Accepted Manuscript

Accepted Manuscript Effects of variety and growth location on the chain-length distribution of rice starches Hongyan Li, Yingli Liu PII: S0733-5210(18)30680-5 DOI: https://doi.org/10.1016/j.jcs.2018.11.009 Reference: YJCRS 2668 To appear in: Journal of Cereal Science Received Date: 7 September 2018 Revised Date: 21 November 2018 Accepted Date: 21 November 2018 Please cite this article as: Li, H., Liu, Y., Effects of variety and growth location on the chain- length distribution of rice starches, Journal of Cereal Science (2018), doi: https://doi.org/10.1016/ j.jcs.2018.11.009. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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ACCEPTED MANUSCRIPT 1 Effects of variety and growth location on the chain-length distribution of rice 2 starches 3 Hongyan Li a,b *, Yingli Liu a, * 4 aBeijing Advanced Innovation Center for Food Nutrition and Human Health, 5 China-Canada Joint Lab of Food Nutrition and Health (Beijing), Beijing Engineering 6 and Technology Research Center of Food Additives, Beijing Technology and 7 Business University (BTBU), 11 Fucheng Road, Beijing 100048, China 8 bThe University of Queensland, Centre for Nutrition and Food Sciences, Queensland 9 Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia. 10 11 *Corresponding author: MANUSCRIPT 12 Hongyan Li, E-mail: [email protected]; 13 Yingli Liu, E-mail: [email protected]; ACCEPTED 1 ACCEPTED MANUSCRIPT 14 Abstract: 15 Five rice varieties with a wide range of amylose content harvested from three 16 different agro-climatic zones (Yanco, Mackay, and Darwin) of Australia are used to 17 explore effects of rice varieties and growth location on the fine structure of rice 18 starches. Number chain-length distributions (CLDs) of amylopectin branches are 19 characterized by fluorophore-assisted carbohydrate electrophoresis (FACE) and 20 parameterized by both empirical subdivision method and biosynthesis-based model. 21 This shows that amylopectin branches with degree of polymerization (DP) ~6-32 22 are not affected by both rice variety and growth location, but rice varieties from 23 Yanco tend to have smaller proportions of intermediate (DP~33-62) and long 24 (DP~63-100) amylopectin branches than those from Darwin and Mackay. The fitting 25 results of starch biosynthesis model keep consistenMANUSCRIPTt with the above observations. 26 Weight CLDs of amylose are parameterized by size-exclusion chromatography (SEC), 27 showing that Yanco rices have significantly higher amylose content and higher 28 proportion of amylose branches with DP~500-5000. The significant interaction 29 between rice variety and growth location indicates that effects of grow location on 30 these fine structures are rice variety-specific. This study could provide implications of 31 environmentalACCEPTED effects on the cooking and eating quality of cooked rice for rice 32 breeders and industry. 33 Keywords: growth location, amylopectin, amylose, chain-length distribution 34 2 ACCEPTED MANUSCRIPT 35 1. Introduction 36 Rice ( Oryza sativa L.) is the second most widely produced cereal crop in the 37 world, which leads all cereal in supplying calories energy intake (Patindol, 38 Siebenmorgen and Wang, 2014). Rice is also adaptable and versatile, which is grown 39 in all continents (except Antarctica) and in more than 100 countries, between 40°S 40 and 53°N latitudes, from sea level to 3000 m in altitude, from dry land to under 1-to 41 2-m-deep water (De Datta, 1981). 42 Consumers consider the cooking and eating quality to be the most important 43 attribute. It is affected by a wide range of factors, such as amylose content, 44 postharvest processing, milling ratio, and cooking methods. Among these, starch 45 structure, especially that the CLDs have a crucialMANUSCRIPT role on rice texture (Li, Fitzgerald, 46 et al., 2017; Li et al., 2016). Starch, comprising ~90% of the dry weight of rice 47 grains, has two types of molecules: amylopectin (AP) and amylose (AM). AP 48 molecules are highly branched glucose polymers with a vast number of short branches 49 and large molecular weights ~10 7-8, whereas AM has a smaller molecular weight 50 (~10 5-6) with few long branches. There are several techniques for starch fine structural 51 analysis: FACE, high-performance anionic-exchange chromatography (HPAEC), and 52 SEC. FACEACCEPTED is the optimal method for determining amylopectin CLDs. It separates 53 molecules based on mass-to-charge ratio and provides baseline resolution between the 54 chains of different DPs, so it directly gives the number distribution of amylopectin. In 55 contrast to SEC, FACE does not suffer from problems of band-broadening, calibration, 3 ACCEPTED MANUSCRIPT 56 and inaccuracies in the Mark-Houwink relation, so FACE data are more accurate. 