Crystallization of fully hydrogenated and interesterified fat and vegetable oil

Owing to public concern regarding the adverse health effects of trans fatty acids, an alternative technology to trans fats has recently become an important issue. The interesterification of fully hydrogenated vegetable oil and liquid oil blends is one of the most versatile options. This paper reports a physical analysis of high-melting fat (HMF) prepared through the interesterification of fully hydrogenated soybean oil and regular soybean oil, and through fractionation. The thermal and structural properties of the HMF blended with salad oil at a mass ratio of 4:1 (called the HMF blend, hereafter), which was prepared as a model fat blend for margarine, were assessed using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized light microscopy (POM). To observe the polymorphic transformation, all samples were aged after crystallization, and the development of granular crystals during the aging process was observed. We found that the granular crystals are made of SOS/SSO, POS/PSO, and (SOS+POS)/(SSO+PSO) molecular compounds, all of which easily transform into β form with a double-chain-length structure.