Measurement of Ice Cream Texture with the Constant Speed Penetrometer

Measurement of Ice Cream Texture with the Constant Speed Penetrometer M. Tan aka, A. M. Pearson and J. M. deMan Department of Food Science University of Gue~h Guelph, Ontario, Canada

Abstract The texture of commercial ice cream was measured with the constant speed penetrometer using three different penetrating bodies. Yield value and apparent viscosity were calculated from the force-time recordings. The effect of different sweeteners on ice cream texture was determined. The yield value appeared to be closely reJ,ated to the sensory evaluation of firmness and to the freezing point depression of the mix. A series of samples of identical composition produced with different overrun was tested. Overrun was inversely related to the yield value. Apparent viscosity was less dependent on the overrun.

Resume La texture de la creme glacee commerciale a ete mesuree avec le penetrometre a vitesse constante. Celui-ci etant utilise avec trois tiges de penetration differentes. Le rendement et la viscosite apparente furent calcules a partir des enregistrements force-temps. L'influence de divers adoucissants sur la texture de la creme glacee fut etablie. Le rendement semble en relation etroite avec la valeur sensorielle de la fermete et avec I'abaissement du point de congelation du melange. Des echantillons de composition identique obtenus de divers lots sous des conditions non identiques (overrun) furent etudies. Les conditions de passe au-dela du point normal sont en relations indirectes avec le rendement. La viscosite apparente est peu influence par le degre de passe au-dela du point normal.

Introduction The effects of sugar, overrun and storage temperature on frozen ice cream texture have been reported by a number of research workers. Turnbow et al., (1946) reported on the effect of sugar on the physical properties of ice cream indicating that sugar lowers the freezing point of ice cream mix. Monosaccharides such as glucose, dextrose and fructose lowered the freezing points to a greater extent than did the disaccharides sucrose, lactose and maltose. This effect of sugar aids in freezing by making it possible to Whip and freeze the ice cream without the mixture becoming too stiff. (Mix without sugar would freeze too rapidly and form a coating of frozen ice cream on the inside of the freezer making further heat transfer impossible.) The low molecular weight sugars lower the freezing point to such an extent that they cannot be used as the only source of sweeteners because of the difficulty of keeping the ice cream firm at the usual storage temperature. However, when 20-27% of sucrose is replaced with corn-syrup solids, the mix viscosity will be somewhat increased, the rate of melting at room temperature will be decreased and normal whipping qualities will be maintained. The main advantage of corn syrup solids is that the solids content of the ice cream can be decreased without increasing the sweetness and without lowering the freezing point of the mix to the same extent as with sucrose. Oorbett and Tracy (1939) found that dextroseSucrose mixes have lower viscosity than all-sucrose Can.

Inst. Food SeL TechnoJ.

J. VoJ. 5, No. 2, 1972

mixes indicating that the type 'of sugar is related to mix viscosity. The effect of sugar in reducing mix viscosity was explained by Leighton ~t al: (1934). They pointed out that the apparent VISCOSIty of. a given colloidal suspension is the result of two maJor factors the viscosity of the liquid phase of the suspensio~ and the ratio of the volume of the dispersed phase to the total volume of the suspension. The addition of a highly soluble nonelectrolyte (sugar) to such a suspension will increase the viscosity of the liquid phase of the susp~nsi.on, but the resu~ting increase in volume of the hqUId phase may so dIlute the suspended phase that the actual viscosity of the whole system may be reduced. Sommer (1951) stated that high viscosity of the mix does not always accompany high whipping ability and good body and texture in the finished ice cream. Reid and Hensley (1951) reported that ice cream containing 10% liquid sucrose and 5% corn syrup was a smoother product with improved meltdown qualities and ~more resistance to chew. Klotzek (1966) investigated the texture of ice cream with the General Foods Texturometer and found that the hardness, cohesiveness and gumminess tended to increase with the higher levels of corn syrup, and that as the overrun increased, hardness and gumminess of samples tended to decrease, whereas adhesiveness and cohesiveness tended to increase. Frazeur and Harrington (1968) prepared ice cream l'amples containing 13% sucrose, 3% corn syrup solids (42 DE regular) and studied the effect of processing temperatures (21 and 15°F) on texture. They reported that ice cream frozen at the lower temperature had a more desirable body and texture. The rheological properties of frozen ice cream have been studied with the parallel plate viscoelastometer (Shaw, 1963; Shama and Sherman, 1966). At low shearing stresses of up to 4000 dyne/cm 2 , the creep compliance with time at -11°0 showed linear viscoelastic behaviour. Detailed analysis of the creep compliance data indicated that the minimum number of components required for the spring-dashpot mechanical model is eight, viz. one spring to define the instantaneous elastic compliance, 2 Kelvin-Vogt units in series to define the retarded elastic compliance, and a dashpot to represent the Newtonian viscosity. Bdulenko (1969) determined the firmness of ice cream as the yield value by using the cone plastometer. The firmness of ice creams at -30°0 was roughly ten times that at -18°0. The present study deals with the application of the constant speed penetrometer to the objective measurement of ice cream texture as influenced by the type of sugar used, the overrun, and the storage ternperature. 105

