Studies on Polymorphism of Monoglycerides. VI.

Abstract

As factors cantrolling the transition rate of 1-monoglycerides from meta-stable to stable type, temperature and time of heat treatment, length of molecular chain, granularity of crystals, and cantamination of impurities can be cited. Therefore, relationship between the transition rate and the length of a molecular chain was examined with odd-and even-acid monoglycerides (C14, C15, C16, C17, C18). 1) In all the glycerides examined, heat treatment in the α-type region of 45°C resulted in the slowing of the transition rate with lengthening of the molecular chain, although the difference between C14 and C15 or C16 and C17 was very slight. In even-acid monoglycerides (C14, C16, C18), this relationship was in a straight line while that in odd-acid monoglycerides (C15, C17) was parallel. 2) Heat treatment of C14, C15, C16 and C17 monoglycerides in the sub-α-type region of 20°C showed that transition rate of C15 was faster than that of C14, and that of C17 was faster than C16, indicating an alternation between odd-and even-acid glycerides. 3) Heat treatment of C14 and C16 monoglycerides in the sub-α-type region and C15 and C17 mono glycerides in the α-type region of 30°C gave results similar to that obtained by heat treatment at 20°C, but the alternation became more slightly than that of 20°C. 4) These experimental results suggested that, as factor controlling the transition rate of mono glycerides, route of transition (sub-α→β and α→β) and the difference in the packing structure of the molecular chain in the meta-stable type (especially in odd-and even-acid) were also important, besides the molecular chain length.