Free fatty acid separation from vegetable oil deodorizer distillate using molecular distillation process

Abstract

Distillates of the vegetable oil deodorization are composed of free fatty acids (FFA), sterols, tocopherols, sterol esters, hydrocarbons and breakdown products of fatty acids, aldehydes, ketones and acylglycerols. The content of free fatty acids in deodorizer distillates varies between 25 and 75%. Due to its high content, free fatty acid separation from deodorizer distillate is an important step to concentrate tocopherols to high purity. Tocopherols are valuable natural substances used in food, cosmetic and pharmaceutical industries. In this work, separation of free fatty acids from soybean oil deodorizer distillate (SODD) was investigated through molecular distillation, using different operating conditions. Evaporator temperature from 100 to 180 °C and feed flow rate in the range of 1.5–23.0 g min −1 were used in the experiments. FFA and tocopherols contents were monitored in each stream generated by the molecular distillation process (distillate and residue streams). The intention is to determine the best operating conditions to produce a material with minimum FFA content and to minimize tocopherol losses during the process. Removal of FFA in the distillate stream resulted in a preliminary concentration of tocopherols, which is removed in the residue stream of the molecular distillation. The results showed that an efficient FFA separation from SODD with the lowest loss of tocopherols requires specific operating conditions. It was possible to obtain a material with 6.4% of FFA and 18.3% of tocopherols from a raw material composed by 57.8% of FFA and 8.97% of tocopherols, using 160 °C of evaporator temperature and 10.4 g min −1 of feed flow rate. These results represent FFA elimination of 96.16% and tocopherol recovery of 81.23%.