Study on acyl migration kinetics of partial glycerides: Dependence on temperature and water activity

Acyl migration phenomenon was often observed during 1,3-positional specificity lipase-catalyzed reactions from triglycerides and partial glycerides, including acyl migration of 1,2-diglyceride (1,2-DG) to 1,3-diglyceride (1,3-DG) and 2-monoglyceride (2-MG) to 1-monoglyceride (1-MG). However, the acyl migration mechanism and kinetics were seldom studied despite of numerous researches on process optimization of 1,3-positional specificity lipase-catalyzed reaction. In this paper, the influence of related factors on acyl migration process as well as their influencing mechanism was further studied. It was found that temperature and water activity were two crucial factors that would influence acyl migration kinetics. Determination of the kinetic parameters under different temperatures revealed that the acyl migration reaction rates were greatly promoted by the increasing of temperature. The acyl migration rates of 1,2-diglyceride and 2-monoglyceride were quite different from each other, which was found to be due to the different activation energies. Further study of how would water influence the acyl migration process showed that water activity rather than water content was a key factor that influenced acyl migration and the acyl migration rate would decrease with the increase of water activity. It was further revealed that water activity influenced the charge dispersion of the transition state, which ultimately influenced the reaction activation energy and then influenced the acyl migration rate.