Abstract: In order to control the formation of fat crystal network structure and optimize the quality of the final product, this work aimed to investigate the effect of lard-based monoacylglycerol (L-MAG) on the isothermal crystallization kinetics, microstructure, thermal behavior, polymorphism and hardness of palm stearin (PS) at different temperatures of 4, 15 and 20 ℃. Our results showed that the types of fatty acids in L-MAG were identical to those in PS, but the contents of fatty acids were different between them. L-MAG could decrease the crystallization rate and extent of PS. However, this effect depended on the concentration of L-MAG and crystallization temperature. The effect of L-MAG on reducing the crystallization rate and the solid fat content value at equilibrium was more significant when the crystallization temperature was higher. Furthermore, this effect was proportional to the concentration of L-MAG in the range of 1% to 4%. Results of differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) suggested that L-MAG could promote the crystallization of low-melting fractions and had little effect on the polymorphism of PS. Moreover, the hardness of PS increased after addition of PS, which could be attributed to the formation of a more compact and orderly crystal network with a high degree of space filling. The crystallization behavior of PS could be modified to improve the quality of the final product by controlling the concentration of L-MAG and crystallization temperature.

Key words: lard-based monoacylglycerol; palm stearin; isothermal crystallization; thermal behavior; polymorphism