Abstract
This experiment was carried out to obtain the basic data for removal the astringency and off-flavor in soybean milk, by means of soaking of soybean in NaOH and $NaHCO_3$ solutions. The changes of phenolic compounds in soybean during soaking were investigated with HPLC and also the changes of flavor and sensority of soybean milk, prepared from soaked soybean were studied. Phenolic compounds of soybean were identified as chlorogenic, p-hydroxybenzoic, p-coumaric, ferulic and gentisic acid and, chlorogenic acid content was greater than the others. The chlorogenic acid of soybean was mainly neutral type and the other compounds were almost acidic type. Up to 85% of the chlorogenic acid was removed by soaking of soybean in 0.1% of NaOH solution for 8 hrs. Phenolic compounds of soybean was almost removed by soaking in 0.1% of NaOH solution at $90^{\circ}C$ for 1 hr. Chemical composition of soybean milks prepared from soaking of soybean in water, 0.1% NaOH and 0.5% $NaHCO_3$ solution were similar. Hexanol content of beany flavor in soybean milk was increased by soaking of soybean in NaOH solution, where as hexanal, propanal, pentanal contents were removed up to 60%. Color of soybean prepared from soaking of soybean in NaOH solution at high temperature were deep yellow but were high whiteness in soybean milk prepared from soaking of soybean in water at low temperature. Sensority of soybean milk prepared from soaking of soybean in 0.1% of NaOH solution at $90^{\circ}C$ for 1 hr was more favorable than the others.
두유의 고삽미와 불쾌취를 제거하기 위한 기초 자료를 얻기 위하여 대두에 NaOH, $NaHCO_3$ 용액을 처리하여 phenol 화합물의 변화를 HPLC로 정량하였고, 두유중의 beany flavor를 GC로 분석하였으며, 두유의 일반성분 및 기호도를 측정한 결과 대두중의 phenol 화합물은 chlorogenic, p-hydroxybenzoic, p-coumaric, ferulic, gentisic acid가 확인되었으며, chlorogenic acid 함량이 가장 높았다. 대두중의 phenol 화합물중 chlorogenic acid는 주로 결합형, 기타 다른 phenol 화합물은 유리형으로 대부분 존재하였다. 대두를 0.1% NaOH용액으로 8시간 침지하였을 때 chlorogenic acid는 85% 이상이 제거되었다. 대두중의 phenol화합물 제거에는 NaOH용액이 효과적이었고, 온도가 높아짐에 따라 제거율도 높아졌으며, 0.1% NaOH용액에게서 $90^{\circ}C$, 1시간처리하였을 때 phenol 화합물은 대부분 제거되었다. 물, 0.1% NaOH 및 0.5% $NaHCO_3$ 용액으로 침지하여 제조한 두유의 일반성분은 처리간에 비슷하였다. NaOH 용액 처리에 의하여 두유의 beany flavor 중 hexanol은 증가하였으나, hexanal, propanal, pentanal은 60% 이상이 제거되었다. NaOH 용액처리, 고온침지처리에 의하여 두유의 yellowness는 증가하였으나 물과 저온 침지처리에서는 whiteness가 증가하였다. 대두를 0.1% NaOH 용액으로 $90^{\circ}C$에서 1시간 처리하여 제조한 두유의 기호도가 가장 좋았다.