Changes of enzyme activity and physiochemical properties during the fermentation of Taiwanese style sufu at different temperatures
|Keywords:||豆腐乳;酵素活性;游離胺基酸;Aspergillus oryzae;發酵溫度;sufu;enzyme activity;free amino acid;Aspergillus oryzae;fermentation temperature||Issue Date:||2009||Abstract:||
不同於中式豆腐乳之製程，台式豆腐乳之釀造乃先分別製備鹽漬豆腐及以Aspergillus oryzae製備豆米麴醪，再將其混合進行發酵。本研究探討在不同溫度 (25℃、37℃及45℃) 下發酵製備台式豆腐乳時，其酵素活性及物化特性之變化。 結果顯示，隨著發酵時間之延長，豆米麴中酵素活性 (protease, lipase, α-amylase, β-amylase) 皆顯著 (p < 0.05) 下降。浸漬液中protease與lipase之活性在發酵前期 (0-8天) 隨著發酵時間之延長有逐漸上升的趨勢，在發酵後期 (8-16天) 則隨著發酵時間之延長呈下降之現象；而α-amylase與β-amylase活性則於發酵4天達最高後，並未隨發酵時間之延長而有明顯之變化。豆腐塊中，各種酵素活性在發酵第4天達最高，其後隨著發酵時間的延長，protease及lipase活性逐漸下降；α-amylase與β-amylase則是隨著發酵時間之延長，活性無明顯變化。發酵完成後，在45℃下發酵者，其浸漬液及豆腐塊中protease及lipase活性均顯著 p < 0.05) 低於在25、37℃下發酵者。 在37℃及45℃下發酵16天後，豆腐乳具有約20%的蛋白質水解率，然而在25℃發酵者其蛋白質水解率僅有12%。經發酵後，台式豆腐乳之總游離胺基酸含量皆顯著地 (p < 0.05) 高於未發酵者。在37℃或45℃下發酵者其總游離胺基酸含量彼此無顯著性 (p > 0.05) 差異，然而皆顯著 (p < 0.05) 高於在25℃下發酵者。豆腐塊及浸漬液色澤隨發酵時間延長而趨於紅褐色，此現象尤以在45℃下發酵時最為明顯。隨著發酵時間之延長，豆腐塊中胺基態氮、滴定酸度及游離脂肪酸含量呈現逐漸增加之趨勢；總氮、pH及硬度則呈降低之趨勢。官能品評試驗結果顯示，在45℃下發酵所得之豆腐乳有最高的綜合評價，而在25℃發酵者最低。鍵字：豆腐乳、酵素活性、游離胺基酸、Aspergillus oryzae、發酵溫度
Different from that of Chinese sufu, the manufacturing process of Taiwanese sufu involves the production of salted tofu and the preparation of rice-soybean koji mash with Aspergillus oryzae separately, and the two are combined during fermentation. This study was conducted to investigate some biochemical changes of Taiwanese sufu during fermentation at different fermentation temperatures (25, 37 and 45℃). The results revealed that the enzyme activity (protease, lipase, α-amylase and β-amylase) detected in rice-soybean koji significantly decreased (p < 0.05) with the extension of fermentation. The activity of protease and lipase in the infusion slightly increased during the early stage of fermentation (0-8 days), but decreased thereafter. Generally, the activity of α-amylase and β-amylase detected in the infusion was the highest after 4-day of fermentation, regardless of fermentation temperature. No significant change in their activity was detected as the fermentation was further proceeded. Activity of these hydrolyte enzymes was also the highest in the tofu after 4-day of fermentation. While protease and lipase activities reduced, and the activities of α-amylase and β-amylase remained constant as the fermentation was extended. At the end of fermentation, the activities of protease and lipase detected in both infusion and tofu were significantly lower (p < 0.05) when fermentation was performed at 45℃ than at 25 or 37℃. After a 16-day of fermentation, sufu fermented at 37℃ and 45℃ showed a protein hydrolysis ratio of 20%, while that of 25℃-fermented sufu was only 12%. The content of free amino acid of sufu after 16-day of fermentation was significantly higher (p < 0.05) than that without fermentation. The free amino acid content of the 37℃- and 45℃-fermented sufu showed no significant difference (p > 0.05) while they were significantly higher (p < 0.05) than that of the 25℃-fermented sufu. During fermentation, the color of tofu and infusion changed from ivory white to reddish brown. This phenomenon was most obvious with that fermented at 45℃. As the fermentation time extended, the content of amino nitrogen, titratable acid and free fatty acid of the tofu increased gradually, while the total nitrogen, pH and hardness decreased slightly. Sensory evaluation showed that the sufu fermented at 45℃ had the highest score in total evaluation, while the score of that fermented at 25℃ is the lowest.eywords: sufu, enzyme activity, free amino acid, Aspergillus oryzae, fermentation temperature.
|Appears in Collections:||食品科技研究所|
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