Effects of pre-deacidification on 3-MCPDE and GE contents of high-acid oils during refining

Abstract

Crude fats and oils may have high free fatty acid (FFA) content depending on raw material quality and processing conditions. Their refining is always a challenge due to refining loss and the formation of some process contaminants such as 3-monochloropropane-1,2-diol esters (3-MCPDE), and glycidyl esters (GE). In this study, crude hazelnut oil having 12.10% FFA was degummed, bleached, and pre-deacidified by a molecular distillation (MD) unit before neutralisation and deodorisation. Changes in FFA, diglyceride(DG), 3-MCPDE, GE, and tocopherol contents were monitored. Almost no changes were detected in FFA and DG contents during degumming and bleaching while the latter resulted in the 3-MCPDE formation and GE reduction. Some tocopherol losses were also observed after these steps. On the other hand, a huge amount of FFA was distilled (from 12.10% to 1.71%) by the MD process performed at 200 °C, 0.25 mbar, as well as with a 53.6% loss of tocopherol. The samples were then subjected to deodorisation before (MD-PHY) and after neutralisation (MD-CHE) at 230 °C under 2 mbar absolute pressure for 2, 4, and 8 h. While some 3-MCPDE and GE formations were detected during MD-CHE, there were almost no formations in these contaminants after MD-PHY. When the bleached oil having 12.10% FFA was also directly deodorised at given conditions, no formations but some reductions in 3-MCPDE and GE contents of the oils were determined, possibly because of esterification of FFA with DGs that are an important precursor of these contaminants.