Chapter 1. Fractionation and concentration of omega-3 by molecular distillation

ROSSI PC; GROSSO NR; PRAMPARO MC; NEPOTE V

Eicosapentaenoic Acid: Sources, Health Effects and Role in Disease Prevention

Nova Science Publishers, Inc.

Lugar: New York; Año: 2012; p. 177 - 203

Certain oils are a rich source of compounds called omega-3, which are polyunsaturated fatty acids that play an essential role in the human diet because of their ability to prevent disease. These acids participate in the production of hormones involved in several physiological systems regulating pain and moisture, while maintaining adequate blood pressure and optimal levels of cholesterol and promoting nerve transmission. Especially two fatty acids, both omega-3 type, the 5,8,11,14,17-eicosapentaenoic acid (EPA, 20:5w3) and the 4,7,10,13,16,19-docosahexaenoic acid (DHA, 22:6w3) are important functional constituents of the human body. The complexity in the preparation process of concentrated omega-3 compounds is mainly based on the similar physicochemical properties of the fatty acids. In this sense, it is difficult to separate them from the other fatty acids in the oil. Simple fractionation processes do not discriminate between different polyunsaturated fatty acids present in an oily mixture, so it is necessary to evaluate the different available alternatives. Nowadays, at commercial production scale, molecular distillation is the most widely used technique. Molecular distillation is a special type of very high vacuum distillation, which takes place in an apparatus constructed so that the distance that the molecules must travel between evaporation and condensation is smaller than their mean free path. In this way, it is possible to avoid an excessive exposure of the product to deteriorating conditions. This feature makes molecular distillation a good alternative for application in the fractioning process of omega-3 fatty acids. The main objective of this chapter is to present a review where it is discussed, in a theoretical and experimental way, the process of fractionation and concentration of ethyl esters of omega-3, using the falling film molecular distillation. It is important to highlight that for obtaining a concentrate of omega-3, it is first necessary to perform a transesterification stage for achieving the separation of the carbon chain of the glycerol molecule. In this reaction, the most favorable condition is achieved by working at high temperatures close to the boiling point of the ethanol. Moreover, the conversion of the reaction increases with increasing the catalyst concentration within the studied ranges. As esters of omega-3 have an intermediate volatility value between those of esters of light fatty acids and the esters ones, it is required to perform two stages of molecular distillation. Working at low temperatures, both stages result in a low separation efficiency. On the other hand, working at very high temperatures the separation efficiency is not favorable, but an optimal point in the process can be found. Several works have shown mathematical models which optimize molecular distillation process, aiming to find conditions which allow a good recovery of ethyl esters of omega- 3 fatty acids with a high degree of purity. Models also allow analyzing the influence of different operating variables.