Mixed powders, particularly when the ingredients have different size, density and shape, tend to segregate during processing and handling, a process that has obvious technological and economic implications. Despite the well recognized consequences of powder segregation, this phenomenon, in food powders has not been systematically studied. Although food powders can almost invariably be regarded as cohesive, selective segregation of certain fine ingredients is not uncommon. This research was designed to investigate the segregation mechanism of food powders with special emphasis on the role of interparticle surface affinity between food powders of different chemical species in regulating the segregation intensity. Since established quantitative segregation criteria for food powders are non-existent, the project also dealt with the development and testing of such criteria and the selection of appropriate experimental procedures for their determination. In order to quantify and monitor segregation intensity, binary mixtures of crystalline, proteinaceous and starchy food powders were subjected to vertical vibration by a specially designed reciprocating device enabling the control of the vibration frequency and to horizontal vibration using a commercial type of shaker. Also, the composition distribution in a container filled with the mixtures was sampled at various locations. Binary mixtures were analyzed by Scanning Electron Microscopy before and after exposure to various levels of relative humidity. Based on their microstructure, they were classified as: random, ordered, partially random, and partially ordered randomized. Also studied were the bulk density and compressibility of binary mixtures, the effect of mixing order on food powder mixture structure and properties (e.g. color) and the migration of fine powders to the surface of particulates of different species as a result of selective affinity.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-7705 |
| Date | 01 January 1985 |
| Creators | BARBOSA CANOVAS, GUSTAVO VICTOR |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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