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Preparation of Rapeseed Protein from Rapeseed Meal in a Reverse Micelle System and the Study on Its Tpwise Enzymatic Hydrolysis

Author: ZhuJunWang
Tutor: JuXingRong
School: Nanjing University of Finance and Economics
Course: Of Food Science
Keywords: Rapeseed Protein Reverse Micelle Sonication Function Properties Stepwise enzymatic hydrolysis Rapeseed Peptide Angiotensin Converting Enzyme(ACE)
CLC: TS201.2
Type: Master's thesis
Year: 2010
Downloads: 83
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Abstract


Rapeseed meal is a by-product of oil extraction, which is formed after the squeezing and defatting process. The content of total protein reaches 35%-45% and can be exploited as food additive because of its good quality. Bioactive peptides can be obtained from protein hydrolysate. However, the meal hasn’t been utilized completely. It is only used for animal feed and fertilizer, thus leading to the waste of resources. Therefore, it’s significant to work on the value-added process of rapeseed meal.The technology of reverse micelles is a new kind of separation method for biological molecule. The simultaneous extraction of protein from rapeseed by reverse micelles, not only improves the traditional technology of abstracting oil, desolvent and toast the meal, but avoids the disadvantage of protein denaturation during the process.On the basis of forward-extraction and backward-extraction combining with sonication, the preparation of rapeseed protein from double-low rapeseed meal was studied and the respective reaction conditions were optimized. Functional characteristics of the rapeseed protein were comparied with the other rapeseed protein.The rapeseed peptide by two enzymes stepwise assisted by sonication was obtained. Proteolysis of rapeseed with this method can result ACE inhibitory activity i n peptides. The main conclusions of the experi ments were as follows:(1) Assisted by sonication, rapeseed protein was extracted from the rapeseed meal in a reverse micelle system. The effects of the Wo, extraction time, pH, K+ concentration, temperature, and the amount of OT were studied. By solving the quadratic regression model equation, the best fit regression equation is Y=0.063X1+0.017X2+0.024X4+0.529. The optimum extraction conditions were achieved by Taguchi Experimental Design in JMP, namely the amount of OT, pH, Wo and extraction time.(2) Research technology was explored is to increase the yield of backward extraction of rapeseed protein, and save the source. In this study, backward extraction procedure was explored for rapeseed protein. After recovery of isooctane and dissolution of residual solid with a small amount of KCI buffer solution, and adding some alcohol, the rapeseed protein was precipitated in the lower aqueous phase by centrifuged. Uniform Design was applied to get the optimum composition of the crucial factors. By statistical analysis of SPSS, the optimum backward extraction conditions were achieved, namely the amount of alcohol 2mL, K concentration 1.2mol/L, the amount of buffer solution 25mL, and pH value 9.5. Under these technical conditions, the backward extraction rate of protein reaches 59.56%%.(3) The differences of functional properties of rapeseed protein extracted by reverse micelle system (OT/isooctane) and prepared by alkali- solution and acid-isolation was inves tigated. Functional characteristics of the two kinds of rapeseed protein were comparied. The results showed that the protein extarcted by reverse micelles was lower on moisture content, ash content and oil content, superior on solubility, foaming capacity and stability, emulsion capacity and stability, but inferior on water absorption capacity. The technology of extraction rapeseed protein from rapeseed meal in a reverse micelle system assisted by sonication was contribute to improving the rapeseed protein in food industry.(4) In this paper, the degree of hydrolysis, index of soluble nitrogen in TCA(TCA-NSI), and peptide recovery ratio of the preparation of the rapeseed peptide by two enzymes stepwise assisted by sonication. The six sorts of compounds combined between Papain Papaya, Protamex, Alcalase, Flavourzyme, and Trypsin were studied. The results showed that the effects of stepwise enzymatic hydrolysis with Papain Papaya firstly and then with Flavourzyme and Trypsin firstly and then with Flavourzyme to prepare peptides, which are better than those of other enzymes, and much more low molecular weight rapeseed peptide with higher degree of hydrolysisand more soluble nitrogen inTCA.(5) Rapeseed protein was pretreated by stepwise enzymatic hydrolysis, with trypsin firstly and then with flavourzyme and study the effects of the degree of hydrolysis (DH) and molecular weight distribution of the rapeseed peptides on the activity of angiotensin converting enzyme (ACE). The results showed that with DH of hydrolyzate increment, the proportion of peptide with low molecular weight (above 3000 daltons) was increased, and the ratio of inhibition on ACE activity showed higher. Proteolysis of rapeseed with this method can result ACE inhibitory activity in peptides. The high quality of rapeseed protein can be used directly in the supplementation of foods and can also widen the field of application of rapeseed protein.

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