Experimental

A

The instrument employed in this work was the constant speed penetrometer descrihed by Tanaka et al. (1971). Aluminum cones with 20°, 40° and 60° angles were used, and the penetration speeds were 0.04 - 0.12 cm/sec. Two rectangular punches of the type descrihed by Bourne (1966) were used. One had a surface area of 0.22cm 2 and a perimeter of 4 cm (punch No. 7), the other had a surface area of 0.80 cm 2 and a perimeter of 8.5 cm (punch No. 4). Experiments were performed at temperatures between -4°C to _7°C with commercial ice cream samples and with experimental samples which differed in overrun. Temperatures 0 f -16.6°C, -14,4 °c, -12.2°C and -11.1°C were used with experimental samples containing different sweeteners. Fat tests were conducted according to the modified Bahcock (Pennsylvania) procedure. Total solids were determined by the method prescribed by the A.O.A.C. Sensory evaluation was based on criteria established by the American Dairy Science Association (Trout et al., 1941), Under this system an ice cream with ideal hody and texture receives a numerical score of 30 points. Freezing point depression of the ice cream mix was determined with a Fiske milk cryoscope. Five different ice cream samples were formulated with different sweeteners (Table 1). The samples were prepared in 15 lbs batches, the mix was pasteurized for 4 min at 74°C and homogenized with a two stage homogenizer, 2,500 psi (176 atm) in the first stage and 500 psi (35 atm) in the second stage. The mix was ,cooled to 14.4°C with tap water. Mix viscosities were determined at this stage. The mix was further cooled on a direct expansion surface cooler to 4.5°C and stored at this temperature overnight. Mix viscosities were again determined after 5 h at 43°C. 'fhe mix was frozen in a hatch-type freezer at an overrun of 90%. The frozen samples were stored overnight in the hardening room at -26°C. The samples were then placed in a freezer cabinet at temperatures of -16.6°C, -14,4°C, -12.2°C or -11.1°C and constant speed cone penetrometer tests performed inside the cabinet.

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8

Composition of Experimental Ice Cream Samples Containing Different Sweeteners.

11.0 11.0 15.0

40

300

Table 1.

%

35

350

:g.200

Milk Fat Serum Solids Sucrose Corn Syrup Solids Dextrose Gelatin Glycerol Monostearate

30

Figure 1 shows the data for sample C using the: 40° cone angle. Curves obtained with the same sample using rectangular punches 4 and 7 are shown in Figures 2 and 3 respectively. The curves obtained with the cone are much more regular in nature than those obtained with the rectangular punches. The interpretation of the latter is more difficult. Figure 1 shows very smooth concave curves; Figure 2 and Figure 3 indicate a yield force at the beginning of the penetration. 'fhe recorded forces for cone penetration depths of 0.5 cm, 1.0 cm, 1.5 cm and 2.0 cm were read for different cone angles and penetration speeds. The penetration stress, F cot (8/2) cos (8/2) /h2 was calculated for different cone angles, depths of penetration and penetration sppeds. (Tanaka et al., 1971). The penetration stress at each penetration depth and for each cone angle was plotted against the penetration speed. The results obtained with sample Dare shown in Figure 4. The number of points shown in this Figure is less than the number of measurements

Four commercial vanilla ice creams coded A-I> were tested. Typical force-time curves for different penetration speeds are shown in Figures 1, 2 and 3. Sample 123

25

(sec)

Force-time curves recorded for constant speed penetration of the cone with 40° angle into sample C at speeds: A - 0.12 cm/sec, B - 0.10 cm/sec, C - 0.08 cm/sec, D - 0.06 cm/sec, and E - 0.04 cm/sec.

250

Evaluation of ice cream texture with the constant speed penetrometer

20

TIME

Results and Discussion

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Force-time curves recorded for constant speed penetration of punch No. 4 into sample C at speeds: A - 0.08 cm/sec, B - 0.06 cm/sec, and C - 0.04 cm/sec. J. Inst. Can. Sci. Technol. Aliment. Vol. 5, No 2. 1972

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Force-time curves recorded for constant speed penetration of punch No. 7 into sample C at speeds: A - 0.12 cm/sec, B - 0.10 cm/sec, C - 0.08 cm/sec, D 0.06 cm/sec, and E - 0.04 cm/sec.

