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An Electronic Recording Instrument for Measurement of Torque During Whipping of Cream and Toppings
An Electronic Recording Instrument for Measurement of Torque During Whipping of Cream and Toppings l\f. Tanaka and J.
~f.
deMan
Department of Food Science University of Guelph Guelph, Ontario
Abstract A household mixer was modified for continuous torque recording during mixing by means of a strain gage transducer connected to a pully on the bowl shaft and operating with an electronic recording attachment. Maximum torque, plateau torque, the time to reach maximum torque, and the slope of the torque curve were determined from the recorded torque~time curve. The addition of sugar to whipping cream resulted in increases in both plateau torque and the slope of torque curve, and decrease in the time to reach maximum torque. This means that the addition of sugar increases the rate of whipping and results in firmer whipped cream. The dilution effect of toppings with milk was determined for some commercial samples. The slope of the torque curve decreased and overrun increased with the addition of milk.
Resume Un malaxeur domestique a ete modifie pour l'enregistrement continu de la torsion au cours du malaxage en raccordant un transmetteur jauge raocorc1e a une pouJie sur l'axe du bol et fonctionnant a l'aide d'un enregistreur electronique. La torsion maximum, la torsion du plateau, Ie teIIliPs pour atteindre la torsion maximum, et la pente de la courbe de torsion ont ete determines a partir de la courbe de la torsion en fonction du temps. L'addition de sucre a la creme a fouetter a augmente la torsion du plateau et la pente de la courbe de torsion, et diminue Ie temps de torsion maximum. Ceci veut dire que l'addition de sucre augmente Ie taux de fouettement et produit une creme fouettee plus ferme. L'effet de la dilution des gla«;ages avec du lait a eM determine sur quelques echantillons du commerce. L'addition de lait a diminue la pente de la courbe de torsion et augmente Ie rendement.
Introduction Fairly extensive work has been done on establishing the mechanism of the whipping 'of cream. Sommer (19:)2) explained the whipping of cream by assuming that air cells are incorporated in the cream and some churning or coalescence of the fat takes place; stiffness or rigidity depends upon (1) the size of the air cells (2) the size and rigidity of the coalesced fat masses (3) the amount of fat and incorporated air, and (4) the stability of the air cells. If the air cells are large, interstices between the cells will be correspondingly large, and small fat masses will be accommodated without any distortion. Only when the fat masses reach such a size that they can no longer be accommodated by the interstices will distortion of the air cells occur. Thus, if the air is coarsely incorporated, more advanced churning is required to attain stiffness' the whipped cream will be coarse in texture both because of the larger air cells and because of the large fat masses. The resulting whipped cream will not be as rigid as a product that contains the same amount of air and fat in a more finely dispersed condition. There is a general relationship between the volume of air or overrun and whipping quality. Creams that Whip rapidly and produce whipped cream of desirable stiffness generally yield a lower overrun than creams of poorer whipping qualities. 1
Mohr (1955) ,outlined the requirements for the production of high quality whipped cream as follows: (1) a whipped product with finely distributed air bubbles (2) a cream of sufficiently high fat content to allow all the air bubbles to be surrounded by fat, (3) the presence of a high proportion of crystallized fat in the fat globules in order to bind as much butter oil as possible after ageing, (4) preventing the formation of too much butter oil, especially during the summer, by whipping the cream at 2° - 4°C and storing it below 10°C to avoid drainage of the aqueous phase. Heiss (1961) studied the effect of the treatment of whipping cream on the firmness, volume increase and serum separation of the resulting whipped cream, and found that cream containing 34% butterfat and a pasteurization temperature of 95°C was best. For testing the whipping qualities of cream, several methods have been developed. Muller (1935) proposed a method for comparing cream with respect to whipping time and stiffness. A power driven whipper was combined with a suitable wattmeter and the stiffness of the cream was observed during whipping by following the wattmeter readings. Muller tested creams ranging from 20 to 39.5 per cent fat and found that maximum overrun occurred shortly before maximum stiffness was reached. Mohr and Koenen (1953) described an instrument for the testing of whipping cream. Two six wired beaters rotate at a fixed speed ill a stationery cylinder surrounded by an ice water Jacket. Resistance to rotation of the beaters was indicated by a milliammeter. De Vleeschauwer (1961) tested the effect of wire shape on the whipping of 40% cream and found that beaters with 3 wires required a longer whipping time but gave a greater ,overrun with some loss in stiffness of the whipped cream, and that the maximum reading on