Differences between the transmission and backscattering dws correlations suggest the formation of a high shear rate band near the surface of a moving cone of a coneandplate geometry at low. Heat transfer and rheology of stirred yoghurt during cooling in plate heat. Steadyshear viscosity of stirred yogurts with varying ropiness journal of rheology 43, 1643 1999. It covers both rheological and sensory evaluation of low fat stirred yoghurt prepared with different combinations of texturizers, like pectin, starches and gelatine. Simulation of stirred yoghurt processing in plate heat exchangers carla s. The headspace composition was assessed in a flask in static mode.
Rheology of stirred yogurt request pdf researchgate. Heat transfer and rheology of stirred yoghurt during. Simultaneous evaluation of shear rate and time dependency. Whether topped with chocolate, mixed with fruits or on its own, premium, indulgent yogurts have become the preferred choice of dessert for the health conscious consumer. Effects of starter cultures on small deformation rheology of. Viscometry rheological characteristics of stirred yoghurt, varying in dry matter content. Spectroscopic prediction of rheological properties of stirred. Solid rheology and texture they describe the flow characteristics of materials but also they can be used to monitor certain processes, e. The present study was performed to evaluate effects of starter properties on the linear viscoelastic behaviour of stirred yoghurt and to compare data with dynamic properties of yoghurt gels produced simultaneously. Stirred yoghurt produced from uht milk enriched with skim milk powder and by using 11 commercial starter cultures was subjected to dynamic rheological measurements with a cone and plate device. This cited by count includes citations to the following articles in scholar. The rheological properties of a lowfat and a fullfat yoghurt were investigated under continuous and oscillatory flow conditions with a rotational coaxialcylinder.
Effects of starter cultures on small deformation rheology of stirred yoghurt effects of starter cultures on small deformation rheology of stirred yoghurt rohm, h kovac a. A rheological study was carried out in order to characterise the stirred yoghurt flow, behaviour, evaluating its dependency both on shear rate and temperature. Rheological behavior of two commercial brands of stirred yogurt were investigated using a haake rv 20 rotational viscometer. Effects of polymerized whey proteins isolates on the quality of stirred yoghurt made from camel milk. Bingham, a professor at lafayette college, in 1920, from a.
Nrs the missing link sensory and rheology study of low. A rheological study was carried out in order to characterise the stirred yoghurt flow behaviour, evaluating its dependency. Attractive electrostatic and disulphide interactions were not involved in the gel rebodying and increasing calcium concentration in the set gel limited rebodying. Differences between the transmission and backscattering dws correlations suggest the formation of a high shear rate band near. Viscometry, journal of texture studies on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Impact of gelation conditions and structural breakdown on the. Once it has been packaged, the stirred gel is stored. The physical attributes of yogurts, including the lack of visual whey separation and. Relation between sensory texture analysis and rheological properties of stirred yogurt volume 66 issue 4 anne skriver, jens holstborg, karsten b. Stress decay behavior of two stirred yogurt samples was evaluated at various shear rates 100500 s. To describe the rheological behaviour of stirred yo. In the present work an experimental investigation was conducted to obtain a correlation for the determination of convective heat transfer coefficients of stirred yoghurt in a plate heat exchanger. Hansen 1, jan larsen 1 and ross clark 2 1 cp kelco, lille skensved, denmark. The aim of this study is to find correlations between rheological parameters and sensory attributes.
The rheological tests revealed that increasing the casein and fat content led to increase the apparent viscosity of the stirred yoghurt and its dependence on. Progress in rheology of biological and synthetic polymer systems influence of corrugation angle in the stirred yoghurt processing in plate heat exchangers luis f. Fortification of banana stirred yogurt with calcium. Simulation of stirred yoghurt processing in plate heat. Three periods of storage at 10 c were chosen for analysis. Creamy stirred yogurt an indulgent treat for all the senses almost everyone enjoys a special treat after dinner. It is a branch of physics which deals with the deformation and flow of materials, both solids and liquids. This study aimed to apply cryoscanning electron microscopy and confocal laser scanning microscopy to determine the optimal temperature for processing buffalo yoghurt. Stirred yogurt is made by fermenting milk and stirring the set curd to break the rigid gel structure to obtain a viscous liquid 33. A rheological study was carried out in order to characterise the stirred yoghurt flow, behaviour, evaluating its dependency both on shear rate and. Stability and rheological properties of stirred yogurts. Rheology of stirred yogurts, journal of texture studies 10. Shear localisation in stirred yoghurt springerlink.
