-Canovas, 1995).

TABLE 1

Chemical Characterization, pH and a, of Commercial Determinations

Fat (g per 100 ml) Moisture (g per 100 g) Carbohydrate (g per 100 ml) Protein (g per 100 ml) Ash (g per 100 g d.m.) Water activity PH CV. Coefficient

variation

Mayonnaises

Sample I

Sample 2

Sample 3

Sample 4

CV%

76.2 16.6 05 1.3 1.5 0.97 3.9

68.6 24.9 1.0 1.3 1.1 0.97 4.0

634 27.9 3.3 1.4 1.1 0.97 4.0

48.0 42.3 8.7 1.0 3.4 0.96 3.7

2.8 ::; 3.5 1.9 0.3 0.6

Rhrological characterization

qf mayotwtise

411

2,4

2,2 -1

-0,5

0

Log frequency

0,s

1

(Hz)

Fig. 1. The storage modulus (G’) versus oscillation frequency for different mayonnaises before stirring (A. sample I; l , sample 2; n, sample 3; +, sample 4) and after stirring ( r, sample 1: :’ . sample 2: 0. sample 3: +. sample 4).

When dealing with rheological characterization there are several choices which differ in applied stress or deformation history. Typical measurements are shear flow (constant deformation history), creep (constant stress history) and oscillatory flow (asymptotic kinematics), which give different information. Therefore researchers arc required to understand better the flow/stress field that is relevant for the specific application, before starting to rheologically characterize every material. Concerning products that are shifted from traditional to light by reducing or substituting fats, it is well known that the viscosimetric characterization results alone may not be sufficient to differentiate them. Even if the modified product shows approximately the same viscosity, nevertheless consumers are capable of feeling sensible differences. Thus a more careful rheological characterization is needed to make a correct formulation. In addition, viscosity measurements are not capable of giving information on the emulsion stability. Thus a better understanding of the link between the structure and macroscopic measurable properties is necessary. This can be achieved by means of a dynamic test at low oscillation amplitudes according to the cooperative theory of flow (Bohlin, 1980) that seemed to apply to systems such as emulsions (de Cindio & Cacace, 1995; Semenzato et al., 1996). The objective of the present work has been to chemically and rheologically characterize traditional and light mayonnaise in order to study the influence of oil content on emulsion structure, by means of the already quoted theory.

D. Peressini et al.

412

16

a 6 -1

-05

0 Log frequency

03

1

(Hz)

Fig. 2. The phase angle versus oscillation frequency for different mayonnaises before stirring (A, sample 1; l, sample 2; n, sample 3: +, sample 4) and after stirring (A, sample 1; C, sample 2; n, sample 3; c, sample 4).

30

1

I

-1

1

-0,5

0 Log frequency

0,5 (Hz)

Fig. 3. The storage modulus decrease percentage, (G’-G:,,,,.,,,,)/G’ x 100, versus oscillation frequency. A, sample 1; l, sample 2; w, sample 3; l, sample 4.

Rheological

characterization

qf tnayont~aisc

41.3

TABLE 2 Values of Fitting Parameters for the Power Law G’ = Ac~J"', Bohlin’s Parameters ; and .4 -Saniples @Jr

LogA

SD/j

z

-.-

SD

stirring

53

2.00 2+X) 2.x2

ONK WOO4 0.0 I2

4

263

I

3 J

I

1 I I.52 1.48

0.46

0~1.36 0. I8h 0.375

OW6

7.83

0.12’)

2el

ON I 1

9.23

0~200

2.54 2.37

0.020 0~012 0914

8.7Y 8.37 h+l4

0.1)03 0.070 0.122

B~fim stirriilg 7

SD.

Standard deviation.