the milliammeter was lower with the 3 wire beaters, but it more nearly coincided with the maximum overrun of the whipped creams. I Hendrickx (1965) also tested the Mohr & Koenen i apparatus with the 3 wire beaters and found that greater overrun was obtained, but the consistency was reduced. Smellie (1966) developed a testing apparatus by combining a small electric domestic mixer with a variable resistance. A specially made basket-shaped whisk was used, about 10 cm in diameter and consisting of 10 wires shaped to the profile of the whipping bowl. Babcock (1922) determined the stiffness of whipped products by the weight in grams required to cause a disk to settle into and displace the cream. The Hill Curd Tensiometer was used which has a round disk of one square inch area instead of the curd knife and the, Can. lnst. Food Science and Technol. J. Vol. 5. No. I, 1972
Fig. 1
Modified mixer for recording torque during whipping of cream and related products. A - View of mixer showing pulley attached under bowl platform. B - View of torque sensing transducer connected to pulley by nylon line. C - Overall view of mixer with transducer amplifier and recorder.
resistance in grams to the passage of this disk into the whipped cream is measured. Smellie (1966) showed that the point at which the whipping of 40% fat cream is normally stopped is past the point of maximum overrun, and the product, although somewhat granular in appearance, is still fairly soft. The cream with the best appearance was obtained at maximum overrun, but had high seepage and was soft. He tested 36% and 40% creams and reported that optimum values of these characteristics did not coincide with the maximum meter reading. The maximum meter reading corresponded to an overrun lower than that obtained at the maximum; at this point the cream was overwhipped and there was also a sharp increase in firmness past the point of maximum overrun. There was also a distinct relationship between overrun and temperature; the lower the temperature the higher the oVerrun. No specific trend was noticed in the relationship between whipping temperature and firmness of whipped product but lower overrun generally meant greater firmness. De Vleeschauwer (1960) tested 40% cream with the Mohr apparatus and found that prolonged aging had little effect on overrun in whipped summer cream Table 1 Mixing Speeds of the Recording Mixer as Related to Instrument Speed Control Description Control Setting 1 2 3 4 5 6 7 8 9
stirring slow mixing pre-mixing creaming cake mixes blending beating whipping heavy beating
~attachments
Spindle Speed r.p.m. 275 329 397 459 532 598 687 771 872 932
-
280 337 410 469 544 610 709 787 892 949
Variation %
1.8 2.4 3.3 2.2 2.3 2.0 3.0 2.1 2.3 1.8
Mean Spindle Speed r.p.m. 278 333 402 464 539 603 697 780 877 940
J. lnst. Can. Science e', Techno!. Aliment. Vo!. 5, No 1, 1972
but stiffness was markedly reduced, however, in the case of winter cream overrun increased with prolonged aging and the loss in stiffness was less marked than with summer cream. For the study of the whipping characteristics of cream and similar products, it is highly desirable to have an instrument that allows continuous recording of the changes in consistency occurring during the whipping process. This report describes the construction of such an instrument and its application in the evaluation of various factors affecting whipping.
Experimental The instrument is a common household mixer (Philips) with a double set of metal beaters. The mixing speed can be varied with a 10 step speed control. The relationship between speed control setting and spindle speed was determined and is presented in Table 1. The bowl is normally placed on a freely rotating platform and this was modified by elongating the shaft supporting the platform and by attaching to it nnder the mixer (Fig. 1) a pulley with a diameter of 6 em. A nylon line was attached to the pulley and connected at the other end to a metal cantilever beam to which four strain gages were bonded according to the full bridge pattern described by Voisey et al. (1966). To prevent the bowl from slipping on the platform, two short pins were soldered to the bowl and holes drilled in the platform to engage the pins. The drag on the bowl caused by increasing viscosity during whipping is converted to a force transmitted by the nylon line to the strain gage transducer beam. The strain gages were connected to a Daytronic model 900 D 3 strain gage amplifier indicator and the output recorded on a 10 mV strip chart recorder. The recorder was electronically damped to obtain an average torque record and prevent excessive "noise" from appearing on the recording. The instrument was calibrated with weights which were attached to the strain gage transducer beam with a nylon line strung over a pulley in front of the instrument. This line was attached at the same position on the beam as the one connection to the bowl platform pulley. The recorded force acts at a distance of 3 cm from the center of the bowl and is expressed as torque in g. cm. Since the torque reading is dependent on sample 2
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Typical torque-time recording of the whipping of cream at spindle speed of 780 rpm.
