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Rheological Behavior of Pineapple and Mango Pulps
Lebensm.-Wiss. u.-Technol., 35, 645–648 (2002)
Rheological Behavior of Pineapple and Mango Pulps D. H. Pelegrine*, F. C. Silva and C. A. Gasparetto
D. H. Pelegrine, C. A. Gasparetto: Department of Food Engineering, Food Engineering Faculty/UNICAMP, P.O. Box 6121, Code: 13.081-970, Campinas/S.P. (Brazil) F. C. Silva: Embrapa Agroindu´stria de Alimentos, Au. das Ame´ricas, 29501, CEP: 13083-970 – Campinas/SP, Brazil (Received October 1, 2001; accepted June 12, 2002)
The rheological behavior of whole and centrifuged mango (Mangı´ fera indica L. var. Keitt) and pineapple (Ananas comusus L. merr var Pe´rola) pulps was analysed at 30 1C, in a rotational viscometer Haake Rotovisco RV-20. The experiments were conducted with measuring system of 45 mm diameter parallel plates (PQ45) with gap of 0.5 mm, at shear rates up to 874 sl. The rheograms were fitted with Casson, Ostwald-of-Waelle and Mizrahi–Berk (M–B) models. The Brix of pineapple and mango pulps were 16.6 and 13.3 1Brix, respectively, and the insoluble solids content was 0.108 g/kg for mango and 0.054 g/kg for pineapple. The best adjustment was obtained with M–B model. It was observed that the pulps presented pseudoplastic behavior, and the suspended solids had great influence on the consistency index.
r 2002 Elsevier Science Ltd. All rights reserved. Keywords: mango; pineapple; rheology; pulp
Introduction Mango and pineapple occupy prominent positions in the world market, being among the main fruits of great commercial importance. Besides the fruits ‘in nature’, their manufactured products, such as juices, nectars, ice creams and jellies, whose basic raw material is the pulp, which is used in the unit operations, such as pumps, agitation, heat exchanger and separations. For such industrial processes to be technically and economically feasible, it is important to have the knowledge of the physical–chemical properties. Among these properties, the rheological behavior is one of the most important, being useful not only as quality measure, but also in projects, evaluation and operation of the process equipments (Ibarz et al., 1996). Because every fruit liquid product is composed by solid particles dispersed in an aqueous phase, its rheological behavior will be influenced by the concentration, chemical composition, size, shape and arrangement of these particles that compose the dispersed phase (Costell and Dura´n, 1982). Queiroz (1998) studied the influence of suspended solids on mango and pineapple pulps and concluded that these particles had great influence on rheology of both pulps. Most fluid foods do not have the simple Newtonian rheological model; in other words, their viscosities are
independent of shear rate or shear stress and not constant with temperature. Therefore, it is necessary to develop more complex models to describe their behavior (Holdsworth, 1971). Some of the most widely used rheological models are the Power Law with two parameters, the Casson with two parameters plus the yield stress, and the Mizrahi–Berk (M–B) with three parameters and yield stress. Usually, the Power Law is used to indicate pseudoplasticity due to dissolved solids, through the fluid behavior index n. Casson is used to demonstrate the effect of suspended material, and M–B model is an attempt to match these two effects. The Ostwald-de-Waelle (Power Law) model is described below as ¼ K _ n Eqn ½1 where t is the shear stress (Pa); _ the shear rate (s1); the K the consistency index (Pa sn) and n the behavior index of the fluid. Several researchers used the Power Law model to describe rheological behavior of fruit pulps, juices and pure´e (Saravacos, 1968; Varshney and Kumbar, 1978; Guariguata, 1981; Lombran˜a and Dı´ as, 1985; Rao et al., 1985, 1986; Xu et al., 1986; Gunjal and Wachmare, 1987). Even so, some foods have the yield stress that is also an important characteristic so their experimental data are not adjusted to the Power Law model with great precision. For that, Casson proposed the following expression:
*To whom correspondence should be addressed. Fax: +55 19 378840227; E-mail: [email protected]
0023-6438/02/$35.00 r 2002 Elsevier Science Ltd. All rights reserved.
