Value-added Utilization Of Protein And Phytic Acid From Rapeseed Prepress-solvent Extracted Meal

Rapeseed Prepress-solvent Extracted Meal (RPEM), the by-product from the most widely applied oil-producing process in China, is a vegetable protein resource with enormous potential.To realize the value-added utilization of rapeseed protein and associated natural products, the following studies were carried out.1、To enhance the protein extraction from RPEM, the by-product from the most widely applied oil-producing process in China, the technical feasibility and effectiveness of RPEM pretreatment by using Polysaccharide Hydrolase Complex (PHC) was evaluated.The hypothesis of breaking down the chemical combination of polysaccharides and protein by enzymatic pretreatment, thus to improve the solubility and extractability of protein in RPEM was demonstrated by observations from SEM characterization, solid-liquid phase equilibrium and protein extraction kinetics.According to the investigation of pretreatment parameters, it is proposed that the appropriate condition for RPEM pretreatment is with PHC loading of2.5%, at a solid to liquid ratio of1:20under pH4.8and50℃for48h.With a process of alkaline extraction and isoelectric precipitation, the yield and purity of Precipitated Protein Isolate (PPI) obtained from the pretreated RPEM were47.66%(improved by52.8%comparing with those from untreated RPEM) and90.89%(up to the purity standard of protein isolate), respectively.2、Process parameters of PPI preparation from PHC pretreated RPEM was optimized to maximize the recovery rate and purity of rapeseed protein. Solubility of rapeseed protein was determined by solid-liquid phase equilibrium experiment.The results shown that the maximum solubility (up to7.1mg/mL) of rapeseed protein was obtained in range of solvent pH above12.8and sodium chloride concentration below0.1%; the minimum solubility (less than0.33mg/mL) of rapeseed protein was obtained in range of solvent pH within3.5-4.3and sodium chloride concentration below0.5%.According to the single factor tests and orthogonal experiment on process parameters, the optimized condition for PPI preparation is PHC pretreated RPEM extracted by alkaline solution for4times at a solid to liquid ratio of1:20and pH13followed by precipitated under pH4.0.Under these conditions, the yield and purity of PPI prepared from the PHC pretreated RPEM were52.41%and85.28%.3、To evaluate the nutritional value of PPI prepared with PHC pretreatment, the amino acid composition and chemical composition of PPI obtained with various process conditions were determined and compared.The PHC pretreatment did not show any significant negative effect on nutritional value of PPI. For PPI prepared with PHC pretreatment, the removal rates of antinational factors, such as glucosinolate s, phytic acid and tannin were above99.9%,96%and71%, respectively. Enzyme loadings of0.25%to0.5%in PHC pretreatment were appropriate for perparation of PPI with the purity higher than83%, which could be improved further by desalting to meet the purity standard of protein isolate (above90%). Furthermore, the cost of the rapeseed PPI products prepared with PHC pretreatment were close to those of soybean protein isolate.It is proposed that the rapeseed PPI preparation process with PHC pretreatment is a promising technique to realize the value-added utilization of RPEM.4、To make fully utilization of rapeseed meal and improve the quality of rapeseed protein, a two-step process for recovery of phytic acid from prepress-solvent extracted rapeseed meal was established.The effects of key parameters on phytic acid extraction, including the pH of acid solution for extraction, the duration of acid solution extraction, the pH and the Ethylene Diamine Tetraacetic Acid (EDTA) concentration of alkaline solution for extraction were investigated.With an acid solution extracting step at pH5.0and50℃for3h and an alkaline solution extracting step at pH12.0and50℃with the supplement of0.1M EDTA followed by acidic precipitation, the phytic acid in cellulase pretreated rapeseed meal can be almost entirely extracted without noticeable loss of rapeseed protein. The crude phytic acid in extracted solution, which then to be purified by calcium hydroxide precipitation with subsequent acidification and ion exchange can lead to a final product with purity of69.96%and yield of58.0%.