MATERIAL

AND METHODS

Four commercial samples of traditional and dietetic mayonnaises (samples 1, 2, 3 and 4) were analysed. Measurements were repeated four times using samples taken from different jars in order to determine any differences between batches. Rheological characterization A controlled stress rheometer (StressTech Rheometer, Reologica Instruments AB. Sweden) was used for rheological characterization. Measurements were performed at 25°C ( kO.2). All samples were allowed to rest for 5 min after loading to alloy induced stress to relax and temperature equilibration. For the dynamic tests, cone and plate geometry was utilized with a cone diameter of 40 mm and a cone angle of 4”. The storage and loss moduli G’ and (;” were measured at frequencies (OJ) ranging between 0.1 and 10 Hz at a strain of I %mthat resulted within the linear viscoelastic region. In order to study emulsion stability. samples were prepared by means of a magnetic stirrer (Ikamag RET-GS 3, Jankc and Kunkel GmbH and Co. KG, IKA-Labortechnik, Staufen, Germany) at 300 rpm for 5 min and immediately tested.

____ S(U?l&Y

I

TABLE 3 Results of Yield Stress and Creep Yield s trm

C’V% YS.

Compliance

(Pa

Tests

‘) x 10

’

C’CT .I

40.6

2.8

3.1

34!

25.4 23.4 IY.4

0.02 0 0

3.6 3.8 7.4

4.2 3.0 5.5

3

3 3

( PN)

and Recovery

CV, Coefticient variation.

D. Peressini et al.

414

1 Shear rate (I/s) Fig. 4. Apparent

viscosity versus shear rate for sample 2 (o), 3 (m) and 4 (+).

0,Ol

0,008

2 0,006 :V 3 v- 0,004 7 0,002

0-l

I

I

0

100

200 Time

300

400

(s)

Fig. 5. Creep and recovery analysis at a stress of 15 Pa. n, Sample 1; o, sample 2; x , sample 3; l, sample 4.

Rheological characterizatiorl of mayonnaise

415

The apparent viscosity, yield stress and creep and creep recovery measurements were performed using a plate-plate geometry (diameter of 40 mm) with a gap of 15 mm. The creep and creep recovery analysis was made at a stress of 15 Pa. Compliance (J) was calculated by extrapolation of the curve obtained in the viscous region to time 0. From the creep test the value of the yield stress was determined by applying a fixed stress. Apparent viscosity was determined at shear rates ranging from 0.4 to4s -I. Chemical analysis Moisture, fat, protein, ash, carbohydrate and pH were determined according to the official methods (AOAC, 1980). Water activity (a,) was measured using the AquaLab CX-2 instrument (Decagon Devices, Pullman, WA, U.S.A.) at 25°C.

RESULTS

AND DISCUSSION

Chemical composition, pH and a, of the different commercial mayonnaises are shown in Table 1. Fat content ranged from 76% corresponding to a normal product to 48% for light mayonnaise, while moisture ranged from 16 to 42% respectively. Obviously, the lower the fat content, the higher the aqueous phase. In order to ensure emulsion stability, gums, modified food starches and starch hydrolysates showing fat-like properties were added to the continuous aqueous phase. Therefore light mayonnaise has a higher content of carbohydrate than traditional mayonnaises (see Table 1). The protein content was about the same for all the samples, with the tendency to be lower for the light mayonnaise. The egg lipoproteins create a stable network at the W/O interface, thus showing a high emulsifying capability that contributes to the equilibrium between the two phases. This implies that a lower stability results from reducing them as in light products. In the oscillatory test all samples exhibited a viscoelastic behaviour with a storage modulus (G’) greater than the loss modulus (G”). To check the emulsion stability the samples were also tested after stirring. The storage modulus vs oscillation frequency for different mayonnaises before and after stirring are shown in Fig. I. Generally speaking it is expected (Ma & Barbosa-Canovas, 1995) that emulsions with a greater fat content show higher values of G’. This was found for all samples except for sample 3 that exhibited a higher storage modulus than sample 2 in spite of the lower oil content, probably because the G’ reduction was counterbalanced by the carbohydrate increase in formulation, that structure the material (Munoz & Sherman, 1990). As expected, light mayonnaise (sample 4) showed the lowest storage modulus. It can be concluded that if fat decrease is considerable, carbohydrate addition is not sufficient to compensate for the fall in rheological properties of traditional products. It was found that mechanical stirring caused a reduction of G’ for all samples (Fig. 1). It is useful also to report the phase angle for the tested samples to have a direct view on whether the different samples behave as liquid or solid. From Fig. 2 it appears that samples l-3 show a more solid-like behaviour than sample 4 (light

