Doctoral Dissertations

Date of Award

8-1970

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

H. D. Swingle

Committee Members

B. S. Pickett, David L. Coffey, Henry Fribourg, Bernadine Meyer

Abstract

The objective of this research was to evaluate the effect of chilling temperatures on the appearance of raw roots of selected sweet-potato cultivars and on the color and flavor of baked roots of these same cultivars. Cultivars selected to give a range of chilling injury susceptibility were NC-212, NC-240 (Jewel),' L-4-73, and Centennial. Storage temperatures of 35° F, 45° F, and 55°Ffor weekly durations up to six weeks were used. This was followed by a one week holding period at 70°F previous to examination. Non-cured and cured roots were evaluated for visual appearance, specific gravity, intercellular space, dry matter content, tissue pH, ascorbic acid content, and chlorogenic acid content. Roots of the NC-212 cultivar were less susceptible to chilling injury as measured organsleptically. NC-240 (Jewel), L-4-73, and Centennial followed in order of their "resistance" to chilling injury. NC-212 did not develop the characteristic dark discoloration following chilling temperature storage. Pithiness in NC-212 often prolonged storage following 35°F storage suggests that this cultivar is not immune to chilling injury. Specific gravity, intercellular space, and percentage dry matter were only slightly influenced by temperature treatments. Tissue pH decreased then increased in non-cured Centennial roots over the six week period. Tissue pH was reduced in cured Centennial roots with low temperature treatment. The reduction of pH was delayed in NC-212 cultivar at low temperature storage. Ascorbic acid content decreased more rapidly in Centennial than in NC-212 at low temperature storage in both cured and non-cured roots but curing tempered the ascorbic acid contents reduction. Chlorogenic acid did not increase in NC-212 at any temperature treatment but did increase in Centennial roots at 35°F and 45°F for both cured and non-cured roots. Little consistent relationship, cultivar to cultivar, was observed between appearance and any of the other variables measured.

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