Preparation Of Protein In Double-low Rapeseed Meal And Its Functional Properties

Rapeseed meal protein has good quality. To develop its resource sufficiently, thedouble-low defatted rapeseed meal was studied in this study. The rapeseed meal wasprepared by traditional press oil technology. Protein preparation from double-lowdefatted rapeseed meal was evaluated respectively by the pulsed ultrasound-assisted andtraditional alkaline methods. Moreover, a comparison study on protein functionalproperties was performed. At last, the experiment on protein extraction which usedmicrowave-assisted method was studied. The main results are shown as follows:(1) The double-low defatted rapeseed meal components were measured, the contentof protein, fat, moisture, ash, tannin, inositol hexaphosphoric acid and thioglucoside is35.75% (N×5.53), 0.91%, 12.73%, 13.98%, 3.53%, 2.21% and 0.71%, respectively.(2) To extract and prepare rapeseed meal protein by traditional alkaline method, theoptimal technologic parameters are as follows: pH 12, dosage liquor temperature 50℃,ratio of water vs materiel 30: 1 (mL/g), extraction time 100 min and precipitation pointpH 4. Under this condition, the extraction ratio of protein, extraction yield and proteincontent (N×5.53) is 60.83%, 26.82% and 59.56%, respectively. The thioglucosidecontent in the extracts is 0.07% which is lower than the standard of China (content ofsodium hyposulfite is less than 1.85%).(3) To extract and prepare rapeseed meal protein by the pulsed ultrasound-assistedmethod, the optimal technologic parameters are as follows: pH 12, ultrasonic power 875W, ratio of water vs materiel 35: 1 (mL/g), extraction time 85 min, on-time of the pulsedultrasonic 3s and off-time 2s, dosage liquor temperature 45℃and precipitation point pH4.5. Under this condition, the extraction ratio of protein, extraction yield and proteincontent (N×5.53) is 83.97%, 52.18% and 68.18%, respectively. The thioglucosidecontent in the extracts is 0.06% which is lower than the standard of China. Comparedwith extraction method of traditional alkaline method, under the case that the pH,ultrasonic power, ratio of water vs materiel and dosage liquor temperature isapproximate for two methods, it is obtained by using the pulsed ultrasonic-assistedextraction that extraction ratio and yield of protein is increased 38.04% and 94.56%respectively, extraction time is decreased 15%. The pulsed ultrasound-assisted methodis superior to traditional alkaline method markedly. (4) The comparison study on functional properties of proteins prepared by the twomethods was performed. On the whole, the Emulsifying Stability, Water HgdrationCapacity, Foaming Capacity, Oil Absorption and Viscosity of the protein prepared bythe pulsed ultrasound-assisted method were superior to the protein prepared bytraditional alkaline method. However, its Solubility, Emulsifying Capacity and FoamingStability were inferior to the protein prepared by traditional alkaline method.(5) Traditional alkaline method and the microwave-assisted method were compared,the initiatory results showed that the microwave-assisted method couldn’t promote theprocess of protein extraction nearly. The non-thermal effect of microwave wasineffective on the extraction of the double-low rapeseed meal protein.