Rheological characteristics of 2 commercial brands of stirred yogurt were evaluated using a haake rotovisco model rv 20 with an m5osc measuring head and mv1 rotor assembly from measured shear stress values under a programmed 3cycle up and downshear rate at 100 s. Whether topped with chocolate, mixed with fruits or on its own, premium. Rheology and sensory profiling of settype fermented milks made with different commercial probiotic and yoghurt starter cultures. Syneresis and rheological behaviors of set yogurt containing green.
Read rheological characterization of stirred yoghurt. If more whey separates out of the yogurt, just stir before serving. Rheological and physical properties of yogurt enriched with. A rheological study was carried out in order to characterise the stirred yoghurt flow behaviour, evaluating its dependency both on shear rate and temperature. Determination of yogurt quality by using rheological and.
Effects of starter cultures on small deformation rheology. A maximum in loss angle was observed during the gel development. Milk was fermented at three different temperatures 37. Qvist skip to main content accessibility help we use cookies to distinguish you from other users and to provide you with a better experience on our websites.
Rheology of stirred yogurts, journal of texture studies. The yoghurt samples were cooled to 25 c by resting in a temperature controlled room 15 c and then stored at 35 c for a period of 12 hours. Rheology of stirred yogurts ramaswamy 1991 journal. Yoghurt properties were followed by dynamic rheometry bohlin universal. Furthermore, a correlation appeared to exist between t 2, water binding, and the rheological properties of the stirred. Box 447, chillan, chile b department of biological systems engineering, washington state university, pullman, wa 991646120, usa received 10 october 2003. Stirred yoghurt is a nonnewtonian fluid, obtained by promoting the growth of lactobacillus delbrueckii subsp. A shift in the temperature dependency was evidenced at 25 c.
Rheological characteristics of 2 commercial brands of stirred yogurt were evaluated using a haake rotovisco model rv 20 with an m. Plasma ldl cholesterol lowering by plant phytosterols in a hamster model. Rheology of stirred yogurts ramaswamy 1991 journal of. Time dependent stress decay rheology of stirred yogurt. Heat transfer and rheology of stirred yoghurt during cooling in plate heat exchangers. For samples from both brands, the upward shearrate flow behavior generally followed the herschelbulkley model and the downward flow curves were linear. Ambient yoghurt production is the same as stirred type whit the difference of the ambient yoghurt is heattreated after fermentation in order to inactivate the lab and so therefore.
Yoghurt properties can be enhanced by the addition or treatment with various additives. Steadyshear viscosity of stirred yogurts with varying. Stirred yogurt is obtained by breaking the gel after fermentation in tanks. It was shown in this work that the simple rheological tests can be used to estimate the structure breakdown rate of stirred yoghurt in pipe flow. Moreover, nethyl maleimide addition had no effect on the stirred yoghurt. Rheological monitoring of structure evolution and development.
Evaluation of rheological, physicochemical, and sensory. However, dynamic rheology has been applied to stirred yoghurt only in commercial samples 16,17. Creamy stirred yogurt an indulgent treat for all the senses. Rheology of stirred yogurt as affected by added milk fat. Chemical, nutritional, rheological, and organoleptical. Structure breakdown of stirred yoghurt in a circular pipe. Heat transfer and rheology of stirred yoghurt during cooling in plate heat exchangers article pdf available in journal of food engineering 572. Rheology is the science of deformation and flow within a material. A rheological study was carried out in order to characterise the stirred yoghurt flow behaviour, evaluating its dependency both on shear rate and.
During the conditioning process stirring, pipe flowing and pumpage, the product is subject to shearing constraints which result in the destructuring of the protein matrix affecting the rheological properties. Dynamic and shear values were measured at 8c and syneresis at 4c. Flavor release and rheology behavior of strawberry fatfree. Yogurt can be classified as pseudoplastic material contains a yield stress that has to be exceeded for flow to be initiated that can be either a viscoelastic fluid if we are dealing with stirred or drinking. The missing link sensory and rheology study of low fat stirred yoghurt heidi l. The yoghurt was stirred to smoothen and to obtain semisolid consistency. Further information has been provided by muller 1973 and sherman 1979.
