MORPHOLOGY AND SIZE DISTRIBUTION OF PALM OLEIN CRYSTALS DURING FRACTIONAL CRYSTALLIZATION WITH BEHENIC ACID

Abstract

Fractional crystallization of palm olein is industrially practiced to produce superolein and soft palm mid fraction for food and non-food products. This process, however, is frequently complicated by prolonged nucleation induction times, sluggish crystal growth rates and inconsistent crystal sizes, often requiring seeding agents for process improvement. This study examined the morphology and size distribution of palm olein crystals during isothermal fractional crystallization at 15 °C with 0.25%, 0.5%, 0.75% and 1% behenic acid using optical microscopy and focused beam reflectance measurement (FBRM). Results showed that the addition of 1% behenic acid to palm olein significantly reduced the nucleation induction time to 30 min compared to 170 min in the control palm olein. Crystal size distribution analysis depicted that the highest crystal population was observed at 0.75% behenic acid concentration, with a mean crystal size of 31 µm. Above this concentration, the count rate decreased and crystal sizes exceeded 100 µm due to crystal growth and agglomeration. Furthermore, the addition of 1% behenic acid accelerated palm olein crystallization and increased the solid fat content of the crystallizing slurry to 22% from 15% in the control palm olein. Microscopic images revealed that behenic acid acted as heterogeneous nuclei, forming the cores of dense spherulites within the bulk oil. The findings from this study have demonstrated the potential role of behenic acid as a nucleation enhancer and crystallization rate promoter in facilitating palm olein fractional crystallization.