以台灣式製程製備豆腐乳時異黃酮素組成及抗氧化活性之變化

Abstract

有別於中式豆腐乳之製程，台灣式豆腐乳之釀造乃先同時進行鹽滷豆干與利用Aspergillus oryzae為菌酛進行米豆麴醪之製備，再將鹽滷過之豆干與米豆麴醪混合進行發酵。本研究根據台灣式豆腐乳之製程在37℃下發酵製備台式豆腐乳，進而探討發酵期間異黃酮素異構物含量及其抗氧化活性（DPPH自由基清除能力、亞鐵離子螯合能力及還原能力）之變化。 結果顯示，經16天發酵完成後之豆腐乳中，其總異黃酮素含量顯著下降 (p＜0.05)。其中aglycones形式異黃酮素含量隨發酵天數增加有明顯增加之趨勢，並伴隨β-glucoside及malonylglucoside形式異黃酮素含量之下降。發酵期間，豆腐乳塊中β-glucosidase活性亦隨發酵天數增加而有提升之趨勢。 發酵後之豆腐乳所呈現對DPPH自由基之清除能力、亞鐵離子螯合能力及還原能力皆顯著高於發酵前之鹽漬豆腐。此外，這些活性隨著發酵時間之延長而上升。

In the present study, sufu was fermented at 37oC with Taiwanese manufacture process. Changes of isoflavone content, distribution profiles and β-glucosidase activity were investigated during fermentation. The antioxidative activity, including DPPH radical-scavenging effect, Fe2+-chelating ability, and reducing power were also examined. The results revealed that the fermentation caused the significant decrease (p < 0.05) of total isoflavone content. A marked increase in the content of aglycone (diadzein, glycitein and genistein), and the significant reduction in the content of malonylglucoside and β-glucoside isoflavone, compared with non-fermented salted tofu were also observed. Activity of β-glucosidase detected in sufu was significantly higher (p < 0.05) than that noted in the non-fermented salted tofu. Results also showed that the DPPH free radical-scavenging activity, Fe2+-chelating ability and reducing power of tofu were enhanced after fermentation.