不同菌酛製備黑豆麴之抗氧化活性與異黃酮素組成

Abstract

摘要 本研究以東方發酵食品常使用之 Aspergillus awamori、Aspergillus oryzae BCRC 30222、Aspergillus sojae BCRC 30103、Rhizopus azygosporus BCRC 31158 及 Rhizopus sp. No. 2 作為菌酛製備黑豆麴，探討發酵黑豆麴及其甲醇萃取物之抗氧化活性，包括 DPPH 自由基清除力、亞鐵離子螯合力、還原力及 Trolox equivalent antioxidant capacity (TEAC)，同時觀察黑豆麴中異黃酮素含量的變化，並進一步比較不同培養溫度及培養時間製備黑豆麴對抗氧化活性與異黃酮素組成之影響。 結果顯示，黑豆對於所有試驗菌株均可作為一生長基質，且黑豆經發酵後，除了以 Rhizopus sp. No. 2 製備之黑豆麴及其甲醇萃取物抗氧化能力較差外，其餘黑豆麴之 DPPH 自由基清除力、亞鐵離子螯合力、還原力及 TEAC 均較未發酵黑豆為佳，其中以 Asp. awamori 發酵者抗氧化能力最強。比較發酵前後異黃酮素之組成，所有發酵黑豆麴中 aglycones 形式之異黃酮素含量皆顯著高於未發酵黑豆，以 Rhizopus sp. No. 2 製備之黑豆麴所含 aglycones 最多。 利用 Asp. awamori 進行培養溫度 (25℃、30℃、35℃) 及培養時間 ( 1-5天) 試驗，發現以30℃發酵為最適合此菌生長之溫度，對於提升黑豆麴抗氧化力及異黃酮素去醣基效果最佳。且當發酵時間為三至四天時，Asp. awamori 黑豆麴具有最強之抗氧化活性與最高含量的 aglycone 形式之異黃酮素。

In the present study, black soybean kojis were first prepared with Aspergillus awamori, Asp. oryzae BCRC 30222, Asp. sojae BCRC 30103, Rhizopus azygosporus BCRC 31158 and Rhizopus sp. No. 2 which are commonly employed as starter organism for the manufacture of oriental fermented foods. Changes of antioxidative activities including α-diphenyl-2-picryl-hydrozyl (DPPH) radicals scavenging effects, Fe2+-chelating ability, reducing power and Trolox equivalent antioxidant capacity (TEAC) and isoflavone content of the black soybean kojis were examined. Besides, effect of cultivation temperature and fermentation periods on the antioxidative activities and isoflavone content of the Asp. awamori-prepared black koji were also investigated. Results revealed that black soybean is a good substrate for the growth of all the test organisms. Methanol extracts of all the black soybean kojis, excepted that prepared with Rhizopus sp. No. 2, exerted higher DPPH free radical scavenging activity, Fe2+-chelating ability, reducing power and TEAC than did the extract of the unfermented black soybean. Among the various kojis examined, koji prepared with Asp. awamori showed the highest antioxidative activity. A higher aglycone content was also noted in all the prepared black soybean kojis than the unfermented black soybean. The highest content of aglycone was found in the koji prepared with Rhizopus sp. No.2. Further preparaing the koji with Asp. awamori at different temperatures (25, 30 and 35℃) and for various fermentation periods (1-5 days) revealed that growth of test organism, the enhancing effect of antioxidative activity and the extent on isoflavone deglucosylation were the highest in koji prepared at 30℃. Koji prepared at 30℃ for 3-4 days showed the highest antioxidative activities and aglycone content.