416

D. Peressini

et al.

mayonnaise). The difference between samples 1-3 becomes more apparent after stirring. In Fig. 3 the storage modulus decrease percentage is reported, (G’G,‘ti,,i”&/G’ x 100, versus oscillation frequency. This is a measure of the emulsion stability. It is interesting to note as the less stable sample was sample 3. This is in accordance with the previous results that considers sample 3 as a more structured material but is also more sensible to deformation. The structure of sample 1 was the most stable because of the lowest G’ decrease percentage, while samples 2 and 4 gave intermediate and similar values. It is necessary to note that the storage modulus decrease percentage is connected with a weak structure. Besides G’ decrease percentage, the absolute value of G’ is important in order to give information on emulsion stability. The experimental data on the frequency sweep tests were correlated according to the following power-law: G’ = Aw’” (mean correlation coefficient 0.998). According to Bohlin’s theory of flow as a cooperative phenomenon (Bohlin, 1980), the coordination number z and the proportional coefficient A (G’ in Pa at 1 Hz) were obtained for all samples (Table 2). On the basis of this theory, emulsions are modelled as a network of rheological units, which interact for establishing system structure. The coordination number z gives the level of these interactions and the coefficient A their magnitude. The z values ranged from 7.83 to 11.52 and between 6.64 and 9.23 for mayonnaises before and after stirring, respectively (Table 2). Sample 3 presented the most complex structure while the light product (sample 4) gave the least number of microstructural interactions of all mayonnaises. Emulsion stability depends on the coordination degree between rheological units (2) and on interaction strength (A). Low values of z and A mean the tendency of dispersed droplets to coalesce when the system undergoes mechanical stress. As a consequence, mayonnaise 4 resulted the most subjected to instability for the lowest values of z and A (Table 2). Sample 1 was the stablest because the highest value of A assured the least changes of the coordination number after stirring (Table 2). Some other interesting information was provided by yield stress and creep and recovery tests (Table 3). A decrease in the yield stress with the decrease in oil content was observed in all products, even if samples 2, 3 and 4 gave similar values. Apparent viscosity curves gave the same results (Fig. 4). This suggests to the food industry that very little or no changes in consistency of light emulsions can result from carbohydrate addition to the continuous phase. Creep and recovery analysis confirmed the results of the dynamic test (Fig. 5 and Table 3). The compliance (J), that is connected with the reciprocal of the elastic modulus of a Hookean body (Jo = l/G) increased from samples 1 to 4 (Table 3). Therefore, the elastic modulus of Hookean body became higher with increasing oil concentration. From these results, it can be asserted that the compact packing of oil droplets into lipoproteic network is responsible for elastic properties and deformation resistence of the emulsion.

CONCLUSIONS The results obtained to date confirm that the rheological characterization is capable of distinguishing rather well between mayonnaise made with a different formulation.

Rizcologicul

chvucterizutior~

of muyotmuisc

417

Thus when preparing a new formulation of hypo-caloric mayonnaise, so as to obtain the same rheological response it is useful to perform the set of rheological measurements described. This may be the only way of obtaining a product with a ‘texture’ or ‘consistency’ similar to that of traditional mayonnaise.

REFERENCES Akoh, C. C. ( IFPi). Lipid-based 35(S).

fat substitutes.

C’titicul

RelGt:s

irt fitod

Scirrlcc

(rtlrl ,Ylhtrotr.

405-430.