1=2 ¼ 0C þ C ð_ Þ1=2
Eqn ½2
doi:10.1006/fstl.2002.0920 All articles available online at http://www.idealibrary.com on
645
lwt/vol. 35 (2002) No. 8
where t is the shear stress (Pa); _ the shear rate (sl); k0C the Casson’s yield stress (Pa)1/2 and kC the plastic viscosity of Casson (Pa s)1/2. Although the Casson model describes well many materials exhibiting yield stress, a more general model with three constants produces a better fit for complex systems. Mizhari and Berk showed that the model above does not adapt to low values of the shear rate when applied to orange and tomato concentrated juices and also for similar systems (Rao and Cooley, 1982), proposing the following equation: 1=2 0M ¼ M ð_ ÞnM
Eqn ½3
where t is the shear stress (Pa); _ the shear rate (sl); kM the consistency index ðPaÞ1=2 ðsÞnM ; nM the behavior index of the fluid and k0M the squared root of the yield stress (Pa)1/2. This paper reports mango and pineapple pulps, rheological behavior including the suspended solids effect. The measurements are important in food industry as a quality indicator, in dimensioning pipes and heat exchanger besides the sensory analyses correlation. Three rheological models were used as tools for calculation of the relationship between the shear stress and shear rate.
cylinders (gap=1.0 mm) and parallel plates with larger gaps (1.0, 1.5 and 2.0 mm) for the same pulps. Besides, the system of 45 mm diameter parallel plates (PQ45) with gap of 0.5 mm becomes more interesting because it allows higher shear rate range, reducing the experimental errors. Gehrke (1996) used the parallel plates in measuring lemon, orange, cashew and passion fruits juices viscosity, and concluded that this is an efficient system. Pelegrine (1999) also used this measuring system on pineapple and mango pulps rheology and concluded the same. First of all, the sample was maintained for 2 min at maximal rotational speed representing 871 s1. Then, the shear rate was lowered for 2 min to the lowest practical speed (nearly still) and then increasing the speed back to 871 s1 in 2 min. This procedure was used in order to avoid measurements at low speed when the system departs from stagnation and the material is somewhat structured. Both at decreasing and increasing shear rate, 20 points of shear stress were obtained, resulting in a total of 40 points, whose average value of shear stress was taken for each shear rate. Three experimental runs were accomplished for each material, and the resulting shear stress was the average of the three experimental values. For each adjusted model, the determination coefficient (R2) and the chi-square (w2) were analysed.
Experimental Procedure Pulps preparation Pulps were produced in a pilot plant from fruits with similar degree of ripeness, as standardized with a penetration texturometer. Then the fruits passed through finishers with a screen of 1.6 mm. The screen of 1.6 mm was chosen aiming the maximum yield in pulp extraction and homogeneous pulp. Part of whole pulp was centrifuged at 15,000 rpm (29,000 g) for 40 min. The pulp was quickly plate-frozen and stored at 20 1C (Bezerra, 1997). Table 1 refers to physical–chemical characteristics of pineapple and mango pulps.
Results and Discussion Rheograms The average values of shear stress vs. shear rate, referring to the pulps analysed are shown in Figs 1 and 2. From Figs 1 and 2, it is observed that the suspended solids have great influence on the rheological behavior of the pulps, and in the case of mango, its absence produced a decrease of 35% in the consistency index and for the pineapple, the reduction was 65%. The experimental runs did not indicate thixotropic effects.