size, the same quantity of sample must be used for comparative studies. For the experiments described in this paper, commercial whipping cream with a fat content of 32% was used. Sample size for all tests was 110 g of cream. POI' testing the effect of sugar, 5%, 10% or 15% of sugar was added to 110 g of whipping cream and dissolved with gentle stirring. The mixture was then whipped at 780 rpm and 10°0. Maximum torque, time to reach maximum torque, the slope of the torque curve and plateau torque were obtained from the torque-time recording. Overrun was determined by weighing a known volume of the whipped product. For the testing of toppings, commercial dry mix products were used. 113 ml of milk were added to one package (60 g) of product, and the mixture whipped at 780 rpm and 10°0. Consistency of the whipped products was determined by a plate penetrometer method. A metal plate with a surface area of 11.3 cm 2 was driven into the product at a constant speed of 0.12 cm/sec and the resulting force recorded (deMan, 19(9). From the recorded force-time curves force readings were made at depths of penetration of 0.12, 0.36, 0.60, 1.20 and 1.80 CIll. Haroness was calculated by dividing the force in grams by the disc area in cm 2 •
Results and Discussion A typical torque recording for the whipping of cream at 10°C and a spindle speed of 780 rpm is presented in Fig. 2. The initial part of the curve shows a gradual increase in torque, followed by a constant portion which will be referred to as "plateau torque". The plateau is followed by a sudden large increase leading to a maximum torque which rapidly falls off to a minimum. The sudden increase and drop in torque coincides with churning of the cream and separation of the emulsion. Spindle speed has a profound effect on the whipping of cream. Reduction of spindle speed from 780 to 697 rpm resulted in change in maximum torque from
3
Typical torque-time recording of the whipping of a whipped toppings at a spindle speed of 780 rpm.
63.6 g. cm to 12.4 g. cm, and time to reach maximum force from 1.6 min. to 11 min. At a speed of 464 rpm no whipping -occurred at all and no increase in torque was observed. . Changing whipping temperature from 10 to 20°C at a speed of 780 rpm decreased maximum torque from 63.6 g. cm to 34.8 g. cm and plateau torque from 18.9 g. cm to 6.0 g. cm. However, the time to reach maximum torque was not affected by temperature. The torque-time recordings of whipped toppings are different in shape from those of whipping cream. A typical torque recording for the whipping of a whipped topping is presented in Fig. 3. The force increases almost linearly with time to a maximum value, thereafter, there is a gradual decline of torque but in no case is there a sudden drop as seen in whipped cream torque recordings. Obviously the whipped toppings are more stable products and not subject to churning. Increasing whipping temperature of the topping from 10 to 20°C resulted in a decrease of maximum torque from 119.5 g. cm to 72.0 g. cm. The change in temperature did not affect the time required to reach maximum torque. The effect of sugar addition to cream OIl the rheological properties ,of the Whipped product was measured. Since maximum torque of whipped cream is not as reproducible as plateau torque, the latter was chosen to describe the effect of sugar addition. The changes in torque curve slope and plateau torque as a function of amount of added sugar are presented in Fig. 4. Addition of sugar up to a level of 15% resulted in increase of plateau torque, indicating a firmer whipped product. Torque curve slope also increased with increasing amount of added sugar. Whipping time (time to reach maximum torque) was reduced by sugar addition ('fable 2). The extent of Table 2 Change in Whipping Time and Overrun of Whipping Cream as Affected by Sugar Addition Sugar Added %
o
5 10 15
Whipping Time Sec.
192 123 138 142
Overrun %
76 78 79
83
Can. lnst. Food Science and Techno!. J. Vo!. 5, No. I, 1972
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Effect of milk volume used in making up topping mix on maximum torque (solid line) and overrun (dotted line).
