Doctoral Dissertations

Date of Award

8-1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

Marjorie P. Penfield

Committee Members

Sharon L. Melton, Hugh Jaynes, Vernon H. Reich

Abstract

In order to investigate the effects of microwave-baking of cakes, 60 combinations of hydroxypropyI methycellulose (1.8, 2.0, 2.2%, fwb), modified pregelatinized potato starch (3.2, 4.2, 5.2, 6.2% fwb), and deionized water (137.5, 150.0, 162.5, 175.0, 187.5% fwb) were used in a modification of the AACC layer cake formulation. The study was a balanced incomplete block. Batter tests included pH, specific gravity, and viscosity. Cake and crumb tests included weight loss and moisture content. Shrinkage, volume, symmetry, and uniformity also were determined. A modified texture profile analysis was done. Gum level was not significant (p<0.05) for most of the objective measurements. Starch content was a significant factor (p<0.05) for pH, viscosity, and chewiness. Water levels influenced al l of the objective batter and cake tests except weight loss and uniformity.

A lexicon of sensory terms and reference standards were developed. Twenty descriptors were grouped into surface appearance, resistance to cut with fork, crumbliness, springiness, texture in the mouth, first bite with the molars, breakdown, ease of chewing, ease of swallowing, and residual. A 7-member panel evaluated the cake formulas using 15-cm scales anchored with bipolar terms. Water influenced (p<0.05) more of the sensory parameters than gum or starch.

Response surface methodology was used to plot the data and help choose formulas for selected studies. The four formulas chosen for these studies represented the extremes on the response surfaces. The selected studies included scanning electron microscopy (SEM) of the crumb, flow patterns of the batter during baking, microscopic evaluation of the fat, subjective crumb evaluation, and a consumer panel. The SEM micrographs clearly showed the potato starch granules. The flow patterns were similar for the four microwave formulas, but were different from the flow in the conventional oven. There was not an obvious difference in the size and distribution of the fat cells among the four batters. The crumb cell size, however, decreased noticeably as starch and water levels increased. Finally, the consumer panel evaluated two of the four formulas and an "ideal" cake. Both of the formulas were similar to the ideal.

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