Numerical simulation of the capillary driven fusion of complex foods as a model system for caking of amorphous food powders
Abstract
Caking of food powders is a process that enhances particle bonding at temperatures lower than the melting point. Facilitated by the plasticizing effect of temperature and moisture it eventually leads to powder consolidation and loss of flowability that cause storage and processing problems. Although there are several mechanisms of caking, with some of them acting simultaneously, the dominant mechanisms governing the caking dynamics of amorphous food powders is the convective transport of the food material towards the bonding region driven by capillarity and resisted by viscosity. The overall objective of this thesis was to develop a rigorous computational framework for the simulation of the capillary driven bonding of complex food materials as a model system for the caking of amorphous food powders, with focus on the effect of environmental conditions and material properties. The framework was developed using Direct Numerical Simulation, that is, by simultaneously solving the full system of partial differential equations governing the capillary driven free-surface flow in a continually deforming particle. Direct numerical simulations enabled detailed examination of physical mechanisms at the small scale of the bonding meniscus which have so far resisted experimental understanding, as well as made predictions that agree well with experimental measurements at the larger scale of the particle size. The rigorous computational analysis enabled predictions of the effect of environmental temperature, humidity, and material composition on the dynamics of caking through their effect on the glass transition temperature. Results are also included demonstrating that both small scale physical phenomena as well as the macroscopic dynamics of caking are profoundly altered by non-Newtonian effects common in many food materials. Results from this thesis not only enhance our current scientific understanding of the physical processes involved in the caking of amorphous powders but the rigorous computational framework developed can have a significant impact on the rational design of more effective methodologies to reduce inefficiency and economic losses during processing and storage of food and agricultural powders arising as a result of caking.
Degree
Ph.D.
Advisors
Corvalan, Purdue University.
Subject Area
Food Science
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