Masters Theses

Kim Anderson

Date of Award

6-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

S. L. Melton

Committee Members

J.R. Mount, M. P. Penfield

Abstract

The effect of 4 levels (0, 10, 20 and 30 g) of each type of defatted soy flour (SF), protein dispersibility indexes (PDI) 20 and 70, at pH values of 5.5, 6.3, 7.1 and 7.9 on gelatinization were determined. Gelatinization variables studied included time to onset of gelatinization, time to maximum viscosity, maximum viscosity (MV) and viscosity at 60 min (V60), for tapioca starch dispersions (30 g/420 ml phosphate buffer) heated in an amylograph. The experimental design was an incomplete randomized block with 3 randomly selected combinations of SF level and pH for each SF being the partial second replication. Surface response methodology was used to show the significant SF level and pH effects on the variables. Level and pH did not affect any of the time variables (P < .05), but did affect MV and V60 in different ways for each SF. In general, MV and V60 increased with increasing SF level at any pH, and had the most effect on V60 in dispersions containing PDI 20 SF.

The effect of 4 substitution levels (0, 33.33, 66.67 and 100%) of each SF, PDI 20 and 70, for shrimp was determined on the chemical composition, color, and texture (force required to break a single chip) of a tapioca-based shrimp chip. A single rep consisted on the 4 levels of the 2 types of SF in the chip, and 2 reps were run. As SF increased from 0 to 100% substitution, the following changes (P < .05) in the chip were found; the protein increased linearly from 1.84 to 11.18%; the fat decreased linearly from 42.75 to 25.50% and the force increased linearly from 286 to 585 g. The chips tended to become darker, redder and more yellow with increasing level of SF, but a significant PDI x SF level interaction was found for the Hunter color "L" and "a" values of the chip. The 100% SF chip was selected for sensory evaluation because its texture was closest to that (723 g) of a commercially produced pork rind which was similar in appearance to the shrimp chip.

Chips containing 100% SF flavored by a commercial shrimp flavor at low and high levels (50 g and 25 g chips/g flavor, respectively) were evaluated by a 57-member panel on an 8-point hedonic scale where 1 = dislike extremely and 8 = like extremely and on a 9-point Food Action Rating Scale. The panel liked the chips with the low flavor level (5.4) better than those with the high flavor level (4.9). Twenty-three of the panel members who said that they would buy the chip liked the chip moderately and would eat it now and then. The hedonic rating of the chip was not affected by age or gender of the judges nor by their attitude towards shrimp flavor (P < .05). However, judges who ate chips several times a week liked the chip significantly less than those who ate chips several times a month or year.

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