Show simple item record

dc.contributor.supervisor Scanlon, Martin (Food Science) en_US
dc.contributor.author Daugelaite, Daiva
dc.date.accessioned 2011-12-14T21:58:29Z
dc.date.available 2011-12-14T21:58:29Z
dc.date.issued 2011-12-14
dc.identifier.uri http://hdl.handle.net/1993/4997
dc.description.abstract The production of highly aerated foods remains a challenge that requires skill to obtain desired appearance and texture. Since foams are fragile and inherently unstable, evaluation of structure changes with time requires a delicate approach. Non-invasive but informative evaluation of changes in aerated food properties is a desired goal to be achieved in this thesis. I studied the aging of egg white foams of different void fraction using two noninvasive techniques - ultrasonic spectroscopy and electrical resistivity - with a view to understanding aging mechanisms that would affect the quality of the final product. To help in interpretation of the results, a commercial high void fraction foam, Gillette (Sensitive), was also analyzed. As a support technique for ultrasound results I used image analysis in order quantitatively evaluate the size of bubbles in the foams. Large increases in attenuation were observed with increasing aging time and frequency. Results were modeled using an effective medium theory originated by Foldy (1945) in order to understand the factors governing foam lifetime and texture. From electrical resistance measurements, liquid fraction changes in an egg white foam column were evaluated quantitatively and qualitatively by using a generalized free drainage model. Although egg-white foams were more prone to changes due to drainage, I observed that for all foams the ultrasonic scaling parameter alfa*lambda/freq was proportional to the square of average bubble size (indicative of a diffusively driven aging process due to disproportionation of bubbles). Slopes of alfa*lambda/freq versus aging time were 6*10-8 and 11*10-8 for egg white foams of void fraction 0.65 and 0.78, respectively, indicating that disproportionation progressed approximately twice as fast in the high void fraction foam. The slopes of alfa*lambda/freq versus aging time were similar for both Gillette foam void fractions (0.93 and 0.91) at a value of 1.5*10–8 s-1, attributable to a lower solubility of isobutane compared to air. By combining ultrasound and electrical resistivity, this thesis has provided novel insights into understanding instability processes occurring in foams. Potentially, ultrasound techniques could be used instead of imaging for foam aging studies, since non-invasive and non-destructive measurements of attenuation and phase velocity permit interrogation of opaque foam structures. en_US
dc.rights info:eu-repo/semantics/openAccess
dc.subject ultrasound en_US
dc.subject food foams en_US
dc.subject electrical resistivity en_US
dc.subject foam imaging en_US
dc.title Time dependent studies of foam stability using image analysis, electrical resistivity and ultrasound en_US
dc.type info:eu-repo/semantics/doctoralThesis
dc.degree.discipline Food and Nutritional Sciences en_US
dc.contributor.examiningcommittee Page, John (Physics) Sapirstein, Harry (Food Science) Cenkowski, Stefan (Biosystems and Engineering) Corredig, Milena (Department of Food Science, University of Guelph) en_US
dc.degree.level Doctor of Philosophy (Ph.D.) en_US
dc.description.note February 2012 en_US


Files in this item

This item appears in the following Collection(s)

Show simple item record

View Statistics