A BIOCHEMICAL STUDY OF CURING PROCESSES IN SWEET POTATOES

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Abstract
A study was made of the N metabolism and the pectic transformations in Maryland Golden sweet potatoes during curing under different combinations of temp. and humidity and also during subsequent storage. The soluble pectin in the sweet potatoes increased slightly during curing. The protopectin showed a corresponding decrease. The total pectic material increased. At the storage temp. the protopectin increased again while the pectin decreased. Some of the increase in protopectin was due to an actual increase of the total pectic substances. This storage synthesis of protopectin continued in the roots as long as they remained alive and sound. The non-protein N in the sweet potatoes at harvest time ranged from 22 to 33% of the total N. Under all of the curing conditions the non-protein N increased and the protein N decreased. Fairly consistent increases in basic, amide, and residual N occurred in all lots but a consistent increase in amino N occurred only in lots cured at the high temps. of 95[degree] and 104[degree]F. The N distribution in the sweet potatoes during storage at 50[degree] to 53[degree]F remained fairly stable during most of the storage period. There was no apparent difference in the N distribution in the proximal and distal halves of the Maryland Golden sweet potato. At 85[degree]F, a high rel. humidity was the decisive factor for effective curing of this var., but there was no conclusive evidence that humidity had any effect on the N metabolism in the roots during curing. The curing of sweet potatoes appears to involve a number of interrelated internal processes. Studies to date do not reveal any one outstanding essential change in the potatoes during curing.