摘要
臺灣的稻作每年同時間生產稉稻、秈稻、稉糯及秈糯，是世界上罕見的國家，去年稻作面積為483143公頃，其中稉稻佔90.2%、秈稻佔6%、稉糯2.4%及秈糯佔1.3%，去年糙米總產量約186.5萬公噸。自從日本佔領臺灣後，開始推廣稉稻，使臺灣的消費者從廿世紀初期漸漸改變他們的米飯食性由食用乾而不黏之秈米，轉變為喜好食用較軟而具黏性之稉米或近年來育成同性質的長秈米。近年來，臺灣稻米品質愈來愈趨重要，因為稻米生產達到自給自足後，消費者隨著生活水準之提昇，對食米品質改良工作不遺餘力。稻米品質之主要構成因素為（1）碾米品質（2）白米外觀（3）烹調及食用品質（4）米飯入口品質（食味）。臺灣主要稻推廣品種皆屬於短粒粗圓形，具有較高碾米率，其糙米、白米及完整米率通常分別為81%~83%、70%~75%及65%~72%，其中以新竹56號之碾米率最高。稉米之透明度大部份是屬於2或3，同時其心白或腹白介於0到2級，臺南9號及新竹56號之白米外觀最漂亮。秈稻粒形比稉稻更具有變化，如臺中秈2號為短粒粗圓形，而臺中秈3號則於中長粒細長形，秈稻由於米粒之形狀或白堊質的關係，通常其碾米率較差，秈米品種間之透明度由等級1到等級5皆有，而心腹白之等級介於0到4的級之間，其中以嘉農秈6號及臺南秈15號米粒外觀最漂亮，而以臺中秈2號高雄秈7號外觀最佳。秈稻之理化性質遠比稉稻複雜，除了糯稻之外，其品種間直鏈性澱粉含量之變異由10%到30%，而稉稻之變異僅15%到21%；秈稻品種間之膠體展延性質包括了軟性、中間性及硬性，而稉稻皆屬於軟膠體性質；秈稻品種間之糊化溫度由低到高糊化溫度皆有，而稉稻品種僅屬於低糊化溫度；秈稻平均之蛋白質含量高於稉稻約2%。目前主要命名推廣之秈稻品種中，如臺中秈3號、臺中秈10號、臺農秈20號及臺秈1號等品種之理化性質與稉稻相似，是屬於低直鏈性澱粉含量、軟膠體及低糊化溫度。一般稉稻米飯的品感優於秈稻，而秈稉稻品種間食味之良劣，易以理化特性加以區分，但稉稻品種間食味之差異很難從理化分析之數值去分等級。經知步研究已擬出一套米飯入口品質測定法，及開發應用米飯質地分析儀測定米飯之物理性，如硬度、黏性、附著性及凝集性等，來補助理化分析之不足，這兩稻方法除了做為在水稻雜交育種後期世代篩選優良食味之新品種系之外，並進行探討米飯入口品質與其他理化性質相關關係之研究。就官能食味特性而言，米飯之口味、黏性、彈性及光澤間相互呈正相關，且均與糙米率、白米率、粒厚、粒寬、總醣、游離糖、水溶性醣、凝膠展性呈顯著正相關；但與粒長、純蛋白質、鹼溶性蛋白、粗蛋白質、直鏈性澱粉、灰分、硫及磷等含量呈顯著負相關；而米飯之色澤與其他性狀間則無相關存在。繼而進行主成分因子分析，獲知共同受第一因子影響者和食用品質有關，為凝膠展延性和食味評估中之外觀、香、口味、黏性、硬性與總評等七項。而鹼性擴散值、直鏈澱米含量、米飯質地之硬度、凝集性、彈力性、黏結性、咀嚼性等七與米飯硬度有關著，則共同受第二因子之因響。第三因子影響者僅有粗蛋白質含量一項。米飯質地中之黏度、均衡度、附著性、黏著性與食味結構指數等五項有關於米飯黏性者則共同受第四因子之影響。稻米品質之好壞除了取決於品種之理化品質及食味外，尚因裁培季節、地點、耕種技術及貯藏方式之不同而異，而其各理化品質性狀之變化趨勢不盡相同。經試驗結果獲知，糙米容積重二期作平均比一期略多，二期作白米之心白、腹白及背白一期作少，透明度較佳。二期作之直鏈澱粉含量、粗蛋白質含量及鹼性擴散程度比一期作高，凝膠展延性質且相反。進一步利用迴歸分析法，分析各季節生產稻米品質之穩定性，發現稻米品質在季節穩定性的高低因品種及品質性狀而異。就性狀間安定性的相互關係而言，直鏈澱粉含量、鹼性擴散度及凝膠展延性之穩定性，可能受同一調節系統的控制，但此一調節體系與其它稻米理化性狀之穩定性間並無相承關係存在。此外從Texturometer之測試獲知在黏性反應二期作比一期作黏，具有0.1以上之差距，臺灣68號比其他品種不具黏性。二期之硬度比一期多出約0.5以上，均衡度二期平均高於一期，一期介於0.095~0.12，二期作介於0.11~0.14。栽培水稻之於肥處理將影響碾米品質，尤其是完整米率，又肥料處理亦影響收獲稻谷水份，而收穫稻谷水份與完整米成極顯著之正相關，糙米百粒重傾向與碾米品質呈負相關，尤其完整米率，而不同土壤所生產之稻谷，其理化品質除了糙米率及鹼性擴散程度外，完整米率、白米透明度、腹白、膠體展流性質、直鏈性澱粉含量及粗蛋白質含量皆有顯著之差異，食味亦有顯著之差別。再經試驗推測土壤質地雖為影響米質的因素，但當地的影響。而稻谷收穫乾燥後之貯藏方式對糙米率、完整米率、粗蛋白質含量及直鏈澱粉含量之影響不大，白米的透明度則隨貯存期的延長而變差，一般袋裝的透明度比散裝佳，稉稻受影響的程度比長秈稻大。白米的黃變米率隨貯存期的延長而增加，以低溫貯存的黃變米率最低，而以無抽風設備之散裝貯存者最高，白米之鹼性擴散程度、膠體展流長期及食味品質等均隨貯存期之延長而降低，其中以低溫貯存之變化最小，袋裝貯存次之，無抽風設備之散裝貯存最差。良質米之生產，除了需具備良好栽培調製技術外，尚需有良好之耕種環境及優良品質之品種。如何選育高品質品種及覓尋規劃良質米產區為近年來農業研究單位之重點工作，經本研究之探討，以米飯入品口質之測試配合白米外觀，將水稻品種之品質劃分五類，即食味優於對照之A及與對照相似之B，配合優良白米外觀，即心腹背白總和等於或少於1之品種，屬於一類良質及二類良質品種。至目前經由此方式陸續檢定出之良質品種計有台中189號、台農68號、台農70號、台南9號、高雄139號、高雄142號、台稉2號、台中秈10號、台農秈20號及越光等10個品種，並推荐為良質米輔導產銷計劃之生產品種。除外不同區域生產之稻米亦採用上述方式檢定其品質，同樣將產米區域規劃為五類，其中一類區及二類區為良質米生產區域，並再配合該區生產之一等或二等糙米品質，歸級為六級稻米中之一級、二級及三級良質米，而其他級數則屬於並通米，不同品質級數之稻米應有不同之會理價格。應用此種分類、分等與分級之模式，由各區農業改良場分工合作，進行探討全省良質米之適栽區的工作。至目前臺中區初步規劃出；彰化縣濁水溪八寶圳之二水及田中、及刺仔埤圳之溪洲、埤頭、北斗及二林共計8450公頃，南投縣濁水溪之同源圳之竹山、民間及南投，及烏溪之草屯共計3850公頃，臺中縣大安溪之外埔、大甲溪之豐原及烏溪之龍井共計3850公頃，臺中縣大安溪之外埔、大甲溪之豐原及烏溪之龍井共計3000公頃，總共臺中區至目前規劃之良質米適栽區為15300公頃，此規劃結果將可做為發展精緻農業推行良質米輔導產銷之依據。
關鍵字
無資料並列摘要