Rheological measurements The rheological measurements were made in a parallel plates Haake Rotovisco rheometer, model RV-20, with plates of 45 mm diameter (PQ45) and gap of 0.5 mm. Such measuring system was chosen because it results in more consistent rheograms and with smaller disturbances when compared with others, such as concentric Table 1
Pulps physical–chemical characteristics Pulps
pH Brix Pectin (g/kg) Insoluble solids (g/kg)
Mango
Pineapple
4.47 16.60 0.098 0.108
3.50 13.30 0.082 0.54
Fig. 1
646
Shear stress vs. shear rate rheogram for mango pulp
lwt/vol. 35 (2002) No. 8
Fig. 2 Shear stress vs. shear rate rheogram for pineapple pulp
Rheological parameters Tables 2–4 present the parameters values obtained from the Ostwald-of-Waelle, Casson and M–B models fitting. The experimental data are in better agreement with the M–B model than with the Casson and Power Law models as seen from Tables 2–4; from these tables it can be noted that the M–B model presents
Table 2
higher R2 values and low w2 values. Because of the close agreement with M–B model, this model was the one that best described all the materials and the discussion about the parameters k and n will be limited to this model. From prior tables, it can be observed the behavior index is smaller than 1 for all cases, concluding that both pineapple and mango pulps present pseudoplastic characteristics, and the pseudoplasticity is larger for the whole pulps, as the behavior indexes indicate. This indicates that the pulps, when unfurnished by the suspended particles, tend to behave as a Newtonian fluid. But n values for the whole pulps do not vary so much between pineapple and mango pulps, indicating that these pulps pseudoplasticity are almost the same as indicated in Table 4. On the other hand, n values for centrifuged pineapple pulp are higher than those for mango pulp at identical conditions indicating that pineapple pulp is more pseudoplastic than mango pulp. The pseudoplasticity is presumably caused by fine suspended particles in pulp. The suspended particle presence had great influence on the consistency index in both pulps, indicating that the particles are greatly responsible for these pulps viscosity.
Rheological parameters of Ostwald-of-Waelle model Pulps
K n R2 w2
Table 3
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
3.63 0.44 0.99 0.26
0.65 0.61 0.99 0.13
5.63 0.15 0.82 1.20
0.65 0.24 0.88 0.05
Rheological parameters Casson model Pulps
K0C KC R2 w2
Table 4
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
2.92 0.20 0.94 0.16
1.29 0.18 0.98 0.05
2.78 0.04 0.81 0.03
1.11 0.03 0.99 0.0003
Rheological parameters Mizhari–Berk model Pulps
K0M KM nM R2 w2
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
0.48 1.60 0.24 0.99 0.001
0.28 0.66 0.33 0.99 0.003
2.05 0.49 0.20 0.93 0.02
1.11 0.03 0.50 0.99 0.0003
647
lwt/vol. 35 (2002) No. 8
Conclusion Three of the most used rheological models including yield stress were compared to describe the behavior of pineapple and mango pulps, under shear in parallel plate system which is most used for fruit pulp characterization. The Mizrahi–Berk model fitted better the experimental data. Therefore, this is a preferred model for complex pulps with high content of insoluble solids. References BEZERRA, J. R. M. V. Rheology of mango pulpFeffect of insoluble solids. Master thesis, 81 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1997) COSTELL, E. AND DURA´N, L. Reologı´ a fisico-quı´ mica de los zumos y pure´s de fruta. Revista