J. lnst. Can. Science et Techno!. Aliment. Vo!. 5, No 1, 1972
VOLUME
(ml )
Effect of milk volume used in making up topping mix on torque curve slope.
the decrease was not greatly affected by the level of sugar addition, the lowest level of sugar caused the largest decrease in whipping time. Overrun was not affected by sugar addition. It appears from these experiments that sugar increases the ease of whipping and results in a firmer whipped cream. Microscopic examination of the whipped products indicated that the sugar containing whipped products had a somewhat coarser dispersion of air than the product without sugar. These results are probably somewhat dependent on the nature of the beater blades and the geometry of the blades and bowl. Literature reports on the effect of sugar on whipped cream are contradictory. Melick (1909) reported that sugar addition improves the properties of whipped cream. Babcock (1922) found that sugar resulted in decreased quality of whipped cream, independent of when the sugar was added or in what form. Such contradictory reports are undoubtedly the result of unsatisfactory methods used in evaluating whipped cream and the instrument described in this study should be of value in the testing of whipped cream and related products. The effect of milk volume on the whipping properties of toppings was determined by adding various amounts of milk to the amount of topping mix contained in one package. Increasing the amount of milk 4
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Hardness of whipping cream determined with the plate penetrometer as a function of whipping time.
used resulted in a decrease in maximum torque reo gistered (Fig. 5). The slope of the torque curve also decreased with increasing amounts of milk (Fig. 6). Overrun increased with increasing amount of mille In this case adding more milk had the effect of incorporating more air into the product which resulted in a softer whipped product. To determine how torque values obtained with this instrument relate to other objective measurements, hardness values of the whipped products were made with the plate penetrometer at regular intervals during the whipping process. Hardness values of whipping cream during the whipping process are shown in Fig. 7. These measurements indicate the same abrupt decrease in hardness after the maximum is reached as is obtained with the recording mixer. The plateau obtained with the latter is not indicated in the plot of hardness values V8. time. A similar curve for a whipped topping is shown in Fig. 8. The curve shows a more gradual increase in hardness and no abrupt hardness loss after reaching the maximum. Such curves, however useful they may be, are of less value than the complete torque-time recordings and
5
WHIPPING TIME Fig. 8
(min)
Hardness of whipped topping determined with the plata penetrometer as a function of whipping time.
involve much more work than the latter. The relative, ly simple modified mixer appears to be a usefu~ device in measuring the whipping properties of creallli and toppings.
References Babcock, C. J. 1922. The Whipping Quality of Cream. U.S. Dept. o~ Agric. Bull. 1075. deMan, J. M. 1969. Food Texture Measurements with the Penetration Method. J. Texture Studies 1: 114. De Vleeschauwer, A. and Deschacht. W. 1960. Study of the Whipping of Cream. Meded. LandbHogesch, Gent 25: 825. De Vleeschauwer, A., Deschacht, W. and Hendrickx, H. 1961. Studies; on the Whipping of Cream. Mllchwissenschaft 16: 125. Heis, E. 1961. Studies on the Effect of the Treatment of Whipping Cream on its Physical Properties. Dtsch. Molkereiztg. 82: 1468. Hendrickx, H. and Moor, H. 1965. Studies on Whipped Cream - 1" Mllk Ind. 57: 39. ! Melick, C. W. 1909. Whipped Cream. Maryland Agr. Exp. Stat. Bun. 136. Mohr, W. and Koenen, K. 1953. Evaluation of the Quallty of Whipped Cream. Dtsch. Molkereiztg. 74: 468. Mohr, W. and Mohr, E. 1955. Whipped Cream - Some Problems. Molkerel Kaesereiztg. 6(2): 34. Mueller, W. S., 1935. A Method for the Determination of the Relative Stiffness of Cream During the Whipping Process. J. Dairy Sci. 18: 177. Smellie, T. J. 1966. Tests for the Whipping Properties of Cream. XVII Int. Dairy Congres. Proceedings E, 357. Sommer, H. H. 1952. Market Milk and Reiated Products. The Olsen Publlshing Co. Milwaukee, U.S.A. . Voisey, P. W., Mlller, H. and Kloek, M. 1966. An Electronic Recording Dough Mixer. Cereal Chem. 43: 408. Received June 17, 1971.
