Phytic acid의 함량이 대두 단백질의 용해성과 소화율에 미치는 영향

Abstract

본 연구는 영양 저해인자로 알려진 phytic acid를 새로운 방법으로 제거한 low-phytate soy protein isolate와 일상적 방법으로 제조한 high-phytate soy protein isolate(SPI) 를 얻어 phytic acid함량이 이들 분리 대두단백의 용해성과 소화율에 미치는 영향을 조사하기 위하여 수행되었다. 그리하여 분리 대두단백의 용해도를 측정하였고, phytic acid의 첨가량과 pH에 따른 phytic acid - 단백질의 결합도를 조사하였으며 phytic acid가 대두 단백질의 소화율에 미치는 영향을 살펴 보았다. 본 실험에서 얻어진 결과를 요약하면 다음과 같다. 1) 분리 대두단백의 phytic acid함량은 high-phytate SPI에서 2.48%이었고 low-phytate SPI에서는 high-phytate SPI보다 71%가 감소되었다. 2) 분리 대두단백의 용해도를 조사한 결과 모든 pH에서 low - phytate SPI의 용해도가 high-phytate SPI의 용해도보다 높았고 특히 pH3.0 ~ 4.0과 pH 8.0 ~ 9.0에서 용해도 차이가 컸으며, 등전점 부근에서는 low-phytate SPI의 용해도가 약간 높게 나타났다. 3) 분리 대두단백은 phytic acid의 첨가량이 많을수록 용해도가 떨어져 침전되었다. 등전점 아래인 pH2.5 ~ 4.5에서는 phytic acid 와 분리 대두단백의 결합도가 높았고 반면, 등전점 위의 pH인 6.5, 8.0에서는 결합도가 낮았다. 4) 분리 대두단백의 소화율에 미치는 영향은 대조구(phytic acid 무첨가)에서 low-phytate SPI의 소화율이 high-phytate SPI보다 7.6 % 높게 나타났으며, 가장 높은 수준의 phytic acid를 첨가했을때 low-phytate SPI는 대조군의 9.7 %, high-phytate SPI는 11.4 % 감소하였다. 단백질 소화율에 미치는 Phytic acid의 저해적 영향은 phytic acid 첨가량이 증가할수록 더 증가하였으며, low-phytate SPI보다 high-phytate SPI에서 그 저해 효과가 약간 크게 나타났다. 5) 이상을 종합하여 볼때 phytic acid함량이 낮은 대두 단백제품을 제조함으로써 대두 단백질의 용해성과 소화율을 향상 시킬 수 있으리라 생각된다.;This study was undertaken to investigate the effect of phytic acid known as an antinutritional factor on the solubility and the digestibility of high-phytate and low-phytate soy protein isolates (SPI) which were obtained by the usual method and newer method, respectively. Experiments were carried out to determine the solubility of two SPI products, effects of added phytic acid and pH on the binding capacity between phytic acid and soy proteins as well as the effect of phytic acid on the digestibility of soy proteins. The results obtained are summarized as follows ; 1) Phytic acid content of boy protein isolates was 2.48% in high-phytate SPI, 71% of which wag decreased in low-phytate SPI. 2) Solubility of low-phytate SPI was higher than that of highphytate SPI at all pH values tested. The difference in solubility was remarkable at pH 3.0-4.0 and 8.0-9.0 ranges while the solubility near isoelectric point was slightly higher in low-phytate SPI. 3) Solubility of soy protein isolates was lowered by adding an increased amount of phytic acid to result in precipitation of the proteins. The binding capacity between phytic acid and soy protein isolates was stronger at pH 2.5-4.5 below the isoelectric point while it was weaker at pH 6.5-8.0 above the isoelectric point. 4) Pepsin digestibility of low-phytate SPl was 7.6% higher than that of high-phytate SPI in control group (no addition of phytic acid). The addition of a Large amount of phytate brought about 9.7% decrease of the digestibility in low-phytate SPI and 11.4% decrease in high-phytate SPI, as compared with the control group. The inhibitory effect of phytic acid toward protein digestibility decreased by the increasing amount of phytic acid added and the effect was slightly higher in high-phytate SPI than in low-phytate SPI. 5) In conclusion, it appears that the production of low-phyt-ate SPI is necessary to improve the solubility and digestibility of soy protein isolates used as a food ingredient.