紅蘿蔔副產物製備豆腐乳與其呈味特性

中式豆腐乳已是歷史悠久的發酵食品，具高營養價值及特殊風味，且受大眾的喜愛。台式豆腐乳之製程有別於中式豆腐乳，在釀造製程上是先進行鹽漬豆腐，再將鹽滷豆腐與米豆麴醪混合進行發酵。依據中國估計結果，豆腐乳每年產量約達30萬噸。近年來，智慧型手機的盛行，人們在長時間的使用上，常會造成眼睛的視力受損，而胡蘿蔔素有助於眼睛維持正常的視覺。蔬果經食品加工製成蔬果汁後，所產生的蔬果渣常被視為廢棄物，學者研究顯示每克的紅蘿蔔渣含0.14毫克胡蘿蔔素，顯示紅蘿蔔產生的副產物紅蘿蔔渣仍有營養價值，因此，本研究為了提升紅蘿蔔副產物的附加價值及開發豆腐乳的新口味，添加不同比例 (0%、10%及20%)的紅蘿蔔副產物於豆腐中，與米豆麴醪混合裝罐製作台式豆腐乳，分別在不同溫度 (25、30及35℃)及發酵時間 (0、7、14及21天)下，測定豆腐乳的酵素活性 (protease、α-amylase、β-amylase及β-glucosidase)、β-胡蘿蔔素及大豆異黃酮素的含量，收集上述之試驗結果，決定最適當的發酵條件，後續分析發酵前與最適條件中0%、10%及20%紅蘿蔔副產物之豆腐乳的色澤、一般組成及呈味特性，供日後作開發紅蘿蔔副產物之豆腐乳產品參考。結果顯示，在酵素活性測定上，0%、10%及20%紅蘿蔔副產物之豆腐乳的protease及α-amylase活性於35℃及第14天最佳，而β-amylase及β-glucosidase的活性於35℃及第21天最佳。在β-carotene含量分析上，0%紅蘿蔔副產物之豆腐乳未檢出β-carotene，10%及20%紅蘿蔔副產物之豆腐乳一開始在不同溫度下發酵第0天至第7天顯著性的降低 (減少約50%)，而後續發酵第7天至第21天則無明顯改變，其中以20%豆腐乳的β-carotene含量最高 (約151~190 μg/g dry sufu)。在大豆異黃酮含量分析上，0%、10%及20%紅蘿蔔副產物之豆腐乳的含糖苷異黃酮daidzin和genistin含量在不同溫度下會隨著時間的增加顯著性的降低，於發酵第14天後呈現趨緩，35℃中10%及20%紅蘿蔔副產物之豆腐乳的daidzein含量於發酵第21天達到最高，分別為89.3及79.3 μg/g dry sufu，0%、10%及20%紅蘿蔔副產物之豆腐乳的genistein含量以35℃與第21天最佳，分別為94.2、144.9及136.0 μg/g dry sufu。綜合以上結果顯示protease、α-amylase、β-amylase、β-glucosidase、daidzein及genistein的含量於35℃最佳，其protease、α-amylase及genistein在第14天最佳，而β-amylase、β-glucosidase及daidzein在第21天最佳，基於protease為品質的重要因素，因此，選擇35℃第14天為最適條件，接續分析未發酵與最適條件之豆腐乳的色澤、一般組成及呈味特性。在色澤分析中，豆腐乳的紅蘿蔔副產物比例增加Hunter a,b值隨著增加，10%及20%紅蘿蔔副產物之豆腐乳呈現橘色，而Hunter L呈降低之現象。Chroma以20%紅蘿蔔副產物之豆腐乳最高，而WI則以0%紅蘿蔔副產物之豆腐乳最高，經發酵後0%、10%及20%紅蘿蔔副產物之豆腐乳的Hunter L,a,b,Chroma及WI沒有顯著性的差異。在一般組成成分分析中，0%、10%及20%紅蘿蔔副產物之豆腐乳於發酵前以粗灰分之含量最高，其次為粗蛋白、碳水化合物及粗脂肪，以粗纖維的含量最低，而經發酵後以碳水化合物之含量最高，其次為粗灰分、粗蛋白及粗脂肪，仍以粗纖維的含量最低。在呈味特性分析上，0%、10%及20%紅蘿蔔副產物之豆腐乳的總核苷酸含量經發酵後顯著性的增加，分別為453、464及445 μg/g dry sufu，0%、10%及20%紅蘿蔔副產物之豆腐乳的總核苷酸含量沒有明顯的差異性，而0%、10%及20%紅蘿蔔副產物之豆腐乳的總游離胺基酸經發酵後顯著性的增加，分別為70.1、59.5及57.3 mg/g dry sufu，以0%紅蘿蔔副產物之豆腐乳的含量最高，0%、10%及20%紅蘿蔔副產物之豆腐乳經發酵後游離胺基酸的呈味特性上以苦味 (16~21 mg/g)為主，其次為鮮味 (11~13 mg/g)及甜味 (14~16 mg/g)，另外發酵前0%、10%及20%紅蘿蔔副產物之豆腐乳的蔗糖經發酵後轉變成葡萄糖和果糖，使總可溶性糖含量顯著性的增加，分別為370、384及406 mg/g dry sufu。綜合以上結果，10%紅蘿蔔副產物之豆腐乳的daidzin及genistin含量較0%及20%紅蘿蔔副產物之豆腐乳高，而10%及20%紅蘿蔔副產物之豆腐乳的總核苷酸、總游離胺基酸及總可溶性糖含量沒有明顯的差異性，因此，10%紅蘿蔔副產物之豆腐乳的生產是可行的。

