Abstract
Polymorphism, temperature of phase transition, enthalpy, and entropy of 4 kinds of cis-monounc saturated monoglyceride (C16 : 1, C18 : 1, C20 : 1, C22 : 1) were clarified, and correlation between unsaturated and saturated monoglycerides was examined.
1) Monounsaturated monoglycerides have β, α, and sub-α type polymorphism but sub-α 2 was not observed even in C20 : 1. Transition rate was the slowest in C22 : 1 and the rate decreased in the order of C20 : 1, C18 : 1 and C16 : 1. The transition behavior of these was similar to that of saturated monoglycerides of below C12.
2) Temperature of phase transition, enthalpy, and entropy of modification examined by DSC tended to become higher with increase in the number of carbon atoms. The interval of transition temperatures |α-β| is wider than that |sub-α - α |. The enthalpy and entropy of cis-monounsaturated monoglycerides for β → smelt and α → melt are approximate to those of saturated monoglycerides for α → melt and sub- α → α transition. 3) Temperature of phase transition, enthalpy, and entropy of cis-monounsaturated monoglycerides were markedly lower than those of saturated monoglycerides, although the rate of their decrease was found to have a regular correlation between unsaturated and saturated monoglycerides. This regularity is considered to be correlated to the difference in the mode of hydrocarbon chain oriented in the crystal layer between saturated and unsaturated monoglycerides.
