Show simple item record

dc.contributor.advisorBenkreira, Hadj
dc.contributor.advisorBeckett, S.
dc.contributor.authorRutson, Sandra M.*
dc.date.accessioned2010-01-21T15:21:27Z
dc.date.available2010-01-21T15:21:27Z
dc.date.issued2010-01-21T15:21:27Z
dc.identifier.urihttp://hdl.handle.net/10454/4200
dc.description.abstractAn investigation has been carried out into the rheology of chocolate in relation to its flow and mixing features in a real industrial environment. The chocolate manufacturing plant of Rowntree at York provided a base for this study. The project aims were: a) to measure the viscous and time dependent properties of chocolate. b) to explain the observed flow properties in relation to the constituents of chocolate. c) to determine the shear rate which, for a given recipe, yields a minimum stable viscosity (of particular commercial value). d) to assess the type of mixer able to provide this duty. The experimental work involved rheological studies with concentric cylinder and tubular viscometers, operated to measure viscosity as a function of shear rate and shearing time. The chocolate samples studied were taken from various points in the manufacture process at Rowntree, York. Model chocolate systems were made from cocoa liquor, and sugar with cocoa butter, which were studied to underpin the basic mechanisms of the flow properties of the total chocolate. Shear thinning in milk chocolate has been shown to be accounted for by surface coating and fat release from the cocoa cellular material. Analysis of the sugar and cocoa butter system gave large hysteresis loops which may be explained as due to agglomeration of the sugar particles. The level of hysteresis was found to be related to the polarity of the liquid phase, such that a more polar fluid results in less hysteresis. Laboratory experiments have revealed that the level of work input to give permanent viscosity reduction for milk chocolate is dependent on the measuring shear rate. The level of optimum shear input for the measuring range 10 to 130 sec 1 is 645 sec for 30 minutes. The apparent viscosity measured at lower shear rates requires much longer ([approx]100 minutes).en
dc.description.sponsorshipYorkreco, Nester York Ltd.en
dc.language.isoenen
dc.rights<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>.en
dc.subjectChocolateen
dc.subjectManufactureen
dc.subjectRheologyen
dc.subjectFlowen
dc.subjectMixingen
dc.subjectWork inputen
dc.subjectHysteresisen
dc.subjectShear thinningen
dc.subjectViscosityen
dc.titleRheology of chocolate. Rheological studies of chocolate in relation to their flow and mixing properties during manufacture.en
dc.type.qualificationleveldoctoralen
dc.publisher.institutionUniversity of Bradfordeng
dc.publisher.departmentPostgraduate School of Studies in Chemical Engineering.en
dc.typeThesiseng
dc.type.qualificationnamePhDen
dc.date.awarded1989
refterms.dateFOA2018-10-24T01:10:08Z


Item file(s)

Thumbnail
Name:
Rutson.pdf
Size:
13.24Mb
Format:
PDF

This item appears in the following Collection(s)

Show simple item record