Preparation Of Oligopeptide Using Enzymatic Methodology From Rice Residues

Rice residues, the by-product from starch syrup industry by using early indica rice or broken rice as raw materials, contain up to50%protein by dry weight and are considered to be an important protein resource. Due to a long time liquefaction treatment and amylase hydrolysis, the proteins are denatured and are poor in solubility. The denatured proteins can be extracted by enzymatic modification in the form of soluble oligopeptides from rice residues. Soluble oligopeptides can be used in food industry, which will not only reserve the nutrition features of rice protein but also be beneficial to digestive absorption. Besides, some rice proteins constituted with specific amino acids acquire the relevant abilities to regulate organisms. The objective of this paper is to optimize the modification of proteins from rice residues and the results are as follows:1. The properties and exploring status of rice proteins, the properties changes and modification research of proteins from rice residues and enzymatic modification of rice residual proteins were reviewed by reading and consulting lots of previous papers. Considering the solubility was the most important functional property, proteins from rice residues were modified by enzyme with the objective of obtaining oligopeptide with good solubility.2. A simple washing process was used to remove dextrin and soluble sugars in rice residues. Based on single factor tests, the best conditions of washing craft was:the temperature60℃, liquid/solid ratio7:1, washing time20min. washed twice. Under these conditions, rice residues were recovered with a protein content of75%.3. Pancreatin was selected to modify rice residual proteins by comparing the enzymatic effect of neutrase, alcalase and pancreatin on rice residues and considering the widely hydrolysis mode of pancreatin. Based on single factor tests, hydrolysis conditions were optimized by using a response surface methodology (RSM) on the degree of hydrolysis (DH) and investigating the relationship between DH and the molecular weight distributions. The optimum values for pancreatin concentration, substrate concentration, temperature, pH and hydrolysis time were found to be1.6g/100g rice residues.1:9(w:v),55℃,8.5and3.0h.4. Powered actived carbon was chosen as decolouring agernt of rice residues hydrolysates solution. On the basis of single factor tests, the optimum conditions were selected by orthogonal test with decoloration rate and nitrogen loss rate as the major indicators. The results showed that the optimum conditions were:temperature60℃.30 min process time, and6.0%amount of powered active carbon. The decoloration rate and the nitrogen loss rate were96.78%and27.43%. The hydrolysates solution decoloured was hyaline and had a good sensory effect.5. Based on the previous results, scale-up test of modification on rice residual proteins was carried out. The crush of raw material was first used in the test. The effectiveness of the proposed method was confirmed and the residual proteins hydrolysates power was obtained. As a result, the total yields and the purity of protein hydrolystes power were42%and84%respectively.6. The properties of protein hydrolysates power were investigated. The quality analysis showed the power met standards of 《Q/AHYY0001S-2012soluble rice rotein)) Functional properties showed the product had a good solubility, but relatively poor other functional properties. The products made by spray-drying and decolorization with molecular weight(Mw) below1000U in the final peptides was over95%, and most of the final peptide were dipeptides or tripeptides. The shape of the product was close to rotundity with uneven surface and different size through SEM analysis, dual characteristics of polypeptides and glycoprotein was proved through FT-IR analysis.