A rheo-optic study of liquid/liquid systems with varying phases, volume fractions and viscosity ratios

Autor: Ourania Gouseti, A.W. Pacek, Nicholas James Watson
Rok vydání: 2020
Předmět:
Zdroj: Food and Bioproducts Processing. 123:251-261
ISSN: 0960-3085
Popis: There is a need to understand the rheology and structure of emulsion-based systems under flow, as they determine quality attributes of foods such as texture, stability and taste. However, simultaneous rheo-optical investigations are challenging partially due the limited (and expensive) equipment available. An in-house rheo-optical device has been used to study the effect of shear (steady shear at 250s−1; increasing-decreasing shear at 0-500-0s−1) on rheology and structure of O/W and W/O systems at viscosity ratios (viscosity of dispersed phase over viscosity of continuous phase) λ = 0.2−68 and volume fractions of dispersed phase φ = 0.05−0.3. The O/W and W/O systems had identical ingredients but inversed phases. First, development of the device and its potential to capture clear images under shear is reported. Then, results for O/W systems at steady shear are compared with predictive rheological models, which typically link relative viscosity with φ and λ. The effective medium model showed best agreement. On increasing-decreasing shear, strong link between rheology and structure was indicated. Finally, relative viscosities of the W/O systems were invariably lower than those of the O/W dispersions with similar φ and λ. The related obtained microstructures appeared to be largely determined by drop breakage, controlled by the viscosities of the individual phases rather than λ. This work indicates a close link between rheology and structure for the investigated systems, and it suggests that the link between morphology and viscosity is complex and depends on the nature of the investigated material.
Databáze: OpenAIRE
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