Enirchment Of Phosvitin Phosphopeptides By Metal Oxide

Egg yolk protein (EYP) is the byproduct of lecithin and also a superior source of protein,it can be used to extract phosvitin phosphopeptides (PPPs) which has biological activities ofpromoting the absorption of calcium. In this paper, TiO2and ZrO2were used to prepare PPPsfrom the hydrolysis polypeptides of EYP, and the metal oxide with better enrichment effectwas modified to improve the grain diameter and separation efficiency, so as to simplify thepreparation procedures and lower the cost of PPPs. This study not only provides a newresearch direction for the comprehensive utilization of EYP, but also provides a new approachfor PPPs enrichment.Firstly，fresh egg yolk powder was used to prepare crude yolk protein enzymaticpolypeptides (crude polypeptides) by defatting, partial dephosphorylation, enzymolysis andlyophilization. During the preparation process, the defatting rate was95.47%, thedephosphorizing rate was38.27%, and the finnal degree of hydrolysis by trypsin was11.51%.Then the crude polypeptides were used to extract PPPs.Secondly, TiO2and ZrO2was used to prepare PPPs from crude polypeptides. At theoptimum condition (initial crude polypeptides pH:4.0, concentration:30mg/mL, reactiontime:20min, reaction temperature:25℃)，the N/P of PPPs-T prepared by TiO2was5.07,when its additive amount was beyond200mg/mL, PPPs-T could obviously prevent theprecipitation of calcium ions, the final addition volum of NaOH solutions was1.64mL; at theoptimum condition (initial crude polypeptides pH:4.0, concentration:40mg/mL, reactiontime:20min, reaction temperature:25℃)，the N/P of PPPs-Z prepared by ZrO2was7.17, ithad a certain effect of preventing the precipitation of calcium ions, when its additive amountwas400mg/mL, PPPs-Z could delay the precipitation of calcium ions by45min, and thefinal addition volum of NaOH solutions was5.26mL. After10times repeated uses, theenrichment effects of PPPs by TiO2and ZrO2were both very stable.Thirdly，TiO2/diatomite composite (TD) was prepared by chemical coprecipitation andcalcination method, and then characterized. The SEM micrograph of TD showed that TiO2was successfully precipitated on the porous surface of diatomite; the prepared TD was withuniform particle size distribution and its median grain diameter was raised to22.89μm. TheFTIR spectrum of TD showed the characteristic absorption peaks of TiO2, SiO2, and also thecharacteristic absorption peak of Ti O Si, which indicated that the synthesis of TD mightinvolve with chemical bonds. The results of TGA analysis showed that the weight loss of thecalcined TD at high temperature was less, which indicated that the calcined TD was with goodthermal stability.Finally, TD was used to prepare PPPs from crude polypeptides. The N/P ratio of thepurified PPPs-TD was5.34at the optimum adsorption conditon (initial crude polypeptides pH:4.0, concentration:40mg/mL, reaction time:20min, reaction temperature:25℃), it wassimilar with that of TiO2and lower than that of ZrO2. The maximum adsorption capacity ofTD (8.12mg/g) was higher than that of TiO2(4.64mg/g). TD was very stable and could bereused, which may be conductive to lower the cost of enrichment. The functional property of PPPs-TD was very strong, when its additive amount was400mg/mL, PPPs-TD couldobviously prevent the precipitation of calcium ions, the final addition volum of NaOHsolutions was1.32mL.This study showed that the purity of PPPs prepared by ZrO2was relatively low and it hada certain effect of preventing the precipitation of calcium ions. While PPPs prepared by TiO2and TD were with higher purity and stronger functional properties of preventing theprecipitation of calcium ions. And TD was very stable, easily prepared and convenient to beseparated from aquous solutions and had great poteintial in large-scale preparation of PPPs.