de Agroquı´mica y tecnologı´a de Alimentos, 22(1), 81–94 (1982) GEHRKE, T. Rheometry of fruit juices. Master thesis, 103 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1996) GUARIGUATA, C. I. Caracteristicas reologicas de productos de frutas tropicales. Archivos Latinoamericanos de Nutricion, 31(4), 666–678 (1981) GUNJAL, B. B. AND WACHMARE, N. J. Flow characteristics of pulp, juice and nectar of ‘Baneshan’ and ‘Neelum’ mangoes. Journal of Food Science and Technology, 24(1), 20–23 (1987) HOLDSWORTH, S. D. Applicability of rheological models to the interpretation of low and processing behaviour of fluid products. Journal of Texture Studies, 2(4), 393–418 (1971)
IBARZ, A., GONC¸ALVES, C. AND EXPLUGAS, S. Rheology of clarified passion fruit juices. Fruit Processing, 6(8), 330–333 (1996) LOMBRAN˜A, J. I. AND DI´AS, J. M. Rheological and chemical changes in stored carrot juice. Canadian Institute of Food Science and Technology, 18(3), 213–219 (1985) PELEGRINE, D. H. Rheological behavior of mango and pineapple pulps. Master thesis, 115 pp. School of Food Engineering/ UNICAMP, Campinas (S.P.), Brazil (1999) QUEIROZ, A. J. Analysis of rheological behavior of pineapple and mango juices. Doctor thesis, 170 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1998) RAO, K. L., EIPESON, W. E., RAO, P. N. S., PATWARDHAN, M. V. AND RAMANATHAN, P. K. Rheological properties of mango pulp and concentrates. Journal of food Science and Technology, 22(1), 30–33 (1985) RAO, K. L., COOLEY, H. J., NOGUEIRA, J. N. AND MCLELLAN, M. R. Rheology of apple sauce: effect of apple cultivar, firmness and processing parameters. Journal of Food Science, 51(1), 176–179 (1986) RAO, M. A. AND COOLEY, H. J. Flow properties of tomato concentrates. Journal of Texture Studies, 12(4), 521–538 (1982) SARAVACOS, G. D. Tube viscometry of fruit pure´es and juices. Food Technology, 22(12), 89–92 (1968) VARSHNEY, N. N. AND KUMBAR, B. K. Effect of concentration and temperature on rheological properties of pineapple and orange juices. Journal of Food Science and Technology, 15(2), 53–55 (1978) XU, S. Y., SHOEMAKER, C. F. AND LUH, B. S. Effect of break temperature on rheological properties and microstructure of tomato juices and pastes. Journal of food Science, 51(2), 399–402 (1986)
648
Rheological Behavior of Pineapple and Mango Pulps D. H. Pelegrine*, F. C. Silva and C. A. Gasparetto
D. H. Pelegrine, C. A. Gasparetto: Department of Food Engineering, Food Engineering Faculty/UNICAMP, P.O. Box 6121, Code: 13.081-970, Campinas/S.P. (Brazil) F. C. Silva: Embrapa Agroindu´stria de Alimentos, Au. das Ame´ricas, 29501, CEP: 13083-970 – Campinas/SP, Brazil (Received October 1, 2001; accepted June 12, 2002)
The rheological behavior of whole and centrifuged mango (Mangı´ fera indica L. var. Keitt) and pineapple (Ananas comusus L. merr var Pe´rola) pulps was analysed at 30 1C, in a rotational viscometer Haake Rotovisco RV-20. The experiments were conducted with measuring system of 45 mm diameter parallel plates (PQ45) with gap of 0.5 mm, at shear rates up to 874 sl. The rheograms were fitted with Casson, Ostwald-of-Waelle and Mizrahi–Berk (M–B) models. The Brix of pineapple and mango pulps were 16.6 and 13.3 1Brix, respectively, and the insoluble solids content was 0.108 g/kg for mango and 0.054 g/kg for pineapple. The best adjustment was obtained with M–B model. It was observed that the pulps presented pseudoplastic behavior, and the suspended solids had great influence on the consistency index.