AOAC (lY80). 0#iciul Methods of’Anu3’sis. 1980. 13th cd. Association of Official Analyt ~cal Chemists. Washington. DC. Bistany. K. L. & Kokini, J. I,. (10X3). Comparison of steady shear rhcological propcrtics and small amplitude dynamic viscoelastic propertics of fluid food materials. Jowwl of’ 7?x/rrre Strtdies. 14(Z), I 13- 124. Bohlin. 1,. ( 1980). A theory of flow as a cooperative phenomenon. Jottrmd of Collor’d (cm/ 1tltetfk.e

Science,

74, 423-434.

C’ampanella, 0. H. & Pelcg, M. (1987). Analysis of the transient coaxial viscosimetcr. Jourtlul of’Rheolo~. 31(h). 439-452.

few of mayonnaise

in

;I

C’hiralt, A., Salazar. J. A. & Fcrragut, V. (1904). Rheological study of O/W emulsions containing dried whole egg and locust bean gum. Jourtlrrl of Tertwe Studies. 25(l), X--4?. de

Cindio, B. & Cacacc. D. (19Y5). Formulation and rhcological characterization of rcduccdcalorie food emulsions. Itttcrttntionul .Jorrrtzal of Food Sciettcc ~rtttl Tkholqq~~. 30(4).

SOS-S 14. Gallegvs, C..

Berjano, M., Guerrcro, A.. Munoz, J. & Flares, V. (IYY2). Transient tlou of mayonnaise dcscribcd by ;I nonlinear viscoelaticity model. Jorrrttul qf Textwe Studies. 23( 2). I s3- 168. Garcia-Navarro. F. P., Berjano-Nunez, M. & Gallcgos-Mantes. C. (IYXX). Rheology of mayonnaises. Grusus-y-Aceites. 39(4/S), 2X l-285. Ma, L. & Barhosa-Canovas. G. V. (1995). Rhcological characterization of mayonnaise. Part 2: flow and viscoelastic properties at different oil and xanthan gum concentration\. Jorrrttctl of’ Food Etginceritlg,

25(3),

409-42.5.

Munoz, J. & Sherman, P. (1990). Dynamic viscoelastic properties of some commercial salad dressings. Jowtrul qf‘ Texture Studies, 21(4), 41 I-426. Paredcs, M. D. C., Rao, M. A. & Bourne, M. C. ( 1988). Rhcological characterization ot salad dressing. I: Steady shear. thixotropy and effect of temperature. Jowttul of Trwrrre .Stw/ie.s. 19, 247-25x.

Parcdes. M. D. C.. Rao. M. A. & Bournc, M. C. (lY8Y). Rheological characterization of salad dressing. 2: Effect of storage. Jowmd of Texture Studies, 20. 235-250. Pans, M., Galotto, M. J. & Subirats. S. (I9Y4). Comparison of the steady rheological charactcrization of normal and light mayonnaises. i+oti Hydrocolloids, 8(3-4). 3XY-400. Semenzato. A., D’Antona, P., de Cindio, B. & Tollardo, A. (1996). Sviluppo di un test prcdittivo dclla stabiliti di cmulsioni cosmetiche mediantc parametri reologici. In Proccwditlgs IV Cotwegtw Nrrziotlulc di Reologiu Appiicutu. Vito Equcnse, l2- IS June. pp. hS -6’). Sctser, C. S. & Racettc, W. (lYY2). Macromolecule replacers in food products. C‘ritictrl Reviews in FCJO~Science utd

Mitrition,

32(X),

27%2Yl.

Singhal. R. S.. Gupta, A. K. & Kulkarni, P. R. (l9Y I). I.ow-calorie fat substitutes. Trcwds it? J+od Scietlce utld Teclmology, 2( IO), 24 I-244. Tunalev. A., Brownscy, G. & Brocklehurst, T. F. (1985). Changes in mayonnaisebased salads during storage. Lehensmittel- Wissenschqft wld-Techologie, 18, 220-224. Weiss, T. J. (1983). Food Oils atid Their Uses. Ellis Horwood, Chichester. U.K.