The rheograms, obtained using a rotational viscometer, included an upward linear ramp. The shear flow behaviour of stirred yoghurt in the coneandplate and cylindrical couette geometries was studied using diffusing wave spectroscopy dws and nuclear magnetic resonance nmr velocimetry. Request pdf rheological characterization of stirred yoghurt. Most of the basic plain yogurts are set yogurts, which are fermented in the container that they are eventually sold in, while most fruitflavored yogurts are stirred yogurts, because flavors and fruit. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Nrs the missing link sensory and rheology study of low fat. A shift in the temperature dependency was evidenced at 25 a. The spme fiber was carefully chosen, and results are presented in detail choice and degradation. Rheological behaviour of lowfat and fullfat stirred yoghurt. Wyss weitzlab group meeng tutorial 10x1035 0 5 10 strain 0 2 4 6 8 10 12 time s. Food rheology is the study of the deformation and flow of food materials 1. A methodology was developed to evaluate simultaneously the shear rate and time dependency of stirred yogurt rheology. Simultaneous evaluation of shear rate and time dependency of stirred yogurt rheology as influenced by added pectin and strawberry concentrate. Development and breakdown of structure in yoghurt studied by oscillatory rheological measurements.
Yoghurt rebodying could not be explained by fulfilling ionic equilibrium. Yoghurt properties were followed by dynamic rheometry bohlin universal rheometer and by penetrometry stevens lfra texture analyzer and the measuring methods were compared. The influence of storage on the aroma release in headspace and rheological properties in strawberryflavored fatfree stirred yogurts was determined. Apr 06, 2004 the influence of storage on the aroma release in headspace and rheological properties in strawberryflavored fatfree stirred yogurts was determined. Most fluid foods including dairy fluids like cream, ice cream mix, stirred yoghurt and liquid infant foods shows complex flow behaviour at different stages of processing and it requires study of its flow behaviour for better control over the processing parameters. Abstract rheological characteristics of 2 commercial brands of stirred yogurt were evaluated using a haake rotovisco model rv 20 with an m. In a typical yoghurt production process, additives and flavours are added after the fermentation process bylund, 1995. The rheological characterization of stirred yogurt with added milk fat, na caseinate or micellar casein and gelatin 4 bloom strengths, starch or a xanthan gumlbg 50. A shift in the temperature dependency was evidenced at 25 degreesc.
Spectroscopic prediction of rheological properties of. Yoghurt is a fermented dairy product, having several health benefits. Chemical, nutritional, rheological, and organoleptical characterizations of stirred pumpkin yoghurt. Effects of starter cultures on small deformation rheology of stirred yoghurt. Pdf heat transfer and rheology of stirred yoghurt during. Ramaswamy, simultaneous evaluation of shear rate and time dependency of stirred yogurt rheology as influenced by added pectin and strawberry concentrate, journal of food engineering, 21, 3, 385, 1994. Steady and dynamic rheological behaviour of frozen soy. The properties of buffalo and bovine milk differ and the procedures developed to make bovine yoghurt may require optimisation for the production of buffalo yoghurt.
C and the three replicates of the stirred yoghurt were analyzed after 1, 7 and 14 d of manufacturing. For thicker, greekstyle yogurt, after incubation, spoon the yogurt into a cheeseclothlined colander set over a. Yoghurt starter culture consists of a blend of streptococcus thermophilus and lactobacillus delbrueckii subsp bulgaricus. Pdf rheological properties of stirred yoghurt as affected by gel ph.
The stirred yoghurt is fermented in a big container and after fermentation the coagulum is destroy gentle, cooled and pumping to the final package to the consumer. Food rheology is the study of the deformation and flow of food materials rao, 1999. Set yoghurt storage modulus depended on ph but not on fermentation time. The factors responsible for the increase in viscosity of stirred yoghurts are therefore in the manufacture of stirred yoghurts, a setstyle yoghurt gel is essentially. Rheology for the food industry gipsy tabilomunizaga a, gustavo v. Simulation of stirred yoghurt processing in plate heat exchangers. Heat transfer and rheology of stirred yoghurt during cooling. The aim of this study was the rheological monitoring of structure evolution and development during the production stages and storage of stirred yoghurt, which was performed by means of steady and oscillatory shear experiments. Most of the basic plain yogurts are set yogurts, which are fermented in the container that they are eventually sold in, while most fruitflavored yogurts are stirred yogurts. Effect of fermentation temperature on the rheology of set.
606 1578 274 961 465 292 1509 1030 571 421 1300 655 1350 1503 138 956 737 163 991 1558 462 1324 437 1325 1229 1009 1623 146 1485 1459 1236 56 361 602 1585 951 790 5 1366 562 214 806 943 1143 1163 664 191 185 693