Both ”Japonica” and ”Indica” type varieties of rice and cultivated in Taiwan. In 1990, the total acreage of rice was 483,143 hectares with a total production of 1,864,590 tons of brown rice. The consumers have changed their habit of eating fluffy rice to sticky rice gradually since the early 20th century. Nowadays, people prefer low amylose shory grain ”Japonica” rice or long grain ”Indica” rice. The amylose short grain ”Japonica” rice or long grain ”Indica” rice. The ”Indica” rice with high amylose content is mainly used to make rice noodles or rice cake. The glutinous rice is mainly used to make rice cake, rice wine, and other food products. In order to meet the needs of consumers and food processors, the research on grain quality becomes an important issue in Taiwan. Rice grain quality is determined by milling quality, grain appearance, cookding and eating qualities, and taste panel test. The grain appearance of the major released ”Japonica” varieties is short in size and round in shape. The recovery rate of the brown rice is from 81 to 83%, the total milled rice rate is from 70 to 75%, and the rate of head rice is from 65 to 72%. Hsinchu 56 has the highest milling yield. The degree of translucency of milled ”Japonica” rice is usually rated 2,3, and 4 grades while the values of white belly and white center is usually between 0 to 2 grades. Tainan 9 and Hsinchu 56 have an excellent grain appearance. The grain type of ”Indica” type rice is more variable in comparisonwith that of ”Japonica” type rice. For example, the rice of Taichung Sen 2 is short sized with bold shape, whereas Taichung Sen 3 is medium long sized with slender shape. The milling recovery rate in ”Indica” rice is always lower, because of its slender grain type or high degree of chalkiness which can cause the broken rice. In general, the rate of brown rice and total milled rice of ”Indica” typeis 2% lower than that of ”Japonica” rice. The degree of translucency of milled ”Indica” rice varied from 1 to 5 grades, while the degree of white belly and white center varied from 0 to 4 grades. Chianung Sen 6 and tainan Sen 15 have excellent grain appearance, but Taichung Sen 2 and Kaohsiung Sen 7 have poor grain appearance. The physico-chemical properties of ”Indica” rice is much more complicated than those of ”Japonica” rice. The amylose content of non-glutinous ”Indica” type varieties ranges from 10 to 30% while that of non-glutinous ”Japonica” type varieties ranges from 15 to 21%. The gel consistency is an ”indicator” of the softness of cookes rice. ”Indica” type varieties has a wider 10 to 30% while that of non-glutinous ”Japonica” type varieties ranges from 15 to 21%. The gel consistency is an ”Indicator” of the softness of cooked rice. ”Indica” type varieties has a wider range of gel consistency than ”Japonica” type varieties. The results of the present experiments ”indicat”ed that the ”Japonica” rice only has the soft gel, but the ”Indica” type varieties have soft, medium and hard gels. The gelatinization temperature of ”Indica” type varieties ranges from low to high, but ”Japonica” type varieties appear low only. The average of protein content of ”Indica” rice is usually 2 % higher than that of ”Japonica” rice. The physico-chemical properties of some ”Indica” cultivars, such that Taichung Sen 3.Taichung Sen 10, Tainung Sen 20, and Taisen 1 were found to be similar to ”Japonica” rice in terms of low amylose content, soft gel, and low gelatinization temperature. Because the differences within physico-chemical properties of low amylose rice are rather small, it is hard to determine the eating quality of rice only by this method. Therefore the taste panel test is used to determine the eating quality of cooked rice. In