Similar physical characteristics but distinguishable sn-2 palmitic acid content and reduced solid fat content of chemically interesterified palm olein compared with native palm olein by dry fractionation: A lab-scale study

摘要

The presence of solid fat content (SFC) of vegetable fats at human body temperature (37 degrees C) has been linked to altered fat digestibility and metabolism. In this study, the possibility of reducing the SFC in chemically interesterified palm olein (CIEPO) while maintaining physical properties similar to native palm olein was explored by dry fractionation. Crystallization at 37 degrees C for 155min produced a CIEPO olein fraction with total fatty acid composition (FAC) broadly resembling that of native palm olein while the high proportion of sn-2 palmitic acid content was maintained at 39.1%. The CIEPO olein fraction has a reduced SFC at 37 degrees C from 8.6 to 4.2%, overall decreased SFC, slip melting point (SMP) at 33 degrees C, a reduced palmitoyl-palmitoyl-palmitoyl (PPP) from 6.0 to 3.7 mol% and lower heating peaks in thermal profile compared with the untreated CIEPO. Both CIEPO olein fraction and palm olein have broadly similar total FAC and SMP below 37 degrees C but very distinguishable sn-2 palmitic acid content. CIEPO olein fraction and native palm olein can be used as effective comparison in human studies because the differences of both fats in PPP content and SFC at 37 degrees C were narrowed. Practical applications: Previous human studies investigating the effects of positional distribution of fatty acids on postprandial lipaemia (abnormally high lipid levels in blood after meal) have yielded contradictory findings. Most of these studies require the use of interesterified fats to distinguish the difference in the sn-2 fatty acid composition when compared with the untreated form of the fats. The inconsistent findings on lipaemic response from these studies have raised the issue on the importance of using groups of test fats with different positional composition but similar physical characteristics in order to differentiate the effects of positional composition from the physical characteristics of test fats. This study serves as a potential solution to the pairing of test fats with distinguishable sn-2 profile by creating a CIEPO fraction from dry fractionation with lowered SFC at 37 degrees C while maintaining the physical characteristics of its untreated form that is suitable to be used in future human clinical studies. Human lipid nutrition studies comparing natural dietary fats with interesterified fats require pairs of test fats possessing similar physical properties but distinguishable sn-2 specific fatty acids content. In the current study, CIEPO was fractionated into olein and stearin at 37 degrees C. Both native palm olein and the CIEPO olein fraction have similar total C16:0 content and SMP below 37 degrees C but distinguishable sn-2 C16:0 content, whilst the differences of both fats in tripalmitin and SFC at 37 degrees C were narrowed.