The Extraction And Property Improvement Of Protein From Pea Starch Noodles’ By-product

Pea is one of the most important and widely used beans in our country. Pea protein arehigh in nutritional value. Pea starch noodles is a traditional Chinese food and it is verypopular in our country. The sour liquid producing methods to produce starch and furtherprocessed to starch noodles were the traditional way to produce pea starch noodles in industry.The theory of it is using Lactococcus lactis and its metabolite (lactic acid) to agglutinatestarch granule to make starch separated from protein and fiber. Pea protein is lost in the wastewater, some industry recover the protein in a simple way and use it as forage. It led to a wasteof resources. We called the protein “The acid precipitation slurry” which produced duringisoelectric precipitation of the protein in waste water.The acid precipitation slurry had a protein content of71.02%, starch content of14.32%with a bad odour. The fatty acid composition analysis showed that most of the fatty acid hadbeen oxidated. Compare the protein of the acid precipitation with pea protein throughSDS-PAGE, we found that some bands of the albumin had lost mainly at92kDa,26kDa,12kDa, globulin and glutelin had partial gathered. The surface hydrophobicity of them aredifferent too. In all, the acid precipitation is much different from pea protein.Using alcohol wash to improve the odour and colour of the acid precipitation slurry. Theoptimum conditions of acid alcohol wash were alcohol concentration80%,50℃,2.5h. Thebest conditions of alkaline alcohol wash were90%alcohol,4%alkaline. The GC-MS resultsshowed that through alcohol wash the volatile caused by lipid oxidation was significantlyreduced.The effect of pH、time、temperature and solid-liquid ratio on protein (pea protein isolateextracted from the acid precipitation slurry that was treated by alcohol wash, we called itAPPI in short) extracton yield were discussed. Considering both nutrition and extraction yield,we selected pH12.0,30℃,30min as the best extraction conditions.34.02%of the proteinwere stayed in the residue, the residue was hard to dissolve in SDS. The amino acid analysisof the residue part that can’t be dissolved in SDS showed that it contained a lot of alaninewhich may be part of peptidoglycan from bacterial cell wall. Funtionality study showed thatAPPI had low solubility and gel strength comprared with soy protein isolate (SPI) but betteremulsibility and foamability compared with pea protein isolate extracted from pea (PPPI).Using Alcalase to improve the nitrogen solubility index (NSI) of APPI, different degreeof hydrolysates were prepared and functionality of them were compared. The results showedthat when the degree of hydrolysis was2%(DH2) the NSI increased from35.78%to58.65%,at DH10NSI reached81.72%. We also study the foam ability and emulsify ability of thehydrolysates, with the DH improve, they first increase then decrease. DH3had the best foam ability and DH2had the best foam stability and emulsify ability. DH2was the bestconsidering all the properties. Using Transglutaminnase to improve the gel strength of APPI,the best conditions were35℃,2.5h,9U/g. The SDS-PAGE showed that with the reactionintensity increase, the quantity of polymers increased. Functionality study showed that themodified protein had a high gel ability and emulsiability but low solubility.