Masters Theses

Date of Award

8-1978

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

J. L. Collins

Committee Members

H. O. Jaynes, S. D. Cunningham

Abstract

The objective of this investigation was to determine the effect of soymeal and cheese on some physical and sensory attributes of tortillas as prepared in Bolivia, and to evaluate the nutritional value of the different mixtures of corn- and soymeals, and cheese. The amount of water required for dough development of the different mixtures containing corn- and soymeals, and cheese to yield a uniform firmness had to be increased as the amount of soymeal was increased, and decreased with the addition of cheese. Firmness of the tortillas decreased as the amount of soymeal was increased. The presence of cheese caused a decrease in firmness. Flexibility of tortillas was increased as the level of soymeal was raised. Cheese improved flexibility. Soymeal produced doughs and tortillas that were lighter, and cheese produced doughs that were darker than those prepared from corn only. The doughs and tortillas become less red and less yellow by addition of soymeal and cheese. The sensory panel did not show a preference for flavor among tortillas containing the different amounts of soymeal. The mean flavor score was slightly lower than like moderately. Tortillas with 30% soy-meal received a lower score for mouthfeel than tortillas at the lower levels of protein. The mean mouthfeel score was midway between like slightly and like moderately. Tortillas with cheese were preferred over those without cheese. Holding the raw soybean in boiling water for 10 minutes destroyed 89.7% of the trypsin inhibitor activity. The cooking process of the tortillas caused up to 3.68% reduction in available lysine. All mixtures of cornmeal, soymeal and cheese were deficient in sulfur-containing amino acids. The mixture containing 90% cornmeal and 10% soymeal was deficient in tryptophan; the mixture containing 90% cornmeal and 10% cheese was deficient in lysine. All other mixtures had adequate amounts of essential amino acids except the sulfur-containing when compared with the FAO provisional pattern. Chemical scores of all mixtures indicate that the sulfur-containing amino acids are the first-limiting; valine, second-limiting; and isoleucine, third-limiting when compared to whole egg proteins. The addition of 10% soymeal to cornmeal increased the protein efficiency ratio (PER) from 35 to 79% of that of casein (PER = 2.5). Soymeal at 20% raised the PER to 94% of that of casein. The diet with 30% soymeal had a PER which was not different from that of casein. Diets containing 10% cheese, soymeal at 10, 20 and 30% had PER values that were not different from that of casein.

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