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標題: | 糯性及高直鏈性澱粉稻米貯藏陳化機制與理化性質探討 Waxy and High-Amylose Rice Ageing Mechanisms and their Physicochemical Properties |
作者: | Yu-Chan Huang 黃玉嬋 |
指導教授: | 賴喜美 |
關鍵字: | 糯米,高直鏈性稻米,貯藏,陳化,酵素活性,澱粉,蛋白質,脂肪酸, Waxy rice,high-amylose (HAM) rice,storage,ageing,enzymatic activity,starch,protein,free fatty acid, |
出版年 : | 2014 |
學位: | 博士 |
摘要: | 稻米貯藏是影響稻米理化性質、煮飯品質及其加工製品性質的重要因子之一。稻米中的組成分主要為澱粉及蛋白質,另含少量的脂質。本論文將探討糯性及高直鏈性稻米之貯藏方式與條件,包括以稻穀或精白米型式貯藏及貯藏溫度與時間對稻米中之澱粉、蛋白質和脂肪的影響及組成分間的交互作用,進而對稻米及澱粉理化性質、膠體性質及煮飯品質的影響。在糥米的陳化過程中,選擇兩種國產糯米—台稉糯1 (TNW1)及台秈糯1 (TCSW1),於不同貯藏條件 (精白米:4及17℃及稻穀:室溫)下貯藏一段時間 (0-15個月)進行探討。研究結果顯示:於所有貯藏條件中,TNW1支鏈澱粉中的短鏈鏈長 (DP=6-15)比例增加、中長鏈鏈長 (DP=16-50)比例減少,但在TCSW1其鏈長變化較小。TNW1米澱粉在經貯藏15個月後,尖鋒黏度 (peak viscosity, PV)顯著提高,但是TCSW1並無明顯變化。在室溫貯藏時,貯藏7及15個月後,TNW1及TCSW1的米穀粉尖鋒黏度逐漸提高。總而言之,糯米於貯藏過程中,內源性酵素活性差異會影響澱粉微結構變化之程度,同時亦會對澱粉及米穀粉糊液黏度造成影響,導致糯米膠體之凝膠強度及米粒吸水膨潤率增加,但米飯烹煮損失率降低。在高直鏈性稻米陳化過程中,選用台中秈17 (TCS17)二種收穫期—TCS17(981)及TCS17(972)進行長時間貯存及磨粉試驗。TCS17(981)及TCS17(972)經碾白後,以精白米型式貯存於4、17及38℃,或以穀粒型式貯存於4℃、室溫及38℃。另外,進行控制陳化貯藏試驗,此乃稻穀先在室溫貯藏15個月後,再於38℃貯藏3個月。4℃貯藏二年期間及17℃貯藏半年期間,可維持其米穀粉糊液黏度,而有恆定的加工品質。綜合貯藏期間理化性質變化包括:蛋白質結構及糊液黏度改變,澱粉酵素活性、膨潤力及溶出物含量下降等。高溫 (38℃)貯藏之精白米 (MR38℃),其脂質於貯藏期間會水解成脂肪酸,使精白米粒表面酸鹼值降低。所生成脂肪酸會和澱粉分子形成複合物及產生其他交互作用,致使其糊液最終黏度顯著提高。38℃貯藏稻穀比精白米型式貯藏者可明顯減緩脂肪酸的形成,但仍無法阻止陳化的發生。貯藏期間蛋白質交聯、變性及不溶性直鏈澱粉含量的提高,均是造成米飯烹煮損失率及表面黏度下降、硬度上升,以及米飯微觀結構改變的主要陳化現象。控制陳化之貯藏條件試驗結果顯示,可先將稻穀於室溫貯藏15個月,再於38℃貯藏3個月,可以得到較高膠體強度及較低水可溶出物之陳化稻米。比較不同貯藏條件 (4及38°C貯藏稻穀)下之乾磨和濕磨米穀粉之糊液黏度與膠體強度,結果顯示,濕磨法可大幅降低因貯藏條件不同所造成之貯藏稻米之理化性質的差異,因此,選擇加工用陳米時需同時考慮磨粉方法 Storage conditions are important factors affecting the physicochemical properties and cooking qualities of rice and rice products. Starch, protein and lipid are the main components in rice grain. The effects of storage conditions (paddy rice, milled rice, time and temperature) on the changes of starch, protein and lipid, and on the interactions between these components in waxy and high-amylose rice grains were discussed in this study. Changes in physicochemical properties of rice grains resulting in their gel consistency and cooking qualities were discussed as well. Two domestic waxy rice varieties, TNW1 (Japonica type) and TCSW1 (Indica type), were chosen for the study of waxy rice ageing at different storage conditions (milled rice: 4 and 17°C; paddy rice: room temperature) for 15 months. The amount of short-chain amlopectin (AP) (DP=6-15) increased but that of long-chain one (DP=16-50) decreased when TNW1 was stored for 15 months at all storage conditions. The change in chain length of TCSW1 AP during storage was smaller than that of TNW1 AP. After 15 months of storage, the peak viscosity (PV) of TNW1 starch paste increased evidently while no significant change in PV was found on TCSW1 starch paste. A gradual increase of the viscosity on the viscogram of the rice flours milled from both TNW1 and TCSW1 stored at room temperature for 7 and 15 months were be observed. Overall, different endogenous amylase activities of aged waxy rice did degrade the AP and changes the fine structure of waxy rice starches with various degrees. At the same time, the residual enzymatic activity affected further on the paste viscosity of waxy rice starch and flour. As a result, a high gel strength and swelling ratio of water uptake and a low cooking loss rice could be obtained. Taichung Sen 17 (TCS17)--TCS17(972) and TCS17(981) were chosen to investigate the physicochemical properties during long period of storage (24 months). Rice samples were stored at 4, 17 and 38℃ for milled rice, 4℃, room temperature and 38℃ for paddy rice. During ageing, lipids were hydrolyzed and free fatty acids (FFA) released, resulting in a low pH of rice grain surface and the formation of FFA-amylose complexed when the milled rice stored at 38℃ (MR38℃),. The FFA-Amylose complexes resulted in the increase of final viscosity (FV) of rice starches paste as well. The degree of lipid hydrolysis decreased even in the paddy rice stored at 38℃, but the ageing was still continuous which could be investigated by examining the common ageing phenomena of aged rice. The increases of the proteins interaction, might be through the formation of disulfide bonds, the degree of enzyme denaturation and the amount of insoluble amylose of high-amylose rice, were the main aging phenomena could result in the decreases of cooking loss and stickiness of cooked rice, and the changes in the microstructure of cooked rice after storage. A two-step storage rice, i.e., paddy rice was first stored at room temperature for 15 months, then transferred to 38℃ for another 3 months, could obtain a gel with high strength but low soluble content. Wet milling could obviously get rid off the differences on the paste and gel properties of rice flours resulting from the various storage conditions of rice. Therefore, it is important to take into consideration of both milling process and ageing conditions for rice processed products applications. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/16937 |
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