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ARS Home » Southeast Area » Raleigh, North Carolina » Food Science Research » Research » Publications at this Location » Publication #56608
Title: EFFECT OF LONG TERM STORAGE ON CELL WALL NEUTRAL SUGARS AND GALACTURONIC ACID OF TWO SWEETPOTATO CULTIVARS

Author
item WALTER W M JR - 6645-10-00
item PALMA C S - NCSU

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sweetpotato consumption has declined over the years in spite of the nutritional benefits and excellent taste of this vegetable. One reason is because few convenience foods containing sweetpotato are available. This is because a successful processing operation has to produce a consistent product from raw material which has been stored for varying lengths of time. This is difficult because the texture of products made from stored sweetpotatoes changes as the storage time increases. Changes in cell wall components can exert significant influence over textural properties, but little is known about this material in sweetpotatoes. The objective of this research was to determine the changes in composition of selected cell wall components during storage of the two most widely used commercial sweetpotato cultivars. We observed no consistent pattern with regard to changes in concentrations of most cell wall components. The only change we eobserved in cell wall components due to long term storage of the roots known to affect texture was the decrease in the apparent molecular size of the pectic substances. Although we were not able to document the exact cause of storage-induced textural changes, the information generated in this research does provide quantitative data regarding cell wall components which will be useful as knowledge increases about the relationship between cell wall composition and textural properties.

Technical Abstract: 'Jewel' and 'Beauregard' sweetpotatoes (SP) were sampled at harvest and after 49, 119, and 217 days of storage. At each sampling date for each cultivar, pectinmethylesterase (PME) activities, and the concentrations of galacturonic acid (GA), galacturonic methyl esters, and cell wall (CW) neutral sugars were determined for both water-soluble (WS) and water- insoluble (IS) CW substances. No polygalacturonase (PG) activity was detected, but both cultivars had active PME systems and, for both cultivars, the GA content of WS increased during storage, while the GA content of IS decreased, reflecting decreases in pectin size. The percent methyl ester content did not change for either cultivar. CW neutral sugar concentrations declined in the order: glucose - galactose - xylose - rhamnose - mannose - arabinose - fucose. For both cultivars, the few cell wall sugar changes which occurred over time were shown to best fit a quadratic model. Thus, the only observed change in CW components which is known to affect firmness was the decrease in IS pectic substances. Changes in CW neutral sugars were minimal and were not observed in both cultivars.