納豆激酶(Nattokinase)係納豆菌(BaciHus subtilis Var. natto)發酵產生的酵素，而酸性環境下納豆激酶之穩定 性易受影響，研究指出可藉由添加劑來增加酵素之穩定性。本研究使用田口試驗設計法進行探討複合添加物 添加於酸性溶液中，不同添加物對納豆激酶穩定性之影響，同時將所得結果應用於含納豆激酶柳橙飮品之開 發。結果顯示，在酸性溶液中添加醣類對酵素活性皆具有保護作用，而添加乳糖具最佳之保護效果；添加之 金屬離子中，CaCljS存在可增加納豆激酶之穩定性；添加不同的食用膠中，除鹿角菜膠外皆能穩定納豆激酶 的活性，其中以阿拉伯膠具有最佳的保護效果；此外，Glycine的添加亦有穩定活性之能力。經最適化後之複 合添加物在第14天可維持納豆激酶50%以上之相對活性，各種添加物中以CaCl2與glycine對提升納豆激酶於酸 性溶液之穩定性最具影響力。將上述結果應用於含納豆激酶柳橙飮品開發具良好之再現性，同時以60°C加熱 30分鐘並儲藏於4°C下，可抑制總生菌數的滋長，並擁有較佳之抗氧化能力，且可避免納豆激酶活性大幅下 降。由感官品評之結果可知，因添加納豆激酶於柳橙汁中所造成之異味與色澤變化，較不被消費者所接受， 但在香味、風味與整體接受度上方面則無顯著差異性，顯示可藉此提升相關產品之經濟價值，亦提供消費者 更多樣的選擇。

Nattokinase is an enzyme produced by Bacillus subtilis Var. natto, but its stability is easy to be affected under low pH condition. Studies showed that it might increase the stability of nattokinase by supplementing additives. The objective of this study was to investigate the stability of Nattokinase with different kinds of additives at low pH by using the Taguchi method, and the results could be used in development of orange beverage containing nattokinase. The results showed that addition of saccharides had effect on protection of enzyme activity, and lactose exhibited the best outcome. The addition of metal ions showed that calcium chloride could increase the stability of nattokinase. Except carrageenan, all of the edible gelatin used increased the stability of nattokinase and the gum arabic had the best effect. In addition, glycine also could increase the stability of nattokinase. In optimal condition, the complex additives retained 50% of its activity of nattokinase on day 14. Among various additives, calcium chloride and glycine were the most effective additives at low pH. Application of the conditions obtained from the above analyses on development of orange beverage resulted in reproducible conclusion. Heating at 60oC for 30 min and storing at 4oC could reduce the total bacterial count, keep better antioxidant activity, and avoid destabilization of nattokinase. The results of sensory evaluation showed that the unique odor and changes of color caused by addition of nattokinase, were not accepted by most consumers, but aroma, flavor and overall acceptability showed no significant differences, indicating that nattokinase can enhance the commercial value of the products and also provide more choices to consumers.