Can. Inst. Food Science and TechnoL J. Vol. 5, No. I, 1972
~f.
deMan
Department of Food Science University of Guelph Guelph, Ontario
Abstract A household mixer was modified for continuous torque recording during mixing by means of a strain gage transducer connected to a pully on the bowl shaft and operating with an electronic recording attachment. Maximum torque, plateau torque, the time to reach maximum torque, and the slope of the torque curve were determined from the recorded torque~time curve. The addition of sugar to whipping cream resulted in increases in both plateau torque and the slope of torque curve, and decrease in the time to reach maximum torque. This means that the addition of sugar increases the rate of whipping and results in firmer whipped cream. The dilution effect of toppings with milk was determined for some commercial samples. The slope of the torque curve decreased and overrun increased with the addition of milk.
Resume Un malaxeur domestique a ete modifie pour l'enregistrement continu de la torsion au cours du malaxage en raccordant un transmetteur jauge raocorc1e a une pouJie sur l'axe du bol et fonctionnant a l'aide d'un enregistreur electronique. La torsion maximum, la torsion du plateau, Ie teIIliPs pour atteindre la torsion maximum, et la pente de la courbe de torsion ont ete determines a partir de la courbe de la torsion en fonction du temps. L'addition de sucre a la creme a fouetter a augmente la torsion du plateau et la pente de la courbe de torsion, et diminue Ie temps de torsion maximum. Ceci veut dire que l'addition de sucre augmente Ie taux de fouettement et produit une creme fouettee plus ferme. L'effet de la dilution des gla«;ages avec du lait a eM determine sur quelques echantillons du commerce. L'addition de lait a diminue la pente de la courbe de torsion et augmente Ie rendement.
Introduction Fairly extensive work has been done on establishing the mechanism of the whipping 'of cream. Sommer (19:)2) explained the whipping of cream by assuming that air cells are incorporated in the cream and some churning or coalescence of the fat takes place; stiffness or rigidity depends upon (1) the size of the air cells (2) the size and rigidity of the coalesced fat masses (3) the amount of fat and incorporated air, and (4) the stability of the air cells. If the air cells are large, interstices between the cells will be correspondingly large, and small fat masses will be accommodated without any distortion. Only when the fat masses reach such a size that they can no longer be accommodated by the interstices will distortion of the air cells occur. Thus, if the air is coarsely incorporated, more advanced churning is required to attain stiffness' the whipped cream will be coarse in texture both because of the larger air cells and because of the large fat masses. The resulting whipped cream will not be as rigid as a product that contains the same amount of air and fat in a more finely dispersed condition. There is a general relationship between the volume of air or overrun and whipping quality. Creams that Whip rapidly and produce whipped cream of desirable stiffness generally yield a lower overrun than creams of poorer whipping qualities. 1
Mohr (1955) ,outlined the requirements for the production of high quality whipped cream as follows: (1) a whipped product with finely distributed air bubbles (2) a cream of sufficiently high fat content to allow all the air bubbles to be surrounded by fat, (3) the presence of a high proportion of crystallized fat in the fat globules in order to bind as much butter oil as possible after ageing, (4) preventing the formation of too much butter oil, especially during the summer, by whipping the cream at 2° - 4°C and storing it below 10°C to avoid drainage of the aqueous phase. Heiss (1961) studied the effect of the treatment of whipping cream on the firmness, volume increase and serum separation of the resulting whipped cream, and found that cream containing 34% butterfat and a pasteurization temperature of 95°C was best. For testing the whipping qualities of cream, several methods have been developed. Muller (1935) proposed a method for comparing cream with respect to whipping time and stiffness. A power driven whipper was combined with a suitable wattmeter and the stiffness of the cream was observed during whipping by following the wattmeter readings. Muller tested creams ranging from 20 to 39.5 per cent fat and found that maximum overrun occurred shortly before maximum stiffness was reached. Mohr and Koenen (1953) described an instrument for the testing of whipping cream. Two six wired beaters rotate at a fixed speed ill a stationery cylinder surrounded by an ice water Jacket. Resistance to rotation of the beaters was indicated by a milliammeter. De Vleeschauwer (1961) tested the effect of wire shape on the whipping of 40% cream and found that beaters with 3 wires required a longer whipping time but gave a greater ,overrun with some loss in stiffness of the whipped cream, and that the maximum reading on the milliammeter was lower with the 3 wire beaters, but it more nearly coincided with the maximum overrun of the whipped creams. I Hendrickx (1965) also tested the Mohr & Koenen i apparatus with the 3 wire beaters and found that greater overrun was obtained, but the consistency was reduced. Smellie (1966) developed a testing apparatus by combining a small electric domestic mixer with a variable resistance. A specially made basket-shaped whisk was used, about 10 cm in diameter and consisting of 10 wires shaped to the profile of the whipping bowl. Babcock (1922) determined the stiffness of whipped products by the weight in grams required to cause a disk to settle into and displace the cream. The Hill Curd Tensiometer was used which has a round disk of one square inch area instead of the curd knife and the, Can. lnst. Food Science and Technol. J. Vol. 5. No. I, 1972
Fig. 1
Modified mixer for recording torque during whipping of cream and related products. A - View of mixer showing pulley attached under bowl platform. B - View of torque sensing transducer connected to pulley by nylon line. C - Overall view of mixer with transducer amplifier and recorder.