r 2002 Elsevier Science Ltd. All rights reserved. Keywords: mango; pineapple; rheology; pulp
Introduction Mango and pineapple occupy prominent positions in the world market, being among the main fruits of great commercial importance. Besides the fruits ‘in nature’, their manufactured products, such as juices, nectars, ice creams and jellies, whose basic raw material is the pulp, which is used in the unit operations, such as pumps, agitation, heat exchanger and separations. For such industrial processes to be technically and economically feasible, it is important to have the knowledge of the physical–chemical properties. Among these properties, the rheological behavior is one of the most important, being useful not only as quality measure, but also in projects, evaluation and operation of the process equipments (Ibarz et al., 1996). Because every fruit liquid product is composed by solid particles dispersed in an aqueous phase, its rheological behavior will be influenced by the concentration, chemical composition, size, shape and arrangement of these particles that compose the dispersed phase (Costell and Dura´n, 1982). Queiroz (1998) studied the influence of suspended solids on mango and pineapple pulps and concluded that these particles had great influence on rheology of both pulps. Most fluid foods do not have the simple Newtonian rheological model; in other words, their viscosities are
independent of shear rate or shear stress and not constant with temperature. Therefore, it is necessary to develop more complex models to describe their behavior (Holdsworth, 1971). Some of the most widely used rheological models are the Power Law with two parameters, the Casson with two parameters plus the yield stress, and the Mizrahi–Berk (M–B) with three parameters and yield stress. Usually, the Power Law is used to indicate pseudoplasticity due to dissolved solids, through the fluid behavior index n. Casson is used to demonstrate the effect of suspended material, and M–B model is an attempt to match these two effects. The Ostwald-de-Waelle (Power Law) model is described below as ¼ K _ n Eqn ½1 where t is the shear stress (Pa); _ the shear rate (s1); the K the consistency index (Pa sn) and n the behavior index of the fluid. Several researchers used the Power Law model to describe rheological behavior of fruit pulps, juices and pure´e (Saravacos, 1968; Varshney and Kumbar, 1978; Guariguata, 1981; Lombran˜a and Dı´ as, 1985; Rao et al., 1985, 1986; Xu et al., 1986; Gunjal and Wachmare, 1987). Even so, some foods have the yield stress that is also an important characteristic so their experimental data are not adjusted to the Power Law model with great precision. For that, Casson proposed the following expression:
*To whom correspondence should be addressed. Fax: +55 19 378840227; E-mail: [email protected]
0023-6438/02/$35.00 r 2002 Elsevier Science Ltd. All rights reserved.
1=2 ¼ 0C þ C ð_ Þ1=2
Eqn ½2
doi:10.1006/fstl.2002.0920 All articles available online at http://www.idealibrary.com on
645
lwt/vol. 35 (2002) No. 8
where t is the shear stress (Pa); _ the shear rate (sl); k0C the Casson’s yield stress (Pa)1/2 and kC the plastic viscosity of Casson (Pa s)1/2. Although the Casson model describes well many materials exhibiting yield stress, a more general model with three constants produces a better fit for complex systems. Mizhari and Berk showed that the model above does not adapt to low values of the shear rate when applied to orange and tomato concentrated juices and also for similar systems (Rao and Cooley, 1982), proposing the following equation: 1=2 0M ¼ M ð_ ÞnM
Eqn ½3
where t is the shear stress (Pa); _ the shear rate (sl); kM the consistency index ðPaÞ1=2 ðsÞnM ; nM the behavior index of the fluid and k0M the squared root of the yield stress (Pa)1/2. This paper reports mango and pineapple pulps, rheological behavior including the suspended solids effect. The measurements are important in food industry as a quality indicator, in dimensioning pipes and heat exchanger besides the sensory analyses correlation. Three rheological models were used as tools for calculation of the relationship between the shear stress and shear rate.
cylinders (gap=1.0 mm) and parallel plates with larger gaps (1.0, 1.5 and 2.0 mm) for the same pulps. Besides, the system of 45 mm diameter parallel plates (PQ45) with gap of 0.5 mm becomes more interesting because it allows higher shear rate range, reducing the experimental errors. Gehrke (1996) used the parallel plates in measuring lemon, orange, cashew and passion fruits juices viscosity, and concluded that this is an efficient system. Pelegrine (1999) also used this measuring system on pineapple and mango pulps rheology and concluded the same. First of all, the sample was maintained for 2 min at maximal rotational speed representing 871 s1. Then, the shear rate was lowered for 2 min to the lowest practical speed (nearly still) and then increasing the speed back to 871 s1 in 2 min. This procedure was used in order to avoid measurements at low speed when the system departs from stagnation and the material is somewhat structured. Both at decreasing and increasing shear rate, 20 points of shear stress were obtained, resulting in a total of 40 points, whose average value of shear stress was taken for each shear rate. Three experimental runs were accomplished for each material, and the resulting shear stress was the average of the three experimental values. For each adjusted model, the determination coefficient (R2) and the chi-square (w2) were analysed.
