| In order to improve functional properties of protein from Tilapia meat, dry-heating reaction of myofibrillar protein and glucose, lactose, chitosan, sodium carboxymethyl cellulose and glucan were studied. Effect of different sugar and modification degree on solubility, emulsifying properties and thermal stability of myofibrillar protein was investigated. The aim of this study was to obtain the theory information related to modification of aquatic protein and development of new protein resources. Main results are as follows:1. At the proportion of 1:1 (w/w) sugar and myofibrillar protein, relative humidity of 65%, temperature of 50℃, degree of glycosylation modification increased with increased reaction time, and solubility, thermal stability and emulsifying properties of reaction products was improved in some degrees. Comparatively, rapid reaction between glucose, lactose and myofibrillar protein was measured, and solubility of reaction increased firstly and then decreased with the extension of reaction time, and no visible effect on emulsifying and thermal stability was obtained. However, slow change between chitosan, sodium carboxymethyl cellulose, glucan and myofibrillar protein were observed. Reaction could be easily controlled at the prior period of Maillard reaction, and solubility, emulsifying properties and thermal stability and of reaction products was improved significantly. In the experimental range, carboxymethylcellulose sodium was the best sugar which improved the solubility and thermal stability of myofibrillar protein. And dextran was the best sugar that could be used to improve the emulsifying properties of myofibrillar protein.2. The results of SDS-PAGE showed that myofibrillar proteins linked small-molecule sugar by covalent bond. The moving speed rate of glycosylation of products increased, and molecular weight increased with increased reaction time. However, the moving speed rate of glycosylation of products from myofibrillar protein and big-molecule sugar had no significant change with increased reaction time, and change of molecular weight was not obvious. The spectral bands of myofibrillar protein were only displayed at SDS-PAGE profile. As a result, in process of glycosylation, selecting suitable sugar and controlling modification were necessary, and reaction must be controlled at the prior period of Maillard reaction. All results showed that dextran could be used as glycosyl donor to improve emulsifying properties of myofibrillar proteins and carboxymethylcellulose sodium could be used as glycosyl donor to improve of solubility and thermal stability of myofibrillar proteins.3. The conditions for dry-heated glycosylation reaction between myofibrillar protein and dextran were optimized using response surface methodology after mono-factor test, and emulsifying activity and stability was determined. The results showed that the optimal reaction conditions were as follows: myofibrillar protein reacted with dextran in weight ratios of 1:3.3, at 72.02℃, 69% relative humidity for 30.62h. Under these conditions, the emulsifying activity index of glycosylation product was 1.908±0.013, the emulsifying stability index was 31.545±0.4, thermal stability was (3.53±0.55)%, solubility in 0.1mol/L NaCl solution was (44.13±0.81)%, solubility in 0.5mol/L NaCl solution was (63.13±1.29)%, and graft degree of the myofibrillar protein-dextran was (23.2±0.3)%. These were not significant different with the model prediction.4. Glycosylation products of myofibrillar protein and dextran prepared under the optimal condition was purified by Sephacryl S-200. The results showed that during the glycosylation reaction dextran was excessed, and existing glycoprotein could be further deduced from overlapped absorption peak. And the eluent was collected from 10th to 25th tubes. The collected sample was analysed by infra-red spectrometric analyzer. The IR analysis results showed that glycosylation reaction could produced between dextran and myofibrillar protein.5. The conditions for dry-heated glycosylation reaction between myofibrillar protein and sodium carboxymethyl cellulose were optimized using response surface methodology after mono-factor test, and solubility and thermal stability of products was determined. The results showed that the optimal reaction conditions were as follows: myofibrillar protein reacted with carboxymethylcellulose sodium in weight ratios of 1:1.4, at 52.45℃, 69% relative humidity for 23.94h. Under these conditions, the solubility of glycosylation product in 0.1mol/L NaCl solution was (82.13±0.32)%, solubility in 0.5mol/L NaCl solution was (88.77±0.21)%, thermal stability was (82.2±0.75)%, the emulsifying activity index was 0.895±0.01, the emulsifying stability index was 12.3±0.4.The graft degree of the myofibrillar protein-dextran was (28.2±0.3)%. These were not significant different with the model prediction. These were not significant different with the model prediction.
|
PDF Full Text Request