Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Paul W. Wilson

Abstract

Roots of Jewel sweet potato cultivar were cured at 32$\sp\circ$C, 80-90% RH for 10 days and stored at 13-16$\sp\circ$C with the same RH. Subjective and objective analyses were performed to determine optimum condition for sweet potato chip development. Frying temperatures of 143, 149, 155, and 160$\sp\circ$C; slice thickness of 1.0, 1.5, 2.0, and 2.5 mm; and four oil types, corn, cottonseed, peanut, and soybean, were studied. Sweet potato roots of the Centennial cultivar were subjected to pre- and post-frying treatments for improving color and reducing oil content of the chips after frying. Roots were cured and stored at the 32$\sp\circ$C temperature and 80-90% RH. A frying temperature of 155$\sp\circ$C in soybean oil and a slice thickness of 1.5 mm were used. Pre-frying treatments that were evaluated were: dehydration at 110$\sp\circ$C for 0, 10, 15, 20, 25, and 30 min; Sodium Acid Pyro Phosphate (SAPP) blanching at 95$\sp\circ$C for 1 min with concentrations of 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, and 1.50%; and coating with Methocel. A post-frying treatment of microwaving in combination with blanching was also tested. The results indicated that good quality chips were produced when raw slices were blanched 0.5% SAPP and partially dehydrated at 110$\sp\circ$C before frying. A superior chip was also obtained by blanching in 0.5% SAPP, followed by a 2.5 min deep fat fry and a 2.0 min post-frying dehydration in a microwave. Four sweet potato cultivars (Centennial, Jewel, L-81-10, and L-80-62) with different storage times were used to determine the effects of cultivar and storage on color and oil content of the chips after frying. Chips prepared right at harvest time yielded the best subjective color ratings of all cultivars. The L-80-62 cultivar had the most preferred bright yellow-orange color. Beta-carotene levels of the chips made from Centennial were higher than those of L-81-10, L-80-62, and Jewel. The major sugars in all cultivars were sucrose, fructose, and glucose; the higher the amount of reducing sugars, the darker the chips appeared. Percent moisture in chips after frying varied between 1-2%. At 4 months storage, L-81-10 produced chips with the lowest fat content after frying while Jewel contained the highest fat content. (Abstract shortened with permission of author.).

Pages

192

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