resistance in grams to the passage of this disk into the whipped cream is measured. Smellie (1966) showed that the point at which the whipping of 40% fat cream is normally stopped is past the point of maximum overrun, and the product, although somewhat granular in appearance, is still fairly soft. The cream with the best appearance was obtained at maximum overrun, but had high seepage and was soft. He tested 36% and 40% creams and reported that optimum values of these characteristics did not coincide with the maximum meter reading. The maximum meter reading corresponded to an overrun lower than that obtained at the maximum; at this point the cream was overwhipped and there was also a sharp increase in firmness past the point of maximum overrun. There was also a distinct relationship between overrun and temperature; the lower the temperature the higher the oVerrun. No specific trend was noticed in the relationship between whipping temperature and firmness of whipped product but lower overrun generally meant greater firmness. De Vleeschauwer (1960) tested 40% cream with the Mohr apparatus and found that prolonged aging had little effect on overrun in whipped summer cream Table 1 Mixing Speeds of the Recording Mixer as Related to Instrument Speed Control Description Control Setting 1 2 3 4 5 6 7 8 9
stirring slow mixing pre-mixing creaming cake mixes blending beating whipping heavy beating
~attachments
Spindle Speed r.p.m. 275 329 397 459 532 598 687 771 872 932
-
280 337 410 469 544 610 709 787 892 949
Variation %
1.8 2.4 3.3 2.2 2.3 2.0 3.0 2.1 2.3 1.8
Mean Spindle Speed r.p.m. 278 333 402 464 539 603 697 780 877 940
J. lnst. Can. Science e', Techno!. Aliment. Vo!. 5, No 1, 1972
but stiffness was markedly reduced, however, in the case of winter cream overrun increased with prolonged aging and the loss in stiffness was less marked than with summer cream. For the study of the whipping characteristics of cream and similar products, it is highly desirable to have an instrument that allows continuous recording of the changes in consistency occurring during the whipping process. This report describes the construction of such an instrument and its application in the evaluation of various factors affecting whipping.
Experimental The instrument is a common household mixer (Philips) with a double set of metal beaters. The mixing speed can be varied with a 10 step speed control. The relationship between speed control setting and spindle speed was determined and is presented in Table 1. The bowl is normally placed on a freely rotating platform and this was modified by elongating the shaft supporting the platform and by attaching to it nnder the mixer (Fig. 1) a pulley with a diameter of 6 em. A nylon line was attached to the pulley and connected at the other end to a metal cantilever beam to which four strain gages were bonded according to the full bridge pattern described by Voisey et al. (1966). To prevent the bowl from slipping on the platform, two short pins were soldered to the bowl and holes drilled in the platform to engage the pins. The drag on the bowl caused by increasing viscosity during whipping is converted to a force transmitted by the nylon line to the strain gage transducer beam. The strain gages were connected to a Daytronic model 900 D 3 strain gage amplifier indicator and the output recorded on a 10 mV strip chart recorder. The recorder was electronically damped to obtain an average torque record and prevent excessive "noise" from appearing on the recording. The instrument was calibrated with weights which were attached to the strain gage transducer beam with a nylon line strung over a pulley in front of the instrument. This line was attached at the same position on the beam as the one connection to the bowl platform pulley. The recorded force acts at a distance of 3 cm from the center of the bowl and is expressed as torque in g. cm. Since the torque reading is dependent on sample 2
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TIME Fig. 2
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Typical torque-time recording of the whipping of cream at spindle speed of 780 rpm.
