Study On Separation Of Protein From Lotus Seed And Its Food Functional Characteristic

Lotus Seed has always been regarded as the high quality goods for its rich nutrients,but until now,there were not system research on its protein composition and molecular properties,specially lacking study about its protein functional properties in domestic and foreign.Therefore,the research in this article was the first time to study on these aspects of Protein in Lotus Seed.In this research,amino acid and thermal denaturation analysis were done after withdrawing the lotus protein. Scavenging activities of four main protein fractions in lotus seed on·OH have been done and their molecular properties,such as molecular weight of protein subunits, isoelectric point were determined by SDS-PAGE and isoelectric focusing electrophoresis(IEF).And the purification of four main protein fractions in lotus seed were done by the means of DEAE-cellulose ion-exchange column chromatography and gel filtration on Sephadex G-200.The optimum extraction conditions of total protein in lotus seeds also have been done,and after that,lotus protein functional properties were studied.The main results were as follows:1.In four main protein fractions of lotus seed,the composition of Val,Phe,Tyr and sulfur containing were higher than standard pattern,but the Ile,Lys and Thr were their limiting amino acids.Differential scanning calorimetry(DSC)analysis has been done and the result showed that the salt-soluble protein had the highest denaturation temperature(104.52℃)and the smallest enthalpy(8.8013J/g),and the water-soluble protein had the largest enthalpy(93.0148J/g).Four main protein fractions can scavenge hydroxyl free radical(·OH)obviously(p<0.01).2.According to the analysis of SDS-PAGE and isoelectric focusing electrophoresis(IEF),there were ten protein subunits(69.4～87.8kDa)and four isoelectric points of protein components(pI4.94～pI5.85)in water-soluble protein in lotus seed,ten protein subunits,(14.2～110.5kDa)and two isoelectric points of protein components(pI5.17～pI5.34)in salt-soluble protein,twelve protein subunits (7.2～97.3kDa)and three isoelectric points of protein components(pI5.40～pI6.31)in acid-soluble protein,and six protein subunits(15.0～46.8kDa)and four isoelectric points of protein components(pI5.51～pI6.46)in alkali-soluble protein.Measured by the means of DEAE-cellulose ion-exchange column chromatography,there were two eluation peaks in water-soluble protein,such as acid-soluble and alkali-soluble proteins,and one peak in salt-soluble protein.Determined by gel filtration on Sephadex G-200,there were ten eluation peaks in water-soluble protein,such as alkali-soluble proteins,two eluation peaks in salt-soluble protein,nine eluation peaks in acid-soluble protein.3.The optimal conditions for total protein of lotus seed were ratio of lotus to solution 1:25,pH11.0,extraction temperature 40℃,and extraction time 3h.Amino acids in total protein extraction were similar to that in lotus powder,but the composition of Val,Tyr,Met and Cys were higher than those in lotus powder.DSC analysis on total protein extraction also has been done and the result showed that its denaturation temperature was 102.2℃and the enthalpy was 57.92J/g.4.Functional properties have been studied using freeze-dried power of total protein extraction from lotus seed by the method of acid precipitation at pI4.50.The oil-holding ratio of protein freeze-dried power increased from 260%to 650%by the increasing of sample quality.The water-holding capacity of protein freeze-dried power reached highest at 50℃.Following sample concentration elevation,foaming capacity of protein freeze-dried power enhanced and reached highest at 1.0% concentration of NaCl.Foam stability reached highest at pH5.0.Emulsifying capacity and stability also increased in the sample concentration range of 1.0%～4.0%,and both were low nearby its pI.The properties of hardness,fracturability,adhesiveness, gumminess and springiness of protein gelation enhanced by the increasing of sample concentration,and this trend was singnificant when sample concentration was higher than 12.0%.Those five properties of protein gelation reached the highest value at pH9.0.