ON THE FORMATION OF GRANULAR CRYSTALS IN FAT BLENDS CONTAINING PALM OIL

The use of palm oil for plastic fats has encountered serious difficulty due to its crystallization properties, one of which is the formation of granular crystals. The granular crystals cause sandy taste and inhomogeneity of fat crystal morphology of end products. In the present study, we analyzed the formation process of these granular crystals. Chemical and physical analyses for triacylglycerol (TAG) compositions, polymorphism and melting points of the granular crystals led to the conclusion that the granular crystals are of the most stable polymorph, beta1, of POP (1,3-dipalmitoyl 2-oleoyl glycerol) with triple chainlength structure. This conclusion was supported by reproducing the formation process of the granular crystals in a model fat blend consisting of POP and rapeseed oil. The following characteristics of beta1 polymorph of POP contribute to the formation of granular crystals in fat blends containing palm oil: (i) beta1 reveals well-defined plate-like crystal morphology, which grows easily into the bulky granular form; (ii) the triple chainlength structure of POP has a tendency to segregate and does not form a solid solution together with other TAGs.