size, the same quantity of sample must be used for comparative studies. For the experiments described in this paper, commercial whipping cream with a fat content of 32% was used. Sample size for all tests was 110 g of cream. POI' testing the effect of sugar, 5%, 10% or 15% of sugar was added to 110 g of whipping cream and dissolved with gentle stirring. The mixture was then whipped at 780 rpm and 10°0. Maximum torque, time to reach maximum torque, the slope of the torque curve and plateau torque were obtained from the torque-time recording. Overrun was determined by weighing a known volume of the whipped product. For the testing of toppings, commercial dry mix products were used. 113 ml of milk were added to one package (60 g) of product, and the mixture whipped at 780 rpm and 10°0. Consistency of the whipped products was determined by a plate penetrometer method. A metal plate with a surface area of 11.3 cm 2 was driven into the product at a constant speed of 0.12 cm/sec and the resulting force recorded (deMan, 19(9). From the recorded force-time curves force readings were made at depths of penetration of 0.12, 0.36, 0.60, 1.20 and 1.80 CIll. Haroness was calculated by dividing the force in grams by the disc area in cm 2 •
Results and Discussion A typical torque recording for the whipping of cream at 10°C and a spindle speed of 780 rpm is presented in Fig. 2. The initial part of the curve shows a gradual increase in torque, followed by a constant portion which will be referred to as "plateau torque". The plateau is followed by a sudden large increase leading to a maximum torque which rapidly falls off to a minimum. The sudden increase and drop in torque coincides with churning of the cream and separation of the emulsion. Spindle speed has a profound effect on the whipping of cream. Reduction of spindle speed from 780 to 697 rpm resulted in change in maximum torque from
3
Typical torque-time recording of the whipping of a whipped toppings at a spindle speed of 780 rpm.
63.6 g. cm to 12.4 g. cm, and time to reach maximum force from 1.6 min. to 11 min. At a speed of 464 rpm no whipping -occurred at all and no increase in torque was observed. . Changing whipping temperature from 10 to 20°C at a speed of 780 rpm decreased maximum torque from 63.6 g. cm to 34.8 g. cm and plateau torque from 18.9 g. cm to 6.0 g. cm. However, the time to reach maximum torque was not affected by temperature. The torque-time recordings of whipped toppings are different in shape from those of whipping cream. A typical torque recording for the whipping of a whipped topping is presented in Fig. 3. The force increases almost linearly with time to a maximum value, thereafter, there is a gradual decline of torque but in no case is there a sudden drop as seen in whipped cream torque recordings. Obviously the whipped toppings are more stable products and not subject to churning. Increasing whipping temperature of the topping from 10 to 20°C resulted in a decrease of maximum torque from 119.5 g. cm to 72.0 g. cm. The change in temperature did not affect the time required to reach maximum torque. The effect of sugar addition to cream OIl the rheological properties ,of the Whipped product was measured. Since maximum torque of whipped cream is not as reproducible as plateau torque, the latter was chosen to describe the effect of sugar addition. The changes in torque curve slope and plateau torque as a function of amount of added sugar are presented in Fig. 4. Addition of sugar up to a level of 15% resulted in increase of plateau torque, indicating a firmer whipped product. Torque curve slope also increased with increasing amount of added sugar. Whipping time (time to reach maximum torque) was reduced by sugar addition ('fable 2). The extent of Table 2 Change in Whipping Time and Overrun of Whipping Cream as Affected by Sugar Addition Sugar Added %
o
5 10 15
Whipping Time Sec.
