國產穀豆作物機能物質之探討

Abstract

國產19種豆類品種中，具有色種皮的黑豆TN3、TN6與紅豆AKS5的抗氧化物質、自由基清除率與還原力為最佳；將大豆發芽處理後，能顯著提昇抗氧化特性，並改善總異黃酮與異黃酮配醣體的量，其中以黃豆KS1發芽處理一天後，總異黃酮含量為最高。篩選出黃豆KS1、KS8與黑豆TN3、TN6，取其乾燥、浸泡與發芽種子，施予濕熱121°C與乾熱190°C的加熱處理。結果顯示，加熱方式與樣品形式的不同，使異黃酮進行不同途徑的轉化；malonylglucoside的熱穩定性差，受熱後即降解。濕熱加熱處理時，malonylglucoside主要轉化成glucoside，其次為acetylglucoside；乾熱加熱處理時，受樣品形態影響較顯著。浸泡與發芽種子在乾熱加熱後，malonylglucoside的降解產物廣泛包括acetyl- glucoside、glucoside與aglycone；乾燥種子受乾熱加熱後，malonylglucoside先轉化成acetylglucoside與glucoside，當加熱持續進行下，acetylglucoside與glucoside將進一步轉化成aglycone，呈兩階段降解。 自國產4種稻米品種中，依抗氧化物質含量、抗氧化性質表現等特性，篩選充實階段的穀粒作為應用的材料。試驗結果選出台稉16號(TK16)與有色稻米光復香糯(KFSW)，於充實第15與18天的樣品利用。穀粒中不分品種以ferulic acid為主要的酚類化合物，其游離態與可溶態含量於充實階段的穀粒中，顯著高於成熟種子；酚類化合物總量也以充實穀粒為高。脂溶性抗氧化物的組成與含量因品種而有差異；TK16的tocols總含量高於KFSW，組成結構皆以a-tocopherol為最多，其次為a-tocotrienol (TK16)或r-tocotrienol (KFSW)，充實期間的穀粒tocol總含量也高於成熟種子。光復香糯的原花青素以catechin為主要的組成單體，且為B-type鍵結。未成熟穀粒原花青素寡聚物的含量高於成熟種子，其平均聚合度約5~6，低於成熟種子的聚合度9~11。根據未成熟穀粒中具有較高機能性成分的優勢，可作為開發稻米新穎應用價值的原料來源。

The dark-coat seeds, black soybean TN3, TN6 and adzuki bean AKS5, had the highest bioactive compounds and antioxidant properties among nineteen domestic legume varieties. After germination, antioxidant abilities and the contents of total isoflavone and aglycone of legumes were significantly improved. Soybean KS1 after 1-day germination contained the highest total isoflavone content. Soybeans, KS1 and KS8, and black soybeans, TN3 and TN6, were soaked, germinated and followed by thermal (121°C moist- or 195°C dry-) treatment. During thermal processing, the malonylglucoside could be converted to glucosides, acetylglucosides or aglycones depending on the pretreatment and processing conditions. The malonylglucosides were lost dramatically, corresponding with the increases of glucosides and acetylglucosides after moist-thermal treatment. The similar results were investigated when the soaked and germinated seeds were dry-thermal treated. In mature seeds, the amount of malonylglucoside totally disappeared when mature soybeans or black soybeans were dry-thermal treated. At the same time, the amounts of acetylglucosides and glucosides increased. When the dry heating prolonged, the acetylglucosides and glucosides degraded and resulted in the increase of aglycones. Based on the total phenolics and flavonoids contents, 15 DAA (days after anthesis) and 18 DAA developing rice grains of TK16 and KFSW domestic rice were used to evaluate the biofunctional components compared to those in mature seeds. Ferulic acid was the most abundant phenolic acid in both immature grain and mature seed. The contents of free and soluble-ester ferulic acid in immature grain were significantly higher than those in mature seed. The most plentiful vitamine E homologue was a-tocopherol, followed by r-tocotrienol in KFSW and a-tocotrienol in TK16. In immature grains, the total amount of tocols was 2-fold higher than that in mature seeds. The proanthocyanidin in KFSW was mainly composed of catechin and connected by B-type interflavan linkage. The level of proanthocyanidin oligomer with mDP (mean degree of polymerization) 5~6 detected in immature grains were higher than that with mDP 9~11 in mature seeds. Immature rice grains, containing remarkable bioactive components, have a great potential for applications in nutraceutical foods.