豆渣為製造豆漿、豆腐與豆花等黃豆加工製品之副產品，由於其水分相當高(約80%)，導致容易腐敗而無法再利用。而以豆渣製成之豆渣納豆其臭味較濃，不易為國人所接受。本研究探討利用豆渣接種納豆菌後，減低豆渣納豆產品臭味與保持生理活性功效之方法。研究結果發現，添加5%糯米粉、5%玉米粉與5%在來米粉皆可降低臭味，但添加5%糯米粉之產物其納豆激酶活性最高。而隨著添加糯米粉含量之增加(由5%增加至15%)，納豆激酶活性並不會改變(28.67-32.60FU/ml)(對照組52.30FU/ml)，但臭味逐漸降低。豆渣中添加10%糯米粉可有效降低豆渣納豆產品之臭味，且維持相當之納豆激酶含量。添加5%竹炭粉可得到與添加10%糯米穀粉品質風味相近的產品。竹炭粉添加時間點以發酵後期幾近發酵完成前加入，效果最佳。
Okara or soymilk residue is the by-product of soymilk, tofu and touhua. The high water content of the okara cause it is easy to spoil and hence is not able to reuse. The smell of the okara natto is very strong, and which leads low willingness of people to consume this kind of products. The purpose of this research is to find a way to produce an okara natto product with low off-flavor and high physiological property. The result finds that adding 5% waxy rice flour, 5% corn flour and 5% indica rice flour could decrease the off-flavor of okara natto. The 5% waxy rice flour added product has the highest nattokinase activity among these three products. The research also finds that the waxy rice flour added from 5% to 15% will not significantly influence the activity of nattokinase (28.67-32.60FU/ml vs. 52.30FU/ml for control), but the off-flavor of okara natto can be decreased. The results proves that adding 10% waxy rice flour will significantly decrease the off-flavor of okara natto and at the same time, maintaining the proper activity of nattokinase in due course. The smell is similar between 5% banboo charcoal powder added and waxy rice flour added product. The best of banboo charcoal powder adding time is the final stage of fermentation.