because of overlap of some nearly identical values. The same treatment was applied to the results obtained with the two rectangular punches. For punch No. 4, the penetration stress, F 10.8 + 8.4 h dynes/cm2 , was calculated for different depths. of penetration and penetration speeds. The expressIOn 0.8 + 8.4 h refers to the total contact area of punch No. 4 at depth of penetration h. The penetration stress at various depths of penetration was plotted against the penetration speed and the results for sample B are shown in Figure 5. For punch No. 7, the penetration stress was calculated from the expression: F/O.22+3.94 h dynes/cm 2 • The penetration stress at various depths of penetration was plotted against the penetration speed and the results for sample B are shown in Figure 6. Yield values and apparent viscosities calculated by three different methods are presented in Table 2. Agreement among yield values and apparent viscosities obtained with the three different penetrating bodies was reasonably good. Overrun, fat content, total solids, and sensory evaluation results of the four ice creams are listed in ;;-

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Table 3. Samples with higher yield value had lower overrun and vioe-versa. The results of the sensory evaluation indicate that sample B which had intermediate values for yield value and apparent viscosity obtained the highest score, sample C, which was one of the softest and had medium apparent viscosity, rated second, sample D, which was the hardest and had the lowest apparent viscosity, rated third, and sample A which was one of the softest and had the highest apparent viscosity, obtained the lowest score. From these results it appears that a combination of yield value and apparent viscosity within a certain Table 2.

Sample

A

Apparent Viscosity and Yield Value of Commercial Ice Cream Samples as Determined with Cone and Rectangular Punches. Yield Value Apparent Viscosity Poise x 105 dyne/cm 2 x 104 Punch Punch Punch Punch Cone No.4 No. 7 Cone No. 4 No.7 3.80 1.42 4.05 2.60

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Can. Inst. Food Se!. Teehnol. J. Vol. 5, No. 2, 1972

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Force-time curves recorded for oonstant speed penetration of sample 2; cone angle 40° at -16.6°C. Speeds: A0.12cm/sec, B - 0.08 cm/sec, and C - 0.04 cm/sec.

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Brookfield Viscometer Scale Readings of Ice Cream Mix at 11 and 3.5°C.

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B'rookfield viscometer scale readings of ice cream mix 2 at different speeds using spindle No. 1 at 1l.7°C.

range is likely to result in a product with a greater sensory acceptability than others. This is particularly true with apparent viscosity, where high values seem to result in reduced acceptance. However, the effect of yield value on sensory properties appears to be less than that of apparent viscosity. Effect of different sweetener combinations Mix viscosities of the ice cream mixes prepared with different sweeteners were determined with the Brookfield LVT rotational viscometer using spindles 1 and 2. A plot of scale readings vs. speed of rotation for sample 2 is shown in Figure 7. The hysteresis effect indicated by the up and down curves demonstrates the non-Newtonian character of the mix. The readings for all of the samples at the two temperatures were not necessarily in the same order and there was much less difference in viscosity between samples at the lower temperature (Table 4).

Hardness measurements with the constant speed cone penetrometer resulted in force-time curves of the type shown in Figure 8. The recorded forces at penetration depths of 0.5, 1.0 and 1.5 cm were deterTable 3.

Overrun, Fat, Total Solids and Sensory Evaluation of Commercial Ice Cream Samples. -----------Overrun Fat Total Solids Sensory Sample Evaluation % % % A B C D

108

115 107 120 100

10.1 10.0 10.2 10.1

40.1 39.2 38.5 39.7

Temp. °C

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4.5 28.0 25.1 27.8 49.6 27.7 68.4 27.2 47.8 12.7

7.3 36.8 38.1 38.3 66.7 35.5 86.6 30.9 63.9 17.2

mined and penetration stress was calculated. Penetration stress at each depth of penetration was then plotted against penetration speed resulting in the type of plot shown in Figure 9. Yield values

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Relationship of penetration speed and stress of sample 2, using the 40° cone. J. Inst. Can. Se!. Teehnol. Aliment. Vol. 5, No 2. 1972

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The effect of temperature change on yield value and apparent viscosity is shown in Figures 10 and 11 for samples 1 and 2 respectively. The effect of temperature on yield value was similar for samples 1 -4 ; sample 5 which contained dextrose showed less change. The effect of temperature on apparent viscosity was similar for samples 2 - 5 with only sample 1 showing less temperature dependence (Figure 10). Table 5 shows that there is a definite relationship

1

2

3

4

5

Apparent Viscosity, Yield Value and Freezing Point Depression of Experimental Ice Cream Samples Containing Different Sweeteners.

16.6 14.4 12.2 ILl 16.6 14.4 12.2 ILl 16.6 14.4 12.2 ILl 16.6 14.4 12.2 ILl 16.6 14.4 12.2 ILl

Freezing Apparent Point Viscosity Yield Value Depression Poise x 105 dyne/cm2 x 105 °C

2.6 2.6 2.9 2.3 12.0 7.5 2.1 3.8 11.0 4.5 6.0 1.0 14.0 12.0 7.5 11.0 6.3 6.0 1.2 3.3

Can. Inst. Food Sel. TeehnoI. J. VoI.