addition to this, the texturometer was used to measure the physical properties of cooked rice, such as hardness, viscousness, cohesiveness and adhesiveness. These two methods were adopted to evaluate the eating quality of new breeding lines/varieties of rice in Taiwan. Studies on the correlations between physicochemical properties were also made using the same criteria. The result ”indica”ted that the sensory evalution was positively correlated with the rates of brown rice and milled rice, grain thickness, grain width, total carbohydrate, free sugar, water soluble sugar, and gel consistency, but was negatively correlated with grain length, true protein, alkaline soluble protein, crude protein, amylose, ash , sulfur and phosphor. However, the color of cooked rice was not correlated with other characters. A factor analysis using principal component solution was carried out by the 20 palatability-concerning physicochemical properties of 16 cultivars of rice (Oryza sativa L). Factor 1, the eating quality related factor is consisted of gel consistency of milled rice, appearance, aroma, flavor, cohesion, hardness, and overall in sensory evaluation of panel test. Factor 2 is considered as a hardness-relating factor which is consisted of alkali spreading value, amylose content of milled rice, hardness, cohesiveness, springiness, gumminess and chewiness of cooked rice. Factor 3 is crude protein content. Factor 4 is considered as a stickiness-relating factor including viscousness, balance, adhesiveness, stickiness, and textural palatability index of cooked rice. In general, the rice qualities are influenced greatly by varieties and cultural practices. The results of this studies ”indica”ted that the average volume weight of brown rice in the second crop was slightly higher than that of the first crop. The rice of second crop had a better grain appearance than that rice of first crop. The rice of second crop had higher alkali spreading value and higher content of amylose and crude protein when compared with those from first crop, but opposite was true for gel consistency. The regression analysis was used to estimate the seasonal stability of physico-chemical properties of rice. Regarding the relationship of stability among characters, results ”Indica”ted that the stability of amylose content, alkali spreading, and gel consistency might be controlled by a regulation system which was independent to the stability of other physico-chemical characters. It was observed from the results of texturometer analysis, that the second crop rice was more sticky than that of first crop by the value of 0.1. Tainung 68 had the lowest value within the varieties studied. The second crop rice was higher in hardness value than that of the first crop by the value of 0.5. The second crop rice had a higher average balance value than that of first crop. The value ranged from 0.12 to 0.95 in the first crop and from 0.11 to 0.14 in the second crop. Furgher studies on the characteristics of balance of eating quality of different varieties are needed to satisfy the demands of domestic consumers. The effect of nitrogen treatment on milling quality was studied in Taichung DAIS. Results showed that the amount of nitrogen had a large effect on milling