關鍵字

呈味特性；酵素活性；紅蘿蔔副產物；豆腐乳

並列摘要

Chinese sufu was a fermented food and developed for a long time by their high nutritional value and special flavor. Taiwanese sufu was different from Chinese sufu, its fermentation was mixing salted tofu and rice-soybean koji. The carotene can reduce visual impairment from long-term use of mobile phones. Fruit produced after processing the residue was often considered as waste. The researches have shown that carrot residue contain 0.14 mg/g carotene. Therefore, this study was to increase the utilization of carrot residue and develop different flavors of Taiwanese sufu. In this experiment, different proportions (0%,10% and 20%) of carrot residue were added to make tofu, and then mixed with rice-soybean koji to ferment at different temperatures (25℃,30℃ and 35℃) and after different times (0,7,14 and 21 days). Further determination of enzyme activity (protease,α-amylase,β-amylase and β-glucosidase),β-carotene and soy isoflavone content of fresh sufu at different temperatures and times fermentation and to choose the most suitable fermentation conditions. Then, to anylazy the color the proximate compositions and taste quality of Taiwanese sufu. The optimal fermentation conditions depend on the higher genistein content and the higher activity of preotease. Hence, the optimal condition for carrot sufu was at 35℃ for 14 days. In the proximate composition, crude ash was the major components in non-fermented carrot sufu. But, the carbohydrate was the major components after fermentation with rice-soybean koji for 14 days. The 5’-nucleotide contents, increased after 14 days of fermentation and were 453,464 and 445 μg/g for 0%,10% and 20% carrot sufu, respectively. The contents free amino acids of non-fermented and fermented carrot sufu were 8.6~10.8 mg/g and 57.3~70.2 mg/g. In the content of soluble sugar, sucrose was major components, before fermentation, but fructose and glucose were increased after fermentation. Overall, different proportions (0%,10% and 20%) of carrot sufu were no significant different in tasty quality. But the contents of daidzein and genistein of 10% carrot sufu were higher than those of 0% and 20% carrot sufu. In addition, the carrot sufu showed orange appearance maybe provide consumers a new choice.