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It was found that the organoleptic ranking of firmness was in agreement with the order of yield values as determined by the constant speed cone penetrometer.

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Temperature dependence of yield value (solid line) and apparent viscosity (dotted line) of sample 1.

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and apparent viscosities were calculated from this data and results are given in Table 5.

Table 5.

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No. 2, 1972

0.412

0.407

0.377

liT Fig. 11.

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Temperature dependence of yield value (solid line) and apparent viscosity (dotted line) of sample 2.

Conclusions The constant speed penetrometer was used successfully f,or the objective evaluation of ice cream texture. Of the three penetrating bodies used, the cone had the advantage of giving curves which could be more easily analyzed than those obtained with the rectangular punches. Yield value and apparent viscosity of the ice cream was calculated from the forcedistance recordings. Organoleptic ranking of firmness was generally in good agreement with the order of yield values determined from the penetrometer data. When ice cream samples differed only in air content, Apparent Viscosity and Yield Value of Experimental Ice Cream Samples With Differing Overrun.

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10

between yield value and freezing point depression, the greater the freezing point depression the lower the yield value. Effect of overrun on ice cream texture To determine the effect of overrun on rheological properties, five samples of ice cream were made up to varying levels of overrun with otherwise identical composition (F to J, Table 6). The samples contained 12% sugar and 4% corn syrup solids and were otherwise formulated as listed in Table 3. Samples were measured with the constant speed cone penetrometer at -7°0 in the freezer cabinet and yield value and apparent viscosity calculated; these results are presented in Table 6. Both apparent viscosity and yield value were inversely related to overrun. Organoleptic ranking of firmness of the samples resulted in the same order of firmness with sample F most firm and sample J least firm.

Table 6.

0.357

X

F G H I .T

--

----

Overrun %

Apparent Viscosity Poise x 105

Yield Value dyne/cm2 x 1()4

41.0 68.7 86.0 110.0 115.0

4.1 3.9 3.6 3.4 2.5

5.9 4.5 4.0 3.5 2.9

109

there was an inverse relationship between overrun and both apparent viscosity and yield value. The objective evaluation of ice cream texture could be performed without difficulty in the storage cabinet so that there was no possibility of temperature changes affecting the measurements.

References Bdulenko, L. D. 1969. Changes In the Firmness of Ice Cream During Storage. Izvestiya Vyrshikj Uchebynkh Zavedenli, Pishchevaya Tekhnologiya 1969: 65. Bourne, M. C. 1966. Measure of Shear and Compression Components of Puncture Tests. J. Food Scl. 31: 282. Corbett, W. J. and Tracy, P. H. 1939. Dextrose In Commercial Ice Cream Manufacture. nllnOls Agr. Expt. Sta. Bull. 452. Frazeur, D. R. and Harrlngton, R. B. 1968. Low Temperature and Conventionally Frozen Ice Cream. Food Technol. 22: 910.

no

Klotzek, L. M. 1966. Objective Evaluation of Body in Ice Cream. J. Dairy Scl. 49: 1285. Lelghton, A., Leviton, A. and Wllliams, O. E. 1934. The Apparent Viscosity of Ice Cream. J. Dairy Ccl. 17: 639. Reid, W. H. E. and Hensley, R. B. 1959. The effect of Retail-Store Environment on the Physical Properties of Vanilla Ice Cream Sweetened with Liquid Sucrose and Corn Syrups. 15th Int. Dairy Congr. 2: 1179. Shama, F. and Sherman, P .1966. The Texture of Ice Cream. 2. Rheological Properties of Frozen Ice Cream. J. Food Scl. 31 :699. Shaw, D. 1963. The Physical Structure of Ice Cream. Rheology of Emulsions. Pergamon Press, London. Sommer, H. H. 1951. The Theory and Practice of Ice Cream Making. Madison, Wisconsin. Tanaka, M., deMan, J. M., and Voisey, P. W. 1971. Measurement of Textural Properties of Foods With a Constant Speed Cone Penetrometer. J. Texture Studies. 2: 306. Trout, G. M., White, W., Downs, P. A., Mack, M. J. and Fouts, E. L. 1941. Official Body and Texture Criticisms of Dairy Products Judged In the National Contest. J. Dairy Scl. 24: 65. Turnbow, G. D., Tracy, P. H., and Raffetto, L. A. 1946. The Ice Cream Industry. John WHey & Sons Inc. New York, N.Y. Received Nov. 25, 1971.

J. Inst. Can. Scl. Techno!. Aliment. Vo!. 5, No 2, 1972