Microwave and water blanching of carrots and sweet potatoes were evaluated with respect to peroxidase inactivation, texture degradation and color changes for obtaining stable frozen stored products. Carrot slices and french fry style sweet potatoes were blanched in a 700 W domestic microwave oven as well as in boiling water for different treatment times. Blanched and unblanched samples were packaged in retort pouches and frozen stored at $-$20$ sp circ$C, and evaluated for peroxidase activity, texture and color before and after blanching, and after 3.5 and/or 7 months frozen storage. Kinetics of peroxidase activity and texture softening due to blanching was described by semi-logarithmic models. All frozen products, except unblanched samples, were of good quality at the end of 7 months storage. Small quality differences were detected in the blanched frozen samples during storage; samples blanched for intermediate times were superior. / Temperature distribution profiles were determined for model foods consisting of a starch gel with different concentrations of protein and fat, as well as commercial frozen and refrigerated prepared foods. Microwave heating of model foods showed considerable nonuniformity in temperature distribution and alarmingly low center temperatures. Prolonged lower power heating or holding after microwave heating did not always elevate center temperatures to safe levels. Addition of protein to the starch gel reduced temperature uniformity and heating rate, while added fat resulted in an opposite trend. / For the commercial foods, center temperatures reached after heating according to manufacturer's instructions were below 70$ sp circ$C indicating some safety concerns. However, longer heating time at lower power levels improved the temperature uniformity as well as the quality and appearance of these foods.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.57010 |
| Date | January 1992 |
| Creators | Fakhouri, May O. |
| Contributors | Ramaswamy, H. S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Food Science and Agricultural Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001324273, proquestno: AAIMM87761, Theses scanned by UMI/ProQuest. |
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