192 123 138 142
Overrun %
76 78 79
83
Can. lnst. Food Science and Techno!. J. Vo!. 5, No. I, 1972
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MILK Fig. 6
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J. lnst. Can. Science et Techno!. Aliment. Vo!. 5, No 1, 1972
VOLUME
(ml )
Effect of milk volume used in making up topping mix on torque curve slope.
the decrease was not greatly affected by the level of sugar addition, the lowest level of sugar caused the largest decrease in whipping time. Overrun was not affected by sugar addition. It appears from these experiments that sugar increases the ease of whipping and results in a firmer whipped cream. Microscopic examination of the whipped products indicated that the sugar containing whipped products had a somewhat coarser dispersion of air than the product without sugar. These results are probably somewhat dependent on the nature of the beater blades and the geometry of the blades and bowl. Literature reports on the effect of sugar on whipped cream are contradictory. Melick (1909) reported that sugar addition improves the properties of whipped cream. Babcock (1922) found that sugar resulted in decreased quality of whipped cream, independent of when the sugar was added or in what form. Such contradictory reports are undoubtedly the result of unsatisfactory methods used in evaluating whipped cream and the instrument described in this study should be of value in the testing of whipped cream and related products. The effect of milk volume on the whipping properties of toppings was determined by adding various amounts of milk to the amount of topping mix contained in one package. Increasing the amount of milk 4
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TIME
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Hardness of whipping cream determined with the plate penetrometer as a function of whipping time.
used resulted in a decrease in maximum torque reo gistered (Fig. 5). The slope of the torque curve also decreased with increasing amounts of milk (Fig. 6). Overrun increased with increasing amount of mille In this case adding more milk had the effect of incorporating more air into the product which resulted in a softer whipped product. To determine how torque values obtained with this instrument relate to other objective measurements, hardness values of the whipped products were made with the plate penetrometer at regular intervals during the whipping process. Hardness values of whipping cream during the whipping process are shown in Fig. 7. These measurements indicate the same abrupt decrease in hardness after the maximum is reached as is obtained with the recording mixer. The plateau obtained with the latter is not indicated in the plot of hardness values V8. time. A similar curve for a whipped topping is shown in Fig. 8. The curve shows a more gradual increase in hardness and no abrupt hardness loss after reaching the maximum. Such curves, however useful they may be, are of less value than the complete torque-time recordings and
5
WHIPPING TIME Fig. 8
(min)
Hardness of whipped topping determined with the plata penetrometer as a function of whipping time.
involve much more work than the latter. The relative, ly simple modified mixer appears to be a usefu~ device in measuring the whipping properties of creallli and toppings.
References Babcock, C. J. 1922. The Whipping Quality of Cream. U.S. Dept. o~ Agric. Bull. 1075. deMan, J. M. 1969. Food Texture Measurements with the Penetration Method. J. Texture Studies 1: 114. De Vleeschauwer, A. and Deschacht. W. 1960. Study of the Whipping of Cream. Meded. LandbHogesch, Gent 25: 825. De Vleeschauwer, A., Deschacht, W. and Hendrickx, H. 1961. Studies; on the Whipping of Cream. Mllchwissenschaft 16: 125. Heis, E. 1961. Studies on the Effect of the Treatment of Whipping Cream on its Physical Properties. Dtsch. Molkereiztg. 82: 1468. Hendrickx, H. and Moor, H. 1965. Studies on Whipped Cream - 1" Mllk Ind. 57: 39. ! Melick, C. W. 1909. Whipped Cream. Maryland Agr. Exp. Stat. Bun. 136. Mohr, W. and Koenen, K. 1953. Evaluation of the Quallty of Whipped Cream. Dtsch. Molkereiztg. 74: 468. Mohr, W. and Mohr, E. 1955. Whipped Cream - Some Problems. Molkerel Kaesereiztg. 6(2): 34. Mueller, W. S., 1935. A Method for the Determination of the Relative Stiffness of Cream During the Whipping Process. J. Dairy Sci. 18: 177. Smellie, T. J. 1966. Tests for the Whipping Properties of Cream. XVII Int. Dairy Congres. Proceedings E, 357. Sommer, H. H. 1952. Market Milk and Reiated Products. The Olsen Publlshing Co. Milwaukee, U.S.A. . Voisey, P. W., Mlller, H. and Kloek, M. 1966. An Electronic Recording Dough Mixer. Cereal Chem. 43: 408. Received June 17, 1971.
Can. Inst. Food Science and TechnoL J. Vol. 5, No. I, 1972