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Keywords:

  • Calcium hydroxide;
  • Refining;
  • Rice bran oil

Abstract

The applicability of calcium hydroxide (lime) in the neutralization of rice bran oil (RBO) was investigated. Crude RBO samples of three different free fatty acids (FFAs) (3.5–8.4 wt%) were degummed, dewaxed, bleached, and neutralized with lime and deodorized. The oils obtained thus were characterized by determining the color, peroxide value (PV), content of unsaponifiable matter (UM), and FFA. Conventionally practiced caustic soda neutralization (at 80–90°C) of FFA has in the present investigation been replaced by a high temperature (150–210°C) low pressure (2–4 mm Hg) reaction with lime. It was observed that neutralization with Ca(OH)2 at high temperature (210°C) and under low pressure (2–4 mm Hg pressure) may substantially reduce the FFA content (0.8 wt%, after 2 h). The deodorized oil was found to be of acceptable color, PV, and content of UM and FFA. Neutralization of oil was also carried out by using NaHCO3 and Na2CO3, nonconventional alkalies for neutralization, and the results were compared with NaOH and Ca(OH)2. Overall recovery of oil in Ca(OH)2 refining process (88.5 ± 0.6 wt%, for Sample 1 containing 8.4%-wt FFA) was found to be more than other competitive processes studied.