quality, especially on the head rice rate. Harvesting moisture related to head rice rate was associated with nitrogen treatment. The 100 kernel weight tended to be negatively correlated with head rice yield. The rice grains produced from different soil type were analyzed for their qualities. The results revealed that there were significant differences in the percentage of head rice, whitebelly, translucency, gel consistency, amylose content, protein content as weel as eating quality among the locations, except the percentage of brown rice and alkali spreading value. In general, not only does soil character give an effect to the rice quality, but other climate factors will affect the grain quality greatly as well. The stored rice grains were sampled to study the effect of storage conditions on the grain qualities. The results ”indica”ted that no significant difference was found in percent brown rice, percent head rice, amylose, and crude protein contents during the storage. However, the translucency of grains was found to be decreased in parallel with the length of storage time. This sotred in sacks exhibited a better grain translucecy in Tainung 67 after the similar length of storage. The percentage of discolored grains increased in parallel with the length of storage period. The smallest value of discolored grain was resulted from the rice stored under the cold condition. The opposite result was obtained when the rice was stored in a bulk without air circulating fan. The values of alkali sprea-ding, gel consistency, and eating, quality decreased with the prolongation of storage period. These rice stored in cold room showed the best cooking and eating qualities while that stored in bulk without air circulating fan showed the worst grain quality. In the present study, the polished rice is grouped into three grades according to its grain appearance and results of panel test. The standard of ranking the rice grade has been established by the author based on the results of several years studies on grain appearance and eating quality. The established standard of rice grading is already adopted by the Taiwan Provincial Food Burean for practical use. Since the rice quality is known to be controlled by variety, soil type, climatic condition, and growing area, therefore, the efforts have been made to identify the high quality rice varieties and suitable areas for their growth. The island wide studies along these lines have been conducted. As a result 10 varieties (Taichung 189, Tainung 68, Tainung 70, Tainan 9, Kaohsiung 139, Kaohsiung 142, Taikeng 2, Taichung Sen 10, Tainung Sen 20, Koshihikari etc.) have been identified to be the high quality rices and are recommended to grow at the most suitable region. At present, a total of 15,300ha of paddy field including 8,450ha in Changhua county, 3,850 ha in Nantou county, and 3,000 ha in Taichung county have been identified to be the suitable areas for production of high quality rice. Similar type of stuides are being continued by the author so that to identify more suitable area for high quality rice production in Southern and Eastern parts of Taiwan. It is hoped that through this type of research work, the production of high quality rice will be further increased in Taiwan.