Isothermal crystallization kinetics of refined palm oil

  • Chen C
  • Lai O
  • Ghazali H
 et al. 
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Abstract

Refined, bleached, and deodorized RBD palm oil was supplied by the Malaysian Palm Oil Board (MPOB). The oil was filtered when hot through Whatman No. 1 filter paper prior to use. (i) Isothermal crystallization. The induction times for crys-tallization (τ) were determined with a Haake (Karlsruhe, Ger-many) Rotovisco RV20 viscometer using an M10 measuring system and an NV St (low viscosity) sensor. Viscosity output was recorded automatically. The temperature of the measur-ing system was controlled by means of water circulated from two water baths via three-way valves. One of the bath tem-peratures was set at 343 K to melt the crystallized oil, whereas the other was held at the crystallization temperature, T c , which was controlled to within ±0.2 K. The palm oil (17.0 ± 0.5 mL) in the sample holder was heated at 343 K for 15 min to destroy any preexisting nuclei and its crystallization mem-ory. The temperature of the viscometer sample holder was then lowered to T c and the viscometer controller was started. The water baths could achieve a cooling rate of 15.0 ± 2.0 K/min. Shear rate of the sensor system was increased from 0 to 100 s −1 within 2 min. Shear rate was maintained at 100 s −1 until the end of the run. We assumed that the effect of shear-ing on induction time was minor at this slow shear rate. The shear rate used in the present study was much lower than those encountered in commercial tempering devices where shear rates of typically 500–12,000 s −1 can be generated (13). Furthermore, all samples were agitated using the same shear rate, which would keep any shearing effect constant. After starting the cooling process and increasing the shear rate, the viscosity was observed to increase until a shear rate of 100 s −1 and the T c were reached, where it stabilized. When

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Authors

  • C. W. Chen

  • O. M. Lai

  • H. M. Ghazali

  • C. L. Chong

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