Abstract
The rheology of β cocoa butter crystal melt suspensions (CB CMS) was investigated directly after crystallization using in-line capillary rheometry (UVP-PD) as well as after tempering at zero deformation using off-line capillary rheometry (CR) and rotational rheometry (RR). CB CMS thixotropy was quantified by RR revealing that structure build up processes at zero deformation were not at equilibrium after 18 h, whereas structure decay occurred mainly in the first 10 s of measurement at γ˙ = 60 s . CR and UVP-PD were identified as preferable methods to probe thixotropic materials due to the short measurement time t and uniform sample deformation history for every γ˙-step. The scaling of the relative viscosity η and the (apparent) yield stress τ /τ as function of deformation history revealed two different regimes. Directly after the crystallization, the CB CMS behaved like a suspension of anisotropic crystals with a fractal dimension D≈1.57, an intrinsic viscosity [η] of 20 and a maximal packing fraction Φ of 0.17 leading to a scaling of η =(1−(Φ /Φ )) . After tempering at zero deformation, crystal aggregation increased the fractal dimension to D=2.6 and the scaling of the relative viscosity η reduced to ~Φ , analogously to a jammed system of elastic particles. V/VI M rel 0 0 max rel SFC max rel SFC −1 app −3.4 2 Show more
Permanent link
https://doi.org/10.3929/ethz-b-000479926Publication status
publishedExternal links
Journal / series
Journal of Food EngineeringVolume
Pages / Article No.
Publisher
ElsevierSubject
Rheology; Thixotropy; UVP-PD in-line rheometry; Capillary rheometry; βV/VI cocoa butter; Herschel-Bulkley fluid; Crystal-melt suspension; Fractal dimension; Jammed suspension; Single crystal AFMOrganisational unit
03345 - Windhab, Erich Josef (emeritus) / Windhab, Erich Josef (emeritus)
08821 - Fischer, Peter (Tit.-Prof.)
Funding
180971 - Industrially relevant Synchronous Multiscale 3D-Printing Process (SYMUS-PD3) for the fast manufacture of tailored texturized and sensory/nutrition-functionalized food systems (SNF)
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Is source of: https://doi.org/10.3929/ethz-b-000508085
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