Influence of Delayed Harvest Time on Physicochemical Properties of Sweetpotato Starch
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_12_03_558_563.doc |
| Abstract: | Summaries. Eight varieties of sweetpotato [Ipomoea batatas (L) Lam] were transplanted in June, and harvested in October, November, December 1999 and January 2000. Starch content and starch properties of the tuberous roots were compared on delaying the harvest date. The shoot tops got blighted in early December and chilling injury rate of roots (average of eight varieties) increased up to 76.7% in January with decrease in temperature. Starch contents in October (24.0 g/100 g fresh weight, fw) and November (25.0 g/100 g fw) were almost the same, but the content decreased remarkably in December (21.2 g/100 g fw) and January (15.5 g/100 g fw). In December and January, the sucrose content of the roots had higher values. Hardness and leaked water percentage (LWP) of the starch gels remarkably increased from November to December (hardness: 76.4 to 112.3 g, LWP: 6.6 to 10.9%). On the contrary, the changes in amy-lose content and pasting properties of the starches were not consistent with decrease in temperature. This suggests that the effect of low temperature on these properties is insignificant after the growth period of sweetpotato. There were significant differences among the varieties in terms of starch retrogradation. The selection of varieties such as Kyushu 123 with the lowest percentage of retrogradation and Kyukei90142-8 with the lowest chilling injury rate will help to lengthen the storage time in the field at least until December. Conclusions. The low temperature (below 15 °C) after the termination of growth period largely promoted retrogradation of sweetpotato starch. The changes in amylose content, thermal properties and pasting properties were not consistent with decrease in temperature. Chilling injury and starch retrogradation were the two main limiting factors for retaining sweetpotato roots in ridges. The selection of varieties, that are tolerant to chilling injury (like Kyukei90142-8), and are less prone to retrogradation, such as Kyushu 123, is necessary to lengthen the harvesting period of sweetpotato. |
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| ISSN: | ISSN 0038-9056 |
