Decolorization of commercial zein via protein precipitation involving organic solvents at low temperatures

The low-temperature organic solvent precipitation of proteins is a reversible denaturation process. In this study, the effect of the low-temperature precipitation decolorization of zein was investigated on the basis of this reversible process by using the pigment clearance rate and zein recovery rate as evaluation indicators. Low-temperature anhydrous ethanol was used as a precipitant. Furthermore, with the volume ratio of precipitator to zein solution (the volume ratio), precipitator temperature and zein solution pH as three factors. A low-temperature precipitation method was compared with an activated carbon adsorption method to determine the decolorization effect of zein via response surface methodology to optimize decolorization. Results showed that the decolorization effect of low-temperature precipitation was significantly affected by precipitator temperature, volume ratio, and zein solution pH. The primary order of their effects was as follows: precipitator temperature > volume ratio > zein solution pH. The decolorization effect of zein was optimal under the following parameters: precipitator temperature of - 30 degrees C, zein solution pH of 6.8, and volume ratio of 2.5:1. Under these conditions, the zein recovery rate and the pigment clearance rate were 86.93 % and 98.72 %, respectively. By contrast, the zein recovery rate and the pigment clearance rate were 68.50 % and 79.22 % under the optimized activated carbon decolorization process, respectively. In conclusion, the effect of low-temperature precipitation decolorization and the recovery rate of zein were obviously better than those of activated carbon decolorization.