發芽及發酵對台灣藜主要機能性成分之影響

Abstract

台灣藜是一種具有豐富營養價值的準穀物藜亞科台灣原生植物，有著穀類紅寶石的美名。除了豐富的膳食纖維、蛋白質、多種必需氨基酸及微量元素外，台灣藜中還含有許多機能性成分，如γ-氨基丁酸（GABA）以及多酚類物質等。γ-氨基丁酸是廣泛存在於植物和動物中的非蛋白質氨基酸，具有神經安定、降血壓、解酒、抗癌等作用。而多酚類物質具有抗氧化、抗發炎等功效。本研究根據GABA的生成代謝途徑來選擇和優化台灣藜發芽及發酵過程的條件，以得到含較多GABA及多酚類物質，且具有高抗氧化能力之台灣藜芽，並探討可能的機制。根據發芽處理的優化實驗，發現在快速吸水后，處於萌芽階段的台灣藜內部酵素的活性顯著增強，伴隨著功能性成分的增加，並在發芽第三天後趨於穩定。而台灣藜在較高的溫度下發芽能積累更多的GABA，與之對應的麩氨酸脫羧酶（glutamic acid decarboxylase enzyme, GAD）也表現出更高的活性。通過抗氧化能力試驗，觀察到在發芽階段各功能性成分與抗氧化能力皆具有較高的相關性。根據GABA的生成途徑，在浸泡時適當補充麩氨酸（glutamic acid, Glu）及其鹽，GAD輔酶磷酸吡哆醛（pyridoxal-5’-phosphate, PLP）以及維生素B6均可以增加GAD的活性以及GABA的含量，但是營養液濃度過高時則會使得發芽受阻，抑制GAD的活性，並減少GABA的累積。在發酵處理階段，本實驗選用了三株常用於食品加工中的微生物，分析不同菌株之發酵處理對台灣藜之影響。結果發現，乳酸菌、酵母菌在發酵的過程中，均可以利用環境中的碳源、氮源，並以自身的酵素將基質中的蛋白質分解，使多種機能性成分，如GABA與總多酚得到積累，並增加其抗氧化能力。綜合上述實驗結果，發芽與發酵確實能顯著增加台灣藜活性成分的積累，未來可針對發芽與發酵過程中的主要酵素與活性成分變化進一步研究，釐清當中的機制，使其在食品尚有更多的應用。

Chenopodium formosanum (djulis) is a native plant with abundant nutritional value in Taiwan, which contains high levels of dietary fiber, proteins, essential amino acids and microelement. Besides, djulis also has many functional components such as γ-aminobutyric acid (GABA) and polyphenols. The γ-aminobutyric acid is a non-protein amino acid widely found in plants and animals, and has functions such as nerve stability, hypotensive, dispelling the effects of alcohol and anti-cancer. Polyphenol is helpful in regulating physiological function like antioxidant and anti-inflammatory, etc. In this study, the conditions of the germination and fermentation were optimized based on the metabolic pathway of GABA, so as to obtain the djulis sprout containing more functional components, including GABA and polyphenol, and having higher antioxidant capacity. According to the optimization experiment of germination, it was found that the activity of the enzymes in djulis was significantly enhanced after rapid water absorption, accompanied by the increase of functional components, and these activities have reached plateau after the third day of germination. Djulis could accumulate more GABA and glutamate decarboxylase (GAD) also showed higher activity at a higher temperature. Through the antioxidant capacity test, it was observed that the functional components have a high correlation with antioxidant capacity during the germination stage. According to the production pathway of GABA, GABA content and GAD activity could be increased by adding glutamic acid or its salts, GAD coenzyme pyridoxal-5’-phosphate (PLP) and vitamin B6 during soaking. However, when the concentration of supplement was too high, it may inhibit the GAD activity and reduce the accumulation of GABA. During the fermentation, three strains of microorganisms commonly used in food processing were selected to study their effects on djulis. The results showed that both lactic acid bacteria and yeast could utilize the carbon and nitrogen sources and decompose the proteins with their own enzymes during the fermentation process, so that a variety of functional components, such as GABA and polyphenols, could be accumulated and the antioxidant capacity increased. Based on the experimental results, germination and fermentation can significantly increase the accumulation of functional components of djulis. However, further studies should be conducted on the changes of the main enzymes and active components during the process of germination and fermentation, so as to clarify the mechanism and make it more applicable in food industry.