Experimental Procedure Pulps preparation Pulps were produced in a pilot plant from fruits with similar degree of ripeness, as standardized with a penetration texturometer. Then the fruits passed through finishers with a screen of 1.6 mm. The screen of 1.6 mm was chosen aiming the maximum yield in pulp extraction and homogeneous pulp. Part of whole pulp was centrifuged at 15,000 rpm (29,000 g) for 40 min. The pulp was quickly plate-frozen and stored at 20 1C (Bezerra, 1997). Table 1 refers to physical–chemical characteristics of pineapple and mango pulps.
Results and Discussion Rheograms The average values of shear stress vs. shear rate, referring to the pulps analysed are shown in Figs 1 and 2. From Figs 1 and 2, it is observed that the suspended solids have great influence on the rheological behavior of the pulps, and in the case of mango, its absence produced a decrease of 35% in the consistency index and for the pineapple, the reduction was 65%. The experimental runs did not indicate thixotropic effects.
Rheological measurements The rheological measurements were made in a parallel plates Haake Rotovisco rheometer, model RV-20, with plates of 45 mm diameter (PQ45) and gap of 0.5 mm. Such measuring system was chosen because it results in more consistent rheograms and with smaller disturbances when compared with others, such as concentric Table 1
Pulps physical–chemical characteristics Pulps
pH Brix Pectin (g/kg) Insoluble solids (g/kg)
Mango
Pineapple
4.47 16.60 0.098 0.108
3.50 13.30 0.082 0.54
Fig. 1
646
Shear stress vs. shear rate rheogram for mango pulp
lwt/vol. 35 (2002) No. 8
Fig. 2 Shear stress vs. shear rate rheogram for pineapple pulp
Rheological parameters Tables 2–4 present the parameters values obtained from the Ostwald-of-Waelle, Casson and M–B models fitting. The experimental data are in better agreement with the M–B model than with the Casson and Power Law models as seen from Tables 2–4; from these tables it can be noted that the M–B model presents
Table 2
higher R2 values and low w2 values. Because of the close agreement with M–B model, this model was the one that best described all the materials and the discussion about the parameters k and n will be limited to this model. From prior tables, it can be observed the behavior index is smaller than 1 for all cases, concluding that both pineapple and mango pulps present pseudoplastic characteristics, and the pseudoplasticity is larger for the whole pulps, as the behavior indexes indicate. This indicates that the pulps, when unfurnished by the suspended particles, tend to behave as a Newtonian fluid. But n values for the whole pulps do not vary so much between pineapple and mango pulps, indicating that these pulps pseudoplasticity are almost the same as indicated in Table 4. On the other hand, n values for centrifuged pineapple pulp are higher than those for mango pulp at identical conditions indicating that pineapple pulp is more pseudoplastic than mango pulp. The pseudoplasticity is presumably caused by fine suspended particles in pulp. The suspended particle presence had great influence on the consistency index in both pulps, indicating that the particles are greatly responsible for these pulps viscosity.
