Effects of Planting Month on Rice Quality of Cultivar TNG 71
|Keywords:||栽植期;水稻;米質;米粒化學組成;Planting month;Rice;Grain quality;Grain chemical composition||Issue Date:||Dec-2009||Publisher:||台灣農藝學會||Journal Volume:||6||Journal Issue:||4||Start page/Pages:||220-232||Source:||作物、環境與生物資訊||Abstract:||
本研究以良質米稻種臺農71 號為參試材料，自2006 年12 月至2007 年11 月期間連續每月於行政院農委會農業試驗所農場試區栽植，分別於收穫時割取穀粒產量來探討不同栽植期對臺農71 號米質之影響。根據試驗結果，不同栽植期具有不同的氣象環境，使得稻作栽培與發育所需生育天數互異，顯然各栽植期存在的環境差異將形成不等稻株生育進展及稻米品質，也發現影響穀粒的碾糙率與碾白率。由穀粒大小與栽植期之分析，發現包括粒長、粒寬、粒厚及千粒重等性狀皆隨著不同栽植期改變，且穀粒長寬比與千粒重之間呈現凸形曲線相關。將各栽植期收穫之穀粒碾製成糙米後，區分出青米粒、被害米粒、死米粒、心腹白米粒及完整米粒等類別，以溫暖的5-7 月份栽植所採收稻穀具有較低比例之完整米粒及較高比例之不良外觀米粒，特別是5 月份栽植者表現最差。反之，冷涼月份之完整米粒比例較高，尤以11-1月份為然。將糙米碾製成白米後，發現1-6月份收獲米粒之白度高於7-12 月份者，並以橫跨一年當中高溫與高日照期的5 月份栽植者最高。栽植期對白米透明度之效應參差不齊，以4-7 月份收獲白米較低，且以5 月份栽植者最低。將米粒進行化學組成分析後，可看出糙米之粗蛋白質、直鏈性澱粉及游離脂肪酸和白米之粗蛋白質、直鏈性澱粉等含量皆受到栽植期影響。糙米與白米之粗蛋白質含量以6-8 月份收獲者較高、1-4 月份收獲者較低，直鏈性澱粉含量在糙米及白米的高低不一，糙米與白米分別以11 月份與4-5 月份較低；糙米中的游離脂肪酸含量則以4 月及11 月較低、6-8 月及12 月較高。經比較穀粒大小對糙米與白米之化學組成效應，發現千粒重高低和糙米化學成分變化無顯著相關，惟和白米之直鏈性澱粉與粗蛋白質呈現曲線關係，尤其與直鏈性澱粉關係達顯著水準。再由白米之化學組成與米粒白度及透明度之相關分析，顯示直鏈性澱粉含量與米粒白度呈現反比，與米粒透明度則呈現正比，但是蛋白質含量高低和米粒白度及透明度無顯著相關。本研究驗證了栽植期環境將造成碾糙率、碾白率及完整米比例的差異，同時相關於米粒大小及米粒外觀，也改變米粒化學組成，此結果可供調整栽植期或選擇合適栽植環境以提高稻米品質之參考。
An annual planting experiment using high-quality rice cultivar TNG 71 was conducted in the experimental farm of Taiwan Agricultural Research Institute (Wufeng, Taichung Hsien) from December of 2006 through November of 2007. Except September and October of 2007, there were 10 seasons of harvested grains collected for studying the effects of planting months on rice quality. Since the time periods required to complete life cycle of rice plants varied in different planting months, apparently growth conditions were unique in each growing season and differences existed in plant development and rice quality among plantings. Results indicated that length, width and thickness of harvested grains, 1000-grain weight, and milling rates of brown rice and milled rice changed with planting months. There was a sigmoidal relationship between grain length to grain width ratio and 1000-grain weight, suggesting that both length and width of rice grains together should be considered for a better grain size and grain filling. The brown rice obtained from rice grains which harvested from different planting periods was classified into several categories, including unripe rice, damaged rice, death rice, white center/belly rice and head rice. Less head rice and more imperfect rice were identified from plants grown in warming planting months from May to July, especially those plants transplanted at May. On the other hand, higher ratio of head rice was found in plants grown in cooling planting months from November to January. The whiteness of milled rice was higher in those plants transplanted from January to June than those from July to December, particularly plants transplanted at May. In terms of the transparency of milled rice, the value was lower in rice grains that transplanted from April to July, with May the least. Results of chemical components analyses indicated the existence of planting months’ effects. The content of crude protein of brown rice and milled rice was higher in plants transplanted from June to August and was lower in those from January to April. The lowest amylose content of brown rice occurred in plants transplanted at November, but the lowest values obtained from April and May for milled rice. The content of free amino acid of brown rice was lower in plants transplanted at April and November and was higher at December and from June to August. No correlation was found between 1000-grain weight and any chemical components of brown rice. However, a curvilinear relationship was shown with amylose and crude protein of milled rice. Further, changes of amylose content were negatively correlated with whiteness of milled rice and were positively correlated with transparency of milled rice. There were no significant relationships between crude protein and whiteness and transparency of milled rice. In summary, results of this study proved the effects of planting months on grain size, grain appearance and grain chemical compositions, and may hence be informative for selecting growing sites and seasons suitable for a better rice quality.
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