Interesterification of fat blends containing high oleic oils: Physical properties and dialkyl-ketones formation assessment

In view of the nutritional disadvantages of partial hydrogenation (production of unhealthy trans fats) interesterification (IE) has emerged to produce suitable fats for trans-free formulations that have improved physicochemical properties. In this context, both chemical (CIE) and enzymatic (EIE) interesterification techniques can be used. However, it has been found that CIE technology may produce process-related by-products known as dialkyl-ketones (DAK). The current study aims at investigating the formation of DAK during IE. Therefore, five edible oils and fats were selected based on their potential use in IE: Elaeis Guineensis palm stearin (POSt), high oleic palm stearin (HOPSt), palm kernel stearin (PKSt), high oleic sunflower oil (HOSO) and high oleic palm oil (HOPO). The investigated blends were divided into HOPO-based blends (POSt:HOPO 50:50, PKSt:HOPO 50:50, HOPSt:HOPO 50:50 and 30:70 wt:wt%) and HOSO-based blends (POSt:HOSO 30:70, 50:50 and 70:30 wt:wt%). They were all subjected to both CIE (using sodium methoxide) and EIE (using TLIM lipase as catalyst); analyses of physical properties and determination of DAK content were performed before and after IE. This study demonstrates that DAK were not formed during the EIE process regardless of the investigated matrix, whereas they were produced during CIE, and that they require sufficient rearrangement of triglycerides (TAG) to be formed. It has also been shown that unsaturated fatty acids are more prone to form DAK regardless of the fat matrix. However, there is no linear relationship between the amount of DAK and the amount of unsaturated fat in the matrix.