The effect of harvest dates on the starch properties of various potato cultivars Takahiro Noda a, * , Shogo Tsuda a , Motoyuki Mori a , Shigenobu Takigawa a , Chie Matsuura-Endo a , Katsuichi Saito a , Wickramasinghe Hetti Arachichige Mangalika b , Akihiro Hanaoka c , Yasuyuki Suzuki c , Hiroaki Yamauchi a a Department of Upland Agriculture, National Agricultural Research Center for Hokkaido Region, Shinsei, Memuro, Hokkaido 082-0071, Japan b Department of Crop Science, Obihiro University of Agriculture Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan c Research and Development Department, Toyo Suisan Kaisha Ltd., Higashishinagawa 3-chome, Shinagawa-ku, Tokyo 140-0002, Japan Received 23 May 2003; received in revised form 1 September 2003; accepted 1 September 2003 Abstract The effect of harvest dates on the starch properties of six potato cultivars was studied. The focus was on the content of amylose and phosphorus, mean granule size, viscosity analysis by rapid visco analyzer, thermal analysis by differential scanning calorimetry, and chain length distribution of amylopectin. A late harvest date significantly enhanced mean granule size, the phosphorus content, peak viscosity and breakdown. Furthermore, a late harvest date led to significant but slight decreases in amylose content, pasting temperature, and gelatinization temperature. In contrast, harvest date had no influences on gelatinization enthalpy on distribution of the shorter chain lengths of amylopectin. The correlation coefficients were calculated among these starch properties, and starch phosphorus content was found to have positively significant correlations with the peak viscosity and breakdown. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Potato starch; Phosphorus content; Pasting properties; Differential scanning calorimetry; Harvest date 1. Introduction The potato is an important upland crop in Japan. The total annual production of potatoes in Japan was approximately 2.96 million tons in 1999, and about 75% of the total production comes from Hokkaido, the northernmost and second largest island of Japan (Mori, 2001). Potatoes for starch production, which account for 35–40% of the domestic output, are grown exclu- sively in Hokkaido. The starch has small amounts of covalently bound phosphate in the amylopectin molecules. Potato starch is unique because it has a higher concentration of phosphate than the starches from other botanical sour- ces (Hizukuri, Tabata, & Nikuni, 1970). A relatively high degree of phosphate substitution in potato starch leads to starch gels with high viscosity (Suzuki, Shiba- numa, Takeda, Abe, & Hizukuri, 1994; Veselovsky, 1940; Wiesenborn, Orr, Casper, & Tacke, 1994). Therefore, potato starch is used in fish paste products, as an ingredient in several types of noodles and in the production of glucose and isomerized-glucose syrup. Starch properties are generally influenced by the cultivars and by environmental factors. The starch properties of potato cultivars vary significantly (Cottrell, Duffus, Paterson, & Mackay, 1995; Ganga & Corke, 1999; Haase & Plate, 1995; Jansen, Flamme, Sch€ uler, & Vandrey, 2001; Kim, Wiesenborn, Orr, & Grant, 1995; Morrison et al., 2000; Sabiniano, Ishibashi, & Hironaka, 1995; Suzuki et al., 1994; Veselovsky, 1940; Wiesenborn et al., 1994), and the developmental stage of a potato also affects starch properties (Geddes, Greenwood, & Mackenzie, 1965; Lui, Weber, Currie, & Yada, 2003; Food Chemistry 86 (2004) 119–125 www.elsevier.com/locate/foodchem Food Chemistry * Corresponding author. Tel.: +81-155-62-9278; Fax: +81-155-62- 2926. E-mail address: noda@affrc.go.jp (T. Noda). 0308-8146/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2003.09.035