Physicochemical Properties of Starches from Potatoes Stored at Low Temperature

Potato tubers (cv., Inka-no-mezame, Inka Red, Kitamurasaki, Danshaku and Kitahime) were stored at 4°C for about 8 months and changes in physicochemical properties of starches isolated from potatoes were examined periodically during storage. Both average granule size and phosphorus content of starches were decreased during low temperature storage. However, the blue values of starches from five cultivars were increased with the increasing duration of storage period. These changes may suggest that amylopectin of the outer surface of starch granules is gradually converted to sugars during cold storage. There was no clear tendency regarding swelling power and solubility of starches during storage. From RVA analysis, the pasting temperature of Inka Red and Inka-no-mezame appeared to be higher than that of other cultivars. During low temperature storage, the difference in pasting temperatures among five cultivars became slightly smaller. Judging from DSC thermograms, To, Tp and Tc of Inka Red shifted in a higher temperature range, while those of Danshaku showed in a lower range. Low temperature storage led to slight increase in ΔH and Tc, while decreasing Tp of all cultivars.