Effects of chemical interesterification on the triacylglycerols, solid fat contents and crystallization kinetics of palm oil-based fats†
The effects of chemical interesterification (CIE) on the physicochemical properties and crystallization kinetics of oil blends containing palm oil (PO) in combination with six other types of oils were studied. The CIE reaction was performed at a reaction temperature of 105 °C for 30 min, catalyzed by 0.3% sodium methoxide. The results showed that the formation of β′ crystals was prominent and the crystallization rate increased significantly when PO was interesterified with beef tallow (BT). The presence of soybean oil (SBO) in the oil blend significantly increased the triacylglycerol (TAG) S/U/U content after CIE. For the sample consisting of a pure vegetable oil base, a gradual change in the crystallization rate was observed and the formation of β crystals was dominant. The S/U/U content in the oil blends that contained palm kernel oil (PKO) decreased after CIE. Together in the presence of SBO, PKO had stronger ability to stabilize S/U/U, enriched the TAG composition (particularly by increasing the C44 TAG content), accelerated the crystallization rate and formed β′ crystals. The addition of a sufficient amount of palm mid fraction (PMF) could improve the high-temperature solid fat content and expand the plasticity range. Changes in the Avrami constant K and n values derived from solid fat content and heat enthalpy also suggested the modification of the crystal growth mechanism through the CIE process.