A laboratory study was made to develop a simple and economic model methods for the systematic determination of functional properties of "Soyprotein isolates" prepared from defatted Soybean meal. These are required to evaluate and to predict how Soyprotein isolates may behave in specific systems and such proteins can be used to simulate or replace conventional proteins.
Data, concerning the effect of PH, salt concentration, temperature, and protein concentration on the functional properties which include solubility, heat denaturation, gelforming capacity, emulsifying capacity, and foaming capacity, are presented.
The results are as follows;
(1) The yield of SPI (Soyprotein isolates) from defatted Soybean meal increases to 83.9% from 73% when the extract solution was 0.02N NaOH solution instead of distilled water.
(2) 2% SPI suspension was lost only 5% solubility by moisture heat at 70℃ for 80 min, but the denaturation by moisture heat at 95℃ reached to 95% of total protein for 20 min.
(3) The suitable viscosity of a dope solution for spinning fiber was found to be 60 poises by using Syringe needle (0.03mm) instead of using spinnerett. The 60 poise of stable viscosity of dope solution was prepared when the concentration of SPI and NaOH were adjusted to 15% 0.6% respectively.
(4) Heat caused thickening and then gelation in concentration above 8% by weight with a temperature threshold of 70℃. At 8-12% protein concentration, gel was formed within 10-30 min at $70^{\circ}$ -100℃ It was, however, disrupted rapidly at 125℃ of overheat treatment. The gel was firm, resilient and self-supporting at protein concentration above 14% and less susceptible to disruption of over heating.
(5) The emulsifying capacity of SPI was correlated positively to the solubility of protein at M=0. At PH of the isoelectric point of SPI, the E.C increased as concentration of sodium chloride increased. Using model system (mixing speed 12,000 Rpm, oil addition rate 0.9ml/sec, and Temperature $20^{\circ}\pm1^{\circ}C$), the maximum E.C. of SPI was found to be 47.2ml of oil/100mg protein, at the condition of PH 8.7 and M=0.6. The milk casein had greater E. C than SPI at lower ionic strength. But at higher ionic strength the E.C of SPI was same as milk casein.
(6) The shaking test was used in determining the foam-ability of proteins. The basic steps required in shaking test consist of shaking 20ml of protein suspension in a stopped 100ml graduated cylinder. The volume of foam formed is measured at 30 sec. after shaking as foam expansion, and that at 30 min after shaking as foam stability. Progressively increasing SPI concentration up to 5% indicated that the maximum protein concentration for F.C was 2%. Sucrose reduced foam expansion slightly but enhenced foam stability. Minima for foaming capacity occurred between $p^H$ 4 and 5, of isoelectric point region of the SPI. These paralled the solubility/PH curve.
The results of comparing milk casein and egg albumin were that foaming properties of SPI were same as egg albumin, and better than milk casein, particullarly in in foam stability. For the practical application of the data described, beef patties substituted with gelated SPI, and imitation ice cream was prepared. Sensory evaluation was carried out. The sensory analyses indicated that the beef patties substituted with gelated SPI to 30% by weight have no detectable difference to the control at the significately level of 0.01 and that the imitation ice cream have significantly difference to the control, especially in the flavor. Thus a further studies are required to either completely mask or eliminate the beany off-flavor in prepared soyprotein isolates.
동방유량에서 공급받은 저변성탈지대두박으로 부터 분리대두단백의 수율은 0.02N NaOH 용액으로 추출하여, 증류수로 추출할때의 73%에서 84%로 증가시켰으며, 이때 제조된 분리대두단백은 92.1%의 단백질 순도를 나타내었다.
분리대두단백 (이하 SPI) 를 70℃에서 moisture heat 을 가하면 80분간에 5%의 변성이 일어났다. 95℃에서는 20분만에 95%의 단백질이 변성되었으며, 계속적인 가열로 인한 추가적 변성은 일어나지 않았다.
SPI의 alkali 현탁액 (dope solution) 은 SPI의 농도 15%, NaOH 농도 0.6% 일 때 7분만에 60 poises의 정도를 나타내고 계속안정된 점도를 유지하였다. NaOH 농도가 0.9%일 때는 시간이 경과함에 따라 증가하였다가 감소되는 경향을 보였다. Syringe nedale (dia 0.3 mm) 로써 모의 실험결과 dope solution의 viscocity가 60 poises일 때가 spinning 하기에 가장 적합하였다. 가열에 의한 gelation은 SPI의 농도가 8%이상이어야 일어나기 시작하였으며 낮은 농도의 SPI 일수록 높은 온도로 가열하여 형성시킨 gel 의 continuity가 떨어져서 120℃의 가열에서도 양호한 continuity 를 갖는 gel 을 형성하려면 SPI 의 농도가 12% 이상이어야 하였다. SPI의 emulsifying capacity 는 solukility와 밀접한 상관관계를 갖고 있었으며 pH 8.7,Nacl 농도 2%일 때 47.2 ml 로 가장 큰 값을 나타내었다. 또 milk casein 과 비교실험에 있어 전반적으로 낮은 E.C를 나타내었으나 염농도가 증가할수록 거의 접근된 E.C 값을 보였고, 어떤 경우 μ=0.3 이고 pH 5.2 일 때는 29.8 로 29.4 인 mil casein 과 거의 같은 E.C 를 보여 주었다.
SPI와 egg albumin, milk casein의 foaming copauty를 비교한 결과 foam expansion 은 28ml 로 47.8ml 인 milk cosein 및 30.8ml 인 egg alkumin 보다 작았으나, foam stability 는 83.9%로 79.9%인 egg albumin 및 12.0%인 milk casein보다 월등하여 egg albumin 과는 거의 동등한 whipping agent 로써의 특성을 가졌다.
12% SPI 현탁액을 100℃로 가열하여 gelation 시킨 SPI gel 을 sausage 의 증량제로 사용하였을 때 SPI gel 로 45%의 meat 을 대체하여도 관능검사결과 유의성 있는 차이를 나타내지 않았다.
또 cooking loss 도 control 13.5%에서 2%로 줄였다.
그러나, SPI 를 MSNF (milk solid notfat) 의 대체로 하며 제조한 Tic cream 의 관능검사결과 25%, 50%의 MSNF 를 SPI 로 대체하여 제조한 제품보다 유의성 있는 차이를 나타내었으며, flavor 가 민감하게 감지되었고 조직은 colntrol 과 별다른 차이가 없었고 25% 대체한 제품은 terture 가 control 보다 월등히 좋았다.
탈지대두박에서 추출한 분리대두단백은 flavor 만 해결된다면 그것의 식품학적 특성에 비추어 기타 어떤 동물성단백질과 대체하여 식품제조시 ingredients 로써 사용이 가능함을 알았다.
