Optimization of fat bleaching in soap production: from laboratory to industrial scale

This paper reports the use of design of experiments (DOE) with the objective of finding optimal industrial conditions for fat bleaching in soaps production. Laboratory experiments were performed evaluating the effects of residence time, temperature and pressure on the resulting fat color by two different colors scales: red (R) and yellow (Y), through light emitted or reflected by the mixture. Statistical analysis as well as a visual analysis of response surfaces indicated that only factors “Time”, “Temperature”, “Pressure” and “Time × Temperature” presented considerable effects on the total color, and an operation with long residence time, low pressures and low temperatures would be ideal for removal of the R and Y colors in an easy and effective manner. The responses found in these experiments were reproduced in industrial equipment, and the fat color results obtained were within the indicated experimental value. This approach is of simple laboratory execution, good reproducibility at the industrial level and also with good fat bleaching efficiency. Our finds indicated that 50 min of residence time, 70 °C and 6.7 kPa would be ideal operation conditions in industrial scale.