蒸穀稉米與秈米之理化性質與儲存性

Physicochemical properties and storage ability of parboiled japonica and indica rices.

葉家豪(Chia-Hao Yeh)

指導教授 ： 葉安義

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702191

摘要

蒸穀米為南亞、西亞以及非洲地區的主要食用米，許多文獻指出蒸穀米具有高完整米率、高營養價值、低病蟲害、較多維生素B1與低GI值等特性。因此期望以臺灣國產稻米製成蒸穀米之技術，改善臺灣稻米生產量過剩的問題，與米飯的升醣指數，降低第二型糖尿病的風險。本實驗探討國產台南11號 (TN11) 稉米以及台中秈10號 (TCS10) 秈米製備蒸穀米之可行性，了解不同米種的蒸穀米之完整米率、米飯質地、微生物菌數、消化性與預估升糖指數等理化性質之差異，以及預煮處理是否有效增加稻米的儲存性。實驗結果顯示，經過預煮處理後，TN11完整米率從69.87%提高到76.13%，TCS10則從56.04%提高至74.44%，有效改善精白過程中碎米的問題。顏色分析的部分，經過預煮處理明顯顏色變深且變黃。熟米飯的質地方面，經過預煮處理的TN11硬度由61.78 N上升至65.07 N，TCS10則從52.87 N上升至55.75 N，並隨著蒸煮時間的增加使蒸穀米米飯質地變更硬且黏著性更低。微生物檢測結果顯示，稻米的總生菌數會因為60℃5個小時的浸泡，將TN11的菌數有效從8.32 × 10^5 CFU/g降低至244 CFU/g。TCS10則從與1.45×10^6 CFU/g降低至18 CFU/g。後續精白處理後菌數也能保持在50 CFU/g以下，仙人掌桿菌數也有類似的結果。脂解酶活性測定發現糠層中脂解酶活性會因高溫的預煮處理，TN11從0.729 U/mL降低至0.206 U/mL，TCS10則從0.568 U/mL降低至0.266 U/mL，有效延緩稻米油質氧化速率。在體外消化試驗也顯示經過預煮處理TN11抗性澱粉含量從5.21%上升至19.18%，TCS10則從5.91%上升至18.87%。eGI值也有顯著性的降低，有效降低米飯的消化性。因此將稻米進行預煮處理可改善稻米的加工成本、微生物、消化性等等性質，可作為臺灣稻米新的加工型態做進一步的推廣。

關鍵字

蒸穀米 ； 體外消化性試驗 ； 預估升糖指數

並列摘要

Parboiled rice has been recognized to have many benefits, including high head rice yield, low insect damage, more vitamin B1 and low GI and etc. Thus, parboiling might be an attractive method to alleviate the excess rice in Taiwan. This study was to explore the feasibility of parboiling using Tainan 11 rice (TN11) and Taichung sen 10 rice (TCS10). Physicochemical properties such as head rice yield, cooked rice texture, microorganism number, digestibility and eGI value and storage ability were measured to examine the suitability of indica rice and japonica rice. Results showed that the head rice yield of parboiled japonica rice increased from 69.87% to 76.13%, and parboiled indica rice increased from 56.04% to 74.44% respectively. Due to the migration of compounds from bran to endosperm and possible maillard reaction, parboiled rice exhibited darker and yellowish color. The hardness of parboiled rice was increased about 5% for both TN11 and TCS10 rice. Increasing steaming time resulted in harder and less sticky texture. Total plate count (TPC) of TN11 were significantly decreased form 8.32 × 10^5 CFU/g to 244 CFU/g and TCS10 decreased from 1.45 × 10^6 to 18 CFU/g by soaking in 60℃water for 5 hours. After polishing, bacteria numbers were less than 50 CFU/g. Bacillus cereus examination has similar results with TPC. Lipase activity of TN11 after parboiling was reduced from 0.729 U / mL to 0.206 U / mL and TCS10 was reduced from 0.568 U / mL to 0.266 U /mL. In vitro digestibility test showed that parboiling resulted in increase in resistant starch content (TN11 was increased from 5.21% to 19.18% and TCS10 was increased from 5.91% to 18.87%). And eGI value was significantly reduced. Therefore, the parboiling could be a potential method to increase the consumption of rice with low in digestibility.

並列關鍵字

Parboiled rice ； In vitro digestibility test ； Estimated glycemic index (eGI)

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AACC approved method 44-15A Moisture -- Air-Oven Methods, the American Association of Cereal Chemists. AACC: 1999.