Rheological parameters of Ostwald-of-Waelle model Pulps
K n R2 w2
Table 3
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
3.63 0.44 0.99 0.26
0.65 0.61 0.99 0.13
5.63 0.15 0.82 1.20
0.65 0.24 0.88 0.05
Rheological parameters Casson model Pulps
K0C KC R2 w2
Table 4
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
2.92 0.20 0.94 0.16
1.29 0.18 0.98 0.05
2.78 0.04 0.81 0.03
1.11 0.03 0.99 0.0003
Rheological parameters Mizhari–Berk model Pulps
K0M KM nM R2 w2
Whole mango
Centrifuged mango
Whole pineapple
Centrifuged pineapple
0.48 1.60 0.24 0.99 0.001
0.28 0.66 0.33 0.99 0.003
2.05 0.49 0.20 0.93 0.02
1.11 0.03 0.50 0.99 0.0003
647
lwt/vol. 35 (2002) No. 8
Conclusion Three of the most used rheological models including yield stress were compared to describe the behavior of pineapple and mango pulps, under shear in parallel plate system which is most used for fruit pulp characterization. The Mizrahi–Berk model fitted better the experimental data. Therefore, this is a preferred model for complex pulps with high content of insoluble solids. References BEZERRA, J. R. M. V. Rheology of mango pulpFeffect of insoluble solids. Master thesis, 81 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1997) COSTELL, E. AND DURA´N, L. Reologı´ a fisico-quı´ mica de los zumos y pure´s de fruta. Revista de Agroquı´mica y tecnologı´a de Alimentos, 22(1), 81–94 (1982) GEHRKE, T. Rheometry of fruit juices. Master thesis, 103 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1996) GUARIGUATA, C. I. Caracteristicas reologicas de productos de frutas tropicales. Archivos Latinoamericanos de Nutricion, 31(4), 666–678 (1981) GUNJAL, B. B. AND WACHMARE, N. J. Flow characteristics of pulp, juice and nectar of ‘Baneshan’ and ‘Neelum’ mangoes. Journal of Food Science and Technology, 24(1), 20–23 (1987) HOLDSWORTH, S. D. Applicability of rheological models to the interpretation of low and processing behaviour of fluid products. Journal of Texture Studies, 2(4), 393–418 (1971)
IBARZ, A., GONC¸ALVES, C. AND EXPLUGAS, S. Rheology of clarified passion fruit juices. Fruit Processing, 6(8), 330–333 (1996) LOMBRAN˜A, J. I. AND DI´AS, J. M. Rheological and chemical changes in stored carrot juice. Canadian Institute of Food Science and Technology, 18(3), 213–219 (1985) PELEGRINE, D. H. Rheological behavior of mango and pineapple pulps. Master thesis, 115 pp. School of Food Engineering/ UNICAMP, Campinas (S.P.), Brazil (1999) QUEIROZ, A. J. Analysis of rheological behavior of pineapple and mango juices. Doctor thesis, 170 pp. School of Food Engineering/UNICAMP, Campinas (S.P.), Brazil (1998) RAO, K. L., EIPESON, W. E., RAO, P. N. S., PATWARDHAN, M. V. AND RAMANATHAN, P. K. Rheological properties of mango pulp and concentrates. Journal of food Science and Technology, 22(1), 30–33 (1985) RAO, K. L., COOLEY, H. J., NOGUEIRA, J. N. AND MCLELLAN, M. R. Rheology of apple sauce: effect of apple cultivar, firmness and processing parameters. Journal of Food Science, 51(1), 176–179 (1986) RAO, M. A. AND COOLEY, H. J. Flow properties of tomato concentrates. Journal of Texture Studies, 12(4), 521–538 (1982) SARAVACOS, G. D. Tube viscometry of fruit pure´es and juices. Food Technology, 22(12), 89–92 (1968) VARSHNEY, N. N. AND KUMBAR, B. K. Effect of concentration and temperature on rheological properties of pineapple and orange juices. Journal of Food Science and Technology, 15(2), 53–55 (1978) XU, S. Y., SHOEMAKER, C. F. AND LUH, B. S. Effect of break temperature on rheological properties and microstructure of tomato juices and pastes. Journal of food Science, 51(2), 399–402 (1986)
648