57 However, because of the inability to quantitatively detect chains above DP ~100, 58 FACE and HPAEC can only give information on amylopectin chains. SEC does not 59 have the same restriction and can therefore be used for the measurement of amylose 60 fine structure (Li and Gilbert, 2018). 61 Starch structure is varied between different rice varieties. Rice varieties are 62 generally classified by amylose content. Starch structure of different rices in terms of 63 amylose content has been extensively investigated (Syahariza et al., 2013). On the 64 other hand, environmental effects on rice structure are also significant. Aboubacar et 65 al. (2006) determined the amylopectin fine structure of long grain rice cultivars 66 planted in different locations in United States, and found that higher growing 67 temperature results in more amylopectin branchesMANUSCRIPT with DP >10 to form consistent 68 crystallites, contributing to higher gelatinization temperatures and enthalpies. Two 69 medium grain rice cultivars from Arkansas and California were determined by 70 Cameron et al. (2007), rices from California had significantly higher amylose content 71 and smaller proportion of chains with DP 13-24. Sar et al. (2014) investigated three 72 rice cultivars with different amylose content from three different agro-climatic zones 73 of Cambodia,ACCEPTED found that starch fine structures are significantly different between 74 cultivars, but not significantly differ between different locations. 75 Rice is Australia’s third largest cereal grain export, and the ninth largest 76 agricultural export. Rice industry generates around $AUD 800 million per year, and 4 ACCEPTED MANUSCRIPT 77 Australia exports rice to 60 major international destinations including the Middle East, 78 the Pacific, North America, and Asia (Fransisca et al., 2015). In Australia, 79 commercial rice production primarily grow in southern New South Wales in areas 80 adjacent to the Murrumbidgee and Murray Rivers, with a small number of farms in 81 Northern Victoria (Sivapalan et al., 2007). In this study, five rice varieties with a wide 82 range of amylose content are harvested from three different agro-climates of Australia 83 (Darwin of Northern Territory: Tropical zone; Mackay of Queensland: Sub-tropical 84 zone; Yanco of New South Wales: Temperate zone); the fine structure of amylose and 85 amylopectin are measured by SEC and FACE, respectively; a biosynthesis model is 86 used to fit number CLDs of amylopectin to supply insights from the view of starch 87 biosynthesis; and effects of growth location on the starch fine structure are also 88 discussed. MANUSCRIPT 89 2. Materials and methods 90 2.1 Materials 91 Five rice varieties were selected for this study: Hom Mali Niaw (HMN), Kyeema 92 (KM), Doongara (DG), Pandan Wangi (PW), IR 64. All 5 rice varieties were planted 93 in 3 different locations of Australia in different seasons: the winter season of Darwin 94 (12.4°S) in NorthernACCEPTED Territory, the summer season of Mackay (21.1°S) in Queensland, 95 and the summer season of Yanco (34.6°S) in New South Wales. Table S1 96 summarizes the major weather conditions during rice growth in these three locations, 97 that is, the mean maximum temperature during the day, the mean minimum 5 ACCEPTED MANUSCRIPT 98 temperature during the night, mean daily sunshine, and mean rainfall. After harvesting, 99 all samples were air-dried and stored at room temperature for 1 month to maximize 100 the milling quality. The samples were milled to white rice with a lab-scale mill 101 (Satake Corp, Japan) and then stored in the fridge at 4 °C. 102 Protease from Streptomyces griseus (type XIV), and LiBr (ReagentPlus) were 103 purchased from Sigma-Aldrich Pty. Ltd. (Shanghai, China). Isoamylase (from 104 Pseudomonas sp. ) and D-glucose (glucose oxidase/peroxidase; GODOP) assay kit 105 were purchased from Megazyme International, Ltd. (Wicklow, Ireland). A series of 106 pullulan standards with peak molecular weights ranging from 342 to 2.35 × 10 6 were 107 purchased from Polymer Standards Service (PSS, Mainz, Germany). 108 8-Aminopyrene-1,3,6,-trisulfonate (APTS) was purchased from Beckman Coulter 109 (Brea, USA). Dimethyl sulfoxide (DMSO, GRMANUSCRIPT grade for analysis) was from Merck 110 Co. Inc. (Kilsyth, Australia). All other chemicals were reagent-grade and used as 111 received. 112 2.2 Extraction, Dissolution, and Debranching of Starch Molecules for 113 Structural Analysis 114 Starch isolation is conducted following the method described by Syahariza et al. 115 (2010). RiceACCEPTED grains were ground into flour with a cryogenic mill (Freezer/Mill 6850; 116 SPEX, Metuchen, NJ) in a liquid nitrogen bath as the cryogenic medium. All samples 117 were extracted and dissolved in DMSO solution with 0.5% (w/w) LiBr (DMSO/LiBr).

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