| In recent years,deep processing industry of egg products developed rapidly in China.The full utilization of egg whites is basically achieved that they are used to extract high-value products such as lysozyme and ovotransferrin,and the remainder can be processed into egg white polypeptides.The egg yolks can be used to extract functional components,including immunoglobulin,lecithin,oil,however,the rest is regard as feed at present,leading to a dramatic reduce in the value of egg yolks.Actually,the defatted egg yolk powder has high nutritional value and is quitely worth developing,because its main components are proteins,including phosvitin,low density lipoprotein and high-density lipoprotein.Consequently,this study was focused on the preparation and functional properties of phosvitin phosphopeptides(PPPs),and the PPPs workshop was designed as well.Here,the defatted egg yolk powder after the extraction of lecithin was used as raw material and egg yolk polypeptides(EYPs)as byproduct were obtained.The specific research contents are as follows:The defatted egg yolk powder was used as raw material and effects of process conditions,including pretreatment and enzymatic hydrolysis on the yield and purity of PPPs were investigated.The optimized process conditions were obtained that initially the defatted egg yolk powder was smashed to pass through 200 meshes screen,and then treated by adding neutral protease at 50 °C,p H 7.After 3 h,the p H value of the enzymatic hydrolysates was adjusted to4.0 for the precipitation of phosvitin,and the hydrolysates were then filtrated by 100 nm ceramic membrane.The filtration and precipitation were EYPs and phosvitin,respectively.The collected phosvitin was partially dephosphorylated and then enzymatically hydrolyzed with compound protease for 3 h at 50 °C,p H 10.After that,the hydrolysates were filtrated with ceramic membrane and the filtrate was collected as PPPs solution.A 200 Da nanofiltration membrane was then used for the desalination and concentration of PPPs solution until the solid content achieved to 15%.Subsequently,1%(w/v)activated carbon was added to decolorize the solution at p H 4.3,50 ℃.After 30 min,the solution was clarified with frame filtration and finally the PPPs powder was obtained using a spray dryer.The yield of PPPs was 10.3% and N/P was 11.2.Analysis on amino acid composition,molecular weight,and metal ion chelating ability of the obtained PPPs was studied.And an in vitro simulated digestion model was used to evaluate the resistance ability to digestion of the metal ion chelating PPPs as well.The results show that the PPPs possesed balanced amino acid composition,with the essential amino acid content of28.3%.And the peptides with a molecular weight of 180-1000 Da accounted for more than 70%,indicating high nutritional value of PPPs.Their chelating ability of calcium and zinc ions was22.8% and 13.1%,respectively,much greater than that of commercial casein phosphopeptides.The results on in vitro simulated digestion showed that the ion release rate of calcium ion chelating PPPs and zinc ion chelating PPPs were both lower than 1%,suggesting that they had great anti-digestion ability and was beneficial to the absorption by human body.Based on the research on the production process of PPPs,the workshop of egg yolk powder with annual processing capacity of 600 tons was designed.The annual consumption of raw,auxiliary material and energy were determined through mass and energy calculation.According to the process requirements,equipment selection,workshop graphic design and piping design were carried out,and relevant drawings were also completed.Finally,technical and economic calculation of the project was performed,and results showed that the investment payback period was 2.76 years,and the break-even point was achived when the annual processing capacity of of egg yolk powder was 29.6% of designed capacity.This indicated that the project has good resistance to risk,and it is practical and feasible. |
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