Carbohydrate Polymers 98 (2013) 241–248 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers jo ur nal homep age: www.elsevier.com/locate/carbpol Changes in physicochemical properties of waxy corn starches at different stages of harvesting Danupol Ketthaisong a,b , Bhalang Suriharn a,b , Ratchada Tangwongchai c , Kamol Lertrat a,b,∗ a Department of Plant Science and Agricultural Resources, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand b Plant Breeding Research Center for Sustainable Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand c Department of Food Technology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand a r t i c l e i n f o Article history: Received 12 April 2013 Received in revised form 10 June 2013 Accepted 15 June 2013 Available online 20 June 2013 Keywords: Waxy corn Kernel maturity Harvesting stage Physicochemical property Starch granule Amylopectin chain length distribution a b s t r a c t Starches were isolated from immature waxy corn kernels harvested at 0, 2, 4 and 6 days after optimum stage (DAO) and from mature kernels at 16 DAO. The starch contents showed varied according to geno- types and harvesting stages. The accumulation of starches showed an increasing trend in relation to delayed harvesting time, from the optimum stage until the physiological maturity stage. Among all har- vesting stages, medium granules had the highest contribution to the total starch volume (60.8–81.5%), followed by large (5.7–30.1%), and small granules (9.1–15.3%). Average chain length distribution of amy- lopectin ranged from DP 14.7 to 16.9 for KKU–UB, DP 16.9 to 17.4 for KKU–JD, and DP 5.7 to 30.1 for Violet white. The pasting behaviors of starches were greatly affected by harvesting times. The peak viscosity of starches increased with delayed harvesting until physiological maturity and then decreased until dried kernels at 35 days after pollination. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Waxy corn as the fresh vegetable has been improved and cul- tivated over East and Southeast Asia for more than a century. This corn is now appearing in the European and American markets in great quantities and is sold as canned corn kernels, frozen corn ker- nels, and frozen corn ears. The market share of waxy corn in seed companies has increased as well, because of its popularity and the wide distribution of suitable growing areas. Farmers in Thailand and Southeast Asia have grown waxy corn as a cash crop in addi- tion to rice for fresh consumption, consumed similar to sweet corn as cooked green ears (Lertrat & Thongnarin, 2008). The corn is sold fresh or as cooked ears at roadside markets, while large-scale farm- ers grow corn for the food industry or for export (Lertrat & Pulam, 2007). Texture is widely recognized as one of the most important deter- minants of the eating quality of waxy corn. It has been observed that Thai consumers prefer sticky and tender corn, whereas others ∗ Corresponding author at: Department of Plant Science and Agricultural Resources, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand. Tel.: +66 43 202 696; fax: +66 43 202 696. E-mail addresses: kamol9@gmail.com, danupol63@gmail.com (K. Lertrat). prefer it mildly sweet. Numerous studies have shown that the basic components of starch can affect the textural properties of several staple food crops such as rice (Kang, Hwang, Kim, & Choi, 2006), potato (Singh, Kaur, Ezekiel, & Guraya, 2005) and sorghum (Cagampang & Kirleis, 1984). A previous report confirmed that physicochemical criteria, such as apparent amylose content, gela- tinization temperature, and gel consistency, are key factors in evaluating the eating and cooking quality of rice; hence, the eat- ing quality essentially reflects the starch properties (Juliano, 1998). Other important starch property parameters have been studied to precisely evaluate factors that determine the quality of cooked rice, such as past viscosity characteristics (Bao & Xia, 1999; Bao et al., 2000; Champagne et al., 1999; Lin, Shi, Wu, & Wu, 2005), and branch chain length distribution of amylopectin (He et al., 2010; Yang et al., 2012). In waxy corn, the main chemical components of starch in the kernels are amylose and amylopectin, and some intermediate materials that retain characteristics of both fractions. Functional properties of starch are affected by the amylose content and branch chain length distribution of amylopectin (Hanashiro, Abe, & Hizukuri, 1996; Kuakpetoon & Wang, 2006). Amylose is lin- ear or slightly branched molecules whereas amylopectin is highly branched molecules. Waxy corn starch contains essentially 100% amylopectin (Perera, Lu, Sell, & Jane, 2001). Therefore, for breeding 0144-8617/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2013.06.016