Compositional Changes in Yam Bean During Storage

Abstract

Abstract Composition of yam bean ( Pachyrrhizus erosis L. Urb) tubers stored at 22° and 12.5°C was monitored monthly for up to 5 months. A continual loss of moisture occurred in tubers at both storage temperatures—after 4 months tubers stored at 22° lost 14.5% of their original weight; those stored at 12.5° lost 9.6%. A higher respiration rate of 15 to 28 ml·kg –1 ·hr –1 occurred during the first 2 months of storage at 12.5°. This was nearly double the respiration rate of tubers stored at 22°. Ethylene was not detected at any time. There are a continual breakdown of starch in tubers. After 3 months, tubers stored at 12.5° had one-sixth the harvest content of starch. At 22°, starch declined to two-thirds the harvest content. The decline in starch content at 12.5° was related to an increase in total sugars in the tuber, particularly sucrose. The sucrose content of the tuber stored at 12.5° tripled over a 3-month period. Glucose and fructose levels declined over the same period irrespective of storage temperature. The results suggest a chilling response that led to a sweeter tuber. Titratable acidity was very low, as was total phenols, and both did not change after harvest.