The Preparation Of Seed Storage Proteins Of Chickpea And Its Protein Peptides' Functional Properties

Chickpea (Cicer arietinum L.), is one of major food legume crops with the third largest pulse in terms of area of the world at present. It has been planted in some provinces in China, such as Qinghai, Xinjiang, Gansu, Yunnan. Little research was performed in chickpea protein extraction and purification, especially in the protein composition, conformation, functional properties and proteolytic modification. In this investigation, an attempt has been made to study the compositions of chickpea storage protein, the isolation of 10S and 7S fraction, characterization of protein peptides of chickpea, the main results are as follows:1,The PI and subunits of albumin and globulin extracted from chickpea was studied. The subunits' distribution and molecular weight of total protein and albumin, globulin were analyzed by gel filtration chromatography and SDS-PAGE. The results showed that the PI of the albumin and globulin of Kabuli type seeds were as:5.4,4.0; the PI of the albumin and globulin of Desi type seeds were as:5.2,4.0. The total storage protein of both Kabuli and Desi gave 8 peakes by the gel filtration chromatography; 13 subunit bands could be detected on SDS-PAGE pattern. The protein subunits of chickpea were distinct from that of soybean. The globulin subunits' band number and molecular weight of Kabuli and Desi were similar, but their albumin subunits' band number and molecular weight were different.2,To determine the appropriate operating procedure for extraction and isolation of 10S and 7S fractions from chickpea storage protein simultaneously, the factors affecting the extraction and isolation(the PI, kinds of extraction solution, diluted times of NaCl solution, and buffer extraction combining with water diluting method) were investigated. And a feasible operating procedure was confirmed. The results indicated that the 10S and 7S fractions could not be isolated by the deposition method of PI. According to the solubility difference between 11S and 7S in NaCl solution, the 11S fraction could be precipitated firstly and then the pH of the supematant was adjusted to p H 5.5 to remove the insoluble intermediate fraction by centrifugation. After then, the supematant was adjusted to pH4.6 to precipitate and isolate the 7S fraction. The purity and of 10S and 7S fractions were evaluated by analytical ultracentrifugation.3,The optimal technical parameters of hydrolyzation reaction by protease from Aspergillus melleus, and protease from Bacillus SP. were studied, the factors affecting the DH and Pf (the pH, temperature, E/S, time) were investigated. The results of orthogonal tests showed that①the peptides prepared by protease from Aspergillus melleus, had the highest DH and Pf when the reaction conditions were pH8, 35℃, E/S 6%, 5h; pH 8, 55℃, E/S 3%, 3h, respectively.②The peptides prepared by Protease from Bacillus SP. had the highest DH and Pf when the reaction conditions were pH8, 65℃, E/S 9%, 5h; pH12, 65℃, E/S 6%, 1h, respectively.③The DH of the peptides prepared by Protease from Aspergillus melleus were higher than that of the peptides prepared by Protease from Bacillus SP; Otherwise the Pf of the peptides prepared by Protease from Aspergillus melleus were lower than that of the peptides prepared by Protease from Bacillus SP.4,The functional properties of soybean protein peptides and chickpea protein peptides produced by enzymatic hydrolysis were studied. The differences of hydrolysis degree, relative antioxidative activity, moisture-absorption, moisture-retention and oil-absorption between soybean and chickpea protein peptides were mainly investigated; besides the influences of the protease kinds used on the functional properties of peptides were also considered. The results showed that①the peptides made by Protease from Bacillus sp. had the highest antioxidative activity and oil-absorption; the peptides made by Papain from papaya latex had the highest Hydrolysis degree; the peptides made by Protease from Aspergillus melleus had the best moisture-absorption.②The hydrolysis degree and relative antioxidative activity of soybean peptides were better than that of Kabuli and Desi peptides.③The Desi peptides had the best oil-absorption, and were better in the relative antioxidative activity and moisture-retention.④Kabuli peptides had better properties both in moisture-absorption and moisture-retention under different relative humidity conditions. Therefore, chickpea protein peptides would be well applied as additive agent in the future.