Implementation of the supercritical carbon dioxide technology in oil palm fresh fruits bunch sterilization: A review

In palm oil production, sterilization is a vital process that can affect the quality of the extracted palm oil. The purpose of sterilization of oil palm fresh fruit bunch (OP-FFB) is to inactivate lipase activity and lipophilic microorganisms, soften the pulp of the fruits and facilitate the stripping process. The current practice of thermal sterilization in the palm oil industry, which utilizes conventional steam sterilization, is ineffective for lipase degradation and microbial inactivation in OP-FFB. The conventional steam sterilization technique operates at temperature 130 °C-160 °C, elevated pressures of 0.15-0.4 MPa, and sterilization time of 60-90 min. This sterilization method also requires huge amounts of water, which in turn demand higher energy usage and generates large quantities of palm oil mill effluent. Thus, waterless sterilization seems as a better option in yielding a high quality palm oil as well as protecting the environment. Supercritical carbon dioxide (SC-CO2) has been found to be a promising sterilization technology in the inactivation of various enzymes and lipophilic microorganisms. This technology inactivates enzymes and microorganisms physico-chemically relatively low temperature (≤60 °C) and moderate pressures (8-40 MPa) without generating residual waste. Thus, the application of SC-CO2 bears the potential to sterilize OP-FFB, as a waterless sterilization technology. The present review was conducted to assess the possible use of SC-CO2 in OP-FFB sterilization and make comparisons to the existing OP-FFB sterilization method. This study also appraises the effectiveness of SC-CO2 in the inactivation of enzymes and microorganisms that lessen the quality the palm oil.