大豆異黃酮為類黃酮素之一種，共有十二種衍生物，已被證實具有減低心血管疾病、預防癌症及減輕更年期症狀等保健功效。豆腐富含大豆異黃酮，是台灣最受歡迎的豆製品，豆腐可藉由添加物改善質地。γ-聚麩氨酸(γ-PGA)是一種微生物發酵聚合物，由1,000~10,000 個D 及L-麩胺酸以γ 胜肽鍵聚合而成的同質多胺，具有保水性，可作為食品添加物。本研究目的為利用高效能液相層析儀(HPLC)觀察添加不同的濃度及分子量γ-PGA 和儲存時間對豆腐大豆異黃酮含量之影響。結果顯示，控制組豆腐中總異黃酮含量為2.40 mg/g，而γ-PGA 豆腐中總異黃酮含量介於2.75 mg/g-3.01mg/g 之間，較控制組高。增加低分子量γ-PGA 的添加濃度，豆腐總異黃酮含量呈現上升的趨勢。然而隨著中分子量和高分子量γ-PGA 添加濃度的增加，豆腐總異黃酮含量呈現減少的趨勢。γ-PGA豆腐中不含葡萄糖苷及含葡萄糖苷的異黃酮含量明顯高於控制組，而含乙醯葡萄糖苷的異黃酮含量則無明顯差異。儲存期間γ-PGA 豆腐中4 種類型的異黃酮以含葡萄糖苷及含丙二醯葡萄糖苷的異黃酮含量有較明顯之改變。添加γ-PGA 的濃度增加，豆腐中總異黃酮的保留率增加。因此，添加γ-PGA 和儲存會影響豆腐異黃酮的安定性。

　　Isoflavone belongs to the class of flavonoids and comprises twelve derivatives. It has several health-promoted functions including the prevention of cardiovascular diseases, cancers, and menopausal symptoms. Tofu is rich in isoflavones and is the most popular soy products in Taiwan. Additives are often used to improve the texture of tofu. Poly-γ-glutamic acid (γ-PGA) is a biopolymer produced by microbial fermentation and is polymerized by 1000-10000 D- and L- glutamic acids with γ-peptide bonds. It possesses the water-holding capacity and can be used as food additive. The objective of this study was to investigate the effects of concentration and molecular weight of γ-PGA and storage on the stability of isoflavones in tofu using HPLC. The results showed that the addition of γ-PGA increased the amount of isoflavones in tofu. Increase the concentration of low MW γ-PGA increased the total isoflavone content in tofu. However, increase the concentrations of medium and high MW γ-PGA decreased the total isoflavone content in tofu. The amounts of aglycones and glucosides in γ-PGA tofu were higher than control, but the amount of acetylglycosides in γ-PGA tofu was not different from control. The amount of malonylglucosides in γ-PGA tofu changed significantly during storage. The addition of γ-PGA caused an increase in isoflavone retention of tofu during storage. Thus, the isoflavone stability in tofu was affected by the addition of γ-PGA and storage.